What's our Best Guess on How the Universe is Expanding?

We've attributed it to dark energy. We don't know much about it, but we guess that it creates the acceleration of the expansion of the universe, as we see in redshift.

@Animore: I understand about light, though dark matter seems to have it's own set of rules. Fascinating.

@SwanSongRebeL: Absolutely it is. And what's interesting is we know next to nothing about dark energy, while we have a grasp of what dark matter is. Saddening, but inspiring.

@Animore: I wish I understood.

@SwanSongRebeL: Don't we all?

@Animore: So we think that dark energy makes gravity repulsive? Perhaps that's how the universe originally expanded?

Well, that's certainly a possibility, but at the Big Bang we're not certain what the laws of physics were like. We're not even certain that there were laws of physics. They were possibly the same, possibly different. If they were the same, could be. But that would bring up the case, where was all the dark energy created, and how? If there was only a singularity. That's why I believe vacuum fluctuations are possibly. They're rare occurrences but given enough time ('time' is a debatable word here) I'd say they would come around sooner or later.

@Animore: what is a vacuum fluctuation? Explain like I'm 5.

@SwanSongRebeL: Well, in simple terms its the random creation of energy (particles.) In more complex terms its the random and temporary change in the amount of energy in a point in space (quoting from Wikipedia.) You may think this defies the laws of physics, but remember from quantum mechanics, at the quantum level things can seem paradoxical.

But basically, it involves the idea that beneath the features of classical physics, there is an area where particles at sudden moments randomly occur for a brief moment in time, then "annihilate themselves".

But the problem with this being a temporary occurrence is solved with the idea of negative energy in the form of gravity. The negative energy of gravity balances out with the positive energy to create a sum of zero, thus allowing for it all to stay. (search for "zero-energy universe" for a better understanding.)

@Animore: Does this have anything to do with the Higgs Boson particle?

@Animore: and how come you seem to know so much about science at such a young age?

Well scientists have actually discovered that as the Higgs Particle reaches a critical value, gravitational waves get sort of enhanced in a way. (https://phys.org/news/2014-08-higgs-boson-earliest-expansion-universe.html)

But this is theoretical, and we still have much to learn about it. But if it's true, and if there's a correlation behind the increase in expansion of the universe and the Higgs Particle, that means that the Higgs Particle really does have a false vacuum, and we could all die from Vacuum Decay. Frightening thought.

And thank you, ha ha, I just enjoy learning. I used to not really like science, but then I started getting into astronomy, and that's what got me interested. Cosmology is my main focus. I enjoy talking about the birth and death of the universe. It's frightening but captivating.

It's frightening but captivating. Absolutely true.