Submitted by No_Adhesiveness_6821 t3_11ag1e2 in space
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Comments
pzerr t1_j9rx8si wrote
Eventually the local area will grow by that rate. Or so the theory goes. At some point it will rip atoms apart.
But ya matter isn't faster than light. The expansion can exceed that but not matter. Is a big distinction and doesn't break casualty.
farox t1_j9rx9w8 wrote
t1: x x x x x x x x x x x x x x x x x x
t2: x x x x x x x x x x x x x x x x x x x
Each x is only one space further apart and has only "moved" a small bit compared to the distance of the first and the last. It took me a while to wrap my head around it as well, but it's space itself that is expanding, very slowly... but everywhere.
datapicardgeordi t1_j9s0a25 wrote
This. The vacuum pressure of black holes on the fabric of spacetime has been slowly increasing the distance between the granules that make up spacetime, calabi yau manifolds.
PyrorifferSC t1_j9s6gfv wrote
That includes matter, correct? So relative distances don't change between bodies/stars/galaxies
WULTKB90 t1_j9s8uzm wrote
Relative distance does change, but the galaxies aren't being pushed apart, rather more space is appearing between them, like a balloon being inflated, if you put 2 dots on the balloon then blow it up the dots don't move, rather the space between them grows, so they aren't moving faster than the speed of light, it is only faster when observed relative to an observer with enough distance.
When it comes to distances far enough out that they are receding away from an observer faster than light can travel the information from them is lost to the observer, without FTL travel the observer could never reach those locations so no information is traveling faster than the speed of light.
PyrorifferSC t1_j9s9dur wrote
That makes sense, thank you!
ieatdirt44 t1_j9shupj wrote
"So no information is traveling faster than the speed of light"---this is the key distinction. I feel like we are on the verge of no longer saying the speed of light, but the speed of causality or information seems more relavant.
[deleted] t1_j9sbfoq wrote
I don’t know if this question makes sense, but if every cubic centimeter of the universe is expanding due to dark matter, why doesn’t that include earth? Like I’m sitting here and neither me nor my house is expanding, so is the expansion only in the vacuum of space? If so, why?
WULTKB90 t1_j9sbzdg wrote
I used the 1mm per cubic centimeter as an example the actual expantion is much smaller though im not sure of the exact values.
But the answer is you, your house, the planet are all expanding. As far as I am aware gravity and the strong nuclear force holds us together against that force. Though some hypothosize that eventually the expantion rate will be great enough to tear atoms apart, its called the big rip. Edit: spelling.
Infernalism t1_j9rxlp6 wrote
You can use the old 'balloon' analogy.
Take a balloon and mark a bunch of dots on the outside of the balloon. Then blow it up.
As you blow it up, the dots expand away from each other, but they're not actually moving, are they? It's the fabric of the balloon stretching.
Likewise, the fabric of space is expanding and stretching. Dark matter is what keeps galaxies connected to each other through this expanding, but the galaxies are spreading apart from each other.
PyrorifferSC t1_j9s6pxo wrote
Does that actually increase the distance between bodies of mass though?
Infernalism t1_j9s73pg wrote
Between galaxies? yes. But something about the dark matter keeps galaxies coherent and condensed rather see the stars within those galaxies spread apart.
PyrorifferSC t1_j9s99qo wrote
Gooootcha yeah I remember that now. I knew there was some caveat about stars not separating from each other, that makes a lot of sense. Thank you!
Confident-Park-8211 t1_j9rybd8 wrote
speed limit is on the light propagating thru space. space can expand at any speed, speed of light has nothing to do with how fast space can expand.
thelastestgunslinger t1_j9ryud9 wrote
There’s a really interesting article about this on space.com
The really interesting thing is that special relativity (which is what says nothing can move faster than light) is about local spacetime, because it requires a local frame of reference. General relativity governs non-local references, and it’s indifferent to the speed of light.
> The notion of the absolute speed limit comes from special relativity, but who ever said that special relativity should apply to things on the other side of the universe? That's the domain of a more general theory. A theory like…general relativity.
It's true that in special relativity, nothing can move faster than light. But special relativity is a local law of physics. Or in other words, it's a law of local physics. That means that you will never, ever watch a rocket ship blast by your face faster than the speed of light. Local motion, local laws.
But a galaxy on the far side of the universe? That's the domain of general relativity, and general relativity says: who cares! That galaxy can have any speed it wants, as long as it stays way far away, and not up next to your face.
It goes deeper than this. Concepts like a well-defined "velocity" make sense only in local regions of space. You can only measure something's velocity and actually call it a "velocity" when it's nearby and when the rules of special relativity apply. Stuff super-duper far away, like the galaxies we're talking about it? If it's not close, it doesn't count as a “velocity” in the way that special relativity cares about.
Special relativity doesn't care about the speed — superluminal or otherwise — of a distant galaxy. And neither should you.
If I think about it too much i start to dislike it. But there it is (probably significantly oversimplified for laypeople).
[deleted] t1_j9rskxh wrote
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OldBob10 t1_j9schk9 wrote
The only thing faster than light is darkness, for no matter how fast light goes, when it arrives it finds that darkness got there first...
space-ModTeam t1_j9sikbu wrote
Your post has been removed. For simple questions like these please use the weekly "All space question" thread pinned at the top of the subreddit.
[deleted] t1_j9rsmqu wrote
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the_fungible_man t1_j9s01gb wrote
Sure it is.
>For example, galaxies that are farther than the Hubble radius, approximately 4.5 gigaparsecs or 14.7 billion light-years, away from us have a recession speed that is faster than the speed of light.
WULTKB90 t1_j9rsz5u wrote
No, any local area of the universe isnt expanding faster than the speed of light, rather the collective growth of the entire universe results in the areas further away from you expanding more.
Thing of it as each cubic centimeter of the universe growing by a millimeter per second. The further out you go the more milimeters per second are added but each local area only grows by 1.