Four questions about cosmology

[Cosmobrain]

I have gathered some questions that have been bothering me for quite a good time.I hope you can ansswer them and help me out. An one paragraph long answer is good enough, no need to go so deep in each one. This can take some time but I hope you'll learn a lot too by answering it
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1. What if there IS a center of the Universe? By analyzing the cosmic microwave background, we can see microwaves that got redshifted due to the expansion of space, right? And the CMB forms like a sphere around the observable Universe, I assume. If we travelled billions of ly to any direction, the waves coming from that direction would be less redshifted than the ones on the other side, right? So can we find the center of the Universe that way?

2. The inflation theory is a complement of the Big Bang theory added to describe the similar temperatures at opposite sides of the Universe. If the Universe was at a single point and it was in contact, why is a theory of inflation needed?

3. Why is the Universe so asymetric? It would make much more sense to say that all galaxies are identical and are at the same distance away from each other, right?

4. What if the whole observable Universe is actually the whole Universe? Howcan we know that there is more light coming?
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That's it so far. I don't wanna flood you with questions. Thanks!

[Schneibster]

I have gathered some questions that have been bothering me for quite a good time.I hope you can ansswer them and help me out. An one paragraph long answer is good enough, no need to go so deep in each one. This can take some time but I hope you'll learn a lot too by answering it

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1. What if there IS a center of the Universe? By analyzing the cosmic microwave background, we can see microwaves that got redshifted due to the expansion of space, right? And the CMB forms like a sphere around the observable Universe, I assume. If we travelled billions of ly to any direction, the waves coming from that direction would be less redshifted than the ones on the other side, right? So can we find the center of the Universe that way?

 

It's too late. The closest the "edges" can be is past the horizon. Unless, of course, we invent FTL-- which seems highly unlikely at this time.

 

If there is, we can't ever find it, in other words.

Edited April 5, 2014 by Schneibster

[Johnny Electriglide]

There has been the description that it is like we are on the surface of a slowly expanding balloon. We can only see so far, and have not found the giant star desert that the center of the universe would be. The CMB has not been noted for red shift, but explains the "asymetry" of galactic clusters.

They say inflation was in the first 1/43rd of a second of the universe's beginning, and the expansion was far faster than light speed in that brief moment.

We can't even observe our universe very well, and certainly not more than the billions of light years we can see, into the past. We can only imagine "now" to places that are so distant and so in the past by the restriction of light speed.

If this universe is like the surface of an expanding balloon, then how about other "balloons" beyond ours? We really can't know, at least in this life.

[Schneibster]

2. The inflation theory is a complement of the Big Bang theory added to describe the similar temperatures at opposite sides of the Universe. If the Universe was at a single point and it was in contact, why is a theory of inflation needed?

 

What makes you think it was a "single point?" It was a vacuum fluctuation. That's small, but it's not a single point; and it instantaneously began expanding, and in 10^-43 of a second (not 1/43; in fact, less than a billionth of a billionth of a billionth of a billionth of a billionth of a billionth of a second), the inflaton-- that is, the cosmological constant, or the Casimir force, or vacuum energy, or zero point energy, or lambda, they're all the same thing-- underwent vacuum decay, and all of its energy was dumped into the newly formed universe and made the Big Bang. Obviously the vacuum fluctuation was bigger than 10^-43 light seconds (that same billionth of a... sequence minus one "billionth," of a foot; something on the order of a Planck length, IOW). As a result, locations on opposite sides of the universe have never been in causal contact. However, locations on opposite horizons are not "opposite sides of the universe," even if the universe is the smallest it can be given the other evidence we have of its size. In fact the largest the horizon can be is about 2/7 of the diameter of the minimum possible universe right now; that will change over time.

 

Incidentally that's not a very good description of the reasons for the addition of inflation theory to the Standard Model, ΛCDM. There are quite a few (I think ten or more) reasons for it, and most recently we've seen gravity waves it predicted in the CMBR. But we can get into that later. Let's get each of your questions answered first.

3. Why is the Universe so asymetric? It would make much more sense to say that all galaxies are identical and are at the same distance away from each other, right?

 

Actually, the universe is remarkably homogenous (symmetric). We are only beginning to detect asymmetries at the ten-billion-light-year scale, for example the Great Wall in Hercules. The answer is, inflation expanded the sizes of tiny quantum fluctuations within the inflating universe from submicroscopic to that ten-billion-light-year scale. These quantum fluctuations also of course exist at scales down to the million light year scale, where clusters of galaxies have formed due to the compression of matter by gravity. So the reasons for these asymmetries are similar, but on vastly different scales.

 

Do you have some other definition of "asymmetry" that you'd like to present?

4. What if the whole observable Universe is actually the whole Universe? Howcan we know that there is more light coming?

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That's it so far. I don't wanna flood you with questions. Thanks!

 

The galaxies near the horizon would behave differently than they do if there were no other galaxies beyond them.

 

There isn't any more light coming from anywhere beyond anything; expansion is now accelerating and every year we can see a light year farther, but all the galaxies have moved out more than a light year. That's due to dark energy.

 

There you go!

 

Feel free to keep asking, I like answering questions like this, it exercises my knowledge and makes me look stuff up sometimes, which generally results in me getting smarter.

 

Oh, and good questions! +1 for that.

BTW if anyone wants real exact numbers,

 

The primal vacuum fluctuation was on the close order of the Planck Length, 16 x 10^-36 meters.

Inflation is estimated to have finished by 10^-43 seconds, by which time the universe was at least a hundred billion light years across.

Inflation was stopped by vacuum decay. At this point, the cosmological constant (which, because it is not mass or energy can be freely created along with the creation of space; it is, in fact, the exponential feedback of increasing spacetime creating increasing cosmological constant creating increasing spacetime that results in the inflation in the first place and makes it so large so fast) dumps all its energy into the newly created empty spacetime.

 

Wikipedia has a timeline; it wasn't accurate the last time I was there, they were still trying to put the inflation after the Big Bang.

Edited April 6, 2014 by Schneibster

[swansont]

1. What if there IS a center of the Universe? By analyzing the cosmic microwave background, we can see microwaves that got redshifted due to the expansion of space, right? And the CMB forms like a sphere around the observable Universe, I assume. If we travelled billions of ly to any direction, the waves coming from that direction would be less redshifted than the ones on the other side, right? So can we find the center of the Universe that way?

The CMB represents a frame where there is a velocity, not a position. You can be at rest WRT the the CMB anywhere. It would be be different, as far as I know, if you were somewhere else.

[beefpatty]

 

What makes you think it was a "single point?" It was a vacuum fluctuation. That's small, but it's not a single point; and it instantaneously began expanding, and in 10^-43 of a second (not 1/43; in fact, less than a billionth of a billionth of a billionth of a billionth of a billionth of a billionth of a second), the inflaton-- that is, the cosmological constant, or the Casimir force, or vacuum energy, or zero point energy, or lambda, they're all the same thing-- underwent vacuum decay, and all of its energy was dumped into the newly formed universe and made the Big Bang.

 

We should be careful to distinguish between the vacuum energy during inflation and that caused by dark energy today. While inflation occurs from a vacuum energy, the inflaton is a scalar particle and should have some underlying particle physics. The cosmological constant is just a measure of the energy density of free space. It could be a process left over from inflation, or similarly a field decaying to it's vacuum expectation value like the inflaton, but in general we separate the two from each other.