Banging In Cycles
The Big Bang. Whether its cause is the will of God or natural cosmic forces is your own choice, but whether it took place isn't up for discussion at this point unless you know a lot more about astrophysics than I or anybody standing near me.
From a singular point, all of the matter in the universe explodes outward with inconceivable force.
Then what?
Setting aside, for a moment, trivial things like the creation of planets and the entirety of Earth's and humanity's history, the only effect so far of the Big Bang is an outward expansion.
Imagine setting a lit stick of dynamite in a bucket of golf balls. The dynamite explodes, the balls travel outward in all dimensions until their force is conquered by other forces like gravity and drag. If you were to pretend that explosion of golf balls was our universe's origin, where we are right now is about half a second after the initial explosion. Stuff is still expanding outward from the origin point of the bang. Currently, the universe is expanding just like spread of those golf balls after the explosion. What happens, though, in the long run?
There are two major theories. One is that the force of the Big Bang cannot be stopped. Matter will continue to travel outward from the origin point forever. As this happens, galaxies spread farther and farther apart, then solar systems spread apart, then planets pull apart, then molecules themselves are pulled apart until eventually every atom in the universe is equally spaced from every other. This is called the Big Rip.
The other theory is that the force of the Big Bang will eventually be overcome. There isn't much drag in outer space, but gravity becomes a factor. As the universe expands its own gravitational force expands. Eventually, the universe itself is so big that it starts to pull itself into itself, and the force from that initial explosion is overcome and begins to run in reverse, as if after the dynamite in the bucket of golf balls triggered a black hole, so that once the golf balls had exploded outwards they were then sucked back inwards to where they started.
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