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skofan t1_j4a9tx3 wrote

Reply to comment by Wonderful_Mud_420 in 87 newly-discovered galaxies, found using Webb space telescope, could be earliest known galaxies in the universe — the first indication that a lot of galaxies could have formed much earlier than previously thought by marketrent

And others say that if you trace back the expansion of the universe you get a pretty decent estimate of how old a galaxy could possibly be.

But since only one of them is a testable hypothesis, i guess we'll never know which is more likely.

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thruster_fuel69 t1_j4b43d1 wrote

We're like those people in the far future who can't see any stars after they all move so far apart. We just don't have the required information available to us. At this point I see no reason to accept either as truth, so I'll just assume it's infinite. An infinite universe is insanely exciting to contemplate.

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skofan t1_j4bwkr6 wrote

sorry, ill try to be serious instead of sarcastic, this is /science after all.

a flat spacetime very much leaves the door open for an infinitely large universe, but right now we're talking about how old it is.

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thruster_fuel69 t1_j4bwxlf wrote

Infinite age is implied, space, time.. spacetime.

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skofan t1_j4c8dak wrote

its really not.

think of a black hole, at the event horizon (named such because of this effect) the escape velocity = C (causality), if you're positioned there, you will appear to be frozen in time for everyone from the outside observing, while from your perspective the entirety of the rest of time will flash by in a litteral instant.

now, since energy cant be created out of nothing, and mass is directly related to energy, if you trace back the expansion of the universe, you reach a point where the entirety of the universe had similar density to a black hole.

now, as our human concept of time is the linear passing of events through causality, and the laws of physics explicitly forbids anything prior to the expansion event to have any influence on events after, it makes no sense to talk about "time".

there may or may not have been some similar set of rules that governed the universe, im nowhere near smart enough to have an opinion on that, but unless you want to redefine what time means, it doesnt really make sense to talk about time prior to the expansion event.

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crimeo t1_j4chogw wrote

So what if it had approaching-infinite density? Big Bang does not preclude infinite age. It could have just been increasingly dense going back FOREVER.

The only special thing that happened "at the big bang" that we have direct evidence of is "radiation started occurring". If radiation simply doesn't occur at higher densities than that, then that wouldn't necessarily be the beginning of matter/energy, merely the beginning of radiation

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skofan t1_j4cip9y wrote

yes, radiation began occuring, which means that the velocity needed to escape the gravity well fell below the speed of light, also known as C, so named because its the speed of causality.

radiation occuring is the beginning of causality in our universe, as time is the passing of events, it hardly makes sense to discuss a time before causality.

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crimeo t1_j4cj6wf wrote

I disagree, if radiation was occurring before but just not escaping a gravity well, then when space expanded, that radiation should still have been there hanging around, liberated by the expansion and still there for us to detect.

It seems to be that radiation did not get trapped but didn't happen at all to even be trapped or not. Like more along the lines of "the way subatomic physics works at very high densities just doesn't make sense for radiation to be a thing, but maybe a bunch of other stuff is"

> its the speed of causality.

Also how do you know this is the case anyway, at hyper intense densities that we've never observed and thus don't know the rules of? Or that the speed of light changes that high, or become unlimited, or that things just start to teleport as the main way stuff happens, or whatever

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skofan t1_j4cszeq wrote

unless you want to redefine the word time, and its meaning or move it to a philosophical discussion sub before continuing, i refuse to have this discussion.

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crimeo t1_j4cvhky wrote

I'm not redefining time at all, it indeed makes sense and I agree that it requires causality.

The problem is that you have no way to establish that causality was not going on before the big bang, because you don't know any of the laws of physics or what the speed of light was or if there even was a maximum speed of light or if movement had different rules in general, or anything else about back then. Nobody does. Because we have no observations of it.

"Assuming this series of things that I have zero basis to assume, there would be no causality, and time requires causality, so there was no time" is obviously not a sound argument. It's valid (syllogism) but not sound (the premises cannot be established as true)

> philosophy

Science extends to saying "I don't know" to things you have no data for.

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thruster_fuel69 t1_j4c922w wrote

Ok I'm no physicist but why do we think space itself is fully contained within a bubble of what we can see? Isn't it silly to assume there's nothing outside our visible bubble when we always see more the further we look? How do we know it's space itself contracting and not just our portion of some much larger explosion?

I feel like maybe that's all explained well enough, but I also know scientists love to smell their own farts and word conjecture as fact.

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crimeo t1_j4ci1tl wrote

We know it's space itself because everything appears to be moving away from us, personally.

The only two ways that's geometrically possible is if we are actually uniquely special and the center of the entire universe, or if everything is moving away from everything else. The second one is considered the only plausible of the two options.

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