How likely is the multiverse?

Most cosmologists believe that at the time when the universe was first formed, its size was not very large. But in the blink of an eye, the universe suddenly expanded dramatically, and its volume increased countless times.

It is very difficult for us to say how big the universe is, because this concept is largely conjecture, but it can be said that it is "much bigger than you think". The expansion model of the universe believes that the actual size of the universe is at least 1,052 times larger than the observable part. Since the observable universe is 90 billion light-years across, this means that the true extent of the universe is too large for us to understand.

Picture 1 of How likely is the multiverse?
In cosmology, the universe expansion or cosmological expansion is the expansion of the universe in the early universe at a speed faster than light.

The expansion theory solves many problems in standard Big Bang cosmology. For example, different regions of the universe may be far apart, but the temperature is roughly the same. According to the expansion theory, these regions were once closely linked until they were separated by the expansion of the universe.

There is another possible outcome of the expanding Universe: the expansion of the universe may not be over yet. In fact, the process may never end. This theory is known as the "permanent expansion theory", which believes that the universe will continue to expand on a large scale forever, and that only a small area of ​​it can sustain a normal and harmonious life. peace, like our universe. Each universe is like an "island" separated by an infinite amount of space, away from each other at a speed faster than the speed of light (since the expansion of the universe is actually faster than the speed of light).

These "islands" in the "multiverse" will never meet, and will never be able to communicate with each other. In fact, we can't even find direct evidence of their existence.

Picture 2 of How likely is the multiverse?
The multiverse is a hypothetical group of universes. Together, these universes include everything that exists: all space, time, matter, energy, information, the laws and physical constants that describe them. The different universes in the multiverse are called "parallel universes", "other universes", "alternative universes", or "multiple worlds".

Although there is no direct evidence, we can nevertheless reasonably speculate whether the multiverse exists or not?

First, we have to verify the expansion of the universe. Although scientists have yet to reach a conclusion, there is indeed evidence that something similar to expansion occurred in the early universe. If cosmic expansion occurs, the laws we observe from fluctuations in the cosmic microwave background do indeed agree with it. Except for the theory of cosmic expansion, there is no theory of the early universe that can do this.

However, the expansion of the universe is not a separate theory, but more of a "category" theory. Different models will assume different laws of physics, different motivating factors, different causes and different effects on the event. Since all of these theories are based on hypothetical models of the early universe, it is still too early to determine which of them is correct.

Physicists speculate that eternal expansion may be a more common scenario, and most cosmological expansion models could point towards this outcome until the end of their evolution. Continuing with this conjecture, if the cosmological expansion theory is correct, then the eternal expansion theory may also be correct, which means that the multiverse may indeed exist.

Picture 3 of How likely is the multiverse?
Early recorded examples of the infinite world idea existed in the ancient Greek philosophy of Atoms, which held that infinitely parallel worlds formed from collisions of atoms. In the third century BC, the philosopher Chrysippus suggested that the world would endure and regenerate forever, effectively suggesting the existence of multiple universes across time. The concept of the multiverse was more clearly defined in the Middle Ages. American philosopher and psychologist William James used the term "multiverse" in 1895, but in a different context.

However, the existence of the multiverse is a really difficult problem for scientists to "digest" for a long time. If the theory of eternal expansion is correct, then there is not just one universe or universes, but infinite universes. Each universe may have its own laws of physics and arrangement of particles. Therefore, if the distribution of matter and energy is limited (after all, there are many ways to make up a universe), there will always be repeated physical situations in an infinite number of times. The universe.

But we can only say that if eternal dilation is indeed universal (that is, it applies to most cosmological expansion models), then a multiverse could exist. A group of physicists published this view in a recent paper.

First, they discovered that permanent expansion is not as common as they first thought. They believe that the reason why cosmologists believe that eternal expansion is common is because of the limited number of models they study.

But the researchers also found that because we still don't know much about the expansion model and how it works, it's hard for us to consider how "common" permanent expansion is. any. They believe that the answer to this question cannot be summed up, and that more research on the expansion of the universe is needed. Therefore, the truth about the multiverse so far is still only conjecture and has not been scientifically confirmed and studied intensively.

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