14 April 2011

On the need for backgrounds in a theory of everything

Yes, I am convinced: Backgrounds are needed.

You may have read that many people claim that the theory of everything must be background-independent. The quantum gravity people often use this requirement to dismiss present string theory. While I agree that string theory is wrong, backgrounds are not the reason. When one physicist explains an observation to another, he uses space and time. He thus uses a background. Why the hell should a theory of everything be different?

A theory of everything still describes what we see, and when we describe what we see using the theory of everything, we will still use space and time, as we do in normal physics. We might use different concepts, more precise ones, more general ones, but why should we dispense with space and time?

Well, say the proponents of this requirement, because space and time must result from the theory of everything, and not be put in. True, space and time must result from a theory of everything, but this does not forbid us to use it. We only have to show that space and time follow from a theory of everything once for all, and then we can use them as we like. After all, they are quite useful...

But why is this requirement so often voiced? Because people have no clue, and because they want to criticize each other. I tried: I do not manage to say anything useful without space and time. In fact, this test told me something important: if somebody requires me to talk without space and time, he is requiring me to talk nonsense!

Ironically, for many people in fundamental research, the requirement of talking nonsense is fulfilled even if they use space and time. But that is a different story. My point here is: the requirement of background-independence is deeply flawed. Long live space and time!

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