First off, let's say that the entire time-space continuum (or everything that ever has, is, or will happen) of our universe can be represented by a clock. The universe itself is born by whatever means (let's use the big bang theory) at 12:00. As time moves forward, so do the hands of the clock. The hands also represent the expansion of the universe. We currently know that our universe is expanding, but it is slowing down. Once the hands reach 6:00, the universe will stop expanding and start shrinking in on itself until it is once again 12:00, or back to the original tiny dense ball of matter that we started from. Let's say that around 2:00, our solar system forms, and around 3:00, the earth is finally in the habitable condition it is now. Life forms around 4:00 and here we are today somewhere around 5:00. In several million, maybe billion, years, the hands of the clock will reach 6:00, and as stated above, the universe will cease to expand. The sentient life across the galaxy will slowly realize this and start to wonder about their not so imminent doom. Then, many billions of years later, the hands of the clock once again reach 12:00, and the universe is nothing more than that original dense ball of matter. But like any normal clock, the rotation does not end there. The hands continue to make their way around the face of the clock all over again, and the universe is once again reborn. Now, we must wonder... is this the first time the universe has existed, or is it the hundredth? Each cycle around the clock could possibly breed a new universe. So I ask you once again, how many times have we been here before?
If I told you that there was absolute nothing on the other side of the wall nearest you, could you imagine it? Try for a second. Try to imagine nothing... Getting a picture of something like ultimate blackness? Well, that's something, isn't it. It is impossible for the human mind to image pure nothingness. You might also enjoy trying to imagine what it would be like if when you died you just stopped existing... no conscious thought or anything like that. Try as you might, you can not succeed in this task, but you might have trouble sleeping after a noble attempt at this type of thought.
Try, for just a moment, to think up something completely new. Something that can not have any basis in anything you have ever seen or heard of before... Can't do this one either, huh? Well that's because it's not possible. The human mind can not visualize nor create something entirely new. So, I pose another question for you. If an alien race came to our planet, and they looked like nothing we had ever seen or heard of before (remember, your brain can not come up with something like this on it's own), would we be able to see them? If not, would we go insane trying to figure out what it was we were observing?