Notes

The universe had a beginning 14 billion years ago, and it’s been expanding ever since. Something that’s expanding should also have an edge right? ❔
Information can’t travel faster than life. We can only see parts of the universe whose light has had time to reach us in the last 14 billion years.

The Observable Universe

Is a sphere with a radius of 45 billion light years. Contains about 200 billion galaxies, each with hundreds of billions of stars.
The edge is more like an edge in time, and in a sense: meaningless. The real universe is bigger than what we can see.
Either the universe is really big but finite. Or it’s truly infinite.
But a finite universe leads to a problem: if it has an edge then there should be something outside that edge. But by definition the universe is all there is, how can there be stuff outside all there is? ❓

Finite Universe

Imagine a tiny ant on an orange. The ant can only see a small piece of the skin, just as we can see only see a small chunk of the universe. If the ant keeps walking it will eventually go back to where it started. The skin of an orange is not infinite but it dosent have a border. The universe could be similar, instead of a sphere it could be a hyper sphere where 3D space is curled on itself.
In a nutshell it all boils down to gravity. Mass creates gravity by bending space time. This bending is strongest where the mass is, but stretches on forever like a point of tension in the fabric of space time itself. It could bend the whole universe back on itself.
If the universe is a hyper sphere it needs to be so big that from our perspective it looks like a flat surface.
Some scientists believe a hyper sphere is too straight forward.
The universe could be like the frosting of a donut. A hyper donut. where there’s not the same amount of stuff in every direction. One could take a different direction and get back to the starting point a lot earlier. Light from far away universes would have a cosmic hall of mirrors effect. We could see far away things in 2 places in different moments in time. Since its light would’ve taken much longer to travel in one direction than the other.

An infinite universe goes on forever with no border.
If the universe is infinite, is it eternal and been there forever? We don’t know
Lot of evidence for the Big Bang. but if the universe is expanding, how can an infinite thing, expand? Cosmic expansion just means that the distant between galaxies is growing with time. Even an infinite space can become bigger. ⬅️