The Big Bang theory is a cosmological model according to which the Universe we know is the result of space-time expansion from an initial state of very high density and temperature infinitely compressed. It is the most widely accepted model today and the observational evidence supporting it is very extensive.
It is generally exemplified by saying that the Universe was concentrated in an infinitely small point in space and that it exploded, hence the Big Bang theory is also known as Big explosion. This great explosion would be the beginning of space-time predicted by the theory of relativity according to the calculations Stephen Hawking, George F. R. Ellis, and Roger Penrose published in the mid-twentieth century.
The Big Bang is estimated to have occurred approximately 13.8 billion years ago, exactly 13.799 ± 0.021 billion years ago. The uncertainty of 21 million years comes from measurements of the beginning of the Universe made by the Planck satellite on the microwave background radiation1which is the remnant radiation from the Big Bang explosion, within the Lambda-CDM model (Lambda Cold Dark Matter). These measurements agree with other measurements and observations, such as those made by WMAP (Wilkinson Microwave Anisotropy Probe).
Applying physical laws, it has been possible to reproduce the history of the Universe up to approximately 10-44 seconds after the Big Bang, known as Planck epochname derived from chrononalso known as Planck time, which is the shortest measurable amount of time. According to quantum mechanics, time you of an event cannot be more precisely determined.
Where:
- h is the Dirac constant, also known as the reduced Planck constant
- G is the universal gravitational constant
- c is the speed of light in a vacuum
But it has not been possible to decipher what happened beyond. In the initial state of the Universe, the density was so high that the known physical laws break down and a gravitational singularity like the one reached at the center of black holes.
in the singularity there is no space or timeso the Universe could not really be concentrated in a point as they say, since the dimensions originated with the Big Bang itself.
Similarly, the Universe could not explode in the common sense of the word; in an explosion there is propagation out into space from a center, but the Big Bang is the expansion of space-time itself. This means that there is no center and that any observer will see from his position that the Universe expands around you in all directions. This is the case in observations made from Earth and so it would be in observations made from anywhere else in the Universe.
What came before or what caused the Big Bang is one of the most important questions in modern science. All attempts to explain the singularity have so far failed. For some scientists, like Stephen Hawking, the answer to these questions is to think about the time before the Big Bang, which would not be possible since time begins at the Big Bang; according to Hawking it would be like wanting to go north of the North Pole.