Universe is expanding?

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Is the universe now expanding?

In that case, the earth should be spinning away from the Sun right?

I've heard that the moon is leaving the Earth 4cm-5cm every year

If we are spinning away from the Sun, average temp. on the earth must be decreasing

Is there any scientific estimation on how long would it be before the temp. drops to an extent that we cannot survive any more??
 

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  • #2
phinds
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The universe is expanding OUTSIDE of gravitationally bound systems such as our galaxy. I recommend the link in my signature.
 
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Just an idle question: Does the universe expand at the same rate everywhere? We know that spacetime is not the same everywhere, so with that I began to wonder about the possible variables of expansion.
 
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phinds
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Just an idle question: Does the universe expand at the same rate everywhere? We know that spacetime is not the same everywhere, so with that I began to wonder about the possible variables of expansion.
Outside of bound systems, the rate of expansion is uniform, but bear in mind that what that means is that things twice as far away are receding at twice the recession velocity. The "rate" is a rate per unit distance and it's something like 1/144th of a percent per million years, so locally (e.g. between nearby galactic clusters) it exhibits little effect but on large cosmological scales it's enormous and the things at the far reaches of the Observable Universe are receding at something like 3c.
 
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locally (e.g. between nearby galactic clusters) it exhibits little effect but on large cosmological scales it's enormous
Like a rubber band being pulled at both ends? In that as it is pulled, the ends(large cosmological scale) stretch sooner than the rest and stretches more, "faster" than the rest of the band and as it is pulled, the center of the band(your "locally") flexes the least and flexes last, approximately?

and the things at the far reaches of the Observable Universe are receding at something like 3c.
This is where I'm looking for something good to "chew" on for a while that explains how the far reaches are receding at 3c, something that explains exactly in detail how they are doing that considering c being the "cosmic speed limit". I understand that it isn't exactly a movement or a speed thing but that doesn't quite do it for me.
 
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phinds
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Like a rubber band being pulled at both ends? In that as it is pulled, the ends(large cosmological scale) stretch sooner than the rest and stretches more, "faster" than the rest of the band and as it is pulled, the center of the band(your "locally") flexes the least and flexes last, approximately?
Sort of, yeah. Sections of the band (bound galactic clusters) don't stretch at all.


This is where I'm looking for something good to "chew" on for a while that explains how the far reaches are receding at 3c, something that explains exactly in detail how they are doing that considering c being the "cosmic speed limit". I understand that it isn't exactly a movement or a speed thing but that doesn't quite do it for me.
There's nothing at all odd about it. There is no proper motion involved so no speed limit is broken.
 
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They say you can find the age of the universe with the expansion (Hubbles constant), when I tried I got over 14 billion years, must have done something wrong.
 
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Is the universe now expanding? Hawking said it could be a matter of expansion and contraction. Like that paddle and ball thing. It may stretch out and be pulled back in. It sounds better when he says it though. :)

In that case, the earth should be spinning away from the Sun right?

I've heard that the moon is leaving the Earth 4cm-5cm every year

If we are spinning away from the Sun, average temp. on the earth must be decreasing

Is there any scientific estimation on how long would it be before the temp. drops to an extent that we cannot survive any more??
 
  • #9
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A number of posts advancing and discussing speculative personal theories have been removed.

Everyone: Please remember the Physics Forums rules prohibiting such postings, and if you do see one please report it instead of replying. The mentors are NOT paid based on the number of posts we remove, so you're not doing us any favors when you give us more work to do.
 
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