The Big Bounce and the shape of the Universe
So we evolved on this rock somewhere in the suburbs of a large galaxy. But looking around (read: into the stars) we are able to figure some things out, like where it all came from and where it is going. There is still a lot to learn, we barely scratched the surface, let’s try to sum up some things we already know.
Until recently the widely or wildly popular theory was that it all started with a Big Bang! But where did this singularity which gave birth to our Universe come from? What triggered the explosion of space, time, energy, matter and information?
Cosmic microwave background should be uniform. However astronomers who observe and analyze it find some irregularities. These irregularities could be the remnants of the previous incarnation of our Universe, the proof for a new interesting theory, which says it wasn’t a Big Bang, but rather a Big Bounce. The Universe existed before, but for some reason, like gravity, it compressed into one spot. For some reason the compression reached a critical point and it all exploded again.
The Universe has been expanding for the last ~14 billion years. It’s likely going to slow down at some point. Whatever caused to compress it before, will stop the expansion and induce a collapse again. Gravity is a force which we know, but we can’t tell for sure yet if that’s the real cause behind the collapse. In fact we can’t even reliably estimate the mass of our galaxy, let alone the whole Universe and that would be necessary to tell whether it’s gravity that pulling it all together or not.
Looking far away with our best telescopes we can see the faint light that gets to us after billions of years. The farther we look, the older the light. The “oldest” light we see is from before about 14 billion years. This is how we estimate the age of the Universe. The shift of the spectrum of the light we see towards red indicates that the Universe is expanding.
Some theories propose that the expansion is not only caused by the matter speeding after the Big Bounce, but also by expansion of the space itself. This would explain why two points of space sufficiently far away from each other escape from each other with a speed which virtually seems greater than speed of light. Therefore if places far away from us escape virtually faster than light, we will never be able to se what’s beyond a certain point.
Because of this “faster-than-light” expansion, the Universe is bigger than what we can see, according to some estimates by an order of magnitude, or even more. The truth is, at this point we don’t even know how big the Universe really is, the estimates vary, we suspect it’s ~14 billion years old but much bigger than that the distance that light would travel in ~14 billion years.
What does the Universe look like, what is its shape? The simplest answer is that it’s filling the inside of an expanding sphere. The shockwave of the initial explosion is really fast, so we can’t get out and see it from outside. Some even propose that there is no space outside, that the space exists only inside of the Universe, which physically makes sense, because what we think of as empty space, completely sterile vacuum, is in fact not empty, but full of energy. Since there is no energy or anything beyond the expanding sphere of the Universe, we can’t treat it as ordinary space as we know it.
I do not really believe that the Universe is an expanding sphere sitting in an unexplainable, unmeasurable, infinite, sterile and pristine void without bounds of end. That does not make any sense to me. But I have my own theory.
In my opinion our Universe is a three dimensional surface of a four dimensional sphere. This is mind boggling and impossible to imagine “from the outside”, but it’s quite easy to grasp from the inside if we compare it to our two dimensional life on Earth. If we were able to freeze the time and then send a spaceship in any randomly chosen direction, the starship would eventually return from the opposite side. This means that to us, confined to the three dimensional space of our Universe, there is no boundary, there is no escape, there is no getting out. No matter where we go, we will eventually get back to where we started.
What I think really expands is the four dimensional sphere on which surface our three dimensional Universe is located. It’s like the Earth was a balloon and somebody was blowing it. When we’re blowing a balloon, its volume expands, so does its surface. The number of atoms on the surface remains the same, only the expansion of the balloon causes them to move away from each other. Similar thing happens to our Universe.
The fourth dimension of the expanding sphere is not time. At some point the Universe will stop expanding and will start collapsing again, but the time will not start going back. (Or will it?)
So what if it’s true, if the Universe has multiple lives, if it is expanding and collapsing back and forth? What is causing it? It could be gravity. My theory is that the behavior of the Universe is like a perfect pendulum. It swings back and forth. When it expands, the expansion is slowing down up to certain point when it stops, then collapses back again, the collapse accelerates until finally the Universe collapses into a singularity and all matter and energy ends up in one spot having maximum “kinetic” energy it bounces and starts expanding again, the expansion decelerates until it stops again at the same point as before. If the contents of the Universe don’t have a place to escape, the process is perfectly conserved and the Universe is bouncing back and forth, forever. And every iteration of the Universe can be different, doesn’t need to be identical, the elements of matter and energy don’t have to follow the same paths as before the bounce.
Maybe it’s like that, maybe not. Even if it is, it does not explain how this all started, where it came from, what’s inside the four dimensional sphere and what’s outside. Will anyone be ever able to find out?