That post was one of the earliest written. I need to revise it, if I can find it.
15 billion years what the scientists estimate for the life of the universe which they assume arose due to the Big Bang. But according to Buddha Dhamma, the whole universe is not destroyed at once (and there was no Big Bang either). It is individual star systems that are born and destroyed in a billion year time scales, but not all at the same time.
According to Buddha Dhamma, the following is what happens:
1. The universe has no traceable beginning, just like life has no traceable beginning.
2. When our Sun blows up in a few billion years, 10,000 other star systems in the vicinity are destroyed due to that blast. In modern science it is called a superrnova.
3. Such 10,000 clusters of world systems blow up from time to time in the universe. Again, such supernova are observed by scientists every year.
4. What science does not know yet is that those star systems, like our Solar system, are re-formed over billions of years. Of course science is not aware of that part yet.
5. When our Solar system is destroyed, not all 31 realms are destroyed. Higher lying brahma worlds (where there is very little of “destructible matter”) are NOT destroyed. That is where all living beings on this Earth ends up before the destruction of the Earth.
6. Then when the Earth is re-formed, those brahmas — at the end of their lifetimes in those worlds — are re-born as humans.
7. Then the life on Earth evolves to other lifeforms too, and eventually is destroyed again after billions of years.
8. So, that is the life cycle. It happens all over the universe at any given time. That is why scientists observe several supernovas even in our own galaxy each year.
This is the story detailed in the Agganna Sutta. It is very complex and requires more background material to discuss in detail. But that is an outline.