Background Radiation from Big Bang

[Kizzi]

I saw a program once about these two scientists who discovered the background radiation of the Big Bang. Initially they thought the source was pigeons nesting in their attenna.

It seems odd to me that any background radiation was detected because since this radiation (which I think was microwaves) would travel at the speed of light away from the Big Bang Source, therefore having overtaken matter as matter moved away from the Big Bang Source, there would be no microwaves to measure!

Imagine a circular pond with a boat travelling from the centre of the pond to the edge. If a stone was thrown in the centre you'd watch the wave overtake the boat. The boat is like the earth, and the stone produced wave is like background radiation. At this point in time the radiation should have been well gone on its way to nowhere?

Am I missing some vital point?

Kizzi

[Tormod]

Originally Posted by Kizzi

Am I missing some vital point?

Yes. You forget that the radiation after the Big Bang permeated all of space (because all of space as we know it was formed during the Big Bang). It has therefore not travelled "from" somewhere but is all over the place - it travels from everywhere to everywhere, and as such looks the same no matter where in the universe you happen to be (this is called microwave anisotropy).

The temperature of the radiation at different times in the age of the universe can be calculated - this was in fact one of the most important scientific data used to estimate the age of the universe to 13.7 billion years.

Read more about this at the WMAP website:
http://map.gsfc.nasa.gov/m_uni/uni_101bbtest3.html

[Jay-qu]

if you didnt get what tormod was trying to say he means - the big bang didnt happen at a point and expanded out like an explosion, it happened every at once, it was an explosion of space...

[Kizzi]

So the Big Bang singularity wasn't a point in space because no space existed before the Big Bang singularity. At the time of the Big Bang space formed.

What I want to know is......1) did space expand like a growing shell of a sphere and matter formed everywhere in the sphere or 2) was space & matter everywhere immediately?

I am under the impression that 1) is the correct answer......I've heard the story that you can extrapolate the movement of stars/galaxys backward to imply that the Big Bang happened at a point, before which no point/space existed.

Kizzi

The WMAP link seems to indicate 1) is correct. Thanks for the link.

[Tormod]

We don't know what shape the universe is. We only know that the observable universe (what we can see) is a sphere, since it is based in the light that reaches us from all directions.

Space was everywhere immediately because space is what makes our universe what it is. This is a difficult concept perhaps, but no matter what shape our universe is it is possible to imagine a place where space (as we know it) does not exist. This would be "outside" our universe.

Matter is, ehm, another matter entirely. Matter was not everywhere but *almost* everywhere. There are several theories on this but for sake of simplicity let's say that almost immediately after the big bang, matter formed. But it was not everywhere, and as the universe grew it did not get more matter so matter was thinly spread out whereas there was more and more space.

Hope that made any sense.

[infamous]

Originally Posted by Tormod

We don't know what shape the universe is. We only know that the observable universe (what we can see) is a sphere, since it is based in the light that reaches us from all directions.
.

Relying on the standard model as a bases for universal evolution and, positioning the Big Bang as the Genesis of all subsequent events, how does the first Law of Thermodynamics fit into the picture? Energy cannot be created nor distroyed and, universal energy remains constant. Wouldn't this mean that the energy of the Big Bang must have come from somewhere else? Doesn't this prove the existence of a source of energy outside our universe which gave rise to the Big Bang? And if this is true, does this mean that energy is eternal in nature, having no beginning and also no end? Or is the first Law flawed in some way or maybe the Big Bang theory itself?

[EWright]

Originally Posted by Tormod

We don't know what shape the universe is. We only know that the observable universe (what we can see) is a sphere, since it is based in the light that reaches us from all directions.

Space was everywhere immediately because space is what makes our universe what it is. This is a difficult concept perhaps, but no matter what shape our universe is it is possible to imagine a place where space (as we know it) does not exist. This would be "outside" our universe.

Matter is, ehm, another matter entirely. Matter was not everywhere but *almost* everywhere. There are several theories on this but for sake of simplicity let's say that almost immediately after the big bang, matter formed. But it was not everywhere, and as the universe grew it did not get more matter so matter was thinly spread out whereas there was more and more space.

Hope that made any sense.

Cosmologists do NOT consider the universe to be spherical! The geometry of the universe is considered most likely to be flat. The CBM only appears spherical because we are measuring something at a point in time; one in which the CBM was everywhere at that time. Therefore it appears equal in all directions and so in measuring in every direction equally from a point we get a spherical shape.

Furthermore, there was no "matter" anywhere after the big bang, because matter is composed of atoms. Need I say more on that one?