Paul Davis has a lot on his mind - or rather, in his mind. As a physicist at the University of Arizona, he conducts research in a wide variety of areas - from the abstract expanses of theoretical physics and cosmology to the more substantive issues of astrobiology, the study of life beyond Earth. Nautilus spoke to Davis, and the conversation naturally turned to the topic of time, which had long held his research interest. The following is an excerpt from this interview, slightly edited and abridged for the sake of clarity.
Is the flow of time real, or is it just an illusion?
The flow of time is an illusion, and, I must confess, I know few scientists and philosophers who are ready to challenge this. The reason for this becomes clear, it is worth asking yourself what is meant by the passage of time. When we say that something like a river flows, it means that at some moment its particle was in a different place than the one in which it was located a moment earlier. In other words, it moves relative to time. However, time cannot move relative to time - it is time. Many people make the mistake of thinking that the statement that there is no time flow means that there is no time in itself. It is nonsense. Of course, time exists. We measure it with a watch. Clocks do not measure streams of time, but lengths of time. Of course, there are periods of time between events - these are exactly what the clock measures.
So where does the sensation of flow come from?
Let me give you an example. Suppose I get up, turn around my axis several times and freeze. In this case, I will have a convincing feeling that the whole world revolves around. I can feel it spinning - although, of course, I know that I am spinning myself. In a similar way, I feel the flow of time, even though I know it is not. Probably, the explanation of this illusion is connected with something in our head and the relationship with memory - the layering of memories and other things in this spirit. Thus, this is only a feature of our perception, and not a property of time itself.
Another thing that confuses people is that they believe that denying the flow of time means denying cause and effect. Of course, events follow in a directed sequence. If you drop an egg, it breaks. The eggs are not collected back. Buildings are crumbling from earthquakes, not growing out of rubble. In everyday life, there are many examples of temporal asymmetry - it is one of the properties of being. It is not a property of time in itself, and the explanation of its nature lies in the earliest stages of the origin of the universe and its initial conditions. This is a completely different and quite worthy study.
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Time doesn't flow. This is a product of our psychology.
Is time the primary constituent of the universe?
Space and time set the boundaries within which we formulate all our theories about the structure of the universe, but some wonder about the likelihood that these properties of being can be secondary or derivative. Perhaps the original laws of the universe are formed in a certain pre-space and time, and space-time is generated by something more primary.
Of course, in everyday life we perceive a three-dimensional world and one time dimension. However, in the Big Bang - we do not really understand how the Big Bang gave birth to the universe, however, we believe that this could be related to quantum physics - it is possible that the phenomena that we call space-time in the usual sense, in which everything seems clear pronounced, perhaps it was not. Thus, the product of the early stages of the existence of the universe can be not only energy and matter, but even space-time itself. We don't know that. This is being investigated.
So time can be derivative?
The idea that the duality of space-time is a secondary quality derived from something simpler, something that lies at the very core of our concept of being, was in the air even before my career began. This was the opinion of John Wheeler, who wrote about it in the 1950s - that there could be some pre-geometry that gave rise to geometry in the same way that atoms create a continuum of elastic bodies - and people continue to think about it.
The trouble is, we cannot observe this. No matter how many suitable mathematical models you come up with, testing them seems hopeless. Most people believe that if there is something like this in the background of space and time, something that differs from our idea of sequential space and time, this something manifests itself only on the so-called Planck scale, twenty orders of magnitude smaller than the size of the atomic nucleus, while our most accurate observation instruments are capable of observing only many orders of magnitude greater. It is very difficult to imagine how we can study something on the Planck scale under any controlled conditions.
If there are many universes, do they follow the same clock?
The comparative relationship of time between different observers in different places is a complex phenomenon even within the same universe. The speed of a clock, say, at the surface of a black hole, will differ markedly from the speed of a clock here on Earth. So even in our universe there is no common time.
However, now we have many universes, each of which has its own time attached in some sense - you can compare them only if there is a way to send a message between them. It all depends on the model of the multiverse you choose. There are many of them, but in the one most often talked about by cosmologists - the multitude of bubbles appearing in the expanding superstructure - there is no way to directly compare the speed of clocks in different bubbles.
Which of the recent changes in the understanding of time do you find the most interesting?
I am especially interested in laboratory studies of time perception, since, in my opinion, this is where rapid progress can occur in the coming years. For example, there are well-known experiments in which at a certain moment people allegedly made a certain free choice, but it turned out that in fact this choice was made a little earlier, but their own perception of time and their actions within a passage of time changed after this event. When we observe the world, it seems to us that we are seeing a sequential and integral narrative, but in fact, sensory information from various organs of perception is poured onto our brain, which it stitches together. He builds it up and presents it as a coherent narrative, creating a sense of self-awareness. Thus, it seems to us that we own ourselves,and everything goes smoothly and smoothly. However, in reality, most of what we perceive is a narrative recreated after the events that happened.
This is especially noticeable in situations where people react much faster than the speed of thought. One has only to remember the piano or tennis players to understand that they cannot make a conscious decision: “This ball is moving here; I should go there and fight him off. During this time, the signal will not have time to reach the brain, and then the motor system. However, they retain this compelling sense that they perceive the world in real time and are in control of themselves. I find it all very exciting.
Have there been any breakthroughs in the study of time in the field of fundamental physics? I think no. New ideas appeared. Fundamental questions are still there; we have already touched on one of them: is time a primary or a derived property? The origin of the time axis, which is an asymmetry of time, is still somewhat controversial. We know that it should be monitored right up to the Big Bang, but there are still a number of different questions about it that we have not found a definitive answer to. However, these are all rather illusory philosophical and theoretical problems than something that sheds light on the dimension of time or its nature.
In addition, we watch our experimental physics colleagues work to improve the measurement of time. At some point, it will become so accurate that it will probably reveal interesting results. There is still a fundamental problem - although most of the laws of physics are symmetric with respect to time, there are a number of processes associated with weak nuclear interactions in which a fundamental violation of this symmetry is supposed to occur. Apparently, this plays a key role in the overall picture of life. I think there is potential for research here. So in particle physics it is still possible to conduct experiments that will give us new knowledge about this temporal asymmetry with weak interaction and a place near the time axis.
John Steele
