Before the big-bang, there was nothing.
But "nothing" is not nothing at all. It is just a definition, a "singularity", a "ceteris-paribus" in order to be able to not needing to be considered within the actual valid theories, as they can't prove with actual mathematics and physics.
"Nothing" before the start of our time, was one point. In it, all things were concentrated. And a point has no dimensions, thus is "nothing - can´t be seen, as you (don't) see...
But surrounding that "nothing" there where tremendous forces, like electromagnetic radiation, pressure and cold. That is not "nothing". It just can´t be considered up to now ...
When universe gets so cold, that even the very strong electromagnetic waves cant destroy and keep destroyed the process of atom-building, then an enormous chain-reaction occurs: the big-bang.
This was the start of our universe, 13.8 billion years ago.
Enormous quantities of energy spread out of "nothing" at enormous temperatures.
A change of status occurred. From nothing to time, space and matter. And a lot of additional forces and constellations.
Out of the energy, among many other things, matter and planets evolve.
Different sizes of stars and planets with different functions, different forces, different directions and different communities.
Looking at them with the time-glasses on your eyes - or with the imagination of physics and mathematics, beautiful images arise.
Mercury, the planet in our solar system nearest to the sun, paints one of the most wonderful pictures. This was so complicated, that Newtons formulas did not work with this planet.
Mercury turns around the sun in elliptic curves with a very small curve at the sun and very wide curve far away from it - as if it might be too hot at the sun-side.
But additionally Mercury continuously turns a 360 degrees circle around the sun, every 360,000 years. And this circle is a spiral - always opening a little bit more - away from the sun.
And as all stars and planets always and continuously try to expand their ways, the universe still today is expanding - even after 13.8 billion years.
Expansion is fundamental. If there would be no expansion, the universe would collapse.
The good notice: actually there is an acceleration in this expansion.
If planets or stars do not have any energy any more, they im- and explode via a super-nova. This happens once within 100 years on average in each galaxy.
From these super-novas, black holes or neutron stars, like pulsars may arise. When a pulsar arises, this at the same time may be the start of a new galaxy, a new stars and planets group.
Thus super-novas are not a counterforce to universal growth - but a help. To old or big constellations with too little energy, collapse, giving the chance to new constellations with new energy to care for more expansion.
Thus the end of one star at the same time may lead to another start. Nice to know.
Pulsars are fast moving neutron stars.
They are one of the most interesting "matters" in universe.
Pulsars not only are the matter between end (after a super-nova-explosion) and beginning (providing good conditions for new gravity and star-building processes).
Within pulsars there might be found solutions to close the gap between Relativity- and Quantum-Theories.
At the end of the life of a Pulsar there might evolve new planets again - out of the particles fog being squeezed by solar winds, or other forces like big comets, planets or stars via gravitation.
The end of something, in our lifes, economies, as well as in universe, it´s always as well the start of something new.
The second result - apart from pulsars - after a super-nova may be a new black-hole - absorbing all the rests of the matter and forces surrounding it.
Black-holes are like "the other side of the medal". If planets or suns do not have enough energy any more - to circumvale and move away and/or keep their sizes (due to the heat keeping matter big) or grow - they will collapse via a supernova and/or be absorbed by or create a black-hole.
Black-holes have a big gravity - absorbing more and more of weakening surroundings.
It´s like a fight between the all-absorbing states against the liberty requiering active and private-(not state-)-oriented people and economy.