The phenomenon of “time” concerns us throughout our lives.One is born ignorant, but at some point realizes that one’s own life is finite when children are born, friends, acquaintances and relatives die; at the latest when your own parents are no longer and you understand that you will be the next one. The phenomenon of time has always preoccupied people. The following quote from Augustine is famous:
So what is the time?
If no one asks me about it, I know; but if I want to explain it to someone when asked, I don’t know. But I can say this with confidence: I know that there would be no bygone time if nothing passed, no future, if nothing were there. But what are those two times, the past and the future, when the past is no longer the past, and the future is not yet?
This is what Augustine wrote about 1600 years ago.For about 500 years now, we have been coming to nature’s attention with physical methods, making observations and experiments. We put together theories that provide inspiration for further observations and experiments. The answers found confirmed many previously philosophically won statements, but did not necessarily make the picture easier.
Newton and classical mechanics
Newton’s motion laws contain time as a parameter.Knowing the location and speed of an object allows us to determine the location of the object at that other time, both in the past and in the future, by inserting a different time. Two characteristics are important here:
- The past and the future are equal here, time can run forwards and backwards, and
- Space and time are a stage on which everything happens.
The findings of thermodynamics have eliminated the equivalence of the past and the future over time and give the time a clear direction.The decisive factor here is entropy. When we bring together a cold and a hot body, the cold becomes warmer and the warm colder. It will never be the other way around.
Entropy also provides the reason why we can remember the past, but not the future.There are fewer different states in the past than in the present and less so in the present than in the future. And remembering means replicating a state at least partially.
Special Theory of Relativity
The most important finding of The SRT is that in objects that move in relation to each other, time runs at different rates.In both objects, the time of the other is slower. In the general case, Newton’s idea of an absolute time is refuted, each object has its own time. What is important is a central realization by Einstein that in order to talk about time, clocks are needed. However, this does not mean machines, but natural processes that take place periodically and whose periods can be counted. Since there are no periodic nature processes without objects, there can be no time (and no space) without objects.
General theory of relativity
The ART adds to the findings of the SRT that not only the movement of an object means a different time sequence, no, it is enough for its mere presence in the vicinity.And that is, the more objects are near an object, the slower the time is from the point of view of an observer looking at both systems from the outside.
Quantum physics deals with the smallest elements of matter.Actually, it is not surprising that there is no more time after a certain smallness of the observed objects. This can be learned from Einstein: if something is so small that there are no more periodic processes, there are no clocks. And where there are no watches, there is no time. This leads quantum physics to two alternative theories about time, for each there are advocates among quantum physicists:
- Time is an illusion and
- Time is an emergent process.
The Big Bang represents a very special state of the universe, which can be considered from very different aspects, all of which come to the same conclusion in terms of time.Some of them:
- From the point of view of thermodynamics, the Big Bang is the highest ordered state, all particles are gathered in one place.
Therefore, there can only be one direction: towards “us”, to the present, to a state of greater disorder.
Quantum fluctuations: Was Newton right?
An interesting finding of quantum physics is that there is no absolute vacuum, even the empty space is filled by a lake of virtual particles.As a result, there is also the possibility of the clocks already mentioned in a vacuum, i.e. periodic natural processes. As a result, time passes even in a vacuum, a little faster than in any area of the universe where there is real matter. In a sense, Newton would be right retrospectively.
Roger Penrose thinks time is the only absolute greatness that existed before the Big Bang.There would therefore be periodic bangs and crunches, each of which would produce new universes with new properties, but all with a course in time. This also fits well with the quantum fluctuations from the previous section.
Stephen Hawking has proposed to deprive the Big Bang of its uniqueness in time.He compares the temporal sequence of the universe with the surface of a sphere. The Big Bang is one of the poles on it. You can walk in the direction of the pole and do not notice when you reach it, because when you continue the hike you suddenly move away from the pole without getting into a “before”.
Carlo Rovelli, a well-known quantum gravity theorist, came up with a similar idea: time is an emergent process.Here, too, the Big Bang is just one of the infinite possibilities of the states, which only preserves its uniqueness by the fact that our life can only run from low to high entropies.
At the end of this article, another (my own) idea of how to counter the paradox, that on the one hand one can give an exact time for the beginning of the universe, but still does not have to answer the question after the before: If we continue to Going towards the Big Bang, the pressures and temperatures continue to rise, i.e. the interactions of all particles take place in ever shorter intervals.Interactions are events.
A mathematical analog:
1 +1/2 + 1/4 + 1/8 + 1/16 + … = 2
Although this sum has a finite result, an infinite number has to be added up for it.Transferred to the Big Bang: Although the time until the Big Bang is finite according to our current knowledge, since then an infinite number of events have taken place. We do not have to answer the question of the before, because there can be no prior to in an infinite number of events.
Conclusion, what is the time for me?
Time is what the clock indicates.(Albert Einstein)