the universe is expanding at an accelerating rate for a supposedly infinite time
therefore every configuration of particles would have taken place, and begun to repeat.
if this is so, then the configuration of particles that made up our solar system, and earth would have taken place once more
according to this theory, there could be another earth out there!
however we wouldn't be able to see this alternate earth, as we
can only see 14 billion (light) years away, as that's the amount of
time since light began to travel, at the big bang.
big bang fuel
the fuel for the big bang, (quantum-something-or-other i'm
not sure) is meant to be extremely efficient.
this leads to the idea that the fuel wasn't all used up in the first big bang, or our big bang.
therefore there could have been other big bangs, before or
after ours, creating separate universes!