[Robert]

I don't understand how the WMAP satellite can measure the age of the universe. It has taken pictures of the cosmic background radiation that shows slight variations in temperature. I understand the radiation is coming to us from the edge of the universe, or the farthest point of the visible universe. Is that right? That confuses me. Imagine you're in an explosion. You will experience radiation from all directions and all distance up to the leading edge of the explosion. How can we see these subtle variations in temperature if the big bang radiation permeates the universe rather than originating from the leading edge of the big bang explosion. Or, if the radiation is only generated from the leading edge of the big bang, why?

I understand there was no light from the big bang until a while after it happened. Is this where the 380,000 years comes from. Was light not created until 380,000 years after the big bang. And now it is detected as microwaves due to redshift?

Or, I think it is not microwaves due to redshift, but rather based on black body radiation calculations.

I'm still confused. I'll look this up (or read further) and post a clarification.

--Robert

[DrCox]

I understand there was no light from the big bang until a while after it happened. Is this where the 380,000 years comes from. Was light not created until 380,000 years after the big bang. And now it is detected as microwaves due to redshift?

From what I understand, the universe was too hot in the beginning to allow e- to stay bounded to p+, causing all hydrogen to be ionized. Photons are emitted and reabsorbed by this gas, creating cosmic microwave background radiation (CMB radiation). And at 380,000 years, the universe cooled enough to allow neutral hydrogen to form. Which lets the CMB radiation escape, filling the galaxy. I imagine that light was allowed to leave at the same time. It is very late, though. I could be horribly wrong.
---
To make sure I was on the right track I read up on page 106 of the book and saw that it say that at 380,000yrs the temp drops to 3,000K allowing photons to travel freely.

Also, I'm not sure about your redshift question, could you elaborate?

I need a bit more time to think over your other questions. : )

[subversion]

This puzzles me as well Robert. Perhaps the CMB we see is not just from the leading edge but is all the radiation between us and the furthest point in the universe. Oh wait, maybe it's that the outer most edge of this radiation field is the oldest, thus we only look at that edge if we want to see back as far as possible. Essentially, when we look at the longest wave lengths, we only see the farthest radiation. The reason it looks like only one layer, or a shell, is because just prior to that moment there was no background radiation because of the intense heat as you said. That could be right, but I'm not entirely sure. Others help?

[DrCox]

From what I get from this link, the fluctuations are only visible at the end of the radiation cloud. I think they look at the outer most part because that is where the image is clear (cloud analogy on link).

And this link, from the same website, has a section at the bottom about using the WMAP to measure the age of the universe.

It's not very clear to me exactly how they do it, but it gets all it's information "by characterizing the detailed structure of the cosmic microwave background fluctuations." Nothing I can find (all the sub links on that page pretty much say the above).

So, it measures the rate of expansion, then knowing the density of the universe(finding this also w/ the satellite), scientists can say how long it took to get there. And would they also add in the time it would have taken to make the amount of CMB in the universe, or is that part of the expansion?

I’m not sure how they get the Hubble constant from the fluctuations since (i thought) the fluctuations were there from the beginning. Or do they measure the distance between the fluctuations? I would very much like to talk to Kaku right now.

[Guille]

drcox,

I guess that talking to Kaku would solve all problems. But this, I think, is quite dificult to acheive.

I think the hubble constant was taken not from observations or experiments but from mathematics.

[DrCox]

WMAP and the Hubble Constant

By characterizing the detailed structure of the cosmic microwave background fluctuations, WMAP is to accurately determine the basic cosmological parameters, including the Hubble constant, to better than 5%. This measurement is completely independent of traditional measurements using Cepheid variables and other techniques. The initial results show the Hubble Constant to be 71 (km/sec)/Mpc, +0.04/-0.03.

That's what I got that from. Do you know of any websites where I can read more about the hubble constant. That would be grand

[Robert]

Originally Posted by <<>>

drcox,

I guess that talking to Kaku would solve all problems. But this, I think, is quite dificult to acheive.

I think the hubble constant was taken not from observations or experiments but from mathematics.

I'll attempt to contact Dr Kaku once we have a few more threads going. I have his email address, but I imagine he gets a lot of email so it might still be difficult to get through to him. I will give it a shot though.

[Robert]

Originally Posted by Robert

Was light not created until 380,000 years after the big bang. And now it is detected as microwaves due to redshift? Or, I think it is not microwaves due to redshift, but rather based on black body radiation calculations.

Originally Posted by subversion

Perhaps the CMB we see is not just from the leading edge but is all the radiation between us and the furthest point in the universe.

I think this equates to the black body radiation I mentioned. On page 56, paragraph 2, Dr Kaku mentions that "Gamow showed that radiation given off by this superhot core would act like 'black body radiation.'" so I think this is the correct answer.

Originally Posted by subversion

Oh wait, maybe it's that the outer most edge of this radiation field is the oldest, thus we only look at that edge if we want to see back as far as possible. Essentially, when we look at the longest wave lengths, we only see the farthest radiation. The reason it looks like only one layer, or a shell, is because just prior to that moment there was no background radiation because of the intense heat as you said.

This is an excellent point, but after thinking more deeply about it, I wonder if the Red Shift is only a factor for specific or discrete sources of light moving away from us. I think it might not apply to a uniform cloud of radiation expanding away from us in all directions. Any agreement on this point?

[Robert]

Originally Posted by DrCox

From what I get from this link, the fluctuations are only visible at the end of the radiation cloud. I think they look at the outer most part because that is where the image is clear (cloud analogy on link).

Checking out this link confirms that the microwave background radiation is caused by the stretching of the universe; stretching the gamma rays into microwaves. But I wonder how black body radiation figures into this. I understand that black body radiation correlates temperature with the frequency of electromagnetic radiation, so that also seems correct. I think both explanations are related, I just don't have a good feel for it yet.

I think the picture on the link provided by DrCox gives a good explanation. This page appears to have some excellent explanations, but I'll have to finish reading it when I return from work later today.

[Casey_deJong]

when we are talking about red shift and measuring the age of light are we factoring in the posibility of their being dense areas in space which light has trouble moving through such as nebulas containing gasses or liquids which we may be missing from our own elemental charts?
Eg if there id oxygen in a nebula which is small maybe to small to detect with current telescopes and that nebula is between us and that which we are measuring or if the stars/galaxies we are measuring are more concentrated in a certain gas would the light not also be effected?

Not to mention the way gravity can bend light meaning a galaxy which is enourmouse putting out a little bit of light could actually be slowwing the speed tha light is travelling to the degree that it would represent a red shift to us.

I think the best way to measure these efects would be to measure the speeds of our closser galaxies and then draw a comparison upon how direction and motion effect the red shift test

Is there any such thing as a space rainbow? A galaxy which through a telescope has expressed the full coulor spectrum even for a breif period of time?
if so this would confirm that there are substances within the universe which could affect the red shift.

Gees i BS a lot but it made sense whwn i wrote it and maybe you can draw something from it.