How is the universe expanding if it always existed?

God did it.

You are correct in suggesting that our universe has not been around for an infinite time; but there has never been a time when our universe did not exist. What we call time is simply a dimension of the universe and, like height/width/depth, came into existence when the universe did.

So there was never a "before" our universe, just as there is not an "outside" our universe. Those terms are literally without meaning.

"[A] driving force had to occur for it to start." How do you know? You're relying on our human experience: indeed, when we see a novel combination of matter/energy we know that a "driving force" produced that combination from previous matter and energy. But we have no experience or intuition regarding the beginning of matter/energy itself--that event was a one-off that no human witnessed.

So: yes, our universe had an onset/beginning; but no, there has never been a time when it did not exist.

Ummmm...yeah? wrote:

What we call time is simply a dimension of the universe and, like height/width/depth, came into existence when the universe did.

That's the metaphysical pitfall that stops modern physicists from making any real progress. None of those things exist, they are just ideas. An abstract framework for looking at and measuring the world. You can imagine a slice of reality corresponding to the idea, but to suppose that slice is real is fallacious.

It's also fallacious to think of time as a "4th" dimension as if it were like linear measurements. It's completely unlike them. It makes as much sense to call temperature or color the "4th dimension."

As long as scientists are poorly trained in humanities, they'll continue making these silly errors.

Bad Wigins wrote:

That's the metaphysical pitfall that stops modern physicists from making any real progress. None of those things exist, they are just ideas. An abstract framework for looking at and measuring the world. You can imagine a slice of reality corresponding to the idea, but to suppose that slice is real is fallacious.

It's also fallacious to think of time as a "4th" dimension as if it were like linear measurements. It's completely unlike them. It makes as much sense to call temperature or color the "4th dimension."

As long as scientists are poorly trained in humanities, they'll continue making these silly errors.

Good points!

I think yeah?'s final point is also correct: the universe has existed for every moment of time--given that "time" is a construct, an abstraction we place on the universe!

I also found the goddidit answer (even if it was intended ironically) interesting. I'm constantly surprised by how many people (including a lot of nonbelievers, who have no excuse!) seem to think that IF

a) a deity was involved in the beginning of the universe, THEN

b) that being perforce must be operating in the universe today.

There is no logical step from a to b!

Time is a flat disk.

The simple and correct answer is light takes time to travel. Each day light travels further and a new part of the universe is revealed to us that did not exist yesterday. So really, the universe is not expanding, it is being revealed to us over time.

sbeefyk1 wrote:

So really, the universe is not expanding...

But it is. That's as well established as about any point in astrophysics.

farts gotta go somewhere

Smoove wrote:

Time is a flat disk.

:)

Not sure if you're trolling but it is well-established since Einstein proposed special relativity that time is a 4th dimension that arises out of the three spatial dimensions.

The universe is a big donut expanding infinitely in every direction but never increasing in size.

Questionnaire wrote:

Which means that universe was not always here and a driving force had to occur for it to start. Kind of like a water droplet into a still body of water. The single droplet created the ripples that expanded outward. The ripples are the effect of expanding, but the cause was the single droplet.

It was pretty much like that. The universe came into existence through a quantum fluctuation. It popped into existence spontaneously, from nothing. A similar process occurs continuously inside the nucleus of a proton, where particles and antiparticles spontaneously come into existence from nothing.

There are some things we humans will simply never know. I don't waste my time with these.......?????

Here's the correct answer: Nobody knows.

You're welcome

Chocolate not wrote:

The universe is a big donut expanding infinitely in every direction but never increasing in size.

Ah, the Homer Simpson theory of the Universe.

Everything expands when it gets warmer.

What if I were to tell you that this universe exists entirely within the mind of a flea?

No wait.... that's just your crack pot attempt at a theory. Carry on...

ClemsonRunner wrote:

Not sure if you're trolling but it is well-established since Einstein proposed special relativity that time is a 4th dimension that arises out of the three spatial dimensions.

That is a theory not an "establishment". Time is a dimension. It does not arise out of the others.

ClemsonRunner wrote:

Not sure if you're trolling but it is well-established since Einstein proposed special relativity that time is a 4th dimension that arises out of the three spatial dimensions.

No, not trolling, and that's precisely the idealist fallacy I was talking about.

Math isn't real, it's an idea that sometimes accurately describes real things. Plotting position over time can be an accurate description of a system, but that doesn't mean some linear super-space exists to correspond to the idea of time.