The number stars (like our sun) in the Milky-way galaxy alone reaches 200 billion. And there are more than 100 billion galaxies spotted so far. But how big is the Milky-way galaxy?If a single star is the size of a tennis ball than place one tennis ball in Singapore the other in Japan. That is the easiest way to illustrate. That's how far apart this 200 billion stars are. The chance for the two stars to collide is so remote, that your chance to win lottery 100 times in one life time is greater than that.

So when the two galaxies colliding they are not actually collide, their stars just pass through each other space. But the gravity of their respective black holes will create the "dance" effect.

Oh btw this clip here has nothing to do with that, just the size of the universe, that's all.

http://www.youtube.com/watch?v=Zr7wNQw12l8

So if there are intelligent beings on a planet circling a star 1 billion light years away, I wonder what religion they have. How do they pray? Did God send the same prophets?

I remember somewhere in the Qur'an it mentioned just that, it says the method is the same. But for us it is just matter of "talking about it" some kind of "WHAT IF - THEN LIKE THIS" which seem we constantly producing those hypothesis. It is a philosophical discussion where the answers are already known would be "I think it should be like this".

But depending on the literacy of those populations concern, which I believe they will encounter the same progress as we are. In here the basis of Islam - First and the Last is Tauhid (monotheism), I am sure that is their basis too when it come to theology. No matter what, they are still just a dot in this gigantic universe, don't you agree?.