The Big Bang is the prevailing cosmological model for the universe. It states that the universe was once in an extremely hot and dense state that expanded rapidly. This expansion caused the universe to cool and resulted in its present size and composition.
The Big Bang theory is based on Albert Einstein’s theory of general relativity, which describes gravity as a curvature of spacetime. According to general relativity, the universe began as a very hot, dense point about 13.8 billion years ago. This point was infinitely small and infinitely dense, and it contained all the matter and energy in the universe.
The universe then began to expand and cool rapidly. As it expanded, the matter and energy in the universe began to clump together, forming galaxies, stars, and planets. The universe is still expanding today, and it is expected to continue expanding for billions of years to come.
The Big Bang theory is supported by a wide range of evidence, including:
- The cosmic microwave background radiation, which is a faint afterglow of the Big Bang.
- The abundance of light elements in the universe, which can only be explained by a hot, dense early universe.
- The redshift of distant galaxies, which indicates that the universe is expanding.
The Big Bang theory is not without its critics, however. Some argue that the theory does not explain the origin of the initial singularity, or the point at which the universe began. Others argue that the theory does not explain the presence of dark matter and dark energy, two mysterious forms of matter and energy that make up about 95% of the universe.
Despite these criticisms, the Big Bang theory remains the best explanation we have for the origin and evolution of the universe. It is a powerful and elegant theory that has withstood rigorous scientific scrutiny.
What is the Big Bang theory simple?
After the expansion, the universe began to cool down. So the first subatomic particles would have formed and then the atoms. Gravity brought these elements together for the development of stars and galaxies.
The Big Bang relates to the notion of cosmic expansion. In 1927, Georges Lemaître noted that if the universe expanded continuously, there must have been a single point of origin in the past.
That origin would be the Big Beng. The growing separation of galaxies that Edwin Hubble discovered in 1929 also served to support this hypothesis.
Scientists like Roger Penrose, George F. R. Ellis and Stephen Hawking, on the other hand, started from Albert Einstein’s theory of general relativity and added notions related to space and time.
These measures allowed them to infer that time and space had a beginning that was finite and that corresponds to the origin of energy and matter.
The current Big Bang theory, combines principles of general relativity theory with several observations about changes in the position of galaxies. This combination allows to extrapolate the conditions of the universe in time.
Following the precepts of the Big Bang, scientists have found that the universe is expanding at a faster rate. This may be due to so-called dark energy.
What was before the big bang?
The short answer is:
The Big Bang is considered to be the beginning of the universe we live in. However, many questions surrounding the Big Bang remain unexplained.
For example, it is unknown whether time only came into being at the time of the Big Bang. Or whether there was time before the Big Bang. In the former case, the question ‘what was there before the big bang’ is of course meaningless.
By the way, nobody knows exactly what time actually is, so it may still take some time before this question is answered.
It is often assumed that the Big Bang not only represented the origin of matter and energy, but also the origin of time and space. Still, there are theories in which space already existed before the Big Bang. Some physicists even speculate about the existence of a complete universe before ‘our’ Big Bang.
In any case
If there was anything before the Big Bang, we will never be able to observe or measure it in our universe. As far as that is concerned, it may well be an academic question.