Where Did Time Come From, and Why Does It Seem to Flow?

Paul Davies has a lot on his mind—or perhaps more accurate to say in his mind. A physicist at Arizona State University, he does research on a wide range of topics, from the abstract fields of theoretical physics and cosmology to the more concrete realm of astrobiology, the study of life in places beyond Earth. Nautilus sat down for a chat with Davies, and the discussion naturally drifted to the subject of time, a long-standing research interest of his. Here is a partial transcript of the interview, edited lightly for length and clarity.

There might be some pre-geometry, that would give rise to geometry just like atoms give rise to the continuum of elastic bodies.

Is the flow of time real or an illusion?

The flow of time is an illusion, and I don’t know very many scientists and philosophers who would disagree with that, to be perfectly honest. The reason that it is an illusion is when you stop to think, what does it even mean that time is flowing? When we say something flows like a river, what you mean is an element of the river at one moment is in a different place of an earlier moment. In other words, it moves with respect to time. But time can’t move with respect to time—time is time. A lot of people make the mistake of thinking that the claim that time does not flow means that there is no time, that time does not exist. That’s nonsense. Time of course exists. We measure it with clocks. Clocks don’t measure the flow of time, they measure intervals of time. Of course there are intervals of time between different events; that’s what clocks measure.

So where does this impression of flow come from?

Well, I like to give an analogy. Suppose I stand up, twirl around a few times, and stop. Then I have the overwhelming impression that the entire universe is rotating. I feel it to be rotating—of course I know it’s not. In the same way, I feel time is flowing, but of course I know it’s not. And presumably the explanation for this illusion has to do with something up here [in your head] and is connected with memory I guess—laying down of memories and so on. So it’s a feeling we have, but it’s not a property of time itself.