Motion of the Primordial Universe Revealed

neutron_p writes "New results from an instrument located high in the Chilean Andes (the Cosmic Background Imager) are giving researchers a clearer view of what the universe looked like in the first moments following the Big Bang. Cosmologists observe a time in the universe's distant past when atoms were first forming. The findings reveal the first movements between these "seeds" that ultimately led to clusters of early galaxies."

Comments

Reading the article

[tod_miller]

New data suggests that the universe expanded rapidly in the first instants after the Big Bang

Which lead to renewed enthusiasm about the name, as apposed to previous suggestions:

The Big Yet Apathetic And Lethargic Singlular Point Of Spontaneous Existence Creation By Magic.

I believe that the Big Bang we hear are echoes of cosmic events that may have happened anywhere. I also think that there was a real bang, when reality and existence in thier mortal plane was created.

If you think that is more crazy than an inexplicable universe full of toothpicks, then please by all means explain yourself.

This has always confused me

[El]

Don't microwaves move in a straigth line? In which case, shouldn't any radiation created by the big bang be at least 13 billion light years away from it's point of origin by now? So, unless they are reflecting off something or the universe wraps around at the edges, why can we still detect them? If they are reflecting off something, then aren't they really just mapping the density of whatever they are reflecting off of? I guess I'm just not clear on what makes this background radiation run around in circles...

Re:This has always confused me

[xenoarch]

First thing, Microwaves and all Light do travel in a stright line, as long as space is not curved, if its curved then the light itself is curved also. Large bodies with high gravity curve space and this is what causes gravitational lensing, bending the light around it.

One of the theories is that the universe is a torus. (donut shape, now don't eat it Homer) But this isn't what makes us see it.

To clear up your confusion, the way I see it is this background of the radaiton is the surface of that intial ball of matter of the universe. We exsist within that ball. The light that was given off 13.7 billion years was in the visable wave lengths, but since it was expanding away from us, this light was red shifted all the way down into the microwave range.

So this microwave light we are percieving, is the light being emmited by the matter shell of the early universe at the time of the early universe. Its only taken this long because the shell was moving away from us.

Clear as Mud?

Re:This has always confused me

[TMB]

Don't microwaves move in a straigth line?

Yes (well, technically it doesn't in a curved space-time, but since the universe is globally flat, any deviations are extremely small on average).

In which case, shouldn't any radiation created by the big bang be at least 13 billion light years away from it's point of origin by now?

Yes.

So, unless they are reflecting off something or the universe wraps around at the edges, why can we still detect them?

Uh... here's where you've lost me. They're going in straight lines - that's why we can see them. When you look straight up and detect CMB photons, they were emitted from a point 13 billion light years away in that direction. When you look straight down, those photons were emitted from a point 13 billion light years away in that direction.

[TMB]

Re:This has always confused me

[xenoarch]

At the time of this radation's "birth" the universe was said to be only as big as either the solar system or the galaxy, so every point in the universe is relativly close to one another, comapred to today. 10^5 verses 10^10, so we could say to see it everywhere we were close to the center of the universe as was every other place. The light from other places of the universe ould only be at most 200,000 years older.

As to the first part. It is due to the severe redshifted nature of this radation that puts it so old and able to be so old. Its one of the wierd poperties of light. At least the accepted theory states.

Also of note the universe is still accelrating which blows my mind.

I like to do math and when trying to comeup with numbers to go through (which i haven't yet) i found a good explnation here.

This type of confusion is common I believe when dealing with non mechical physics. Relies on fundementals elsewhere that the eggheads can't explain in even a 10 minute sound bite to us laymen.

I've had similar confusion with the idea of the light barrier, not even my college physics teachers could straighten out until I read Brian Greene's "Ellegant Universe"

Re:This has always confused me

[Hard_Code]

The answer in layman's terms I think is: yes, the universe expanded faster than light, which is why we still see light from the big bang - it didn't all "whoosh" past us.

Re:This has always confused me

[Zaak]

...the universe would have to have expanded at several times the speed of light in those first 400,000 years...

Yes. During inflation the universe expanded not at several times the speed of light, but rather doubled its size every 10^-34 of a second. After about a hundred doublings the inflationary period ended and expansion slowed to (locally) sub-light speeds.

The microwave background didn't come from the big bang though. It was actually emitted from the surface of last scattering when the universe became transparent for the first time--around 300k years after the big bang.

...we'd have to be sitting at pretty close to the center of the universe...

The "center of the universe" is not well-defined. If the universe is topologically closed, then it has neither center nor boundary, like the surface of the earth. If the universe is topologically open, then it is infinite in size and similarly has neither center nor boundary.

TTFN

Re:This has always confused me

[wanerious]

It's not a foolish question, but a very subtle and often misunderstood point. It is necessary in cosmology for *coordinate* velocities to exceed that of light. That's ok. What's not ok is for any arbitrary clump of matter to exceed the speed of light getting from one point to another. In reference to the balloon example, it's ok for the balloon to expand as fast as it wants, but we have a speed limit in getting from one dot to another.

Re:This has always confused me

[Zaak]

Pardon me but if the universe expanded in such a manner wouldn't that be against the theory of relativity. What about breaking causality?

Well IANAP, but I'll explain what I understand of it.

Relativity requires that no signal can travel faster than the speed of light. During inflation, nearby parts of the universe move away from each other faster than the speed of light. However, because there is no signal traveling FTL, causality is not violated.

TTFN

Re:This has always confused me

[Christopher Thomas]

If I understand you correctly then you are saying that if there is a particle at some point and the point is moving because of expansion then the particle will not move with the point (or with the same rate)

The particle moves with the point. This causes particles at sufficiently distant locations in the universe to be moving faster than light relative to each other.

This is still consistent with relativity. The usual way of explaining this is to say that the particles are standing still, and space itself is moving. I'm not sure that explanation is really meaningful, but it's handy as an introduction.

The upshot of relativity is that you only get FTL relative motion through movement of space itself (corresponding to certain types of curved spacetime), and that once something is moving FTL relative to you, you aren't going to see it again (it's fallen down a black hole or is past an expanding universe's horizon of observable space). Certain even more exotic geometries of spacetime let you see these things again, but it's an open question whether or not this can actually happen (these are the kinds of geometries you use for time travel).

If space is not deformed - i.e., you have flat space, with no extremely large masses - then you aren't able to cause particles to move FTL relative to you, no matter what reference frame you're observing from.

I hope this clears things up a bit.

Re:This has always confused me

[Alsee]

Several others have tried to answer, but I don't think you got any clear and correct answer.

The thing that is confusing you is that you have the very common image of the big bang being like a hand grenade explosion in the vacuum of space. You are picturing there is some point in the middle of our universe that was the center, from which everything spread out. The big bang is is no normal explosion, it was an explosion of space not in space, and there is no center in our universe.

In order to explain a picture of what it *is* like we need to imaging the universe is 2D instead of 3D. Imagine we live in a 2D sheet of rubber rather than 3D space. Now lets curve that sheet of rubber around into a ballon. We live in the surface of that ballon. There is *nothing* inside or outside the skin of the ballon - not even a vacuum. Our universe *is* the skin. You, me, the sun, the stars, they are specs within that skin.

That ballon is expanding. In the past the was smaller. Imagine running backwards, srhinking that ballon down to a point. That point would be the big bang. It was in the past, sort of in the center of our current ballon. That point is not anywhere in our universe, it is not on the skin of the ballon.

Now to explain the microwaves we see from the big bang. When you run backwards all of the stars and dust and gas were closer together in the skin of that smaller ballon. Go back far enough and everything in our universe was squashed togther - everywhere. There was very little space itself for it all to fit in. All of the space in our universe was filled with a dense hot soup of glowing particles.

So that glow came from everywhere in our universe. No matter what direction we look, that point umpteen billion light years away was glowing umpteen billion years ago. The very spot we are at now was glowing umpteen billion years ago, and if someone billions of light years from here were to look at us they would see that old glow from here.

Did that make sense?

-

More information

[TMB]

The press release at the CBI website is much more informative.

The big news is that they've measured the polarized power spectrum, and it agrees extremely well with the theoretical predictions. Which means that not only do the density fluctuations match what's expected, but the matter is moving in the gravitational field of those density fluctuations exactly as expected.

[TMB]

Re:The motions

[mcmonkey]

Put your hands on your hips (or somebody else's) and bring your knees in tight.

Re:This has always confused me - me too

[TMB]

Presumably the universe and the matter in it could not expand more rapidly than light.

Those two statements are different... matter cannot move faster than the speed of light, but the expansion of the universe can.

In fact, the expansion of the universe doesn't have a physical velocity associated with it - it's a fractional rate of change. So if the universe expands at "0.1 Gyr^-1", then proper distances increase by 10% per gigayear (*). If the distance you're interested in is larger than 10 billion light years, then it increases at faster than the speed of light. But that same rate of expansion corresponds to a much smaller velocity if you're dealing with a much smaller distance.

A photon's important length is its wavelength, lambda. This wavelength increases because of universal expansions at a rate of lambda * H_0... or about 10^-24 m/s for an optical photon (wavelength of 500nm). But this isn't even a real velocity, it's just the rate of change of the wavelength - even if it were greater than the speed of light, it has nothing to do with causality.

(*) This rate of expansion (also known as the Hubble constant, H_0) is, for historical reasons, usually expressed in units of km/s/Mpc... but you'll notice that the km and Mpc cancel out, giving a fractional rate. If the Hubble constant is 70 km/s/Mpc (consistent with current measurements), that is equal to 0.072 Gyr^-1.

[TMB]