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The Feynman Lectures on Physics (The New Millennium Edition) #1
The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat
“The whole thing was basically an experiment,” Richard Feynman said late in his career, looking back on the origins of his lectures. The experiment turned out to be hugely successful, spawning publications that have remained definitive and introductory to physics for decades. Ranging from the basic principles of Newtonian physics through such formidable theories as general relativity and quantum mechanics, Feynman’s lectures stand as a monument of clear exposition and deep insight.
Timeless and collectible, the lectures are essential reading, not just for students of physics but for anyone seeking an introduction to the field from the inimitable Feynman.
968 pages, Kindle Edition
First published January 21, 1963
957 people are currently reading
4657 people want to read
About the author
Richard P. Feynman
258 books6,623 followersRichard Phillips Feynman was an American physicist known for the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as work in particle physics (he proposed the parton model). For his contributions to the development of quantum electrodynamics, Feynman was a joint recipient of the Nobel Prize in Physics in 1965, together with Julian Schwinger and Sin-Itiro Tomonaga. Feynman developed a widely used pictorial representation scheme for the mathematical expressions governing the behavior of subatomic particles, which later became known as Feynman diagrams. During his lifetime and after his death, Feynman became one of the most publicly known scientists in the world.
He assisted in the development of the atomic bomb and was a member of the panel that investigated the Space Shuttle Challenger disaster. In addition to his work in theoretical physics, Feynman has been credited with pioneering the field of quantum computing, and introducing the concept of nanotechnology (creation of devices at the molecular scale). He held the Richard Chace Tolman professorship in theoretical physics at Caltech.
-wikipedia
See Ричард Фейнман
He assisted in the development of the atomic bomb and was a member of the panel that investigated the Space Shuttle Challenger disaster. In addition to his work in theoretical physics, Feynman has been credited with pioneering the field of quantum computing, and introducing the concept of nanotechnology (creation of devices at the molecular scale). He held the Richard Chace Tolman professorship in theoretical physics at Caltech.
-wikipedia
See Ричард Фейнман
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February 5, 2011
Four decades ago, I once dared to walk into the office of Mr. S C Mookerjee, our Professor and Head of Department in Physics at St. Aloysius' College, Jabalpur, and there I took his permission to look up his personal library. There were three attractive red-colored cloth volumes of Lectures in Physics by Richard P. Feynman. I picked up the first volume and upon a cursory glance, I happened to read this paragraph, in utter admiration and reverence:
"A poet once said, 'The whole universe is in a glass of wine.' We will probably never know in what sense he meant it, for poets do not write to be understood. But it is true that if we look at a glass of wine closely enough we see the entire universe. There are the things of physics: the twisting liquid which evaporates depending on the wind and weather, the reflection in the glass; and our imagination adds atoms. The glass is a distillation of the earth's rocks, and in its composition we see the secrets of the universe's age, and the evolution of stars. What strange array of chemicals are in the wine? How did they come to be? There are the ferments, the enzymes, the substrates, and the products. There in wine is found the great generalization; all life is fermentation. Nobody can discover the chemistry of wine without discovering, as did Louis Pasteur, the cause of much disease. How vivid is the claret, pressing its existence into the consciousness that watches it! If our small minds, for some convenience, divide this glass of wine, this universe, into parts -- physics, biology, geology, astronomy, psychology, and so on -- remember that nature does not know it! So let us put it all back together, not forgetting ultimately what it is for. Let it give us one more final pleasure; drink it and forget it all!"
— Richard P. Feynman
I now find that this paragraph has captured hearts all over the globe and, therefore, it is internationally famous.
"A poet once said, 'The whole universe is in a glass of wine.' We will probably never know in what sense he meant it, for poets do not write to be understood. But it is true that if we look at a glass of wine closely enough we see the entire universe. There are the things of physics: the twisting liquid which evaporates depending on the wind and weather, the reflection in the glass; and our imagination adds atoms. The glass is a distillation of the earth's rocks, and in its composition we see the secrets of the universe's age, and the evolution of stars. What strange array of chemicals are in the wine? How did they come to be? There are the ferments, the enzymes, the substrates, and the products. There in wine is found the great generalization; all life is fermentation. Nobody can discover the chemistry of wine without discovering, as did Louis Pasteur, the cause of much disease. How vivid is the claret, pressing its existence into the consciousness that watches it! If our small minds, for some convenience, divide this glass of wine, this universe, into parts -- physics, biology, geology, astronomy, psychology, and so on -- remember that nature does not know it! So let us put it all back together, not forgetting ultimately what it is for. Let it give us one more final pleasure; drink it and forget it all!"
— Richard P. Feynman
I now find that this paragraph has captured hearts all over the globe and, therefore, it is internationally famous.
April 21, 2013
The most wonderful gift from my brother on my 17th birthday. At first I didn't realize what I was holding in my hands. But it gradually became clear that this book is a work of genius. Feynman has explained every concept of Physics so beautifully. No wonder these lectures are still cherished by all.
Best one to get all the concepts cleared and at the same time, have fun learning about the Physics of the world around us.
Feynman is one of the reasons I fell in love with Physics.
Best one to get all the concepts cleared and at the same time, have fun learning about the Physics of the world around us.
Feynman is one of the reasons I fell in love with Physics.
December 30, 2016
My notes while reading the book:
It's funny that I'm reading this book while I haven't read any medical textbook in full despite being a doctor!
Delayed reading it for 2 week ls while I read QED: The Strange Theory of Light and Matter, which was mentioned in the Preface - I might have read all of Feynman's popular science books by this time (all during this year btw).
The textbook is an introductory for science majors and therefore doesn't require prior reading beyond high school science.
Style is engaging and author makes hard topics easy to grasp.
Author doesn't give us ready formulas as has been done in school; he goes through the trouble of explaining how we got them in the first place.
While many parts of the book are easy to understand, many other parts are very hard; you have got to be a math genius in order to understand them.
There are no exercises to help see the implications of the equations and how they play out in practice.
Feynman's impressions at the beginning about the book being hard for many people are spot on.
Intro about Feynman and the history of publication of these volumes. It was planned from the beginning to tape-record the lectures and turn them into a course textbook. The lectures were given between 1961 and 1963 (before my father was born!). The book went through many editions and many corrections were made to it.
[The preface acknowledgement into sections were really long - it took me more than 30 minutes (and I'm being conservative here) just to get past that!]
Chapter 1: Atoms in Motion
1-1: Introduction
"This two-year course in physics is presented from the point of view that you, the reader, are going to be a physicist."
"We do not yet know the all the basic laws [of nature]; there is an expanding frontier of ignorance."
"Everything we know is only some kind of approximation, because we know that we do not know all the laws [of nature] as yet."
Some words on the nature and philosophy of science. [Very similar to David Deutch presentstion of Karl Popper ideas about guessing then testing the guesses. Imagination as a source of new ideas.]
"Even a very small effect sometimes requires profound changes in our ideas" [very similar to what Deutch says in The Fabric of Reality.]
1-2: Matter is made of atoms
[Interestingly David Deutch in a chat with Sam Harris said this line "Matter is made of atoms" would be the most important he would want to tell to future civilizations if a disaster happened.]
This is in fact Feynman's idea, and Deutch adopted it from him!
Magnify water a billion times to see the oxygen and hydrogen atoms; they are really small, like an apple compared to Earth. The unit used is angstrom (10^-10 meter).
Heat as jiggling motion of atoms [billiard balls model of 19th century thermodynamics]. Force = pressure * area. Pressure is propotional to density. Compression (slow) increases the temperature (and vice versa).
Solids, liquids and gasses from the atomic point of view.
Solids arranged in crystalline array. Hexagonal arrangement of ice and why its size decreases when it melts. Only water and type metal decrease in size when they melt; the remaining increase in size.
Helium doesn't become solid even at absolute zero, unless we also increase the pressure.
1-3: Atomic processes
Balance between water vapor and liquid water. Explains why evaporation leads to increased temperature. Air dissolving into water.
[He makes everything interesting and easy to understand!]
Dissolution of salt in water. How temperature affects this; not well understood.
1-4 Chemical reactions
Carbon burning in oxygen. This produces energy (heat), when it is enormous we get flames. The formed molecule is CO or CO2 depending on the amount of oxygen available.
Every substance is so form of arrangement of atoms; some more complicated than others. Detective work (i.e. organic chemistry) must be done to understand these arrangements. Why names of molecules are complicated in organic chemistry (they have to describe complex arrangements precisely).
The atomic hypothesis. Brownian motion.
"There is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics."
Chapter 2: Basic physics
2-1 Introduction
The scientific method is observation, reason and experiment. Fundamental physics compared to a chess game rules; just because you understand the rules doesn't mean you understand the reason behind every move, in addition every once in a while we discover new laws, just like casteling in chess.
[Feynman description of science with regard to how new theories are formed, how problems arise etc are very similar to Deutch summary of Popper's ideas. I can't figure how Feynman could criticize philosophy of science when he is truly engaged in it.]
Unifications (or amalgamations). Heat and mechanics, electricity magnetism and light, and quantum mechanics of chemistry (unified all of chemistry). Can we unify all things?
2-2 Physics before 1920
Inertia and forces (EM and gravity). 92 elements. Electromagnetic force is dominant in the atomic level, it is much stronger than gravity. Atic number decides particle properties.
History of the development of the atomic models.
Electromagnetic field. EM spectrum and frquency.
2-3 Quantum physics
Strangeness of QM. Netwon laws of motion do not apply. Uncertainty principle (delta x delta p more than or equal to h/2). Probabilistic nature of QM (exact events cannot be predicted, only probabilities can).
Wave particle duality. photons. QED.
2-4 Nuclei and particles.
This was before QCD or Standard Model were developeded. They had a table based on leptons, mesons and baryons, mass and charge. [QED is ~20 years more up to date than this. Here they were still playing with the huge amounts of particles trying to fit them into a table and quarcks are not even mentioned yet].
Chaoter 3: The relationship of physics to over sciences
3-1 Introduction
"If a thing is not a science, is it not necessarily bad. For example, love is not a science. So if something is said not to be a science, it does not mean that something is wrong with it; it just means that it is not a science."
3-2 Chemistry
In principle all chemistry is reduceble to QM. Statistical mechanics. Organic and inorganjc chemistry. Inorganic chemisty is reduced to physical chemisty and quantum chemistry. Organic chemistry to biochemistry to biology or molecular biology.
3-3 Biology
Nerves and physics (charges etc).
[His talk about how muscles work is not accurate/up to date].
Kerb cycle. Importance of isotopes (therefore physics e.g. Carbon 12, 13 and 14) to discover the cycle. Enzymes. DNA.
3-4 Astronomy
"Poets say science takes away from the beauty of the stars - mere globs of gas atoms. I too can see the stars on a desert night, and feel them. But do I see less or more? The vastness of the heavens stretches my imagination - stuck on this carousel my little eye can catch one - million - year - old light. A vast pattern - of which I am a part... What is the pattern, or the meaning, or the why? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined it. Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were a man, but if he is an immense spinning sphere of methane and ammonia must be silent?"
Helium was discovered on Sun and Technetium.
We know the interior of stars better than the interior of Earth. Formation of elements in stars.
3-5 Geology
Weather prediction and the problem of turbulent flow [in The Edge of Uncertainty this is named as one of the still unresolved problems].
3-6 Psychology
From the very first sentence says psychoanalysis is not a science and is a medical process at best or even just witch doctoring.
We don't know much about how brain works.
3-7 How did it get that way?
Question about the history of physics, were the laws of pgysics always the same as they are now?
Mentions the problem of turbulent flow as unsolved for over 100 years.
Chapter 4: Conservation of energy
4-1 What is energy?
Physics offers no definite answers. We calculate the total and it is always the same. It comes in many forms. Explains this an anology.
4-2 Gravitational potential energy
Perpetual motion machine thought experiment. Gravitational potential energy is the energt whicj an object has because if its relationship in space, relative to the Earth (gravitational potential energy = weight * height). This is true as long as we are not too far from Earth.
Potential energy:
Change in energy = force * distance force acts through
Using conservation of energy to solve some problems. [doesn't explain them well, he magically arives at an answer and I can understand how he did it].
Principle of virtual work.
4-3 Kinetic energy
Potential energy converted to kinetic energy
Kinetic Energy = height * weight.
K.E. = WV^2/2g
Both are approximate formulas.
4-4 Other forms of energy
Elastic energy for stretched springs.
Heat energy. This isn't a new form of enegy; it's just kinetic energy-internal motion.
Other forms of energy
Mass as enery E = mc^2
Conservation laws, of linear momentum, of angular momentum, of charges, of baryon [actually quarks] and of leptons.
Chapter 5: Time and Distance
5-1 Motion
Quantitative observations make us arrive at quantitative relationships.
Galileo experiments on motion. At first he measured time with his pulse.
5-2 Time
Hard to define. We base the definition on the p
repetition of some apparently periodic event.
5-3 Short times
A day and an hour glass to measure time. Pendulum for shorter periods. Electrical pendulums for shorter periods, known as oscillators
Predicted being able to measure less than 10^-12 seconds accuracy [Phemto second by Ahmed Zowail.] Time can also be measured by dividing distance over speed.
Are there limits to the small measurement of time?
5-4 Long times
Year. Tree rings. River-bottom sediments. Radioactive material. Explains radioactive half life and etc. Measuring the age of Earth.
5-5 Units and standards of time
Earth days aren't perfectly periodic, they increase slowly [as a result of the tidal evolution with Moon.] Atomic clocks.
5-6 Large distances
Triangulation (i.e. paralex). [He says Euclic was right when assuming space was flat, but this was actually only confirmed several years after his death]. Getting absolute distances from relatives ones. Radar observance.
Use of light dimming. Global clusters. [Type 1A supernovae of course are the best].
5-7 Short distances
Light microscope. Elecron microscope (10^-8). Triangulation of scattered x-rays (10^-10). Use of beam of high energy particles at a thin slab of material then calculating can get us the size of the nucleus (10^-15).
The meter was in the past decided to be pai/2 * 10^-7 * radius of Earth.
Limits on measurement of speed, location and time (uncertainty principle). Time with energy and position with momentus (therefore velocity).
Chapter 6: Probability
"The true logic of this world is in the calculus of probabilities." -by James Clerk Maxwell
6-1 Chance and likelihood
"Any physical theory is a kind of guesswork."
We use probability when we don't have complete knowledge. How to measure probability.
6-2 Fluctuations
Normal distribution curve and fluctuations.
Pascal trianle or binomial effect.
(n above k) = n!/k! (n-k)!
P(k, n) = (n above k)/2^n
Bernouli or binomial probability.
6-3 The random walk
Related to Brownian motion.
Mean square distance.
How do we know if the coin is not honest.
Margin of error = 1/2*root of N
6-4 A probability distribution
Motions of a molecule in a gas is just like a random walk. Probability density.
6-5 The uncertainty principle
Delta x * Delta v >= h/2m
"If we try to 'pin down' a particle by forcing it to be at a particular place, it ends up by having a high speed. Or if we try to force it to go very slowly, or at a precise velocity, it 'spreads out' so that we do not know very well just where it is. Particles behave in a funny way!"
Electron is a probability cloud. In the Hydrogen atom, this could is as big as the Hydrogen atom!
"In its efforts to learn as much as possible about nature, modern physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities."
Chapter 7: The Theory of Gravitation
7-1 Planetary motions
F = ma
F = G m1m2/r^2
The history of discovery of gravity. The ancients, Copernicus, Tycho Brahe, Kepler.
7-2 Kepler's laws
3 laws:
1. Orbits are elliptical (adheres to the rule r1 + r2 = 2a).
2. The radius vector from the Sun to the planet sweeps out equal areas in equal intervals of time (i.e. planets move faster when closer to the Sun).
3. T is proportional to a^3/2.
7-3 Development of dynamics
Discovery of inertia by Galileo and further development by Newton (a body will keep going forward in a uniform speed unless acted upon by a force which change its speed or diecrtion).
This meant that there was no need for the angels pushing the planet. There was a force toward the Sun.
7-4 Newton's law of gravitation
A universal law of gravity. Deduced it from Kepler's third law. The inverse sequare law. Applies to Earth, Moon, Sun and everywhere. One of the most profound generalizations.
"The moon falls in the sense that it falls away from the staight line that it would pursue if there were no forces."
Escape velocity. Moon and tides. Earth-moon tidal system.
7-5 Universal gravitation
Why Earth is round, but not so round. In 1656, Roemer measured the speed of light from Jupiter's moons. Adams and Le Verrier predict Nepton from Uranus weird orbit.
Spinning galaxies with angular momentum. Gravity extends for millions of light years if not billions.
7-6 Cavendish's experiment
Measured the gravitational constant G, and therefore weighted the Earth!
7-7 What is gravity?
Newton did not know how gravity worked; the machinery behind it. Several proposals were made, but they were wrong.
When do the constants come from? We don't know.
7-8 Gravity and relativity
Einstein. Mass and energy. The need to quantize gravity.
Chapter 8: Motion
8-1 Description of motion
Will talk about classical mechanics at first.
8-2 Speed
Problems with motion the ancients faced. Zeno paradoxies.
To get speed measurement more accurately, smaller time and distance intervals should be taken. Invention of differential calculus by Newton and Leibniz.
V = lim (e > 0) x/e where v = velocity, x = the infanticimal distance and e = the infanticimal time.
Solves the limit approches zero question.
8.3 Speed as a derivative
◇ = delta
V = lim (◇t>0) ◇s/◇t = ds/dt
[His explaination of what where are doing with calculus is way better than what we were taugh in school where we only had to solve without understanding. This is especially true since calculus was invented to solve physics problems and not as an abstract idea.]
Table for simple differentiation.
8-4 Distance as an integral
Integration is the sum when lim (t>0).
$ = summa aka integration sign
S = $ v(t) dt
Differentiation is opposite to integration, the first is always possible analytically, while the latter is impossible sometimes.
8-5 Acceleration
A second derivative. a = d^2 s/dt^2
Distance is acceleration integrated twice
How to do it in three dimensions instead of just 1 as we did earlier.
A parabola is the motion of any freely falling body that is shot out in any direction
Chapter 9
Newton's Laws of Dynamics
9-1 Momentum and force
Newton's second law. Will use approximations here such as that mass doesn't change with velocity.
F = m * dv/dt = ma
Acceleration at right angles a = v^2/R where R is radius. Therefore, from F and m, you can get a, then from it you can get R.
9-2 Speed and velocity
Velocity is magnitude and direction, while speed is only the magnitude.
9-3 Components of velocity, acceleration, and force
Motions in the x, y, and z directions are independent if the forces are not connected.
9-4 What is the force?
Newton's first law = inertia, second laws = F=ma, third law = equality of action and reaction.
Free fall under gravity:
Vx = V0 + gt
X = X0 + V0t + 0.5 gt^2
9-5 Meaning of the dynamical equations
Relating acceleration to the force. If we know both x and v at a given time, we know the acceleration (which equals -x(t)), therefore we know the new velocity and new time.
9-6 Numerical solution of the equations
Hard to understand fully.
9-7 Planetary motions
Calculates them. Very long calculations, but with the same level of complexity as above. They had bery premitive calculators at this time and they were nkt available for everyone, so these calculations took long time unless you were at an institute which had the machines.
Chapter 10: Conservation of Momentum
10-1 Newton's third law
Numerical methods (arithmatic) as done in the previous chapter can solve complicated problems involving more than 2 bodies, whereas the powers of mathematical analysis are limited.
There are even more complicated problems which both can't solve and for them we need general principles such as conservation of energy and conservation of momentum.
Action = reaction.
10-2 Conservation of momentum
m1v1 + m2v2 + m3v3 + ... = a constant
F = dp/dt
Principle of relativity (Galileo's relativity). You cannot differentiate between standing still and moving at a steady speed [the ship example.] From this author will derive the lawsof conservation of momentum.
Symmetry of mass and velocity.
10-3 Momentum is conserved
To confirm this with experiment; air trough (gets rid of friction).
If mass is the same, then v = 1/2(v1+v2).
The principle is really easy to understand with the diagrams.
10-4: Momentum and energy
Elastic collisions only lose minimal energy in heat and vibration. Collisions between atoms such as those in gases are nearly elastic.
In elastic collisions between bodies of similar mass, velocities are exchanged.
Rocket propulsion.
10-5 Relativistic momentum
Above equations show that when getting near to speed of light you gain mass.
Electromagnetic field momentum.
In QM momentum is mv when particles and wave number/centimeter when waves. Newton laws do not hold in QM, but conservation of momentum does
Chapter 11: Vectors
11-1 Symmetry in physics
Laws of physics are the same everywhere. If we move a machine or all of its parts elsewhere it will work the same
11-2 Translations
Proofs the above mathematically and shows there is no special origin for the laws to work from.
11-3 Rotations
The same in all directions. The effect of angular orientation. Proves this mathematically just like above.
11-4 Vectors
All laws of physics are invariant or symmetrical under translation of axes and rotation of axes. The vector analysis is to allow us to do things faster and easier.
Quantities with no direction (e.g. temperature) are called scalars, while those with a direction (velocity, acceleration, force, momentum, displacement) are called vectors. The symbol r is used for vectors and they have components (x, y, z).
11-5 Vector algebra
Multiply by a constant. Addition. Subtraction. Differentiation.
Velocity = dr/dt = lim (◇t>0) ◇r/◇t
*Maximum limit for Goodreads reviews reached!*
It's funny that I'm reading this book while I haven't read any medical textbook in full despite being a doctor!
Delayed reading it for 2 week ls while I read QED: The Strange Theory of Light and Matter, which was mentioned in the Preface - I might have read all of Feynman's popular science books by this time (all during this year btw).
The textbook is an introductory for science majors and therefore doesn't require prior reading beyond high school science.
Style is engaging and author makes hard topics easy to grasp.
Author doesn't give us ready formulas as has been done in school; he goes through the trouble of explaining how we got them in the first place.
While many parts of the book are easy to understand, many other parts are very hard; you have got to be a math genius in order to understand them.
There are no exercises to help see the implications of the equations and how they play out in practice.
Feynman's impressions at the beginning about the book being hard for many people are spot on.
Intro about Feynman and the history of publication of these volumes. It was planned from the beginning to tape-record the lectures and turn them into a course textbook. The lectures were given between 1961 and 1963 (before my father was born!). The book went through many editions and many corrections were made to it.
[The preface acknowledgement into sections were really long - it took me more than 30 minutes (and I'm being conservative here) just to get past that!]
Chapter 1: Atoms in Motion
1-1: Introduction
"This two-year course in physics is presented from the point of view that you, the reader, are going to be a physicist."
"We do not yet know the all the basic laws [of nature]; there is an expanding frontier of ignorance."
"Everything we know is only some kind of approximation, because we know that we do not know all the laws [of nature] as yet."
Some words on the nature and philosophy of science. [Very similar to David Deutch presentstion of Karl Popper ideas about guessing then testing the guesses. Imagination as a source of new ideas.]
"Even a very small effect sometimes requires profound changes in our ideas" [very similar to what Deutch says in The Fabric of Reality.]
1-2: Matter is made of atoms
[Interestingly David Deutch in a chat with Sam Harris said this line "Matter is made of atoms" would be the most important he would want to tell to future civilizations if a disaster happened.]
This is in fact Feynman's idea, and Deutch adopted it from him!
Magnify water a billion times to see the oxygen and hydrogen atoms; they are really small, like an apple compared to Earth. The unit used is angstrom (10^-10 meter).
Heat as jiggling motion of atoms [billiard balls model of 19th century thermodynamics]. Force = pressure * area. Pressure is propotional to density. Compression (slow) increases the temperature (and vice versa).
Solids, liquids and gasses from the atomic point of view.
Solids arranged in crystalline array. Hexagonal arrangement of ice and why its size decreases when it melts. Only water and type metal decrease in size when they melt; the remaining increase in size.
Helium doesn't become solid even at absolute zero, unless we also increase the pressure.
1-3: Atomic processes
Balance between water vapor and liquid water. Explains why evaporation leads to increased temperature. Air dissolving into water.
[He makes everything interesting and easy to understand!]
Dissolution of salt in water. How temperature affects this; not well understood.
1-4 Chemical reactions
Carbon burning in oxygen. This produces energy (heat), when it is enormous we get flames. The formed molecule is CO or CO2 depending on the amount of oxygen available.
Every substance is so form of arrangement of atoms; some more complicated than others. Detective work (i.e. organic chemistry) must be done to understand these arrangements. Why names of molecules are complicated in organic chemistry (they have to describe complex arrangements precisely).
The atomic hypothesis. Brownian motion.
"There is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics."
Chapter 2: Basic physics
2-1 Introduction
The scientific method is observation, reason and experiment. Fundamental physics compared to a chess game rules; just because you understand the rules doesn't mean you understand the reason behind every move, in addition every once in a while we discover new laws, just like casteling in chess.
[Feynman description of science with regard to how new theories are formed, how problems arise etc are very similar to Deutch summary of Popper's ideas. I can't figure how Feynman could criticize philosophy of science when he is truly engaged in it.]
Unifications (or amalgamations). Heat and mechanics, electricity magnetism and light, and quantum mechanics of chemistry (unified all of chemistry). Can we unify all things?
2-2 Physics before 1920
Inertia and forces (EM and gravity). 92 elements. Electromagnetic force is dominant in the atomic level, it is much stronger than gravity. Atic number decides particle properties.
History of the development of the atomic models.
Electromagnetic field. EM spectrum and frquency.
2-3 Quantum physics
Strangeness of QM. Netwon laws of motion do not apply. Uncertainty principle (delta x delta p more than or equal to h/2). Probabilistic nature of QM (exact events cannot be predicted, only probabilities can).
Wave particle duality. photons. QED.
2-4 Nuclei and particles.
This was before QCD or Standard Model were developeded. They had a table based on leptons, mesons and baryons, mass and charge. [QED is ~20 years more up to date than this. Here they were still playing with the huge amounts of particles trying to fit them into a table and quarcks are not even mentioned yet].
Chaoter 3: The relationship of physics to over sciences
3-1 Introduction
"If a thing is not a science, is it not necessarily bad. For example, love is not a science. So if something is said not to be a science, it does not mean that something is wrong with it; it just means that it is not a science."
3-2 Chemistry
In principle all chemistry is reduceble to QM. Statistical mechanics. Organic and inorganjc chemistry. Inorganic chemisty is reduced to physical chemisty and quantum chemistry. Organic chemistry to biochemistry to biology or molecular biology.
3-3 Biology
Nerves and physics (charges etc).
[His talk about how muscles work is not accurate/up to date].
Kerb cycle. Importance of isotopes (therefore physics e.g. Carbon 12, 13 and 14) to discover the cycle. Enzymes. DNA.
3-4 Astronomy
"Poets say science takes away from the beauty of the stars - mere globs of gas atoms. I too can see the stars on a desert night, and feel them. But do I see less or more? The vastness of the heavens stretches my imagination - stuck on this carousel my little eye can catch one - million - year - old light. A vast pattern - of which I am a part... What is the pattern, or the meaning, or the why? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined it. Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were a man, but if he is an immense spinning sphere of methane and ammonia must be silent?"
Helium was discovered on Sun and Technetium.
We know the interior of stars better than the interior of Earth. Formation of elements in stars.
3-5 Geology
Weather prediction and the problem of turbulent flow [in The Edge of Uncertainty this is named as one of the still unresolved problems].
3-6 Psychology
From the very first sentence says psychoanalysis is not a science and is a medical process at best or even just witch doctoring.
We don't know much about how brain works.
3-7 How did it get that way?
Question about the history of physics, were the laws of pgysics always the same as they are now?
Mentions the problem of turbulent flow as unsolved for over 100 years.
Chapter 4: Conservation of energy
4-1 What is energy?
Physics offers no definite answers. We calculate the total and it is always the same. It comes in many forms. Explains this an anology.
4-2 Gravitational potential energy
Perpetual motion machine thought experiment. Gravitational potential energy is the energt whicj an object has because if its relationship in space, relative to the Earth (gravitational potential energy = weight * height). This is true as long as we are not too far from Earth.
Potential energy:
Change in energy = force * distance force acts through
Using conservation of energy to solve some problems. [doesn't explain them well, he magically arives at an answer and I can understand how he did it].
Principle of virtual work.
4-3 Kinetic energy
Potential energy converted to kinetic energy
Kinetic Energy = height * weight.
K.E. = WV^2/2g
Both are approximate formulas.
4-4 Other forms of energy
Elastic energy for stretched springs.
Heat energy. This isn't a new form of enegy; it's just kinetic energy-internal motion.
Other forms of energy
Mass as enery E = mc^2
Conservation laws, of linear momentum, of angular momentum, of charges, of baryon [actually quarks] and of leptons.
Chapter 5: Time and Distance
5-1 Motion
Quantitative observations make us arrive at quantitative relationships.
Galileo experiments on motion. At first he measured time with his pulse.
5-2 Time
Hard to define. We base the definition on the p
repetition of some apparently periodic event.
5-3 Short times
A day and an hour glass to measure time. Pendulum for shorter periods. Electrical pendulums for shorter periods, known as oscillators
Predicted being able to measure less than 10^-12 seconds accuracy [Phemto second by Ahmed Zowail.] Time can also be measured by dividing distance over speed.
Are there limits to the small measurement of time?
5-4 Long times
Year. Tree rings. River-bottom sediments. Radioactive material. Explains radioactive half life and etc. Measuring the age of Earth.
5-5 Units and standards of time
Earth days aren't perfectly periodic, they increase slowly [as a result of the tidal evolution with Moon.] Atomic clocks.
5-6 Large distances
Triangulation (i.e. paralex). [He says Euclic was right when assuming space was flat, but this was actually only confirmed several years after his death]. Getting absolute distances from relatives ones. Radar observance.
Use of light dimming. Global clusters. [Type 1A supernovae of course are the best].
5-7 Short distances
Light microscope. Elecron microscope (10^-8). Triangulation of scattered x-rays (10^-10). Use of beam of high energy particles at a thin slab of material then calculating can get us the size of the nucleus (10^-15).
The meter was in the past decided to be pai/2 * 10^-7 * radius of Earth.
Limits on measurement of speed, location and time (uncertainty principle). Time with energy and position with momentus (therefore velocity).
Chapter 6: Probability
"The true logic of this world is in the calculus of probabilities." -by James Clerk Maxwell
6-1 Chance and likelihood
"Any physical theory is a kind of guesswork."
We use probability when we don't have complete knowledge. How to measure probability.
6-2 Fluctuations
Normal distribution curve and fluctuations.
Pascal trianle or binomial effect.
(n above k) = n!/k! (n-k)!
P(k, n) = (n above k)/2^n
Bernouli or binomial probability.
6-3 The random walk
Related to Brownian motion.
Mean square distance.
How do we know if the coin is not honest.
Margin of error = 1/2*root of N
6-4 A probability distribution
Motions of a molecule in a gas is just like a random walk. Probability density.
6-5 The uncertainty principle
Delta x * Delta v >= h/2m
"If we try to 'pin down' a particle by forcing it to be at a particular place, it ends up by having a high speed. Or if we try to force it to go very slowly, or at a precise velocity, it 'spreads out' so that we do not know very well just where it is. Particles behave in a funny way!"
Electron is a probability cloud. In the Hydrogen atom, this could is as big as the Hydrogen atom!
"In its efforts to learn as much as possible about nature, modern physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities."
Chapter 7: The Theory of Gravitation
7-1 Planetary motions
F = ma
F = G m1m2/r^2
The history of discovery of gravity. The ancients, Copernicus, Tycho Brahe, Kepler.
7-2 Kepler's laws
3 laws:
1. Orbits are elliptical (adheres to the rule r1 + r2 = 2a).
2. The radius vector from the Sun to the planet sweeps out equal areas in equal intervals of time (i.e. planets move faster when closer to the Sun).
3. T is proportional to a^3/2.
7-3 Development of dynamics
Discovery of inertia by Galileo and further development by Newton (a body will keep going forward in a uniform speed unless acted upon by a force which change its speed or diecrtion).
This meant that there was no need for the angels pushing the planet. There was a force toward the Sun.
7-4 Newton's law of gravitation
A universal law of gravity. Deduced it from Kepler's third law. The inverse sequare law. Applies to Earth, Moon, Sun and everywhere. One of the most profound generalizations.
"The moon falls in the sense that it falls away from the staight line that it would pursue if there were no forces."
Escape velocity. Moon and tides. Earth-moon tidal system.
7-5 Universal gravitation
Why Earth is round, but not so round. In 1656, Roemer measured the speed of light from Jupiter's moons. Adams and Le Verrier predict Nepton from Uranus weird orbit.
Spinning galaxies with angular momentum. Gravity extends for millions of light years if not billions.
7-6 Cavendish's experiment
Measured the gravitational constant G, and therefore weighted the Earth!
7-7 What is gravity?
Newton did not know how gravity worked; the machinery behind it. Several proposals were made, but they were wrong.
When do the constants come from? We don't know.
7-8 Gravity and relativity
Einstein. Mass and energy. The need to quantize gravity.
Chapter 8: Motion
8-1 Description of motion
Will talk about classical mechanics at first.
8-2 Speed
Problems with motion the ancients faced. Zeno paradoxies.
To get speed measurement more accurately, smaller time and distance intervals should be taken. Invention of differential calculus by Newton and Leibniz.
V = lim (e > 0) x/e where v = velocity, x = the infanticimal distance and e = the infanticimal time.
Solves the limit approches zero question.
8.3 Speed as a derivative
◇ = delta
V = lim (◇t>0) ◇s/◇t = ds/dt
[His explaination of what where are doing with calculus is way better than what we were taugh in school where we only had to solve without understanding. This is especially true since calculus was invented to solve physics problems and not as an abstract idea.]
Table for simple differentiation.
8-4 Distance as an integral
Integration is the sum when lim (t>0).
$ = summa aka integration sign
S = $ v(t) dt
Differentiation is opposite to integration, the first is always possible analytically, while the latter is impossible sometimes.
8-5 Acceleration
A second derivative. a = d^2 s/dt^2
Distance is acceleration integrated twice
How to do it in three dimensions instead of just 1 as we did earlier.
A parabola is the motion of any freely falling body that is shot out in any direction
Chapter 9
Newton's Laws of Dynamics
9-1 Momentum and force
Newton's second law. Will use approximations here such as that mass doesn't change with velocity.
F = m * dv/dt = ma
Acceleration at right angles a = v^2/R where R is radius. Therefore, from F and m, you can get a, then from it you can get R.
9-2 Speed and velocity
Velocity is magnitude and direction, while speed is only the magnitude.
9-3 Components of velocity, acceleration, and force
Motions in the x, y, and z directions are independent if the forces are not connected.
9-4 What is the force?
Newton's first law = inertia, second laws = F=ma, third law = equality of action and reaction.
Free fall under gravity:
Vx = V0 + gt
X = X0 + V0t + 0.5 gt^2
9-5 Meaning of the dynamical equations
Relating acceleration to the force. If we know both x and v at a given time, we know the acceleration (which equals -x(t)), therefore we know the new velocity and new time.
9-6 Numerical solution of the equations
Hard to understand fully.
9-7 Planetary motions
Calculates them. Very long calculations, but with the same level of complexity as above. They had bery premitive calculators at this time and they were nkt available for everyone, so these calculations took long time unless you were at an institute which had the machines.
Chapter 10: Conservation of Momentum
10-1 Newton's third law
Numerical methods (arithmatic) as done in the previous chapter can solve complicated problems involving more than 2 bodies, whereas the powers of mathematical analysis are limited.
There are even more complicated problems which both can't solve and for them we need general principles such as conservation of energy and conservation of momentum.
Action = reaction.
10-2 Conservation of momentum
m1v1 + m2v2 + m3v3 + ... = a constant
F = dp/dt
Principle of relativity (Galileo's relativity). You cannot differentiate between standing still and moving at a steady speed [the ship example.] From this author will derive the lawsof conservation of momentum.
Symmetry of mass and velocity.
10-3 Momentum is conserved
To confirm this with experiment; air trough (gets rid of friction).
If mass is the same, then v = 1/2(v1+v2).
The principle is really easy to understand with the diagrams.
10-4: Momentum and energy
Elastic collisions only lose minimal energy in heat and vibration. Collisions between atoms such as those in gases are nearly elastic.
In elastic collisions between bodies of similar mass, velocities are exchanged.
Rocket propulsion.
10-5 Relativistic momentum
Above equations show that when getting near to speed of light you gain mass.
Electromagnetic field momentum.
In QM momentum is mv when particles and wave number/centimeter when waves. Newton laws do not hold in QM, but conservation of momentum does
Chapter 11: Vectors
11-1 Symmetry in physics
Laws of physics are the same everywhere. If we move a machine or all of its parts elsewhere it will work the same
11-2 Translations
Proofs the above mathematically and shows there is no special origin for the laws to work from.
11-3 Rotations
The same in all directions. The effect of angular orientation. Proves this mathematically just like above.
11-4 Vectors
All laws of physics are invariant or symmetrical under translation of axes and rotation of axes. The vector analysis is to allow us to do things faster and easier.
Quantities with no direction (e.g. temperature) are called scalars, while those with a direction (velocity, acceleration, force, momentum, displacement) are called vectors. The symbol r is used for vectors and they have components (x, y, z).
11-5 Vector algebra
Multiply by a constant. Addition. Subtraction. Differentiation.
Velocity = dr/dt = lim (◇t>0) ◇r/◇t
*Maximum limit for Goodreads reviews reached!*
October 2, 2011
Well worth the read (listen) if you have any interest in physics or mathematics. I listened to the audio recording rather than reading a transcript. Excellent material. Feynman was such an exciting and funny speaker.
August 27, 2020
Fairly easy to take in, hard to retain. Chapters vary widely in difficulty.
4+ stars instead of 5 because really I think this should be listened to, not read. A lot of Feynman’s charm is lost and equations are harder to take in in text form. Nevertheless, it’s probably as enjoyable and easy to read as a textbook is going to get.
4+ stars instead of 5 because really I think this should be listened to, not read. A lot of Feynman’s charm is lost and equations are harder to take in in text form. Nevertheless, it’s probably as enjoyable and easy to read as a textbook is going to get.
November 20, 2023
My son saw me reading this last month, looked at the page full of differential equations, and remarked, "Some light reading, Dad?" Well, actually, yes! So much here! in an introductory course! That every student at Cal Tech, regardless of major, was required to take these classes is amazing. And if I had Feynman as my instructor, with this as the intro, I think my life would have be quite different. Not that my professor, Dr. V. V. Raman, whose grandfather won a Nobel, was a slouch, but this had meat and my freshman class had basics of simplified mechanics. I changed majors a few times, dropped out, eventually went back and became a mechanical engineer and I've never lost the love of this stuff (and am happy with my life). And this is definitely something I should have read long ago. It's a long read now - Vol 2 is even longer and I expect to stretch it out over next year as I did this one for 2023. The narrative is infectious and you can feel the excitement that Feynman had, and conveyed, for the material.
Feynman is eminently quotable. A sampling:
[on actually measuring positions of planets and how they moved]
This was a tremendous idea—that to find something out, it is better to perform some careful experiments than to carry on deep philosophical arguments.
{This is the idea. Philosphers tend to ask questions with no answers (although some of them think they come up with answers). Science looks for answers to real questions.}
[Universal gravitation]
This phenomenon showed that light does not travel instantaneously, and furnished the first estimate of the speed of light. This was done in 1676.
[on precision of definition]
Perhaps you say, “That’s a terrible thing—I learned that in science we have to define everything precisely.” We cannot define anything precisely! If we attempt to, we get into that paralysis of thought that comes to philosophers, who sit opposite each other, one saying to the other, “You don’t know what you are talking about!” The second one says, “What do you mean by know? What do you mean by talking? What do you mean by you?,” and so on.
{Love it!}
[more on philosophers]
...what is an object? Philosophers are always saying, “Well, just take a chair for example.” The moment they say that, you know that they do not know what they are talking about any more. What is a chair? Well, a chair is a certain thing over there … certain?, how certain? ”
{45 years I've been saying they don't know what they are talking about...}
[on relativity]
Poincaré made the following statement of the principle of relativity: “According to the principle of relativity, the laws of physical phenomena must be the same for a fixed observer as for an observer who has a uniform motion of translation relative to him, so that we have not, nor can we possibly have, any means of discerning whether or not we are carried along in such a motion.”
[on cocktail party philosophers]
When this idea descended upon the world, it caused a great stir among philosophers, particularly the “cocktail-party philosophers,” who say, “Oh, it is very simple: Einstein’s theory says all is relative!” In fact, a surprisingly large number of philosophers, not only those found at cocktail parties (but rather than embarrass them, we shall just call them “cocktail-party philosophers”), will say, “That all is relative is a consequence of Einstein, and it has profound influences on our ideas.””
[on notation]
We could, of course, use any notation we want; do not laugh at notations; invent them, they are powerful. In fact, mathematics is, to a large extent, invention of better notations.
Feynman is eminently quotable. A sampling:
[on actually measuring positions of planets and how they moved]
This was a tremendous idea—that to find something out, it is better to perform some careful experiments than to carry on deep philosophical arguments.
{This is the idea. Philosphers tend to ask questions with no answers (although some of them think they come up with answers). Science looks for answers to real questions.}
[Universal gravitation]
This phenomenon showed that light does not travel instantaneously, and furnished the first estimate of the speed of light. This was done in 1676.
[on precision of definition]
Perhaps you say, “That’s a terrible thing—I learned that in science we have to define everything precisely.” We cannot define anything precisely! If we attempt to, we get into that paralysis of thought that comes to philosophers, who sit opposite each other, one saying to the other, “You don’t know what you are talking about!” The second one says, “What do you mean by know? What do you mean by talking? What do you mean by you?,” and so on.
{Love it!}
[more on philosophers]
...what is an object? Philosophers are always saying, “Well, just take a chair for example.” The moment they say that, you know that they do not know what they are talking about any more. What is a chair? Well, a chair is a certain thing over there … certain?, how certain? ”
{45 years I've been saying they don't know what they are talking about...}
[on relativity]
Poincaré made the following statement of the principle of relativity: “According to the principle of relativity, the laws of physical phenomena must be the same for a fixed observer as for an observer who has a uniform motion of translation relative to him, so that we have not, nor can we possibly have, any means of discerning whether or not we are carried along in such a motion.”
[on cocktail party philosophers]
When this idea descended upon the world, it caused a great stir among philosophers, particularly the “cocktail-party philosophers,” who say, “Oh, it is very simple: Einstein’s theory says all is relative!” In fact, a surprisingly large number of philosophers, not only those found at cocktail parties (but rather than embarrass them, we shall just call them “cocktail-party philosophers”), will say, “That all is relative is a consequence of Einstein, and it has profound influences on our ideas.””
[on notation]
We could, of course, use any notation we want; do not laugh at notations; invent them, they are powerful. In fact, mathematics is, to a large extent, invention of better notations.
May 21, 2017
I have some mixed feelings about this book. I read it as a third year undergraduate student of Physics, so, I new most (if not all) of the content presented here, however, this was originally intended as an introductory book for someone who has just finnished secondary school. Therefore I must take into consideration both view points.
This book presents introductory physics in a completely different way than the classical textbooks of the matter, and has its advantages and disadvantages, and because of its vast extent there were various different degrees of quality throughout the book. Some things were absolutely extraordinary, bortherline genius ways to teach the fundamental ideas like his chapters on vectors, rotation and the second law of thermodynamics. Other chapters were more akin to a regular presentation of the topic, the harmonic oscilator for instance is one of those.
However, some ideas were only really suitable for someone who already knows the subject at hand, because they may be very clever and insightful but, there are far from clear for a begginer, this was the cases with the conservation of linear momentum and the conservation of energy. Unfortunately, some ideas have not aged very well, because of revision in the way we view the world, like his discussion of relativistc mass, a concept which has been almost completely abandoned, or the fact that quarks had not yet been discovered at the time of writing, so he mentions many times the fact the they did not understand the structure of hadrons, when in fact we already have that knowledge in the present.
All in all, I think it is definitely a must read if you are already familiar with the ideas presented here, because it is a completely different way of approaching these topics, which is sure to teach you a lot (my case). On the other hand, I cannot recommend this book to its originally intended audience, the fact that this approach is completely different makes some ideas really hard to follow if you are not already familiar with the topic, however, some chapters are really good and can serve this purpose. The lack of exercises and examples of application also contributes to this idea.
My real rating would have to be 4/5 for someone who already is familiar with these subjects and 3/5 for someone unfamiliar with them.
This book presents introductory physics in a completely different way than the classical textbooks of the matter, and has its advantages and disadvantages, and because of its vast extent there were various different degrees of quality throughout the book. Some things were absolutely extraordinary, bortherline genius ways to teach the fundamental ideas like his chapters on vectors, rotation and the second law of thermodynamics. Other chapters were more akin to a regular presentation of the topic, the harmonic oscilator for instance is one of those.
However, some ideas were only really suitable for someone who already knows the subject at hand, because they may be very clever and insightful but, there are far from clear for a begginer, this was the cases with the conservation of linear momentum and the conservation of energy. Unfortunately, some ideas have not aged very well, because of revision in the way we view the world, like his discussion of relativistc mass, a concept which has been almost completely abandoned, or the fact that quarks had not yet been discovered at the time of writing, so he mentions many times the fact the they did not understand the structure of hadrons, when in fact we already have that knowledge in the present.
All in all, I think it is definitely a must read if you are already familiar with the ideas presented here, because it is a completely different way of approaching these topics, which is sure to teach you a lot (my case). On the other hand, I cannot recommend this book to its originally intended audience, the fact that this approach is completely different makes some ideas really hard to follow if you are not already familiar with the topic, however, some chapters are really good and can serve this purpose. The lack of exercises and examples of application also contributes to this idea.
My real rating would have to be 4/5 for someone who already is familiar with these subjects and 3/5 for someone unfamiliar with them.
September 3, 2022
Como todo físico, y, más aún, como todo físico teórico que se precie, he pasado por esta serie de tres volúmenes que todos hemos visto tantas veces en nuestras vidas:
La sucesión de acontecimientos a la hora de aproximarnos al libro es también bastante estándar en los físicos:
1.- Llegas en primero. Eres de los buenos de tu clase del bachillerato. Has entrado en una carrera difícil pero eres el rey (la reina) del mambo.
2.- Comienzas con el tomo 1. Mola mucho. Este señor sabe explicar las cosas y lo hace ameno.
3.- Por primera vez, un concepto obvio para el autor en el tomo I se te escapa. No lo pillas, vuelves varias veces sobre el tema pero sabes que te falta algo. Lo atribuyes a que aún no has dado las matemáticas necesarias.
4.- Te pierdes en los tomos II y III como nunca te has perdido antes. Te sientes tonto. Cierras los Feynman. No se lo cuentas a nadie.
5.- Dejas pasar X meses
6.- Vuelves al Feynman al acabar primero, ahora que has superado una física, un cálculo y un álgebra y eres un master del Universo.
7.- Repetir pasos 3 al 5
8.- Vuelves en segundo, en tercero, en cuarto (en quinto los ancianos como yo, en el máster los actuales).
Ahora sí, cada vez que ves con nuevos ojos una explicación sobre termodinámica o magnetismo, sobre gravitación o física cuántica, empiezas a reconocer el GENIO que era Feynman, e intuyes un poco cómo funcionaba su cabeza.
No recomiendo estos libros, por tanto, como fuente única de estudio. Hay otros (en mis tiempos el TIpler, Tipler/Mosca) introductorios que tienen multitud de ejercicios y que definen los conceptos de manera clásica y comprensible. Pero, al mismo tiempo, estos Feynman son completamente imprescindibles para cualquier físico. Hay que volver a ellos, siempre. Son una obra maestra.
Volume I: mainly mechanics, radiation, and heat
Volume II: mainly electromagnetism and matter
Volume III: quantum mechanics
La sucesión de acontecimientos a la hora de aproximarnos al libro es también bastante estándar en los físicos:
1.- Llegas en primero. Eres de los buenos de tu clase del bachillerato. Has entrado en una carrera difícil pero eres el rey (la reina) del mambo.
2.- Comienzas con el tomo 1. Mola mucho. Este señor sabe explicar las cosas y lo hace ameno.
3.- Por primera vez, un concepto obvio para el autor en el tomo I se te escapa. No lo pillas, vuelves varias veces sobre el tema pero sabes que te falta algo. Lo atribuyes a que aún no has dado las matemáticas necesarias.
4.- Te pierdes en los tomos II y III como nunca te has perdido antes. Te sientes tonto. Cierras los Feynman. No se lo cuentas a nadie.
5.- Dejas pasar X meses
6.- Vuelves al Feynman al acabar primero, ahora que has superado una física, un cálculo y un álgebra y eres un master del Universo.
7.- Repetir pasos 3 al 5
8.- Vuelves en segundo, en tercero, en cuarto (en quinto los ancianos como yo, en el máster los actuales).
Ahora sí, cada vez que ves con nuevos ojos una explicación sobre termodinámica o magnetismo, sobre gravitación o física cuántica, empiezas a reconocer el GENIO que era Feynman, e intuyes un poco cómo funcionaba su cabeza.
No recomiendo estos libros, por tanto, como fuente única de estudio. Hay otros (en mis tiempos el TIpler, Tipler/Mosca) introductorios que tienen multitud de ejercicios y que definen los conceptos de manera clásica y comprensible. Pero, al mismo tiempo, estos Feynman son completamente imprescindibles para cualquier físico. Hay que volver a ellos, siempre. Son una obra maestra.
January 13, 2023
Misleadingly adventurous! Even as somebody not present in the crowded Caltech lecture halls, you can sense the pure excitement radiating from Feynman as he describes everything from gravity to quantum mechanics. What’s even more astonishing is how intentional, meaningful, and simple he illustrates everything. It’s hard to dispute Feynman’s title (from Six Easy Pieces) as “Most Brilliant Teacher” after going through the first volume. The only “complaint” I would have is that the lectures often jump to topics that often require background knowledge. Specifically, the jump from Work/Potential Energy to the Special Theory of Relativity and Relativistic Momentum leaves a gap of over 200 years(!) of physics, which just doesn’t really sit right with me
April 23, 2016
Like most others who get a chance to know about him, I adore what was Richard Feynman and find him a source of continual inspiration. I study physics at university, and I've given this book a try. It gives clear access to his mind, and I have taken away countless gems that have built up concepts in my mind. I've struggled with it's nature though - I've tried to appraoch it like any other textbook, and found it just doesn't work like that. It's not for systematic study. Instead, I dip into it and read a chapter now and then when it's relevent and can add to current study - more for motivation and inspiration than anything.
April 9, 2014
Excellent and well written, but also awe-inspiring and thought-provoking book I've ever come across with. I do recomend it amply! Two thumps up! If you are in the deal to figure things out, this book is one of those which can help you in that way. This book is indeed a work of a genius. Feyman has this odd quality of explaining the concepts of physics so beautifully. It's an excellent gift for a science lover. I may add that the language of this book is written in a tremendous lucid way.
January 28, 2013
Richard Feynman was amazing!
Listening to the book instead of reading it made it seem more like being at a lecture.
Sometimes pretty heavy going but overall a very good introduction to modern physics.
Listening to the book instead of reading it made it seem more like being at a lecture.
Sometimes pretty heavy going but overall a very good introduction to modern physics.
December 16, 2012
Read & Reread & read again..
Want to read
March 2, 2016the universe in a glass of wine and psychics in 752 pages
July 22, 2016
I stretched my old brain more in the last week than in the previous 20 years.
December 2, 2019
Legendary !
February 19, 2022
The book is not just a lecture on physics! It is wonderful story about nature, it’s laws and how we see them! The Feynman Lectures is not only teaching you about physics but is opening your mind, and using imagination allowing you to see the world from much wider perspective. I was not expecting that I will be that much excited reading this book! ❤️❤️❤️
February 25, 2021
only hv read relativity related chapters.
January 1, 2024
mechanics and heat aren’t my favourite topics but this was a fun little overview. i like that it’s technical enough to teach a course off of but also entertaining enough that i could just read it. i look forward to the other two more
Read
October 2, 2022feynmanlectures.caltech.edu/info/
▶Chapter 1.Atoms in Motion
The atoms are 1 or 2×10−8 cm in radius. Now 10−8 cm is called an angstrom. the molecules are drawn so that there is a 120∘ angle between the hydrogen atoms. In actual fact the angle is 105∘3′, and the distance between the center of a hydrogen and the center of the oxygen is 0.957 Å.
if you wish to evaporate water turn on the fan! blow on soup to cool it!
carbon attracts oxygen much more than oxygen attracts oxygen or carbon attracts carbon. Therefore in this process the oxygen may arrive with only a little energy, but the oxygen and carbon will snap together with a tremendous vengeance and commotion, and everything near them will pick up the energy. A large amount of motion energy, kinetic energy, is thus generated. This of course is burning
The atoms are so small that you cannot see them with a light microscope—in fact, not even with an electron microscope.
▶Chapter 2.Basic Physics
“the world” is something like a great chess game being played by the gods, and we are observers of the game. We do not know what the rules of the game are; all we are allowed to do is to watch the playing. Of course, if we watch long enough, we may eventually catch on to a few of the rules.
electricity, magnetism, and light, which were found to be different aspects of the same thing, which we call today the electromagnetic field
Whether there are a finite number of pieces, and whether there is even a border to the puzzle, is of course unknown. It will never be known until we finish the picture, if ever.
what are things made of and how few elements are there?
What is the machinery of interaction between atoms?
the chemical properties of a substance depend only on the number of electrons.
we can make those waves artificially, for example with the synchrotron here at Caltech
Quantum mechanics has many aspects. In the first place, the idea that a particle has a definite location and a definite speed is no longer allowed. Philosophers have said before that one of the fundamental requisites of science is that whenever you set up the same conditions, the same thing must happen. This is simply not true, it is not a fundamental condition of science. The fact is that the same thing does not happen, that we can find only an average, statistically, as to what happens.
quantum electrodynamics. This fundamental theory of the interaction of light and matter, or electric field and charges, is our greatest success so far in physics.
light and gamma rays are all the same, they are just different points on a frequency scale
we make quantum nucleodynamics using the pions just like Yukawa wanted to do, and see if it works, and everything will be explained.” Bad luck. It turns out that the calculations that are involved in this theory are so difficult that no one has ever been able to figure out what the consequences of the theory are, or to check it against experiment, and this has been going on now for almost twenty years!
One MeV is equal to 1.783×10−27 gram.
The fact that a particle has zero mass means, in a way, that it cannot be at rest.
To summarize it, I would say this: outside the nucleus, we seem to know all; inside it, quantum mechanics is valid—the principles of quantum mechanics have not been found to fail.
▶Chapter 3.The Relation of Physics to Other Sciences
all living things have a great many characteristics in common. The most common feature is that they are made of cells.
the Krebs cycle, the respiratory cycle. These very large and complicated things are called enzymes.
the most useful tool of all for analyzing this fantastically complex system is to label the atoms which are used in the reactions. Thus, if we could introduce into the cycle some carbon dioxide which has a “green mark” on it, and then measure after three seconds where the green mark is, and again measure after ten seconds, etc., we could trace out the course of the reactions. What are the “green marks”? They are different isotopes.
the chemical properties of atoms are determined by the number of electrons, not by the mass of the nucleus.
The structure of the substance DNA was studied for a long time, first chemically to find the composition, and then with x-rays to find the pattern in space.
Certainly no subject or field is making more progress on so many fronts at the present moment, than biology. in an attempt to understand life, it is that all things are made of atoms, and that everything that living things do can be understood in terms of the jigglings and wigglings of atoms.
with a spectroscope we can analyze the frequencies of the light waves and in this way we can see the very tunes of the atoms that are in the different stars.
earth sciences, or geology. First, meteorology and the weather.
▶Chapter 4.Conservation of Energy
There is no known exception to this law—it is exact so far as we know. The law is called the conservation of energy.
In order to verify the conservation of energy, we must be careful that we have not put any in or taken any out. Second, the energy has a large number of different forms, and there is a formula for each one. These are: gravitational energy, kinetic energy, heat energy, elastic energy, electrical energy, chemical energy, radiant energy, nuclear energy, mass energy. If we total up the formulas for each of these contributions, it will not change except for energy going in and out.
There are two other conservation laws which are analogous to the conservation of energy. One is called the conservation of linear momentum. The other is called the conservation of angular momentum. There is another law, the conservation of leptons.
Our supplies of energy are from the sun, rain, coal, uranium, and hydrogen.
▶Chapter 5.Time and Distance
One such device is the electron-beam oscilloscope, which acts as a sort of microscope for short times. This device plots on a fluorescent screen a graph of electrical current (or voltage) versus time.
We have also discovered that nature has sometimes provided a counter for the years, in the form of tree rings or river-bottom sediments.
Carbon-14 has a half-life of 5000 years. By careful measurements we can measure the amount left after 20 half-lives or so and can therefore “date” organic objects which grew as long as 100,000 years ago.
Uranium, for example, has an isotope whose half-life is about 109 years, so that if some material was formed with uranium in it 109 years ago, only half the uranium would remain today. When the uranium disintegrates, it changes into lead. An extension of this method, not using particular rocks but looking at the uranium and lead in the oceans and using averages over the earth, has been used to determine (within the past few years) that the age of the earth itself is approximately 4.5 billion years. It is encouraging that the age of the earth is found to be the same as the age of the meteorites which land on the earth, as determined by the uranium method. It is now believed that at least our part of the universe had its beginning about ten or twelve billion years ago.
Until very recently we had found nothing much better than the earth’s period, so all clocks have been related to the length of the day, and the second has been defined as 1/86,400 of an average day. These are the so-called “atomic clocks.” These clocks keep time to an accuracy of one part in 10⁹ or better. Within the past two years an improved atomic clock which operates on the vibration of the hydrogen atom has been designed and built by Professor Norman Ramsey at Harvard University. He believes that this clock might be 100 times more accurate still.
We have found by experience that distance can be measured in another fashion: by triangulation. Two telescopes at different places on the earth can give us the two angles we need. It has been found in this way that the moon is 4×10⁸ meters away.
t the Jet Propulsion Laboratory the distance from the earth to Venus was measured quite accurately by a direct radar observation. This, of course, is a still different type of inferred distance. We say we know the speed at which light travels (and therefore, at which radar waves travel), and we assume that it is the same speed everywhere between the earth and Venus. We send the radio wave out, and count the time until the reflected wave comes back. From the time we infer a distance, assuming we know the speed.
How do we measure the distance to a star, which is much farther away? Fortunately, we can go back to our triangulation method, because the earth moving around the sun gives us a large baseline for measurements of objects outside the solar system. If we focus a telescope on a star in summer and in winter, we might hope to determine these two angles accurately enough to be able to measure the distance to a star.
Coupling this information with other evidence, we conclude that this concentration of clusters marks the center of our galaxy. We then know the distance to the center of the galaxy—about 10²⁰ meters.
Photographs of exceedingly distant galaxies have recently been obtained with the giant Palomar telescope. One is shown in Fig. 5–8. It is now believed that some of these galaxies are about halfway to the limit of the universe—1026 meters away
It is difficult to continue to smaller scales, because we cannot “see” objects smaller than the wavelength of visible light (about 5×10⁻⁷ meter).
With an electron microscope, we can continue the process by making photographs on a still smaller scale, say down to 10⁻⁸ meter (Fig. 5–9). By indirect measurements—by a kind of triangulation on a microscopic scale—we can continue to measure to smaller and smaller scales. First, from an observation of the way light of short wavelength (x-radiation) is reflected from a pattern of marks of known separation, we determine the wavelength of the light vibrations.
For nuclear sizes, a different way of measuring size becomes convenient. We measure the apparent area, σ, called the effective cross section. If we wish the radius, we can obtain it from σ=πr², since nuclei are nearly spherical. Measurement of a nuclear cross section can be made by passing a beam of high-energy particles through a thin slab of material and observing the number of particles which do not get through. From such an experiment we find that the radii of the nuclei are from about 1 to 6 times 10⁻¹⁵ meter. The length unit 10⁻¹⁵ meter is called the fermi, in honor of Enrico Fermi.
It might be thought that it would be a good idea to use some natural length as our unit of length—say the radius of the earth or some fraction of it. The meter was originally intended to be such a unit and was defined to be (π/2)×10⁻⁷ times the earth’s radius. It is neither convenient nor very accurate to determine the unit of length in this way. For a long time it has been agreed internationally that the meter would be defined as the distance between two scratches on a bar kept in a special laboratory in France.
▶Chapter 6.Probability
It is, however, more convenient to deal with another measure of “progress,” the square of the distance: D2 is positive for either positive or negative motion, and is therefore a reasonable measure of such random wandering.
▶Chapter 7.The Theory of Gravitation
This idea that the moon “falls” is somewhat confusing, because, as you see, it does not come any closer. The idea is sufficiently interesting to merit further explanation: the moon falls in the sense that it falls away from the straight line that it would pursue if there were no forces.
That fits very well with the inverse square law, because the earth’s radius is 4000 miles, and if something which is 4000 miles from the center of the earth falls 16 feet in a second, something 240,000 miles, or 60 times as far away, should fall only 1/3600 of 16 feet, which also is roughly 1/20 of an inch.
By knowing G from this experiment and by knowing how strongly the earth attracts, we can indirectly learn how great is the mass of the earth! This experiment has been called “weighing the earth” by some people, and it can be used to determine the coefficient G of the gravity law.
In the Einstein relativity theory, anything which has energy has mass—mass in the sense that it is attracted gravitationally. Even light, which has an energy, has a “mass.” When a light beam, which has energy in it, comes past the sun there is an attraction on it by the sun. Thus the light does not go straight, but is deflected. During the eclipse of the sun, for example, the stars which are around the sun should appear displaced from where they would be if the sun were not there, and this has been observed.
▶Chapter 8.Motion
▶Chapter 9.Newton’s Laws of Dynamics
▶Chapter 10.Conservation of Momentum
▶Chapter 11.Vectors
the laws of physics are symmetrical for translational displacements
▶Chapter 12.Characteristics of Force
▶Chapter 13.Work and Potential Energy (A)
advance our understanding
▶Chapter 14.Work and Potential Energy (conclusion)
▶Chapter 15.The Special Theory of Relativity
c , or 186,000 mi/sec
velocity of the earth through the Michelson-Morley experiment
▶Chapter 16.Relativistic Energy and Momentum
earth is turning on its axis can be determined without looking at the stars, by means of the so-called Foucault pendulum
We really do not have such a thing as absolute rotation; we are really rotating relative to the stars
▶Chapter 17.Space-Time
One can calculate the Doppler effect using E=p and E=hν
▶Chapter 1.Atoms in Motion
The atoms are 1 or 2×10−8 cm in radius. Now 10−8 cm is called an angstrom. the molecules are drawn so that there is a 120∘ angle between the hydrogen atoms. In actual fact the angle is 105∘3′, and the distance between the center of a hydrogen and the center of the oxygen is 0.957 Å.
if you wish to evaporate water turn on the fan! blow on soup to cool it!
carbon attracts oxygen much more than oxygen attracts oxygen or carbon attracts carbon. Therefore in this process the oxygen may arrive with only a little energy, but the oxygen and carbon will snap together with a tremendous vengeance and commotion, and everything near them will pick up the energy. A large amount of motion energy, kinetic energy, is thus generated. This of course is burning
The atoms are so small that you cannot see them with a light microscope—in fact, not even with an electron microscope.
▶Chapter 2.Basic Physics
“the world” is something like a great chess game being played by the gods, and we are observers of the game. We do not know what the rules of the game are; all we are allowed to do is to watch the playing. Of course, if we watch long enough, we may eventually catch on to a few of the rules.
electricity, magnetism, and light, which were found to be different aspects of the same thing, which we call today the electromagnetic field
Whether there are a finite number of pieces, and whether there is even a border to the puzzle, is of course unknown. It will never be known until we finish the picture, if ever.
what are things made of and how few elements are there?
What is the machinery of interaction between atoms?
the chemical properties of a substance depend only on the number of electrons.
we can make those waves artificially, for example with the synchrotron here at Caltech
Quantum mechanics has many aspects. In the first place, the idea that a particle has a definite location and a definite speed is no longer allowed. Philosophers have said before that one of the fundamental requisites of science is that whenever you set up the same conditions, the same thing must happen. This is simply not true, it is not a fundamental condition of science. The fact is that the same thing does not happen, that we can find only an average, statistically, as to what happens.
quantum electrodynamics. This fundamental theory of the interaction of light and matter, or electric field and charges, is our greatest success so far in physics.
light and gamma rays are all the same, they are just different points on a frequency scale
we make quantum nucleodynamics using the pions just like Yukawa wanted to do, and see if it works, and everything will be explained.” Bad luck. It turns out that the calculations that are involved in this theory are so difficult that no one has ever been able to figure out what the consequences of the theory are, or to check it against experiment, and this has been going on now for almost twenty years!
One MeV is equal to 1.783×10−27 gram.
The fact that a particle has zero mass means, in a way, that it cannot be at rest.
To summarize it, I would say this: outside the nucleus, we seem to know all; inside it, quantum mechanics is valid—the principles of quantum mechanics have not been found to fail.
▶Chapter 3.The Relation of Physics to Other Sciences
all living things have a great many characteristics in common. The most common feature is that they are made of cells.
the Krebs cycle, the respiratory cycle. These very large and complicated things are called enzymes.
the most useful tool of all for analyzing this fantastically complex system is to label the atoms which are used in the reactions. Thus, if we could introduce into the cycle some carbon dioxide which has a “green mark” on it, and then measure after three seconds where the green mark is, and again measure after ten seconds, etc., we could trace out the course of the reactions. What are the “green marks”? They are different isotopes.
the chemical properties of atoms are determined by the number of electrons, not by the mass of the nucleus.
The structure of the substance DNA was studied for a long time, first chemically to find the composition, and then with x-rays to find the pattern in space.
Certainly no subject or field is making more progress on so many fronts at the present moment, than biology. in an attempt to understand life, it is that all things are made of atoms, and that everything that living things do can be understood in terms of the jigglings and wigglings of atoms.
with a spectroscope we can analyze the frequencies of the light waves and in this way we can see the very tunes of the atoms that are in the different stars.
earth sciences, or geology. First, meteorology and the weather.
▶Chapter 4.Conservation of Energy
There is no known exception to this law—it is exact so far as we know. The law is called the conservation of energy.
In order to verify the conservation of energy, we must be careful that we have not put any in or taken any out. Second, the energy has a large number of different forms, and there is a formula for each one. These are: gravitational energy, kinetic energy, heat energy, elastic energy, electrical energy, chemical energy, radiant energy, nuclear energy, mass energy. If we total up the formulas for each of these contributions, it will not change except for energy going in and out.
There are two other conservation laws which are analogous to the conservation of energy. One is called the conservation of linear momentum. The other is called the conservation of angular momentum. There is another law, the conservation of leptons.
Our supplies of energy are from the sun, rain, coal, uranium, and hydrogen.
▶Chapter 5.Time and Distance
One such device is the electron-beam oscilloscope, which acts as a sort of microscope for short times. This device plots on a fluorescent screen a graph of electrical current (or voltage) versus time.
We have also discovered that nature has sometimes provided a counter for the years, in the form of tree rings or river-bottom sediments.
Carbon-14 has a half-life of 5000 years. By careful measurements we can measure the amount left after 20 half-lives or so and can therefore “date” organic objects which grew as long as 100,000 years ago.
Uranium, for example, has an isotope whose half-life is about 109 years, so that if some material was formed with uranium in it 109 years ago, only half the uranium would remain today. When the uranium disintegrates, it changes into lead. An extension of this method, not using particular rocks but looking at the uranium and lead in the oceans and using averages over the earth, has been used to determine (within the past few years) that the age of the earth itself is approximately 4.5 billion years. It is encouraging that the age of the earth is found to be the same as the age of the meteorites which land on the earth, as determined by the uranium method. It is now believed that at least our part of the universe had its beginning about ten or twelve billion years ago.
Until very recently we had found nothing much better than the earth’s period, so all clocks have been related to the length of the day, and the second has been defined as 1/86,400 of an average day. These are the so-called “atomic clocks.” These clocks keep time to an accuracy of one part in 10⁹ or better. Within the past two years an improved atomic clock which operates on the vibration of the hydrogen atom has been designed and built by Professor Norman Ramsey at Harvard University. He believes that this clock might be 100 times more accurate still.
We have found by experience that distance can be measured in another fashion: by triangulation. Two telescopes at different places on the earth can give us the two angles we need. It has been found in this way that the moon is 4×10⁸ meters away.
t the Jet Propulsion Laboratory the distance from the earth to Venus was measured quite accurately by a direct radar observation. This, of course, is a still different type of inferred distance. We say we know the speed at which light travels (and therefore, at which radar waves travel), and we assume that it is the same speed everywhere between the earth and Venus. We send the radio wave out, and count the time until the reflected wave comes back. From the time we infer a distance, assuming we know the speed.
How do we measure the distance to a star, which is much farther away? Fortunately, we can go back to our triangulation method, because the earth moving around the sun gives us a large baseline for measurements of objects outside the solar system. If we focus a telescope on a star in summer and in winter, we might hope to determine these two angles accurately enough to be able to measure the distance to a star.
Coupling this information with other evidence, we conclude that this concentration of clusters marks the center of our galaxy. We then know the distance to the center of the galaxy—about 10²⁰ meters.
Photographs of exceedingly distant galaxies have recently been obtained with the giant Palomar telescope. One is shown in Fig. 5–8. It is now believed that some of these galaxies are about halfway to the limit of the universe—1026 meters away
It is difficult to continue to smaller scales, because we cannot “see” objects smaller than the wavelength of visible light (about 5×10⁻⁷ meter).
With an electron microscope, we can continue the process by making photographs on a still smaller scale, say down to 10⁻⁸ meter (Fig. 5–9). By indirect measurements—by a kind of triangulation on a microscopic scale—we can continue to measure to smaller and smaller scales. First, from an observation of the way light of short wavelength (x-radiation) is reflected from a pattern of marks of known separation, we determine the wavelength of the light vibrations.
For nuclear sizes, a different way of measuring size becomes convenient. We measure the apparent area, σ, called the effective cross section. If we wish the radius, we can obtain it from σ=πr², since nuclei are nearly spherical. Measurement of a nuclear cross section can be made by passing a beam of high-energy particles through a thin slab of material and observing the number of particles which do not get through. From such an experiment we find that the radii of the nuclei are from about 1 to 6 times 10⁻¹⁵ meter. The length unit 10⁻¹⁵ meter is called the fermi, in honor of Enrico Fermi.
It might be thought that it would be a good idea to use some natural length as our unit of length—say the radius of the earth or some fraction of it. The meter was originally intended to be such a unit and was defined to be (π/2)×10⁻⁷ times the earth’s radius. It is neither convenient nor very accurate to determine the unit of length in this way. For a long time it has been agreed internationally that the meter would be defined as the distance between two scratches on a bar kept in a special laboratory in France.
▶Chapter 6.Probability
It is, however, more convenient to deal with another measure of “progress,” the square of the distance: D2 is positive for either positive or negative motion, and is therefore a reasonable measure of such random wandering.
▶Chapter 7.The Theory of Gravitation
This idea that the moon “falls” is somewhat confusing, because, as you see, it does not come any closer. The idea is sufficiently interesting to merit further explanation: the moon falls in the sense that it falls away from the straight line that it would pursue if there were no forces.
That fits very well with the inverse square law, because the earth’s radius is 4000 miles, and if something which is 4000 miles from the center of the earth falls 16 feet in a second, something 240,000 miles, or 60 times as far away, should fall only 1/3600 of 16 feet, which also is roughly 1/20 of an inch.
By knowing G from this experiment and by knowing how strongly the earth attracts, we can indirectly learn how great is the mass of the earth! This experiment has been called “weighing the earth” by some people, and it can be used to determine the coefficient G of the gravity law.
In the Einstein relativity theory, anything which has energy has mass—mass in the sense that it is attracted gravitationally. Even light, which has an energy, has a “mass.” When a light beam, which has energy in it, comes past the sun there is an attraction on it by the sun. Thus the light does not go straight, but is deflected. During the eclipse of the sun, for example, the stars which are around the sun should appear displaced from where they would be if the sun were not there, and this has been observed.
▶Chapter 8.Motion
▶Chapter 9.Newton’s Laws of Dynamics
▶Chapter 10.Conservation of Momentum
▶Chapter 11.Vectors
the laws of physics are symmetrical for translational displacements
▶Chapter 12.Characteristics of Force
▶Chapter 13.Work and Potential Energy (A)
advance our understanding
▶Chapter 14.Work and Potential Energy (conclusion)
▶Chapter 15.The Special Theory of Relativity
c , or 186,000 mi/sec
velocity of the earth through the Michelson-Morley experiment
▶Chapter 16.Relativistic Energy and Momentum
earth is turning on its axis can be determined without looking at the stars, by means of the so-called Foucault pendulum
We really do not have such a thing as absolute rotation; we are really rotating relative to the stars
▶Chapter 17.Space-Time
One can calculate the Doppler effect using E=p and E=hν
December 30, 2024
In his first volume Richard Feynman discusses Newtonian mechanics, the special theory of relativity, optics, quantum behaviour, statistical mechanics, thermodynamics and waves. He usually starts with a simple example and then shows how really complex the subject is by discussing many subtleties involved and affecting it to reveal his deep thinking about it.
What I specifically like about his presentation is that he always talks about the limits of our knowledge and what is still unknown. As the has been compiled from Feynman's live lectures, his conversational inimitable style makes his readers to return to lectures again and again.
What I specifically like about his presentation is that he always talks about the limits of our knowledge and what is still unknown. As the has been compiled from Feynman's live lectures, his conversational inimitable style makes his readers to return to lectures again and again.
February 17, 2016
This collection is a set of recordings of Feynman's first presentation of his famous re-interpretation of the freshman physics lectures on quantum mechanics, recorded at Caltech in 1961. I got the audiobooks, with the intention of listening to them in the car, and absorbing some physics as I drove.
Well... it was a nice idea, but the reality is that, to put it in mathematical terms, (level of concentration required to follow the audiobook) + (level of concentration required to drive the car safely) > (quantity of concentration I have available). So something had to give - either drive the car into a tree, or find a more relaxed place to listen.
The trouble is, even then, that some of the lectures just don't work terribly well as audio-only. They might have been bearable as videos, where you can see what Feynman is writing, but hearing him rapidly talk his way through what he is writing, try to keep all of the equations in mind and still follow the lecture is not very comfortable.
Some of the pieces are easier to follow than others - the lectures on Gravity and Motion are OK, but Amplitude, for example, is an auditory snake-pit of writhing equations.
If your applied maths or physics experience is recent, you might fare better, but it's (harrumphety-mumble) years since I needed to differentiate or integrate anything, so I'm going to call this a failed experiment and resort to the book, the rather optimistically named, "Six Easy Pieces"
I was also a little disappointed in Feyman's presentation - for someone who comes across in print, and on TV, as a very engaging and humourous person, the Feynman of these lectures is a bit mumbly and dull, to be honest.
Well... it was a nice idea, but the reality is that, to put it in mathematical terms, (level of concentration required to follow the audiobook) + (level of concentration required to drive the car safely) > (quantity of concentration I have available). So something had to give - either drive the car into a tree, or find a more relaxed place to listen.
The trouble is, even then, that some of the lectures just don't work terribly well as audio-only. They might have been bearable as videos, where you can see what Feynman is writing, but hearing him rapidly talk his way through what he is writing, try to keep all of the equations in mind and still follow the lecture is not very comfortable.
Some of the pieces are easier to follow than others - the lectures on Gravity and Motion are OK, but Amplitude, for example, is an auditory snake-pit of writhing equations.
If your applied maths or physics experience is recent, you might fare better, but it's (harrumphety-mumble) years since I needed to differentiate or integrate anything, so I'm going to call this a failed experiment and resort to the book, the rather optimistically named, "Six Easy Pieces"
I was also a little disappointed in Feyman's presentation - for someone who comes across in print, and on TV, as a very engaging and humourous person, the Feynman of these lectures is a bit mumbly and dull, to be honest.
November 13, 2016
My review refers to the Audible audiobook (http://www.audible.com/pd/Science-Tec...).
While the charisma emanated by R. Feynman's emblematic figures set high the expectations regarding this audiobook, the fact that the "audiobook" is in fact the audio recording of frontal lectures accounts for the audiobook to be much less enjoyable that one would expect it to be. You can just imagine how differently you phrase things depending on whether the listener is in front of you or not. Last but not least, the fact that the lectures happened quite some time ago doesn't help the quality of the audio.
I think that the book might be a great pleasure to listen to for those who already know quite a bit of physics, but is of little amusement to beginners and intermediate physics students.
After some time listening it, I just realized my time could be better spent on some audiobooks which are actually properly designed to be an auditory experience.
While the charisma emanated by R. Feynman's emblematic figures set high the expectations regarding this audiobook, the fact that the "audiobook" is in fact the audio recording of frontal lectures accounts for the audiobook to be much less enjoyable that one would expect it to be. You can just imagine how differently you phrase things depending on whether the listener is in front of you or not. Last but not least, the fact that the lectures happened quite some time ago doesn't help the quality of the audio.
I think that the book might be a great pleasure to listen to for those who already know quite a bit of physics, but is of little amusement to beginners and intermediate physics students.
After some time listening it, I just realized my time could be better spent on some audiobooks which are actually properly designed to be an auditory experience.
Want to read
March 24, 2012The Feynman Lectures on Physics
Feynman, Leighton and Sands
This beautiful three volume set (sold individually in the silver paperbacks– and possible to order as a hardback set in red) is a perfect gift for a science lover (or scientist) Bringing together the lectures which made up the introductory physics course at Caltech as taught by Richard Feynman they cover mechanics, radiation, heat, quantum mechanics, electromagnetism and matter; it is a comprehensive set of lectures by one of the worlds greatest science educators and most well known Physicists.
Feynman, Leighton and Sands
This beautiful three volume set (sold individually in the silver paperbacks– and possible to order as a hardback set in red) is a perfect gift for a science lover (or scientist) Bringing together the lectures which made up the introductory physics course at Caltech as taught by Richard Feynman they cover mechanics, radiation, heat, quantum mechanics, electromagnetism and matter; it is a comprehensive set of lectures by one of the worlds greatest science educators and most well known Physicists.
August 10, 2007
Best explanation of physics ever
January 18, 2024
En las lecturas de Feynman se ofrece una clase magistral sobre el funcionamiento del mundo. Es una visión del mundo de la física, un acercamiento a las leyes del universo.
Las notas están a medio camino entre el ensayo y el libro de texto, y combinan con maestría la descripción teórica con los ejemplos. Dentro de la descripción teórica, se describen las teorías, con rigurosidad matemática, pero sin entrar en una excesiva complejidad. Feynman intenta describir cada fórmula y expresar el sentido físico de la misma, explica el fenómeno, y a partir de él realiza la formulación matemática. Junto a descripción teórica se explican diferentes ejemplos que muestran las leyes físicas en acción, despertando la curiosidad y permitiendo interrelacionar los diferentes aspectos (mecánica, electromagnetismo, termodinámica) que rigen el comportamiento físico del universo.
En el primer tomo se hace un repaso general a la física clásica. Comenzando por una introducción, leyes del movimiento, mecánica newtoniana, relatividad especial, la radiación en sus diferentes versiones (geométrica, campos y cuántica), teoría cinética, termodinámica y ondas. Dejando electromagnetismo para el segundo volumen y la mecánica cuántica para el tercer volumen.
La forma de estructurar el libro es canónica, con capítulos con diferentes temas, y con pequeños apartados. Con bloques de capítulos dedicados a diferentes temas. Al principio de cada capítulo se resume el anterior y se da una visión general del mismo, y al final se recapitula lo expuesto. Los apartados son breves, discutiendo una fórmula, un aspecto físico o dando un ejemplo, si es necesario se recuerda algo expuesto en capítulos anteriores, se interconectan los diferentes fenómenos. Pero dentro de tener una estructura clásica los capítulos y apartados son magistrales, la estructura del libro es en si misma magistral.
Para alguien con estudios de física o ingeniería el nivel de dificultad no es elevado, y el libro se puede seguir de una manera amena. Las lecturas permiten recordar lo ya estudiado, aportando un punto de vista diferente, y la capacidad de conectar diferentes fenómenos. Así la analogía entre el oscilador mecánico y eleléctrico, la relación entre un oscilador y la radiación, y esta con la radiación de cuerpo negro, etc nos dan una visión completa de los fenómenos. Es un libro absolutamente magistral que ojala hubiese descubierto años antes!
INTRODUCTION (1-6)
La física serían las leyes que gobiernan el mundo. Esto es lo que pretendemos conocer, pero conocer las leyes no significa conocer el mundo, simplemente poder interpretarlo. La materia está hecha de átomos en continuo movimiento. Las leyes que nos rigen son aquellas de los átomos a gran escala. Así el movimiento de los átomos sería el calor o la temperatura, y explicaría la presión, disolución, difusión, evaporación, etc.
La física clásica sería la anterior a 1920 y la irrupción de la mecánica cuántica. En ella el universo se presentaría por partículas y fuerzas. Estaría compuesta por la mecánica newtoniana, electromagnetismo, óptica, química y relatividad especial. El electromagnetismo se presentaría como las ondas propiciadas por las cargas, similar a las ondas producidas en el agua por un objeto.
La llegada de la mecánica cuántica estableció la dualidad partícula onda o el principio de incertidumbre. El principio de incertidumbre es el responsable de la formación de los átomos, al dar niveles de energía a los electrones, e impedir que colapsen contra el núcleo.
La física proporciona el punto de partida para otras ciencias, es el equivalente moderno de la filosofía natural. La física moderna se podría considerar que comienza con Galileo, cuando intenta probar experimentalmente las teorías que había sobre movimiento. Gran parte de la física anterior se debía a los principios filosóficos de aristóteles o la escolástica y carecía de base experimental.
NEWTONIAN MECHANICS (7-14)
Kepler primero fórmulo las leyes de movimiento gravitatorio mediante sus tres leyes i) los planetas orbitan en elipses con el sol en uno de sus focos, ii) que los planetas barren áreas iguales en tiempos iguales, iii) que el cuadrado de los periodos es proporciona al cubo del semiaxes de la elipse. A su vez Galileo estudiaba el movimiento, y los sistemas inerciales. Posteriormente las leyes de Newton permitían derivar las leyes de Kepler.
Mediante las leyes de Newton y el cálculo diferencial es posible estudiar la órbita de los planetas o galaxias. También explicar las mareas, como la atracción de la luna y rotación terrestre, para ciclos de cuatro veces al día. Para estudiar la constante de gravitación universal se puede hacer estudiando la torsión de un cable, tal como hizo Cavendish.
Así se definen la velocidad o la aceleración y los conceptos de derivadas e integrales.. Hasta Galileo, y Newton, y el cálculo diferencial el movimiento era un misterio. Así están las paradojas de Zenón. Los griegos no comprendían que una infinitud de pasos infinitesimales puedan dar lugar a un resultado finito.
La primera ley de Newton es el principio de inercia de Galileo, la segunda que un cambio cambio de movimiento necesita una fuerza, la tercera que a toda acción equivale una reacción. Hay fuerzas fundamentales (gravedad, electromagneticmo) y hay fuerzas empíricas (fricción, dragging, fluidos). En las fórmulas empíricas se simplifican los diferentes efectos mediante fórmulas simples, sin embargo un análisis exhaustivo indica las limitaciones de estas fórmulas. Las fuerzas conservativas son aquellas en las que el trabajo en una curva cerrada es siempre cero, independientemente de la curva. En estos casos se puede definir una función potenial que indica la energía en cada punto.
RELATIVIDAD ESPECIAL (15-17)
Galileo con su teoría de la relatividad indicó que las leyes de la física son independientes del marco de referencia. Sin embargo, con la aparición de las leyes de Maxwell y la invariabilidad de la velocidad de la luz esto no estaba tan claro. Así pues, para mantener invariable la velocidad de la luz, habría que hacer el espacio y el tiempo relativos. Lo que llevaría también a una nueva formulación de masa y energía.
La relatividad de espacio y tiempo se puede demostrar con las transformaciones de Lorentz. El espacio se acorta en la dirección axial, mientras se mantiene en la dirección transversal.
Para las relaciones de momento y energía hay que incluir la masa relativista, de esta forma se conserva el momento. Y la energía sería la energía en reposo (masa) más el momento. Conforme aumenta el momento, aumenta la masa, y aumenta la inercia, tendiendo asintóticamente a c.
La variabilidad de la masa se puede demostrar por conservación de momento de dos partículas identicas en direcciones opuestas al chocar. Además cuando dos partículas con momento nulo chocan y se unen, la energía se ha de conservar, por lo que es necesario que la masa aumente.
Las relaciones entre momento y energía en dos sistemas de referencia son análogas a las transformaciones de Lorentz para espacio (momento) y tiempo (energía).
Ejemplos de la relatividad especial son el experimento de Michelson Morley, en el que no se observó variación c midiendo en las direcciones de movimiento y perpendiculares al movimiento terrestre. O la desintegración de una partícula en movimiento, e.g. un muón tendría un tiempo de vida muy corto en su sistema, pero al estar en movimiento a velocidades cercanas a c, para nosotros su tiempo de vida sería mucho mayor.
CLASSICAL MECHANICS (18-25)
En ausencia de fuerzas externas, el movimiento de un sólido rígido puede caracterizarse como el movimiento de su centro de masas más una rotación donde el eje pasa por el centro de masas. Un cuerpo en rotación experimenta la fuerza centrígua, y aceleración de coriolis. La conservación del momento angular da lugar al movimiento de los giroscopios.
Un oscilador armónico se estudia mediante ecuaciones diferenciales. Tenemos la rigidez, la inercia, y el rozamiento. Un oscilador sin rozamiento tiene una frecuencia característica, y con rozamiento tendrá una resonancia.
Es posible relacionar un oscilador mecánico con uno eléctrico. Donde el voltaje es la amplitud, la corriente la velocidad, R el término de rozamiento, C la rigidez y L la inercia rigidez del sistema. La computación analógica reproduciría sistemas mecánicos mediante el uso equivalente de circuitos eléctricos.
Las resonancias son típicas de sistemas lineales y están presentes en todos los aspectos de la naturaleza. Desde los péndulos, a las resonancias atómicas y nucleares. Los sistemas de ecuaciones diferenciales son fundamentales ya que la mayor parte de los problemas los podemos resolver con ellos (e.g. las ecuaciones de Maxwell, o oscilaciones alrededor de un punto).
ELECTROMAGNETIC RADIATION (26-38)
La radiación electromagnética se puede explicar de tres formas: óptica geométrica, campos electromagméticos o teoría cuántica. Así la luz tendría dualidad partícula (fotón) onda (electromagnética), caracterizada por la intensidad y longitud de onda. En función de longitud de onda tenemos las diferentes tipos de radiación (visible, ultravioleta, radio, rayos X etc).
La óptica geométrica se basa en el índice de refracción para el trazado rayos, y es válida cuando las longitudes del problema son mucho mayores que la longitud de onda. Así se establecen conceptos como la distancia focal (distancia a la que focaliza un haz paralelo), y se puede estudiar el diseño de lentes o espejos. Una versión más avanzada sería el principio de mínimo tiempo de Fermat. Según él la luz se movería según la trayectoria que minimiza el tiempo de propagación. Así la propagación de la luz en el agua sería similar a un socorrista que debe ir de la playa a un punto en el mar minimizando el tiempo total.
La teoría electromagnética fue desarrollada por Maxwell en 1860, y es un hito de la física al sintetizar la teoría eléctrica con la óptica. Otras síntesis serían el calor y la mecánica (teoría cinética de gases) o la mecánica cuántica y la electrodinámica cuántica.
El campo eléctrico es la suma del campo creado por una carga, que varía cuadráticamente con la distancia, más un término de retardo, más un término radiativo proporcional a la aceleración y que varía inversamente con la distancia.
En el caso de que la oscilación de la carga sea harmónica y menor que la longitud de onda tenemos un dipolo. Estos tienen radiación direccional. Si tenemos varias fuentes, se dan fenómenos de inferencia, que dependen de la distancia entre las fuentes y su desfase. Así es posible obtener patentes de interferencia, y emisiones más direccionales que sirven para estudiar la distancia entre los gratings, o lo que es lo mismo, la posición de los átomos.
El índice de refracción se produce por la excitación de los electrones de un material cuando es sometido a un campo (la luz). Las del material produce un campo adicional que induce un desfase con respecto a la fuente incidente, que originaría el índice de refracción. Si se considera un efecto de amortiguación en la resonancia de los electrones tenemos las frecuencias de resonancia, y la absorción de la luz.
El scattering de la luz depende de la longitud de onda. Al tener mayor dispersión el azul que el rojo, vemos el cielo azul, o los atardeceres rojos. La acumulación de partículas juntas hace que el scattering sea en fase, lo que hace que el scattering de gotas de agua sea mucho mayor que en moléculas sueltas. Es por ello que en las nubes, vemos desaparecer el azul.
La luz tiene el campo en el plano perpendicular a la propagación. Si la dirección tiene una forma esta esta polarizada. Los materiales pueden responder diferente a la polaridad de la luz. Por ejemplo si son critales o fibras alargados en una dirección responderán de manera no isotrópica, tratndo de manera diferente a la luz en una u otra dirección, materiales birefrigentes.
La reflexión también depende de la polarización. Si el haz incidente está polarizado en el plano de incidencia, y el haz reflejado y refractado forman 90º no habrá reflexión. De esta manera es posible conocer los coeficientes de reflexión y refracción en lo que serían las fórmulas de Fresnel.
La propagación del campo lleva una corrección temporal, el campo que observamos es el emitido en el tiempo -r/c. Esta corrección da lugar a un estrechamiento en el emitido por un oscilador con velocidad cercana a c, esto da lugar a picos de campo, y es el origen de la radiación sincrotrón.
El efecto Doppler se produciría por el corrimiento de frecuencia al observar un cuerpo en movimiento. Se da para la luz, pero también para el sonido.
La teoría cuántica nos dice que a nivel atómico el comportamiento es similar al de las ondas, siempre que no alteremos el comportamiento con una medida. Así electrones a través de una rendija tienen un patrón de onda, pero si se intenta observar visualmente se obtendría un patrón clásico, es decir los fotones de la medición visual habrían alterado la medida.
Una onda se puede definir como e^(i(ωt-kr)), en el caso de los fotones vector de onda (k) y frecuencia están relacionados por la velocidad de la luz, y en partículas generales por la longitud de onda de Broglie.
TEORÍA CINÉTICA GASES Y TERMODINÁMICA (39-46)
Mediante la combinación de la mecánica newtoniana con probabilidad se obtiene la teoría cinética de gases. Que explica el comportamiento asumiendo choques entre los atomos.
La ley de Boltzman indica la probabilidad de una partícula con una energía determinada es proporcional a exp(-E/kT). Lo que da la densidad de población para diferentes energías (potencial, cinética, vibracional).
La energía interna se incluye tanto la energía cinética cómo rotaciones y vibraciones, siendo PV=nRT=(γ-1)U. Por cada grado de libertad la energía promedio será E_x=1/2 kT. Para un gas monoatómico, U=3/2kT, para gas biatómicos la energía es U=7/2kT, siendo 3/2 la cinética, 2/2 de la rotacional, 1/2 la vibracional y 1/2 la potencial del oscilador.
El calor específico es la variación de energía interna con la temperatura. Aunque a bajas temperaturas varía ya que al haber niveles de energía cuantizados, la energía de vibración o la rotacional no llegan a aparecer.
En equilibrio térmico, se producen ruidos debido a las vibraciones. Así el ruido aporta tiene siempre una potencia al sistema, que proviene del equilibrio térmico. El equilibrio térmico también se da por radiación. Si se aplica teoría clásicas obtiene la ley de Raileigh, y da una energía de radiación infinita lo que era uno de los problemas fundamentales de la teoría cinética. Para solucionarlo es necesario asumir que la radiación sólo se emite en niveles discretos de energía. Así la energía promedio del oscilador no sería kT, si no ℏω/(e^(ℏω/kT)-1), obteniendo ley de radiación de Plank.
El movimiento browniano es similar al problema del caminante, con el cuadrado de la distancia variando con el tiempo. Así la teoría cinética se puede utilizar para estudiar el equilibrio y las tasas de cambio en fenómenos como evaporación, thermionic emision, ionización plasmas o reacciones químicas. En el caso de la radiación, Einstein estudió cual sería el equilibrio entre dos niveles excitados, asumió que se pasa de un estado a otro absorbiendo fotones, mediante emisión, y mediante emisión inducida. Al comparar con la ley de radiación de Planck obtiene que los fotones absorbidos tienen energía ΔE=ℏω. Es como si en el transitorio entre los dos niveles, el electrón entrara en resonancia y emitiese un fotón con frecuencia característica. La emisión inducida se da debido a que ayuda al electrón a entrar en resonancia.
Si en lugar de estudiar los fenómenos atómicos, se estudian las propiedades generales del sistema tenemos las leyes de la termodinámica. La primera lay es la conservación de energía. La segunda ley indica que la entropía del universo siempre aumenta. Definiendo la entropía como S=Q/T. Siendo la entropía una propiedad física de la sustancia. Así el calor debe ir de una temperatura caliente a una fría, o indica que para extraer trabajo en un ciclo es necesario que haya dos temperaturas, y se obtiene un rendimiento máximo(T2-T1)/T1. Y la tercera ley indicando que la entropía a temperatura cero es cero.
Mediante argumentos termomecánicos es posible obtener expresiones de manera equivalente a la teoría cinética, obteniendo la forma de la variación y no el valor exacto. Así es posible obtener la fórmula de ClasiusClapeiron para el equilibro vapor-liquido P=P_0 e^(-L/RT) , o que la radiación varía con la temperatura a la cuarta.
Feynman explica la imposibilidad de pasar calor de una fuente fría a una caliente con un experimento con un trinquete. Debido a las vibraciones térmicas hay intercambio en ambas direcciones y el trinquete funciona como un diodo, con una dirección preferencial, pero que funciona en las dos direcciones, llegando al equilibrio.
ONDAS (47-52)
El sonido se produce por variaciones adiabáticas de presión/densidad/desplazamiento en el sonido.
En el caso del transporte del sonido en ondas electromagnéticas, la onda se descompone en tres ondas, con la frecuencia de la onda portadora (ω_c), y con la distorsión en dos bandas ω_c+ω_m y ω_c-ω_m. Así se propaga la radio y la TV analógica.
Para la propagación de ondas hay que estudiar el efecto del tren de ondas. Así la velocidad de grupo, v_g=dω/dk, menor que la velocidad de propagación en el medio (luz o sonido), y la velocidad de fase (velocidad de cada cresta) v_p=ω/k, que puede ser mayor que la velocidad de luz o sonido.
Si una onda la confinamos en una caja, las soluciones son modos con k=πL/n. Cualquier solución es combinación de los modos. En cuántica los modos serían los posible estados.
Cuando un objeto va más rápido que la velocidad del sonido, se produce una onda de choque. Esto es así porque en la zona perturbadda la temperatura detrás es mayor, lo que da lugar a una velocidad del sonido mayor, acumulándose una presión en la onda de choque. El frente de la onda de choque es cónico, con un ángulo igual a la velocidad del objeto entre la velocidad del sonido. La onda de choque pasa con el sonido, o con la luz en medios con índice de refracción, y sería el origen de la radiación Cherenkov.
Las leyes de la física son simétricas (mecánica, electromagnetismo). La simetrías ser��an traslación en spacio y tiempo, rotación, sistema inercial (lorenzt), inversión tiempo o espacio, intercambio e partículas idénticas, fase cuánitca y cambio materia/antimateria. Un apartado donde no se descubrió simetría, es en la desitegración beta, donde los electrones tienen a tener spin en una dirección. Anque al estudiando en detalle, si se cambiase materia por antimateria, la simetría se seguiría dando.
Las notas están a medio camino entre el ensayo y el libro de texto, y combinan con maestría la descripción teórica con los ejemplos. Dentro de la descripción teórica, se describen las teorías, con rigurosidad matemática, pero sin entrar en una excesiva complejidad. Feynman intenta describir cada fórmula y expresar el sentido físico de la misma, explica el fenómeno, y a partir de él realiza la formulación matemática. Junto a descripción teórica se explican diferentes ejemplos que muestran las leyes físicas en acción, despertando la curiosidad y permitiendo interrelacionar los diferentes aspectos (mecánica, electromagnetismo, termodinámica) que rigen el comportamiento físico del universo.
En el primer tomo se hace un repaso general a la física clásica. Comenzando por una introducción, leyes del movimiento, mecánica newtoniana, relatividad especial, la radiación en sus diferentes versiones (geométrica, campos y cuántica), teoría cinética, termodinámica y ondas. Dejando electromagnetismo para el segundo volumen y la mecánica cuántica para el tercer volumen.
La forma de estructurar el libro es canónica, con capítulos con diferentes temas, y con pequeños apartados. Con bloques de capítulos dedicados a diferentes temas. Al principio de cada capítulo se resume el anterior y se da una visión general del mismo, y al final se recapitula lo expuesto. Los apartados son breves, discutiendo una fórmula, un aspecto físico o dando un ejemplo, si es necesario se recuerda algo expuesto en capítulos anteriores, se interconectan los diferentes fenómenos. Pero dentro de tener una estructura clásica los capítulos y apartados son magistrales, la estructura del libro es en si misma magistral.
Para alguien con estudios de física o ingeniería el nivel de dificultad no es elevado, y el libro se puede seguir de una manera amena. Las lecturas permiten recordar lo ya estudiado, aportando un punto de vista diferente, y la capacidad de conectar diferentes fenómenos. Así la analogía entre el oscilador mecánico y eleléctrico, la relación entre un oscilador y la radiación, y esta con la radiación de cuerpo negro, etc nos dan una visión completa de los fenómenos. Es un libro absolutamente magistral que ojala hubiese descubierto años antes!
INTRODUCTION (1-6)
La física serían las leyes que gobiernan el mundo. Esto es lo que pretendemos conocer, pero conocer las leyes no significa conocer el mundo, simplemente poder interpretarlo. La materia está hecha de átomos en continuo movimiento. Las leyes que nos rigen son aquellas de los átomos a gran escala. Así el movimiento de los átomos sería el calor o la temperatura, y explicaría la presión, disolución, difusión, evaporación, etc.
La física clásica sería la anterior a 1920 y la irrupción de la mecánica cuántica. En ella el universo se presentaría por partículas y fuerzas. Estaría compuesta por la mecánica newtoniana, electromagnetismo, óptica, química y relatividad especial. El electromagnetismo se presentaría como las ondas propiciadas por las cargas, similar a las ondas producidas en el agua por un objeto.
La llegada de la mecánica cuántica estableció la dualidad partícula onda o el principio de incertidumbre. El principio de incertidumbre es el responsable de la formación de los átomos, al dar niveles de energía a los electrones, e impedir que colapsen contra el núcleo.
La física proporciona el punto de partida para otras ciencias, es el equivalente moderno de la filosofía natural. La física moderna se podría considerar que comienza con Galileo, cuando intenta probar experimentalmente las teorías que había sobre movimiento. Gran parte de la física anterior se debía a los principios filosóficos de aristóteles o la escolástica y carecía de base experimental.
NEWTONIAN MECHANICS (7-14)
Kepler primero fórmulo las leyes de movimiento gravitatorio mediante sus tres leyes i) los planetas orbitan en elipses con el sol en uno de sus focos, ii) que los planetas barren áreas iguales en tiempos iguales, iii) que el cuadrado de los periodos es proporciona al cubo del semiaxes de la elipse. A su vez Galileo estudiaba el movimiento, y los sistemas inerciales. Posteriormente las leyes de Newton permitían derivar las leyes de Kepler.
Mediante las leyes de Newton y el cálculo diferencial es posible estudiar la órbita de los planetas o galaxias. También explicar las mareas, como la atracción de la luna y rotación terrestre, para ciclos de cuatro veces al día. Para estudiar la constante de gravitación universal se puede hacer estudiando la torsión de un cable, tal como hizo Cavendish.
Así se definen la velocidad o la aceleración y los conceptos de derivadas e integrales.. Hasta Galileo, y Newton, y el cálculo diferencial el movimiento era un misterio. Así están las paradojas de Zenón. Los griegos no comprendían que una infinitud de pasos infinitesimales puedan dar lugar a un resultado finito.
La primera ley de Newton es el principio de inercia de Galileo, la segunda que un cambio cambio de movimiento necesita una fuerza, la tercera que a toda acción equivale una reacción. Hay fuerzas fundamentales (gravedad, electromagneticmo) y hay fuerzas empíricas (fricción, dragging, fluidos). En las fórmulas empíricas se simplifican los diferentes efectos mediante fórmulas simples, sin embargo un análisis exhaustivo indica las limitaciones de estas fórmulas. Las fuerzas conservativas son aquellas en las que el trabajo en una curva cerrada es siempre cero, independientemente de la curva. En estos casos se puede definir una función potenial que indica la energía en cada punto.
RELATIVIDAD ESPECIAL (15-17)
Galileo con su teoría de la relatividad indicó que las leyes de la física son independientes del marco de referencia. Sin embargo, con la aparición de las leyes de Maxwell y la invariabilidad de la velocidad de la luz esto no estaba tan claro. Así pues, para mantener invariable la velocidad de la luz, habría que hacer el espacio y el tiempo relativos. Lo que llevaría también a una nueva formulación de masa y energía.
La relatividad de espacio y tiempo se puede demostrar con las transformaciones de Lorentz. El espacio se acorta en la dirección axial, mientras se mantiene en la dirección transversal.
Para las relaciones de momento y energía hay que incluir la masa relativista, de esta forma se conserva el momento. Y la energía sería la energía en reposo (masa) más el momento. Conforme aumenta el momento, aumenta la masa, y aumenta la inercia, tendiendo asintóticamente a c.
La variabilidad de la masa se puede demostrar por conservación de momento de dos partículas identicas en direcciones opuestas al chocar. Además cuando dos partículas con momento nulo chocan y se unen, la energía se ha de conservar, por lo que es necesario que la masa aumente.
Las relaciones entre momento y energía en dos sistemas de referencia son análogas a las transformaciones de Lorentz para espacio (momento) y tiempo (energía).
Ejemplos de la relatividad especial son el experimento de Michelson Morley, en el que no se observó variación c midiendo en las direcciones de movimiento y perpendiculares al movimiento terrestre. O la desintegración de una partícula en movimiento, e.g. un muón tendría un tiempo de vida muy corto en su sistema, pero al estar en movimiento a velocidades cercanas a c, para nosotros su tiempo de vida sería mucho mayor.
CLASSICAL MECHANICS (18-25)
En ausencia de fuerzas externas, el movimiento de un sólido rígido puede caracterizarse como el movimiento de su centro de masas más una rotación donde el eje pasa por el centro de masas. Un cuerpo en rotación experimenta la fuerza centrígua, y aceleración de coriolis. La conservación del momento angular da lugar al movimiento de los giroscopios.
Un oscilador armónico se estudia mediante ecuaciones diferenciales. Tenemos la rigidez, la inercia, y el rozamiento. Un oscilador sin rozamiento tiene una frecuencia característica, y con rozamiento tendrá una resonancia.
Es posible relacionar un oscilador mecánico con uno eléctrico. Donde el voltaje es la amplitud, la corriente la velocidad, R el término de rozamiento, C la rigidez y L la inercia rigidez del sistema. La computación analógica reproduciría sistemas mecánicos mediante el uso equivalente de circuitos eléctricos.
Las resonancias son típicas de sistemas lineales y están presentes en todos los aspectos de la naturaleza. Desde los péndulos, a las resonancias atómicas y nucleares. Los sistemas de ecuaciones diferenciales son fundamentales ya que la mayor parte de los problemas los podemos resolver con ellos (e.g. las ecuaciones de Maxwell, o oscilaciones alrededor de un punto).
ELECTROMAGNETIC RADIATION (26-38)
La radiación electromagnética se puede explicar de tres formas: óptica geométrica, campos electromagméticos o teoría cuántica. Así la luz tendría dualidad partícula (fotón) onda (electromagnética), caracterizada por la intensidad y longitud de onda. En función de longitud de onda tenemos las diferentes tipos de radiación (visible, ultravioleta, radio, rayos X etc).
La óptica geométrica se basa en el índice de refracción para el trazado rayos, y es válida cuando las longitudes del problema son mucho mayores que la longitud de onda. Así se establecen conceptos como la distancia focal (distancia a la que focaliza un haz paralelo), y se puede estudiar el diseño de lentes o espejos. Una versión más avanzada sería el principio de mínimo tiempo de Fermat. Según él la luz se movería según la trayectoria que minimiza el tiempo de propagación. Así la propagación de la luz en el agua sería similar a un socorrista que debe ir de la playa a un punto en el mar minimizando el tiempo total.
La teoría electromagnética fue desarrollada por Maxwell en 1860, y es un hito de la física al sintetizar la teoría eléctrica con la óptica. Otras síntesis serían el calor y la mecánica (teoría cinética de gases) o la mecánica cuántica y la electrodinámica cuántica.
El campo eléctrico es la suma del campo creado por una carga, que varía cuadráticamente con la distancia, más un término de retardo, más un término radiativo proporcional a la aceleración y que varía inversamente con la distancia.
En el caso de que la oscilación de la carga sea harmónica y menor que la longitud de onda tenemos un dipolo. Estos tienen radiación direccional. Si tenemos varias fuentes, se dan fenómenos de inferencia, que dependen de la distancia entre las fuentes y su desfase. Así es posible obtener patentes de interferencia, y emisiones más direccionales que sirven para estudiar la distancia entre los gratings, o lo que es lo mismo, la posición de los átomos.
El índice de refracción se produce por la excitación de los electrones de un material cuando es sometido a un campo (la luz). Las del material produce un campo adicional que induce un desfase con respecto a la fuente incidente, que originaría el índice de refracción. Si se considera un efecto de amortiguación en la resonancia de los electrones tenemos las frecuencias de resonancia, y la absorción de la luz.
El scattering de la luz depende de la longitud de onda. Al tener mayor dispersión el azul que el rojo, vemos el cielo azul, o los atardeceres rojos. La acumulación de partículas juntas hace que el scattering sea en fase, lo que hace que el scattering de gotas de agua sea mucho mayor que en moléculas sueltas. Es por ello que en las nubes, vemos desaparecer el azul.
La luz tiene el campo en el plano perpendicular a la propagación. Si la dirección tiene una forma esta esta polarizada. Los materiales pueden responder diferente a la polaridad de la luz. Por ejemplo si son critales o fibras alargados en una dirección responderán de manera no isotrópica, tratndo de manera diferente a la luz en una u otra dirección, materiales birefrigentes.
La reflexión también depende de la polarización. Si el haz incidente está polarizado en el plano de incidencia, y el haz reflejado y refractado forman 90º no habrá reflexión. De esta manera es posible conocer los coeficientes de reflexión y refracción en lo que serían las fórmulas de Fresnel.
La propagación del campo lleva una corrección temporal, el campo que observamos es el emitido en el tiempo -r/c. Esta corrección da lugar a un estrechamiento en el emitido por un oscilador con velocidad cercana a c, esto da lugar a picos de campo, y es el origen de la radiación sincrotrón.
El efecto Doppler se produciría por el corrimiento de frecuencia al observar un cuerpo en movimiento. Se da para la luz, pero también para el sonido.
La teoría cuántica nos dice que a nivel atómico el comportamiento es similar al de las ondas, siempre que no alteremos el comportamiento con una medida. Así electrones a través de una rendija tienen un patrón de onda, pero si se intenta observar visualmente se obtendría un patrón clásico, es decir los fotones de la medición visual habrían alterado la medida.
Una onda se puede definir como e^(i(ωt-kr)), en el caso de los fotones vector de onda (k) y frecuencia están relacionados por la velocidad de la luz, y en partículas generales por la longitud de onda de Broglie.
TEORÍA CINÉTICA GASES Y TERMODINÁMICA (39-46)
Mediante la combinación de la mecánica newtoniana con probabilidad se obtiene la teoría cinética de gases. Que explica el comportamiento asumiendo choques entre los atomos.
La ley de Boltzman indica la probabilidad de una partícula con una energía determinada es proporcional a exp(-E/kT). Lo que da la densidad de población para diferentes energías (potencial, cinética, vibracional).
La energía interna se incluye tanto la energía cinética cómo rotaciones y vibraciones, siendo PV=nRT=(γ-1)U. Por cada grado de libertad la energía promedio será E_x=1/2 kT. Para un gas monoatómico, U=3/2kT, para gas biatómicos la energía es U=7/2kT, siendo 3/2 la cinética, 2/2 de la rotacional, 1/2 la vibracional y 1/2 la potencial del oscilador.
El calor específico es la variación de energía interna con la temperatura. Aunque a bajas temperaturas varía ya que al haber niveles de energía cuantizados, la energía de vibración o la rotacional no llegan a aparecer.
En equilibrio térmico, se producen ruidos debido a las vibraciones. Así el ruido aporta tiene siempre una potencia al sistema, que proviene del equilibrio térmico. El equilibrio térmico también se da por radiación. Si se aplica teoría clásicas obtiene la ley de Raileigh, y da una energía de radiación infinita lo que era uno de los problemas fundamentales de la teoría cinética. Para solucionarlo es necesario asumir que la radiación sólo se emite en niveles discretos de energía. Así la energía promedio del oscilador no sería kT, si no ℏω/(e^(ℏω/kT)-1), obteniendo ley de radiación de Plank.
El movimiento browniano es similar al problema del caminante, con el cuadrado de la distancia variando con el tiempo. Así la teoría cinética se puede utilizar para estudiar el equilibrio y las tasas de cambio en fenómenos como evaporación, thermionic emision, ionización plasmas o reacciones químicas. En el caso de la radiación, Einstein estudió cual sería el equilibrio entre dos niveles excitados, asumió que se pasa de un estado a otro absorbiendo fotones, mediante emisión, y mediante emisión inducida. Al comparar con la ley de radiación de Planck obtiene que los fotones absorbidos tienen energía ΔE=ℏω. Es como si en el transitorio entre los dos niveles, el electrón entrara en resonancia y emitiese un fotón con frecuencia característica. La emisión inducida se da debido a que ayuda al electrón a entrar en resonancia.
Si en lugar de estudiar los fenómenos atómicos, se estudian las propiedades generales del sistema tenemos las leyes de la termodinámica. La primera lay es la conservación de energía. La segunda ley indica que la entropía del universo siempre aumenta. Definiendo la entropía como S=Q/T. Siendo la entropía una propiedad física de la sustancia. Así el calor debe ir de una temperatura caliente a una fría, o indica que para extraer trabajo en un ciclo es necesario que haya dos temperaturas, y se obtiene un rendimiento máximo(T2-T1)/T1. Y la tercera ley indicando que la entropía a temperatura cero es cero.
Mediante argumentos termomecánicos es posible obtener expresiones de manera equivalente a la teoría cinética, obteniendo la forma de la variación y no el valor exacto. Así es posible obtener la fórmula de ClasiusClapeiron para el equilibro vapor-liquido P=P_0 e^(-L/RT) , o que la radiación varía con la temperatura a la cuarta.
Feynman explica la imposibilidad de pasar calor de una fuente fría a una caliente con un experimento con un trinquete. Debido a las vibraciones térmicas hay intercambio en ambas direcciones y el trinquete funciona como un diodo, con una dirección preferencial, pero que funciona en las dos direcciones, llegando al equilibrio.
ONDAS (47-52)
El sonido se produce por variaciones adiabáticas de presión/densidad/desplazamiento en el sonido.
En el caso del transporte del sonido en ondas electromagnéticas, la onda se descompone en tres ondas, con la frecuencia de la onda portadora (ω_c), y con la distorsión en dos bandas ω_c+ω_m y ω_c-ω_m. Así se propaga la radio y la TV analógica.
Para la propagación de ondas hay que estudiar el efecto del tren de ondas. Así la velocidad de grupo, v_g=dω/dk, menor que la velocidad de propagación en el medio (luz o sonido), y la velocidad de fase (velocidad de cada cresta) v_p=ω/k, que puede ser mayor que la velocidad de luz o sonido.
Si una onda la confinamos en una caja, las soluciones son modos con k=πL/n. Cualquier solución es combinación de los modos. En cuántica los modos serían los posible estados.
Cuando un objeto va más rápido que la velocidad del sonido, se produce una onda de choque. Esto es así porque en la zona perturbadda la temperatura detrás es mayor, lo que da lugar a una velocidad del sonido mayor, acumulándose una presión en la onda de choque. El frente de la onda de choque es cónico, con un ángulo igual a la velocidad del objeto entre la velocidad del sonido. La onda de choque pasa con el sonido, o con la luz en medios con índice de refracción, y sería el origen de la radiación Cherenkov.
Las leyes de la física son simétricas (mecánica, electromagnetismo). La simetrías ser��an traslación en spacio y tiempo, rotación, sistema inercial (lorenzt), inversión tiempo o espacio, intercambio e partículas idénticas, fase cuánitca y cambio materia/antimateria. Un apartado donde no se descubrió simetría, es en la desitegración beta, donde los electrones tienen a tener spin en una dirección. Anque al estudiando en detalle, si se cambiase materia por antimateria, la simetría se seguiría dando.
November 9, 2016
This book is primarly focused on advanced introductory physics, and unlike high school physics this volume of Feynman's Lectures goes in depth of the things that are taught in high school physics such as kinematics and energy which is a common high school science subject however Feynman goes in depth and talks about the gravitational constant and the equations neccisary to figure out the potential energy in an object and how to calculate the speed of an object without certain variables and etc. This book also consists of complex equations as well as complex scenarios, it talks about quantum physics and eventually theoretical physics, and if you would like to prepare for a physics major then this will most definetly help you.
Some of the things I disliked about this particular volume was that it did not include any practice worksheets so that I can retain the information that I had learnt. Another thing that I disliked was that they did not include hyperlinks to Feynman's lecture videos where he thoroughly explains the concept of the chapters. Despite all of this, Feynman Lectures are the number one physics lecture books if you want to be in a particular field that involves advanced physics.
Somethings I would like for Cal tech to change are inserting hyperlinks to the video lectures as well as including some of the newer evidence that we have found in the field of quantum and theoretical physics because the theories and quantum lectures that are included on the book are somewhat old.
Despite all of this if you truly want to learn physics on a higher scale then this book is definetly for you.
Some of the things I disliked about this particular volume was that it did not include any practice worksheets so that I can retain the information that I had learnt. Another thing that I disliked was that they did not include hyperlinks to Feynman's lecture videos where he thoroughly explains the concept of the chapters. Despite all of this, Feynman Lectures are the number one physics lecture books if you want to be in a particular field that involves advanced physics.
Somethings I would like for Cal tech to change are inserting hyperlinks to the video lectures as well as including some of the newer evidence that we have found in the field of quantum and theoretical physics because the theories and quantum lectures that are included on the book are somewhat old.
Despite all of this if you truly want to learn physics on a higher scale then this book is definetly for you.
April 23, 2021
Richard Feynman's collection of lectures on theoretical physics are some of the greatest explanations of complex theoretical and mathematical concepts of all time. Feynman's unique story-telling aproach to understanding and explaining the mysteries of the Univese is on full display in this first volume of his collection of speaches. The Feynman Lectures on Physics Vol 1 is primarily focused on explaining the concepts of mechanics, radiation, and heat in both quantum and relativistic terms. One example of Feynman's signtiture explanatoty technique that is used in the book is his explanation of entropy. Richard Feynman explains how that if you pour white paint and blue paint into a bucket, that the natural way that the paint will distribute itself is inhernetly random, and therefore the two paints will natrually flow together to create on homogenous paint. however, the paints will never naturally seperate themselves back into one half that is white and one half that is blue. This explanation, and the many more that are utilized in this book and in this series, provides a clear explanation of what entropy is and how it works without ever mentioning anything technical or complex. This is the reason that Richard Feynman is called "The Great Explainer", because he is able to put complex topics in common place speach. I would recomend this book to anyone and everyone who has even a small interest in phsycis and would like to learn more about some of the conceptual building blocks of modern theoretical physics. Overall, this book lived up to my expectations of what a collection of Richard Feynman's lectures would be.
January 1, 2018
Celeberrima raccolta di lezioni di fisica di base del premio Nobel Richard Feynman.
In giro se ne trovano versioni ottimamente ri-trascritte digitalmente, ad es. qui: http://www.feynmanlectures.caltech.edu, perciò non accontentatevi di copie anastatiche di scarsa qualità.
Per ora ho finito il primo volume: la fama è meritata. Io un minimo di background scientifico-tecnologico ce l'ho, ma avendo letto tutto il volume d'un fiato, non so quanto materiale mi rimarrà impresso. Ho notato con piacere che mi è restato addosso un po' dell'ottimismo contagioso dell'autore, la fiducia che ogni fenomeno che ci capita sotto gli occhi si può arrivare a spiegare.
E soprattutto mi rimane il metodo: l'intuizione, la comprensione viene prima della trattazione matematica -- che, pure se limitata agli argomenti delle scuole superiori, è presente (un minimo di freschezza nella materia aiuta, se si vuole seguire tutto per bene). Ma la matematica è manipolata con destrezza da Feynman, attraverso spericolate semplificazioni che come per magia avvicinano maggiormente al nocciolo della realtà fisica, spogliandolo di ogni distrazione analitica superflua.
E' sicuramente un'opera influente, da consigliare assolutamente ad un giovane che sia in procinto di fare delle scelte sul proprio futuro, ma anche agli ex-giovani come me che vedranno certamente rinfocolata la loro passione per la conoscenza, spesso soffocata dalle afflizioni della vita quotidiana.
In giro se ne trovano versioni ottimamente ri-trascritte digitalmente, ad es. qui: http://www.feynmanlectures.caltech.edu, perciò non accontentatevi di copie anastatiche di scarsa qualità.
Per ora ho finito il primo volume: la fama è meritata. Io un minimo di background scientifico-tecnologico ce l'ho, ma avendo letto tutto il volume d'un fiato, non so quanto materiale mi rimarrà impresso. Ho notato con piacere che mi è restato addosso un po' dell'ottimismo contagioso dell'autore, la fiducia che ogni fenomeno che ci capita sotto gli occhi si può arrivare a spiegare.
E soprattutto mi rimane il metodo: l'intuizione, la comprensione viene prima della trattazione matematica -- che, pure se limitata agli argomenti delle scuole superiori, è presente (un minimo di freschezza nella materia aiuta, se si vuole seguire tutto per bene). Ma la matematica è manipolata con destrezza da Feynman, attraverso spericolate semplificazioni che come per magia avvicinano maggiormente al nocciolo della realtà fisica, spogliandolo di ogni distrazione analitica superflua.
E' sicuramente un'opera influente, da consigliare assolutamente ad un giovane che sia in procinto di fare delle scelte sul proprio futuro, ma anche agli ex-giovani come me che vedranno certamente rinfocolata la loro passione per la conoscenza, spesso soffocata dalle afflizioni della vita quotidiana.
February 4, 2021
This book is famous among physicists and physicist wannabes. Is it a good book? Well, that depends on why you're reading it. If you're reading it to learn physics for the first time, abandon it for a more modern student-friendly textbook or online course, or heck - go to a university and learn it, but if you're a physics novice, do
NOT
start here! Unless you're young Sheldon or that smart to begin with. If you already know physics with at least a undergraduate senior level of learning or if you're a competently trained and educated physics teacher or science historian or mathematically adept philosopher of science, this book (and the other two volumes) is a must read. Feynman's approach to each and every topic is novel, fundamental, and often sheer magic. To get the Feynman perspective on physics is like learning it anew. The kindle publication is excellently formatted. Equations are flawlessly rendered through vector graphics that scale with the chosen text size instead of embedded picture files that are tiny and blurred. This is the model for how to publish a technical kindle book. The only downside is that the cover is grey instead of red. There's interesting history behind this book being red.
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