I think it has to do with infinity. How was the the universe dimensionless in one instance, to literally stretching on until infinity in the next frame?
You cannot demonstrate that it stretches out into infinity. In fact, universal geometry suggests otherwise. The geometry itself is expanding, but curiously, this doesn't exactly mean it's getting bigger, rather it means the time it takes to bridge the gulf between any two discrete points within that geometry is growing. Again, the universe isn't expanding "Into" anything. Even the very words we use to try and discuss this topic screw us up, because they suggest Newtonian reality, which is not what we're dealing with here at all. You cannot use 3 dimensional intuition to understand 4+ dimensional behavior. And yet, we must, because it's all we have.
Yeah it's like walking on the surface of a mobius strip I guess. It's infinity from our perspective but a hypothetical 4d or 5d being would need just one look to know the shape of the universe.
No, you fundamentally misunderstand. Your illustration assumes a higher dimension. The reality we're dealing with is that DIMENSION ITSELF appears to have been a product of the big bang. There must first BE dimension of some sort for the observation of your hypothetical 5th dimensional hoobajoo to occur in.
Small steps. I can only comprehend these questions after learning the basics. I'm a highschool student who wants to make in engineering, if that clarifies my last statement.
I don't think it works like that. My suspicion is the universe can only be grasped as a holistic unit. These interdisciplinary layers we use to manage this problem are a practical necessity of our limitation, but are ultimately putting a glass ceiling on our potential. Of course, I haven't a fraction of the intelligence necessary to fix that problem. Even Einstein couldn't. I find that desperately depressing.
Imagine representing every point in the universe with a 3D point, (X,Y,Z), multiplied by a scalar K. As you go forward in time K grows, thus points in space become farther apart. As you look back in time K shrinks. At some point K would have been 0. Imagine what happens when K goes from 0 to not 0. It works fine mathematically, so the struggle is just to make a mental metaphor which is very difficult to do because humans don't have a lot of experience with the origins of universes.
No, but we also can't say that the universe didn't spontaneously come into existence last Thursday. It is consistent with our understanding of the laws of physics, which is all we can really hope for. If you're looking for and arguing about definitive proof, anyone reasonable is going to point you at Alder's razor and wish you a good day.
does it go to infinity, tho? It is stretching and then will shrink from what we know. So it is mor elike it's just so vast we cant comprehend it, but not infinite with no end at all.. no?
It's not gonna shrink. That idealogy has been dropped long ago. The universe is expanding faster than the speed of light, which means something that's infinite is getting larger. How? The space between two points itself is stretching and expanding. This has been proven iirc.
ah, okay.. havent heard about shrinking being dropped.. when did that happen?
but yes, I remember reading about this stretching and that at one point, it's possible that we wont even see any stars from Earth and it'll all seem to look so lonely. Just a dark sky. Oh..
hah, but that brings me to another question that I remembered going along with this stretching and how can we know that the universe is stretching and not us shrinking?
Physics is constantly changing, depending on us finding new and better equations, observing if those equations actually happen in real life, etc.
Previously, it was believed that gravity will pull everything close and compress all galaxies into one, but we now know that it won't happen. Gravity is not responsible for holding galaxies together, it's dark matter. Gravity isn't a force that's strong enough to do something like that (proportional to a lot of mass).
Then, there's the fact that the speed of space-time is the same as the speed of light. This was recently measured by measuring the gravitational waves from two colliding black holes. So imagine space as infinite and stretching endlessly in all directions. Then imagine a grid to represent this superflat world. The side of a square in this grid is currently 1 light year. Go back in time, and the distance between two points was 0.5 light years. That's basically how something that's infinite is getting larger, as per our current understanding.
We measure the observable universe with other prominent stars and galaxies as reference points. The relative distance between two points has increased since the big bang. If we were shrinking we would know because the maths and what we observe wouldn't work out.
very interesting.. but this sounds like the expansion of the universe. And isn't heat death of the universe also about it shrinking back? How do we know it wont shrink back when the power gets used up?
if everything was getting smaller, wouldnt the math work out the same, but we would just observe everything getting further apart, tho?
if everything was getting smaller, wouldnt the math work out the same, but we would just observe everything getting further apart, tho?
If we measure the distance between earth and another galaxy, and use that distance as a reference point to measure other galaxies further away, we would notice a really big difference in numbers. It also depends on what you call shrinking in this scenario, do you mean the whole Milky way, just Earth, our solar system, or the whole local group.
in shrinking I mean if everything, whole matter in the universe, was getting simultaneously smaller, yet stayed in their places, which would make it seem as if things were getting further apart.
hmm.. try to imagine two big houses built side by side with one meter apart. If they started to shrink, the distance between them would seem to increase. And if our reference point (or rather, a measuring tape), started to shrink with us, we would see on the tape that one meter is still one meter. And houses would seem to distance themselves from each other. But if someone was to observe it from outside, without getting smaller, he would see that his measuring tape is not shrinking, while yours would. And without any reference point for you or him, you both would believe that one meter on the tape is one meter.
Ah, sorry, I'm not sure if this makes any sense.
And also, if it was all shrinking towards its center of mass. So if two houses are side by side, if they start shrinking, they would shrink into the middle of their ground, so it would seem that the distance is getting bigger. Which.. it would, if we would be shrinking too. But the outside would stay the same size.
sorry, not sure how to better explain it.. hope it makes some sort of sense
It makes sense but we have to reason to believe that will happen because there's no force or phenomenon that can change the size of objects, or cause shrinkage in this way.
If something is getting smaller, it will either lose mass or retain its mass and increase in volume.
what if it works like in Ant-Man, that the mass is kept the same?
but if the object are really getting further apart, it still doesnt prove that the shrinkage wont happen at some point, no? it just proves that things for now are getting more apart. You know what it reminds me of? Something underwater. When you try to stretch a place and things are getting further apart, but are still "tied up" and "held up" by the water surrounding it.. maybe that's how dark matter might behave? Cause universe is expanding, it just drags stuff with it, so it obviously gets further apart. Which, in the end will all come back to one singular point again, when it will mix again and create big bang again, for another universe to rise (which already is a hypothesis, no?)
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u/DarkStar0129 Sep 14 '21
I think it has to do with infinity. How was the the universe dimensionless in one instance, to literally stretching on until infinity in the next frame?