My first thought was a little basic, the idea was eventually with technology we would have the power to be able to create anything we wish, possibly even more than what god could ever conceive. (I mean we've already achieved Cilit Bang cleaner)
So at the end of our lifetime as a human, wether it be the universe or solar system/planet, we could in theory ensure life, including human existence would exist by planting a seed, this could involve going back in time and ensuring or even creating the big bang.
However you should ignore that as it's dribble, I then carried on with a better theory, IF genetic memory exists, which is the idea in humans and animals it would be instincts and personality that's past through genes exist. Essentially this can be proven as elements can come together to create things, there must be some internal makeup that means it exists in the way it does. Iron oxide is common on Mars, but is also found on earth, 2 different planets housing the same formula, this happens all over the universe with different minerals, this proves in different places the same outcomes exist.
Carrying this idea on, we can essentially think, there is a 'God' particle, meaning before we existed, the universe knew how to create us, perfectly, and all that came before and what will come after. All codes for creation exist, and have existed since the big bang.
But what if there's more too it? Theory suggests the Big Bang is a a point in time, and from then the universe expanded, and like an explosion will then come back on it self, I believe this is called the crunch. What if when the crunch happens, and we go back to nothing (just atoms colliding) that it then becomes a big bang again. If this creates a universe, which it will, then maybe the universe that's created has all the particle and makeup of the original universe, creating humankind once again, continuing our survival, potentially doing it differently.
This would be an infinite cycle, it could be our billionth life cycle of humans inhabiting this 'earth' or a very similar existence.
Or, the idea of parallel universes or other dimensions, are actually just continuing variations of this universe. And we individually have existed a billion times and will continually exist a billion, and infinitely more.
And when this happens we continually make an alternate decision to what we have done in the last existence. Like how the variations work in the idea of a parallel universe.
So this universe could be a cycle where it continue to form almost exactly the same way each time, we live, die and and are reborn infinitely.
Another thought is, and I must confess, I do not believe in ghosts, but if this idea of what people see, as 'ghosts' could be entities of people that should have existed in that universe, but maybe for some reason have not, as with only one universe been constantly reborn, maybe there are anomalies that fail to carry on, but still push their presence into the current universe.
This could explain how people believe that these 'ghosts' communicate like normal proper and do normal things, because essentially they are acting how they would if they were there.
Wether or not it makes any sense or has any validity, i think it shows that potentially we were always meant to exist, as the universe had us planned, and in every universe we are likely to exist, because our makeup is in the universes memory. And with multiple universes whether side by side or continuing one after another supports the idea we are supposed to exist, as scientists ponder parallel universes means we have presence within the genetic makeup of all universes. So don't worry, we will live again.
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