Shape Of The Universe
When I ask you to imagine the shape of our universe, what image is formed in your mind?
For some, it may be an endless, shapeless, infinite domain. For others, it may be three-dimensionally flat, remaining say, it may be a gigantic sphere. In reality, it’s still a matter of debate among physicists. So we don’t exactly know what the shape of our universe is, but there are some theories, let us explore them(I’ll try my best to keep everything in layman’s terms):
Infinite Universe?
An infinite universe would mean that at some point, everything starts to repeat because infinite is a very very very big number and there’re only a limited number of combinations of atoms. So the combination of atoms will begin to repeat itself which means there will be another you and another me very far in the universe. In fact, if it’s truly infinite then there will be infinite you and me. But can it really be infinite? Quantum Gravity theory suggests that nothing can be infinite in nature and it’s one of the most promising theories that explains fundamentals of space and time.
With Borders?
The universe with borders may sound practically possible, but if we start to think about it and imagine it, it becomes more absurd than the former one. If there are borders, then what’s beyond those borders? Is the universe expanding inside some other larger space? If so, then what about the borders of that space? And so on.
Then What?
Two years after publishing the General Theory of Relativity, Einstein decided to use his formulated equations to calculate the shape of the whole universe. Either universe could be infinite or with borders. Einstein finds another alternative: finite universe with no boundary. But how?
Like Earth, its surface has no boundary but a finite surface area because Earth is a sphere i.e. it’s a curved surface. If I start walking from a point on Earth straight, I will eventually come back to the same point after circumnavigating the whole Earth. And same is the case with our universe according to Einstein.
So, for the universe to be finite and borderless, it has to be curved. But can we imagine such a curved space? Einstein suggested the shape of the universe to be a “3-sphere” or a Hypersphere. It’s a sphere in a higher dimension, very hard to imagine. Still, let’s try:
3-sphere or Hypersphere
If you imagine the hemispheres of Earth, we can say that the northern hemisphere is surrounded by the southern hemisphere and vice-versa, because whenever you get out of one hemisphere, you’ll always end up in the other hemisphere. But, here we are talking about a sphere. To imagine a hypersphere we go one more dimension beyond. Just like our previous example, here we’ll have to imagine a ball surrounded by another ball such that when we leave one ball we end up in another. Pulling your hair? You can watch a really interactive video here explaining a hypersphere visualization if you’re curious. (I would suggest though)
Einstein proposed this solution to the problem of the boundary of the universe in 1917. And from here, the “Era of cosmic exploration” started, like the mystery behind the birth of the universe, the big bang theory, etc. But this was just the beginning of this cosmic fascination. Today, many other theories are arising regarding the shape of the universe like 3-dimensionally flat, closed like a sphere, or open like a saddle.
Still here? Well, I hope this was not too overwhelming for you (cause it was for me). This article was heavily inspired by a chapter of the book: Reality Is Not What It Seems by Carlo Rovelli. A great read explaining the origin of space and time, quantum gravity, and the cosmos, in a very easy language without any prior knowledge.
Our kind is still searching for answers about the origin of the universe and unraveling new mysteries every day, but there’s still much to uncover. The more we understand about our universe, the more we wonder about its existence, and ask ourselves only one thing: How Little Do We Know?
