“The scientific method entails two assumptions that are so basic that, even if you spell them out, they are still difficult to keep in mind. First: that the observer stays the same while the world changes. Second: that cause precedes effect.

But the very nature of the experiment we are conducting means that the second of these assumptions is thrown into doubt. We are deliberately attempting to engineer an event in which effect chronologically precedes cause.

If one of these assumptions is under threat, why not the other?”