Questions: what caused the siingularity to explode? How big was the singularity? And I guess a question that's been asked by others, where's the "center," in other words, from what point did it start at, that is, assuming someone believes it started 'somewhere'?
The most abundant elements in the universe (today) is the hydrogen, and it is what the molecular clouds and all the stars are most made of.
And hydrogen was even more abundant before the formation of galaxies and stars. Neutral atoms, when protons and electrons balanced out the charges of the atoms, first occurred at the Recombination Epoch (this epoch started 378,000 years after the Big Bang), as I said before in my previous post.
This bonding of electrons to the lighter elements (hydrogen, helium and lithium atoms) during Recombination Epoch, made the universe transparent for the first time. The transparent universe also allowed decoupled photons to travel freely from the still expanding universe, which I have already mentioned before in my previous post.
BEFORE the Recombination Epoch, the universe was still hot and dense, because these elements were ionized, meaning without electrons bonded to atoms’ nuclei, hence matters were in “plasma” state.
There is a period - 10 seconds after the Big Bang and lasting for 20 minutes - a period known as the Big Bang Nucleosynthesis (BBN), where atoms formed, nuclei were the shells for protons (and neutrons for deuterium, helium and lithium atoms) but no electrons bonded to these nuclei, hence matters were “ionized” and “plasma” state.
So for 378,000 years, matters (hydrogen, deuterium, helium and lithium) were hot and dense matters, but it was cooler than periods or epochs BEFORE the Big Bang Nucleosynthesis. The further back in time you look, the hotter and denser was the universe.
The earliest epoch that the Big Bang theory proposed, was the Planck Epoch, that started after the Big Bang, at 0 second, and lasting for 10^-43 second.
This Planck Epoch is period where the universe was at infinitely hot and dense state, that -
- there were no four separate fundamental forces (gravitation, strong nuclear, weak nuclear & EM), that they were unified as one force,
- and that the extremely dense and hot plasma cannot separate fundamental elementary particles.
It is only when the universe started expanding that universe became increasingly cooler for particle to be distinguishable, and each force separated from unified force.
The entire universe from the Planck Epoch was the singularity, and the universe was expanding from this singularity, was cosmic expansion, it was not an explosion, despite Hoyle referring to it as a “Bang”.
If you compare explosion to the universe expanding, explosion from a bomb, would cause the immediate area of explosion to sudden increase in temperature.
The expanding universe actually made the universe increasingly cooler, not hotter.
In the earlier 1980s, several astrophysicists introduced the Inflationary Epoch (or the Cosmic Inflation) to Big Bang theory, where the universe (singularity) expanded exponentially for a short period of time, increasing the size of universe. This cooled the universe very rapidly.
The Inflationary Epoch started around 10^-36 second (after the Big Bang) and ended between 10^-33 and 10^-32 seconds.
Before the Inflationary Epoch, the singularity was the whole universe. When the singularity expanded, so did everything within the universe, therefore there was no “centre” of the universe.
Like
@Aupmanyav said it is absurd to talk about “centre of the universe”, with expanding universe.
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