Uniform temperature of the Universe

[Silvestru]

Hello,

 

I noticed a bad trend in science mass media where a information with factual basis is presented or a study made by qualified scientists and then comes the crazy media assumptions caused by a need to excite the uninterested public.

 

I had such a case with the Uniform temperature of the Universe. I was trying to find a pertinent explanation for this but all I was able to find is gibberish.

 

Can someone please explain the uniform temperature given the young state of the universe? (as I read and discount as gibberish is that the universe must have had expanded faster than the speed of light for this to happen).

[Bender]

The homogeneity of the universe is strong evidence of inflation theory, which states that when the universe was really young, it expanded really fast.

 

Space did indeed expand faster than light, but the matter in that space didn't move faster than light relative to that space, so no problems there. In fact, galaxies far enough outside the observable universe are expected to still be receding from us at a rate higher than the speed of light, which is why we'll never observe them.

 

One of the reasons inflation is introduced is because otherwise the universe before inflation would have been too big to reach thermal equilibrium, and there should be much larger variations in the cosmic background radiation. (At least, that is how I understood it)

[Silvestru]

Hmm I can make sense of that now. Thank you Bender. The way I read it first was colliding with my personal understanding of the speed of light (and gravity etc).

 

I think of c as the speed limit of this Universe like a computer that has the limit of x frames per second and will never be able to support more than that.

[Strange]

Another important point is that the speed of light limit only applies "locally" to things passing each other.

 

The expansion of the universe is a scaling effect (not a "speed"). This means that the speed at which any two points are separating is proportional to how far apart they are (by simple geometry). This means there are (and probably always have been) points that are far enough apart that the speed of separation is greater than c. We can even see galaxies that are receding at more than the speed of light.

[Silvestru]

We can even see galaxies that are receding at more than the speed of light.

 

Hmmm how can we see the galaxies if they are receding at more than the speed of light? haven't these speeds always been constant? I understand that the universe is expanding at more than the speed of light so how can we see these galaxies?

"a few minutes later"

 

Put the keyboard down Strange haha sorry I just found the answer explained in a very nice manner.

 

It perfectly explains all your points. Thank you!

 

Edited May 9, 2017 by Silvestru

[Delta1212]

That was pretty good. I could quibble a little bit at the end, since even a finite universe wouldn't need to be expanding into anything, but since nothing said was strictly wrong, like I said, quibbling.