This is Earth 4

Think of the multiverse as a parking garage. Each floor has a door where you can enter an alternate version of your universe. It is not infinite as some people think. In fact, it is finite. We are living in Earth 4.

Many of the earths have had catastrophic events (flooding and ice ages due to asteroid strikes). Some never recovered. Some have. This will happen again including on Earth 4. But it will not wipe out all of humanity. Our knowledge and technology will survive.