Maybe the universe has no beginning and end, and time has no beginning.
Hubble The universe in the eyes. NASA / ESA
The Big Bang theory believes that the universe was born from a "singularity" and time and space have its starting point. So people often come up with the idea: What was the universe like before the "Big Bang"? But if we can't get the answer according to the theory of relativity, because the appearance of " singularity " means that the theory of relativity is invalid in this case.
Quantum Mechanics has made great achievements in describing the microscopic world. So many scientists want to combine the theory of relativity and quantum mechanics to invent a so-called quantum gravity theory to explain the two biggest mysteries in the universe that cannot be explained by the theory of relativity: the interior of the black hole and the beginning of the universe. This kind of theory is also called the "theory of everything," and many versions have been derived, but so far, none of them has substantial credibility.
In order to solve this contradiction, Bruno Bento, a physicist at the University of Liverpool at , UK, further developed a novel theory: "causal set theory", trying to redefine the nature of space and time. , To discuss the origin of time and the universe.
According to common understanding, time and space are continuous. In continuous time and space, two points in time and space can be infinitely close. But "Causal Set Theory" believes that time and space are not continuous, but can be divided into countless tiny basic units. We can call the basic unit of these space-time "space-time atoms".The existence of "space-time atom" causes two points in space-time to be infinitely close. The scale of "space-time atom" is the limit of the approach of two points in space-time.
This is like looking at a computer screen and discovering that the image on the screen is actually composed of pixels. Therefore, the distance between any two points in the image can never be less than the width of one pixel.
Bruno Bento believes that "causal set theory" can not only explore the nature of time and space, but also provide people with information on the role of time, and what the passing of time means, what the past means, whether there is a future, etc. A new direction of thinking.
"Causal Set Theory" believes that the passage of time is a physical manifestation, not an illusion or imagination of the human brain. In the "causal set theory", a "causal set" can also amplify the "space-time atom" at a certain moment and make it larger and larger.
Because space-time in "causal set theory" has a minimum scale, space-time cannot become infinitely small, and "singularity" cannot appear. Once the "singularity" does not exist, the beginning of the universe does not exist.
Although in the original version of "Causal Set Theory", this "causal set" of the modern universe was born out of nothing. But in Bento's version, the "big bang" is not a starting point, but an infinite past.
Once the universe has no starting point and always exists, then what we know as the " big bang " is just a special moment in the evolution of the universe, the eternal "causal set". This question also became meaningful before the "big bang".
It is not yet known whether this theory is compatible with the current theory used to describe the evolution of the universe after the Big Bang. But the researchers believe that such a framework is feasible at least at the mathematical level.
.Reference
If time had no beginning
https://arxiv.org/abs/2109.11953
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