Basically there are two possibilities:
1. Matter came into being in a certain way and can disappear.
2. Matter has always been there and will always be there.
Due to the law of conservation of energy, option 2 is the correct one.
The law of conservation of energy means that energy cannot come from nothing and cannot disappear.
According to E=mc^2, matter can be converted into energy and vice versa.
Just as it is impossible to create a perpetual motion machine, it is impossible for matter to come from nothing.
It also means that when we look back, there is an infinite amount of time that has passed and when we look forward,
there is an infinite amount of time to come. And this is true for every point in time.
In a vacuum, virtual particles can spontaneously arise. If there is no source of energy (or source of matter), this can
only happen if pairs of particle and antiparticle are created, so that the sum is zero on all levels. If the sum is zero
on all levels, they also disappear without leaving a trace.
The Casimir effect proves that they can exert pressure.
In the case of Hawking radiation (the evaporation of a black hole), the matter comes from the black hole.
Before the Big Bang there was a black hole that contained as much matter as an entire universe. Due to the collapse of matter orbiting
the black hole, the temperature and pressure in the core of the black hole reached the critical value, which ignited the reaction
for the Big Bang.
Space is infinitely large, our universe is the radiation and matter that was hurled into space by the Big Bang.
Since space is infinitely large, it makes sense that there are an infinite number of universes. Matter keeps coming together, so big bangs keep occurring.
Dark matter contains no electric charge, no magnetic field, and does not react with radiation or emit radiation. The only influence it has on ordinary
matter, is through gravity.
Dark matter does not collide with ordinary matter but passes right through it.
Ordinary matter and dark matter attract each other through gravity.
Dark matter will also accumulate in a black hole because it is attracted by gravity.
