Time is layers for all I know. And you're right, I mean what proof do we have that Earth as it is now was the first and only one that is as is now? This fact will also negate all religions as they were started by humans in "this" earth's life cycle which is basically proof that there ain't no god watching over us and that there never was and never will be. I also think that Earth is a living matter, a living being, and like all living beings, it will die. I mean, it is made of water, earth and air just like we are made of skin and different tissues, of fat and everything. There are definitely life cycles to earth, they're just longer than any of us will ever know. I find something stupid though, that we started counting time when Jesus was born... or died... whatver, it had something to do with him. It is pure bunks. There was definitely time before Jesus and there was time before there even was an earth. Another thing that is interesting in the earth's life cycles is that "aliens" might actually be old earthlings that survived long enough in the earth's life cycle to discover and travel to other planets, I don't think that's too crazy.