If the big bang was a uniform explosion...

[TheChort]

OK, here's what I know (probably with many inaccuracies, but feel free to correct me):
The "oldest" picture of the universe we have is the Cosmic Microwave Background Radiation image.
It shows a constant background radiation that exists throughout the universe at a constant 3 Kevin (K).

We initially believed that there were no fluctuations in that radiation level, until we took the picture I linked to above, which shows variances of micro kelvins. Those differences are evidence showing slight differences that could account for hydrogen coming together to form stars, and eventually, other galaxies.

But what theories do we have to explain the initial differences in these radiation levels?

 

[TheChort]

Ok, I just finished reading the thread about how we know the age of the universe ... Text
and it was pretty fun

silverpig said

So what is this stuff? Well there are 4 types that fit so far. Matter, dark matter, radiation, and {vacuum energy, quintessence, whatever you want to call it}. Matter is the self gravitating clumpy stuff we know and love. Dark matter is similar to matter except it is very weakly interacting. It gravitates but goes through things. Radiation is the standard stuff we also know and love. The other thing is something that drives the expansion of space.

So you take this equation, mix in varying amounts of this stuff, make sure it adds to 1 (this is a condition of a flat universe), pack it all together into something very small, add some quantum fluctuations, let your simulation rip and see what happens.

I think what I'm basically asking is where the "quantum fluctuations" came from.

 

[Nexworks]

I think what I'm basically asking is where the "quantum fluctuations" came from.

I think that could only be answered if we knew WHY the big bang occured.

 

[silverpig]

The big bang started off as something very small, so small that quantum mechanics defined how everything worked. In this very small thing there were random quantum fluctuations in density/energy. There was a very short period of time called the inflationary period where the universe grew from a very small size to a still-very-small-yet-many-orders-of-magnitude-larger size exponentially. All of these quantum fluctuations were then frozen out into the macroscopic world.

Do some reading on it, but I seem to recall that this expansion actually exceeded the speed of light (allowed because no piece of matter was moving through local space at faster than c, but the space itself was expanding such that the distance between two points was increasing faster than c).

 

[PepperBreath]

On top of what's already been mentioned, "clumping" as it where of the universe isn't unusual. They've shown in experiments in microgravity that different materials will all tend to clump together when left to their own devices. The range was from salt, dirt, water, etc.

 

[Chaotic42]

Originally posted by: silverpig
Do some reading on it, but I seem to recall that this expansion actually exceeded the speed of light (allowed because no piece of matter was moving through local space at faster than c, but the space itself was expanding such that the distance between two points was increasing faster than c).

So theoretically with you standing 2LY away, I could write a message down on a piece of paper expand the space between the paper and me, compress the space between the paper and you, and get a message to you in less than two years?

 

[f95toli]

Originally posted by: Chaotic42

Originally posted by: silverpig
Do some reading on it, but I seem to recall that this expansion actually exceeded the speed of light (allowed because no piece of matter was moving through local space at faster than c, but the space itself was expanding such that the distance between two points was increasing faster than c).

So theoretically with you standing 2LY away, I could write a message down on a piece of paper expand the space between the paper and me, compress the space between the paper and you, and get a message to you in less than two years?

Yes. In theory this is (as far as we know) possible, although it would require an enormous amount of energy.
Btw, this is how the warpdrive in Star Trek is suppose to work.

 

[TuxDave]

Originally posted by: Chaotic42

Originally posted by: silverpig
Do some reading on it, but I seem to recall that this expansion actually exceeded the speed of light (allowed because no piece of matter was moving through local space at faster than c, but the space itself was expanding such that the distance between two points was increasing faster than c).

So theoretically with you standing 2LY away, I could write a message down on a piece of paper expand the space between the paper and me, compress the space between the paper and you, and get a message to you in less than two years?

But then again, what would 'compressed space' be perceived as. If you compress space and you exist in that space and everything around it relatively looks the same, would you not notice anything changing?

I think it would be a little more obvious from a 3rd party observer looking at our space but not existing in it but for people in it, I have a weird intuition telling me that you wouldn't be able to tell any warping of space if you exist in it meaning it'll all look straight and normal to you. You can find evidence of warped space when you start observing strange phenomenon like a star that gets duplicated in space but to you it looks like their both in straight lines right in front of you.

 

[silverpig]

Originally posted by: TuxDave

Originally posted by: Chaotic42

Originally posted by: silverpig
Do some reading on it, but I seem to recall that this expansion actually exceeded the speed of light (allowed because no piece of matter was moving through local space at faster than c, but the space itself was expanding such that the distance between two points was increasing faster than c).

So theoretically with you standing 2LY away, I could write a message down on a piece of paper expand the space between the paper and me, compress the space between the paper and you, and get a message to you in less than two years?

But then again, what would 'compressed space' be perceived as. If you compress space and you exist in that space and everything around it relatively looks the same, would you not notice anything changing?

I think it would be a little more obvious from a 3rd party observer looking at our space but not existing in it but for people in it, I have a weird intuition telling me that you wouldn't be able to tell any warping of space if you exist in it meaning it'll all look straight and normal to you. You can find evidence of warped space when you start observing strange phenomenon like a star that gets duplicated in space but to you it looks like their both in straight lines right in front of you.

I'd have to think about it a bit more, but I think you'd experience time dilation. Gravitational fields are curved spaces and you feel time dilation. I'm not sure if this extension works though without more thought.

 

[heymrdj]

I still have to ask where big bang material cam from in the first place. As far as I go abck it comes to, Where did that come from.

 

[f95toli]

Originally posted by: heymrdj
I still have to ask where big bang material cam from in the first place. As far as I go abck it comes to, Where did that come from.

Mass is just energy and the total energy of the universe is, as far as we know, exactly zero.
If you add all the energy "contained" in mass (E=mc^2) +kinetic energy+all the photons etc to the negative potential gravitational energy you get zero.
Note that there is nothing "weird" about negative energy. In this case it simply refers to the fact that objects are moving AWAY from each other despite the fact that gravity is an attractive force; hence the potential energy is negative.
This is incidently known as "The free lunch" in cosmology.

 

[Analog]

Originally posted by: f95toli

Originally posted by: heymrdj
I still have to ask where big bang material cam from in the first place. As far as I go abck it comes to, Where did that come from.

Mass is just energy and the total energy of the universe is, as far as we know, exactly zero.
If you add all the energy "contained" in mass (E=mc^2) +kinetic energy+all the photons etc to the negative potential gravitational energy you get zero.
Note that there is nothing "weird" about negative energy. In this case it simply refers to the fact that objects are moving AWAY from each other despite the fact that gravity is an attractive force; hence the potential energy is negative.
This is incidently known as "The free lunch" in cosmology.

I thought matter is accelerating away from each other, that gravity will never "pull back" all the matter again. This is supposedly due to dark energy. Any thoughts?

 

[silverpig]

Matter isn't necessarily accelerating anywhere. The space between matter seems to be expanding causing the perceived effect of acceleration.

Dark energy is so much of a mystery right now that we have absolutely no idea what it is. Heck, dark matter, which should be much simpler, is still beyond us.