Where does time come from and why does it seem to us that it flows?


Paul Davies has a lot to think about. He works as a physicist at Arizona State University and conducts research in many fields, from abstract fields of theoretical physics and cosmology to astrobiology, the study of life outside the Earth. We conducted an interview with Davies, and the conversation naturally turned to the topic of time - one of his long-standing interests.

Is the passage of time a reality or an illusion?

The passage of time is an illusion, and, frankly, it is unlikely that many scientists and philosophers will disagree with this. The cause of illusiveness is visible, if it stops and thinks about - what does this even mean, “the passage of time”? When we say that something flows like a river, we mean that part of this river is at some point in a different place from that in the past. In other words, it moves in time. But time cannot move in time - time is time. Many people mistakenly start to believe that the statement that time does not flow, in fact, says that there is no time, that it does not exist. This is bullshit. Time exists. We measure it for hours. Clocks do not measure the passage of time, they measure time intervals. Naturally, there are time intervals between different events; it is these clocks that measure.

So where does this impression of flow come from?

I can offer you an analogy. Suppose I get up, turn around a few times, and then stop. I will have the full impression that the whole universe is spinning. I will feel that it is spinning - although I, of course, know that it is not. Similarly, I feel the flow of time, but I certainly know that this is not so. Probably, the explanation of this illusion is connected with something in your head, and it is probably connected with memory — the laying off of memories, etc. So this feeling that we have, but not the property of time itself.

And one more thing that people mistakenly assume: that the denial of the passage of time is the denial of the asymmetry of the world. Of course, events in the world occur in a directed sequence. Drop the egg on the floor and it will break. You did not see the eggs going back. Buildings collapse after earthquakes, and do not rise from the heaps of debris. In everyday life there are many examples of asymmetry in time, this is a property of the world. This is not a property of time, and an explanation for this must be sought at the very early stages of the life of the Universe, and in its initial conditions. This is a completely separate and respectful topic.

Is time fundamentally for the universe?

Time and space are the platform on which we formulate all our current theories about the Universe, but there are doubts as to whether they are original or derived properties of the Universe. It may be that the fundamental laws of the universe are formulated in terms of any subspace and sub-time, and space-time arises from something more fundamental.

In everyday life, we obviously feel the three-dimensional world and one-dimensional time. But in the Big Bang - we don’t know exactly how the Universe emerged from the Big Bang, but we believe that quantum physics may be related to this - it is possible that this concept that we call classical space-time, where everything seems to be good determined then did not exist. It is possible that not only the world of matter and energy, but also space-time itself is the result of a special early state of the Universe. This is unknown to us, this issue is being studied.

Can time be derivative?

This dichotomy that space-time can be a derivative, a secondary property — that something is derived from something more primitive, something that lies at the very bottom of the description of nature — existed even before I began my career. John Wheeler was sure of this and wrote about it in the 1950s — that there could be some kind of pre-geometry from which geometry flows, just like a huge variety of flexible bodies is made up of atoms — and people work with this idea.

The problem is that we have no possible experiments in this area. You can come up with all sorts of mathematical models, but checking them out looks pretty hopeless. I think this is due to the fact that most people believe that even if there is some incomprehensible subspace and subtime, then any departure from our idea of ​​continuous space-time can manifest itself only in the so-called. "Planck scale", which is 20 orders of magnitude smaller than the atomic nucleus, and our best tools at the moment are able to probe the scales only by many orders of magnitude more. It is very difficult to imagine how we can get to the Planck scale in a controlled way.

If there are multiple universes, are their clocks synchronized?

Comparing the course of time by different observers in different places is a delicate matter even inside our Universe. The speed of the clock, for example, near the surface of a black hole, will be very different from the speed of movement on Earth. So there is no common time in the universe.

But if we have a multiverse, then it would be possible to check whether the proper times of the universes differ from each other only if there is the possibility of transmitting signals from one universe to another. It depends on the multiverse model. There are many models, but in the one about which cosmologists often argue - when bubbles of universes appear in a certain superstructure - there is no direct way to compare the hours of clocks in two different bubbles.

What do you think about the most interesting new developments in their understanding of time?

I am particularly attracted by the work on the perception of time, because I believe that this area in the near future expects rapid progress. For example, there are well-known experiments in which people seem to make a free choice at certain moments, and then it turns out that the decision was made a little earlier, but their own perception of time and their actions were somehow edited by the brain. When we observe the world, we see a consistent and smooth unfolding of events, but in fact, the senses just bombard the brain, which brings it all together. He integrates it and provides already consistent presentation. Therefore, we still have the feeling that we are in control and everything is combined with everything. But in fact, this is all the presentation, recreated after the events.

What is especially surprising is that people react much faster than thought. You can simply follow the work of a pianist or tennis player to see that the apparent awareness of their actions: “the ball flies from here, I’d better move there and hit it,” cannot be such. There is simply not enough time for the signal to pass to the brain, then through the motor system and back. Still, it’s a complete impression that they are watching the world in real time and controlling everything. It seems to me that this is very surprising.

Is there anything new about time in fundamental physics? Yes, not especially. There are new ideas. I think that the fundamental problems have not gone away. We have already discussed one: is time a secondary or fundamental property? Yes, and about the origin of the arrow of time, the asymmetry of the world in time, there is still debate. We know that this needs to be tracked back to the Big Bang, but there are various problems along the way that we have not solved yet. But these are all theoretical and philosophical questions in terms of measuring time and its nature.

Of course, we always expect our experimental colleagues to improve time measurements. At some point they will learn to do it so well that we will surely see the appearance of all sorts of unusual effects. There is an outstanding fundamental problem - although the laws of physics are mostly symmetric in time, there is one set of processes associated with weak interaction, in which there is a small fundamental disorder of this symmetry to time reversal in the other direction. But this effect plays an important role. I think in this direction there is still much to dig. So in particle physics, you can still carry out experiments that can reveal this asymmetry to a change in the direction of time, which exists in weak interactions, and show how this all relates to the arrow of time.

Source: https://habr.com/ru/post/406001/

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