# B Universe is expanding?

1. Apr 18, 2016

### kenny1999

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??

2. Apr 18, 2016

### phinds

The universe is expanding OUTSIDE of gravitationally bound systems such as our galaxy. I recommend the link in my signature.

3. Apr 18, 2016

### Burnerjack

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.

4. Apr 18, 2016

### phinds

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.

5. Apr 19, 2016

### Droidriven

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?

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.

6. Apr 19, 2016

### phinds

Sort of, yeah. Sections of the band (bound galactic clusters) don't stretch at all.

There's nothing at all odd about it. There is no proper motion involved so no speed limit is broken.

7. Apr 19, 2016

### Jim60

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.

8. Apr 19, 2016

### tobyr65

9. Apr 24, 2016

### Staff: Mentor

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