"The world goes on," says Henri Bergson (1859-1941), one of the most influential philosopher 20th century, and adds that further examination of duration introduces us to invention, continuous creation of new things, where the question of duration is the only science inextricably linked with the rest of the world. "The existence in which we are most convinced and which we know best is undeniably our own. Because we have concepts about all other external objects that can be considered external and superficial, but we perceive ourselves from the inside, deeply" states Bergson in the discussion of evolution of life and the existence of the world, and in it also of time, with which he opens his iconic book Creative evolution. "All our belief in objects, all our actions on the systems that science singles out, really rest on the idea that time does not encroach on them", believes Bergson, who recognizes that science always operates with coincidences of moments that may or may not be simultaneous, but which are independent of our inner experience. But what is time, actually?
DIFFERENT PRESENT OBSERVERS
The time that we intuitively experience, the time that we think is unique and that "flows" does not exist in fundamental physics. In physics, which has been dealing with it since Galileo performed the first experiments at the beginning of the 17th century and thus founded modern physics, the question of time arose already on the first morning, when it was necessary to measure how long a ball falls from a height or rolls on a steep plane, so physicists have dealt with time as much as philosophers, and they completely agree, from the very beginning, that it is relative. The basic, obvious idea behind it is that there is no single "now" in relativity - different observers have different present. That more or less understandable idea escalated over time into a series of shocking conclusions, primarily those reached by Albert Einstein (1879–1955), when as an employee of the Patent Office in Bern, he wrote two papers on which he based the Special Theory of Relativity. Various additional ideas will appear later, for example in quantum and statistical physics the arrow of time (past → future) will be connected to the concept of entropy, a measure of disorder, and with the General Theory we will understand time as part of the geometry of the universe.
"When a man sits at lunch with a pretty girl for an hour, it seems to him that only a minute has passed. But if he sits on a hot stone for just one minute, it will last longer than an hour," Einstein allegedly told his secretary Helena Dukas, explaining the relativity of time. Although many of the quotes attributed to Einstein are invented or mistakenly attributed to him, this witty epigram was apparently used by the famous German-American physicist many times, and was first published in 1954, in James Simpson's collection of quotations. Credited with numerous ideas that marked physics, but also other sciences in the 20th century, Einstein tied the flow of time to the observer with the theory of relativity, changing the intuitively clear view of time that originated from Newton - that time is absolute and universal for the entire universe.
Apparently, time is the same everywhere in the universe, whether it is inhabited or not, quite independently of the inner human experience that Bergson refers to, and which eluded Einstein in this quote. But if we consider the question of the duration of a lunch, with or without good company, we will see that much more than the girl or the stone is related to the place from which we look at the case, whether we are having lunch or watching lunch from the side. Namely, with minimal repairs, the clock will measure that one lunch lasts almost the same viewed from Earth and from some dead planet where life does not think of starting from the beginning, where there is no food, let alone a lunch served with an accompanying dessert with ice cream and chocolate or alternatively, a fasting or vegan menu.
However, the first question is whether the one who is eating is stationary or moving and that his speed is close to the speed of light. How does that matter? It is only important if we measure the length from the side, from the perspective of the waiter who served the lunch, while it doesn't matter to the one who is having lunch, his length depends only on himself. All the paradoxes and all the conclusions of the Special Theory of Relativity from the miraculous year 1905 relate to this - we do not measure time in the same way in all systems of reference. Seen from the side it can last less and that's why a twin ages faster on a spaceship which is very fast than the one on Earth will age.
INFLUENCE OF THE GEOMETRY OF THE UNIVERSE
photo: pexells...
But it's not all about where we look, there's something about geometry, that is, the question of what space-time is like around us. Here we are talking about the consequences arising from Einstein's General Theory, which he arrived at at the very end of the First World War, and which was the first universal theory about the universe. As the person having lunch gets closer to the center of the galaxy, things get somewhat complicated, as some lunches can become too heavy, both for digestion and for further conversation, since due to the physical reasons of the distribution of density in the galaxy closer to its center, the mass is denser, which astronomers call the central star oval. It has nothing to do with the amount of ice cream, nor carbohydrates in general, but the fact that the space-time in the center, close to the black hole, is more and more curved and therefore time closer to the center of the galaxy flows more and more slowly, so for every hundred light-years of distance, a minute is lengthened by a second or two.
Such shortenings of time in physics are called dilations. They are a consequence of the geometry of space and they exist, but they are obviously small. The exoticism of Einstein's time dilations is causing excitement among science communicators and fans of clever films such as Interstellar Christopher Nolan, where astronauts travel through a time wormhole. However, they are realistically insignificant at 27.000 light-years, which is how far the Earth is from the center, let alone on the even further periphery of the galaxy, while closer to its center they become more noticeable, but they remain in fractions of a second and you have to go very close, in fact too close to the center to really spoil someone's daily decisions when to schedule a famous lunch, when to pick up the children from kindergarten, and when finally to sit in the garden and calmly observe how, while the stars appear in the sky, the evening peace reigns. Only the wind blows through the canopy. But when you get to the galactic center and enter it, the dilation of time really becomes dramatic, although the evening in that place does not offer any comfort, and the starry sky is nothing but a black hole.
We can think about it in a very extreme way, and still rely on modern physics. The massive black hole sgA*, located at the center of the Milky Way, is more than four million times heavier than the Sun, and it turns out to be of the Kerr type and rotates at 60 percent of the theoretically possible speed, which due to astrophysical circumstances actually means that it can be approached very close. All the way to the place where the black hole makes a very steep and very deep gravitational pit, which is why time slows down dangerously at that place (it is at half of the so-called Schwarzchild radius, and that practically means on the fence itself, in the yard of this gigantic fury that swallows photons of light, where everything is torn apart by tidal currents, but can still be maintained in orbit).
It is certainly not a place where any story could take place, but for beings who would be able to live there, the dilation is quite noticeable - only one minute would pass, while on Earth it would stretch out for a full five days. These beings in the vestibule of the black hole, who, if they survive there, must at least be some kind of gods, because of the dilation of time by only 80 years, which is the human age, they can watch as many as 150.000 years pass on Earth, which is the entire period of existence of the species Homo Sapiens Sapiens. It is hard to imagine, however, that even the gods could live all eight decades in half the Schwarzchild radius.
These thought-provoking dilations are, as said, predicted by Albert Einstein's General Theory of Relativity. But it is easy to establish that, apart from the fact that they are based on the famous postulates about the highest speed in space and the principle of relativity, and at the same time observed in space, they are actually very small - they could not even be compared to that break in the conversation when everyone shuts up during lunch until the waiter serves them. It seems to us that time with Einstein seems to flow in the same way in every corner of the galaxy.
FROM NEWTON TO ROVELLI
photo: pexellsIT PASSES, BUT IT'S ALWAYS THERE: Time
The plot is that Einstein's vision of time and in general, the modern experience of time for all of us, is based on some previous, older concepts. For example, on that of Isaac Newton, who showed a tendency to see universals everywhere, both in money and in time, which many see as the same thing, and it is no coincidence that, in addition to physics, he was also successful in hunting counterfeiters. Namely, there was a view left from Newton which for some reason was intuitively adopted and more widespread than his famous laws - that time universally, homogeneous and the same everywhere.
However, Newton's universality of time, generally accepted as manners at every luncheon in the author's time, were not entirely palatable to thinkers of other eras. Even Leibniz, a fantastic genius of human thought with the flaw that he excessively hated Newton and found faults in everything, thought that this did not have to be the case, so he criticized his opponent explaining that time is not universal, but relational. According to Leibniz, time is a sequence of successive events and that just as there is no empty space but only relationships between objects, time is not an independent background, but exists only when there are events. Spinoza thought even uglier things - that time is an illusion and a matter of our limited view, Kant had some transcendent ideas about time as a way of cognition and a form of human intuition, and as we have seen, Bergson sought time in human experience, pointing out that scientific time is not the same as time of consciousness.
Some fans of the study of quantum gravity thought that time itself emergent phenomenon, that it emerges as we see a flock as a whole that goes left and right in the sky, although a flock is only a group of birds flying together, that is, that on a microscopic level the world is static, and that time is an illusion that emerges - the flock of our macroscopic view. Physicist Carlo Rovelli with his bestselling book Order of the team brought the topic of time back among contemporary interests. Combining physics, philosophy and personal experience, Rovelli, who was engaged in quantum gravity research, claims that time "disintegrates" into relationships between events - the world is a network of processes, not things in time. Since there is no universal "now" in relativity, the arrow of time arises from statistics and the growth of entropy, where Rovelli shows that the world is a network of events and relationships, in which the past and future are the result of the limited knowledge of the observer.
Time, like space, is an intimate thing for every being, so the spectrum of how we experience and interpret it is far wider than a few philosophical schools and the conclusion about the universality of a morbid mind like Newton's. There are also those who do not care about time, those who are constantly at war with it, those in whose company everything takes longer and others who waste it mercilessly. But all of us, no matter what we think about him, we exist in time and inevitably, we change, no matter how much we worry about our health from one lunch to the next. Because as soon as there is time, there is also evolution, as a basic law in the known universe. It is also worth considering that those who manage time will easily manage evolution as well. But we usually don't think about it. And that is quite expected, nothing strange, nothing different than we worry about the nature of time, although it is a gigantic mystery that we literally live from birth to death.
