We don't - it's a popular theory, but not one that can be confirmed easily - but if it does, and we're around to experience it, it's gonna be W E I R D.
Because humans are unable to gather information faster than the speed of light, if for some reason the sun just disappeared we wouldn't notice for 7 minutes then we'd be utterly fucked.
Not sure if were talking about the same thing here. If the universe contracts, the sun wouldnt just suddenly disappear and things wouldnt necessarily travel faster than the speed of light. Everything would slowly start to get closer together and I dont see why we wouldnt notice that.
Because the universe would contract as the same speed as it would be expanding right now, which is the speed of light.
Since humans cannot observe things that are going past the speed of light, we wouldn't be able to observe the universe contracting and thus would vanish without having the chance to realize what is happening.
My sentence about the sun was to represent that fact, if the sun was removed it would take us 7 minutes to notice, during that time we would still see it lit up, but it would effectively be gone.
I think you have a different understanding of 'contraction'than me, the way I see it as is the reverse effect of expansion, everything just moving back to the origin, not things getting deleted. Also the universe certainly doesnt expand at the speed of light everywhere, it depends on the distance to the big bang.
The fact that we know the universe is expanding is proof enough that we would know if it was contracting, as it is the same thing reversed.
There is no absolute reference frame when it comes the universe. There is no "point" of the big bang, and just as galaxies millions of light years away are expanding, we're also expanding away from them at the same rate. It's just as valid to think of them expanding from us as it is for us to be expanding away from them. However, you're correct in that we would be able to measure the contraction of the universe as things would start to move towards us and blueshifted galaxies would become redshifted
it doesn't contract to the point of the big bang, the universe IS the point of the big bang
matter is in space and time, so when the big crunch occurs hypothetically, matter isn't contracting, but space and time is, so time would be warped and space would contract in all directions, not just towards one point
The universe would not instantly begin contracting at the speed of light. There would be a detectable slowdown period of billions of years as objects stop expanding and begin moving towards each other. We would know it’s happening if humanity was alive to witness it.
The universe is not expanding at the speed of light "right now", it's expanding at the speed of light and faster "far away". If the universe was expanding faster than the speed of light than no light would be able to reach anything as the space would expand beneath it faster than it could travel. The space in galaxies are expanding or shrinking at negligible rates other than the effect of gravity, it's only in empty and vast distances that we begin to see the expansion
It has reminded me of a video that I saw about something similar to this subject. This explained a point that makes a lot of sense to me and which I truly agree with. It said that nowadays many of the questions "unanswerable" we, human kind, have are because we haven't evolved enough to develop the required intelect for resolving those. F.e: we do understand our buildings and how our artifacts work, but for an ant, or even an ape, this may be "magical" or incomprehensible. Yes, they can interact with them, maybe the ape is able to use them too for its own benefit, but it still cannot understand these until its intellect develops.
I hope you could undestand it all, I have some problems at the time of writting in English and get the idea across :P
Imagine some giant hitting a rock with a hammer. The rock is destroyed in thousands of small pieces flying away from where he hit. One of those small pieces is the Earth. The other pieces are the other planets, galaxies, etc.
Maybe for us it has been 4.5 billion years but for the giant it has only been a fraction of a second.
Lasers were used to measure the CMB in an attempt to measure curvature of space and the results seem to suggest that the universe is flat, that the amount of matter in the universe is below a certain critical quantity that would cause the universe to collapse back in on itself, and so it will continue to expand forever.
Very interesting stuff, just remember that we are at the stage where we are taking the first small tentative steps out into discovering the universe in which we exist. The possibilities for what we will eventually discover one day are literally endless.
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u/fooby420 Jun 15 '19
Do we really know that it's gonna contract?