There is a hypothesis by some that global warming is not caused mainly by carbon dioxide, but by an increase in the energy released by the sun.
But back on topic...
Let me translate the explanation into string theory.
A Big Bang just beyond the scope of our universe.
If we are on a giant 4-dimensional membrane, a collision with another membrane could cause a Big Bang. There is of course no reason to believe our Big Bang was unique, and another can happen anywhere, anytime. The other, colliding membrane would be a parallel universe.
If this is the case, there may be other such universes around, greatly increasing the chance of other intelligent life existing. We'd better pick up the pace of technology development and start space colonization, or risk being overrun one day.
String theory has an alternate explanation for this phenomenon: Gravity from a parallel universe.
If there turns out to be nothing there in the place the universe is moving towards, this would be the reason. According to the theory, only gravity is free to pass through from one membrane to another. So there could be a super-massive "parallel universe" nearby in the 5th or higher dimension. I.e. there is another membrane nearby, possibly the one that caused our Big Bang. I.e. we may see another Bang.
[quote name='xPo']Now they think that a very big part of the universe, that we cannot see (they are calling it a parallel universe), has a huge volume of mass on it, and the rest of the universe is accelerating around it... like our solar system, where the planets spin around the sun???[/quote]
No, we are moving toward it. Like if the Earth stopped spinning around the sun and started falling towards it (on a collision course) instead.
Except this is complicated a bit because the universe is expanding as well as sliding toward something.