At present, the most widely accepted theory is of course the Big Bang theory. This is the most influential theory in modern cosmology. Its main point is that the universe once had an evolutionary history from hot to cold. In this process, the universe is constantly expanding, making the density of matter evolve from dense to sparse, just like a huge explosion. One of the founders of this theory is Gamov. 1946, Gamov, an American physicist, formally put forward the big bang theory, arguing that the universe was formed by a singularity with almost infinite energy and density about/kloc-0.4 billion years ago. Einstein's general theory of relativity lets us know the general shape of the universe and how matter is distributed. This is a theory to trace the origin of the universe, which led to the Big Bang theory. Moreover, the big bang theory is supported by microwave background radiation and Hubble's law. So it is widely accepted by people.
However, this theory only supports singularities. The Big Bang theory can't find a strong support point to explain how the singularity came into being and what happened before it came into being.
Big bounce theory has existed since 1922. In other words, the universe may not have originated from the Big Bang, but from Big bounce. In other words, the universe may not originate from a "singularity", but from the collapse and rebound of the universe before, a bit like the sudden rebound of a spring compressed to the limit. Then repeat the process. Big bounce's theory is based on the combination of general relativity and loop quantum gravity (LQG), which is a mathematical formula used by scientists to describe the existence of Big bounce. Quantum physics is not included in general relativity, but it is the basic theoretical support of Big bounce's theory. This theory is based on the so-called "loop quantum gravity" (LQG), which is an attempt to unify quantum mechanics and general relativity, and it is itself a manifestation of the effect of gravity on the universe. Its basic connotation is that the universe can be regarded as many intertwined rings, thus giving space a structure similar to atoms and making it something similar to matter.
All kinds of theories and unresolved doubts make people think hard about the unsolved mystery.
Recently, the strong evidence supporting Big bounce's theory comes from the observation point in Antarctica, that is, gravity was discovered in the early days of the birth of the universe. This shows that in the early days of the birth of the universe, it did go through a series of very rapid expansion stages, which is consistent with Big bounce's theory.
Researchers in Imperial College London, London, England and some scientists including Dr. Stephen Galen also put forward Big bounce theory, that is, there is a minimum volume, but not zero, and the maximum expansion, but not infinite. Theoretically, they compared Big bounce to a lung that can automatically expand and contract. This means that the universe is circular.
Pessimistically speaking, Big bounce's theory assumes that expansion will eventually reach a critical point, and then it will shrink rapidly, which is called the Great Collapse. In this process, the universe will collapse, and all substances will be pulled in to form a black hole, which will eventually be unified into a huge black hole. With the increase of entropy, this huge black hole will eventually collapse until it becomes a singularity. Because the quantum effect of gravity is repulsive, it will expand again after meeting all the necessary conditions for re-expansion. In this way, Big bounce will go round and round. That is, destruction-rebirth will be repeated indefinitely.
My friend, what do you think of the origin of the universe?