CMB Photons

We see galaxies and their light as they were in the past. Do we see the CMB photons today as they were in the past, too?

If yes, then, is the CMB going to disappear in the future out of detectable range?

 

Log in or Sign up to hide all adverts.

IMO: . . . Yes . . . . with a caveat . . . . Yes ONLY IF CMB is a 'left-over' from a one-time Big Bang event. If CMB is 'continually' produced by alternative mechanism(s) . . . . probably NOT!

 

Log in or Sign up to hide all adverts.

Alternative mechanisms like what?

 

Log in or Sign up to hide all adverts.

I don't think anyone could answer that! The uniformity within the CMB suggests that it occurred globally far enough in the past that, it is not affected by the presence of locally dynamic systems or objects.., stars, galaxies and galactic clusters. IOW It does not appear that those objects we see in the universe, in visible, infrared and x ray spectrums, contribute to the CMB. If they did we should see more variation associated with nearby structures — i.e. galaxies etc...

Currently a best guess is that the CMB originates from a cosmologically global event further in the past than our current light horizon... i.e. the BB.

 

But we see CMB photons from that event. Event and photons go together, yes? Big Bang was opaque, but decoupling era was transparent. How about the photons; do we see them as they were in the past, or as they are now?

 

No, we see the CMB as it is today. The photons of the CMB which we detect are right here, impacting on the microwave detector. If we were seeing them as they were when they were released, we would see they have a temperature of about 3000 K, instead of the 2.73 K we see them at.

 

I'm nonplussed, AlexG. What are the differences between photons of distant galaxies and the photons of the CMB?

The CMB photons are even farther than the light of a much distant galaxy, no?

 

Very crudely.., the CMB is what we detect in all directions when we don't look directly at a distant star or galaxy etc.. The CMB seems to be comming from no specific identifiable source.

One way to think of it in terms of the BB is that early in the beginning of the universe, when it was just becoming transparent, what we detect today as the CMB was comming from everywhere in the at that time much smaller universe. Everywhere, because today it seems to be the same in all directions...

The temperature difference is due to the photon density, then and now. If you focus a laser with a wide beam its temperature is far less than when it is focused into a tight beam. When the universe was beginning there was a point where photons popped into existence throughout the smaller universe. The photon density was far greater then than it is now. As time passed to today and the universe expanded, the photon density diminished in the larger volume of the expanding universe.., and photons which where earlier even in the visible spectrum have redshifted so far that they are now in the microwave spectrum.

We think of our light horizon as defining har far the furthest object we can detect is from us. The furthest galaxy etc.. Though the CMB is composed of photons which also travel at the speed of light, they seem to originate from a time beyond what we think of as our light horizon today.

So to answer your question, "The CMB photons are even farther than the light of a much distant galaxy, no?"

Yes.

I hope I did not mangle that too badly or just confuse things more...

 

When you look at the photons coming from a distant galaxy, they show you how that galaxy looked in the past. If the galaxy was 5 billion lys away when the photons began their journey, then we see the galaxy as it was 5 billion years ago. But the CMB are not the photons of something far away. The CMB are the photons which have been filling space everywhere since 377000 years after the BB. The CMB photons that we see here are the same as the CMB photons which are currently on the other side of the observable universe.

 

To answer YOUR query, there are alternative ideas about the source of CMB discussed elsewhere on Sciforims. Visit Alternative Theories and pertenent other subfora. If I were bold enough to be more specific, I would be accused of 'trolling', 'advertisng', or posting 'nonsense' by certain Sciforums moderators.

 

AlexG disagrees with you.

Yeah, that makes sense. So the CMB is here and now, not in the distant past.

LOL. Thanks, wlminex.

 

Tashja, the light from galaxies is here and now also. I don't see the disagreement.

The light we see is here and now in both cases, but it gives us a picture of way back then....

We "see" the CMB density as less than it was.., way back then, but the same would be true of the light from galaxies.

The difference is that the light from galaxies, started at a galaxy, where the CMB began from everywhere in the universe way back then.., before there were galaxies.

In either case we see the light we see today, today. In either case if the universe were not expanding what we would see today, in each case would be different. They would both be redshifted less and they would both have a higher photon density. The CMB would be hotter and the light from distant galaxies brighter. Both the temperature and brightness are a measure of photon density.

 

I see. Thanks, OnlyMe.

 

I doubt that 2.7K background radiation(CMBR) is radiation in the early days of the universe.

Please Register or Log in to view the hidden image!

Wow! it’s perfect. Beautiful results, 10000%.
However, if we considering that 2.7K background radiation(CMBR) is 3000K radiation in the early days of the Universe, namely age of CMBR is about 13.7Gy. Length of path of CMBR is about 13.7Gly. On path of CMBR, numerous galaxy and heat source are existed. Of course, I know that WMAP image of CMB temperature anisotropy.

It is too perfect, too clean, too beautiful result. Therefore, I doubt it. Really personal opinion.

 

IMO: One might also contemplate that CMBR arises as a product of a 'continuous' mechanism (process) that is yet unrecognized in which the measured 2.7 deg is a characteristic signature of said mechanism. BTW: It's also curious how the above-posted graphic is quite similar to plots of the Bremmstralung background seen in x-rays.

 

Anything you have to say about this is nonsense.

 

So empirical measurements should be in doubt because they have a close correlation? Really ignorant unscientific opinion.

 

It makes sense to read the literature on this subject. For your case reading the following link can be informative.
http://ned.ipac.caltech.edu/level5/Glossary/Essay_lss.html
Empirical studies of the CMBR have revealed so much about the evolution of our universe. WMAP being the most recent experiment. You can find all the details about this research at WMAP.
http://map.gsfc.nasa.gov/universe/bb_tests.html

Something to keep in mind as you review this cosmological science.
At last scattering the CMBR photon energy is < needed for any further interaction with matter. This means the total CMBR photons are a constant. The total energy of the CMBR is constant. The energy density of the CMBR decreases as the universe 'gets bigger'.

 

Not a bad (or unexpected) response . . . from a SM groupie . . . . . 'right back to ya', Bruce!

 

BTW: Bruce . . . what about the CMBR interaction with "mass" comprisisng the CMBR detector? . . . albeit negligible in the overall scheme, it represents a mass interaction . . . . might there also be other mass interactions?