Alternate sources for 3K background radiation?

[Graviman]

I am new to this forum, and am not certain whether this question merits a serious response, or will be laughed out. I have studied undergrad relativity (Various metrics etc), but have not made much headway with tensor maths - yet. So here goes...


Something i have often wondered, is whether there could be any other sources for the microwave radiation measured by Penzias and Wilson. I understand that this is seen to be the Big Bang massively doppler shifted, to lower the frequency. One explanation i have heard was that the photons/wavelengths stretched as the universe explanded - presumably in a manner similar to gravitaional redshifting.

What i am puzzled by is whether these are seen to be the original photons, or are they re-radiated from matter (dark presumably) now cooled to the 3K mean? If the universe is considered a fluid this makes sense to me, as it expands. I realize the recent Perlmutter discovery of cosmological constant causing acceleration puts a twist on everything.

Perhaps on the more speculative side: Is there any evidence of a previous Big Bang, from for example background radiation shifted into the ULF bandwidth? If there was any such evidence, would it be masked by the microwave noise?

Perhaps risking the wrath of respectable physicists: Is there any alternative source that might produce this background radiation? I gather Fred Hoyle felt that matter was created to fill the intergalactic voids. This need not have been matter, and in fact could be spontaneous photon emission from vacuum...

Also, hopefully a clear-up point: If all the matter was concentrated at a point, isn't this a black hole? I gather a viable solution in gen rel is a white hole, or is this where inflation comes in?


OK, is that me disbarred for life then?

Mart

 

[Garth]

Hi Mart, welcome to these Forums!

No need to fear being barred from here for simply asking questions, especially important questions like yours.

Yes, there are other suggestions for explanations of the CMB.

Fred Hoyle had a mass field theory (Hoyle: F. 1975 ApJ 196:661-670 "On the origin of the microwave background") in which the mass of atoms grew the further away they were from a cosmic zero-mass boundary. The universe was static and regions of negative mass particles existed beyond the boundary, which we interpret as the BB. At the boundary the atoms were of infinite size and thermalised with the photons coming from stars beyond. Hence the CMB was the smeared out radiation from negative mass galaxies 'beyond'.

Eric Lerner has a Plasma cosmology theory and again the universe is static, there was no BB.

Another possibility is that the radiation comes from the zero point energy field - see post 15 by turbo-1 in the thread: absorption in 'CMBR' wavelengths - observations? processes?

I firmly believe that WMAP's CMB anisotropies are all functions of the movements of the WMAP probe relative to the vacuum, and that the CMB is the temperature of the vacuum, and not a cosmological relic.

I must say these other suggestions have a lot of work to do in order to explain cosmological observations as well as the standard LCDM GR model, especially the peaks in the CMB anisotropies power spectrum, which match that predicted by a flat space Friedmann model exactly. (Although as I constantly emphasise they are consistent with a conformally flat model as well.

My own position is the standard model fits the data well, but only after some major adjustments such as the necessity for Inflation, non-baryonic Dark Matter and Dark Energy, none of which has been confirmed by laboratory physics. You will find many posts about this here.

Therefore I would argue that it would be prudent not to be too confident about the standard model and always be prepared to ask questions such as yours and consequently to examine alternative theories thoroughly.

Garth

 

[SpaceTiger]

I understand that this is seen to be the Big Bang massively doppler shifted, to lower the frequency.

The term "Big Bang" can be a bit misleading. In actuality, the idea of a true beginning to the universe is far beyond what would be testable with modern science. When scientists talk about the "Big Bang Theory", they're usually referring to the idea that the universe has expanded from a much, much smaller size. This may not be an issue of confusion for you, but I always get uneasy when someone says something like, "we're seeing the Big Bang", so forgive my need to clarify for other folks.

What i am puzzled by is whether these are seen to be the original photons, or are they re-radiated from matter (dark presumably) now cooled to the 3K mean?

The majority of the photons we see were emitted (or "last scattered") at a time when the universe was about 1000 times smaller than its current size. For much more detail, see this thread:

https://www.physicsforums.com/showthread.php?t=72153&highlight=microwave"

The photons were probably scattered almost entirely off of matter that is now visible (i.e. not dark) because dark matter is believed to be made of very weakly interacting particles.

I realize the recent Perlmutter discovery of cosmological constant causing acceleration puts a twist on everything.

The creation of the CMB would be almost completely blind to the cosmological constant because the energy density of this "dark energy" would have been negligibly small at recombination (assuming the cosmological constant is the dark energy). The reason we can use the CMB as a probe of dark energy is that the photons have been traveling to us throughout cosmic time, and so their distribution has been effected by the more recent changes in the energy content and evolution of the universe.

Perhaps on the more speculative side: Is there any evidence of a previous Big Bang, from for example background radiation shifted into the ULF bandwidth?

I suspect (though I can't say definitively) that any other background radiation that could be detected by our telescopes would have been scattered and thermalized in the early history of the current "Big Bang". It's an interesting question.

If there was any such evidence, would it be masked by the microwave noise?

I don't think the 2.7 K CMB would have any impact on this hypothetical ULF CMB. From the detection standpoint, there would be no trouble distinguising them, since they would lie at completely different frequencies.

Perhaps risking the wrath of respectable physicists: Is there any alternative source that might produce this background radiation?

Nobody's going to get angry at you for asking questions. The basic source of the CMB is on pretty solid theoretical ground. As Garth said, you would be very hard-pressed to explain all of the current observational evidence in any other way. Many of the things we try to use the CMB for (like measuring dark energy or testing inflation) are still up for debate, but the radiation itself is thought to be pretty well understood. The community views the steady state theory as dead, Fred Hoyle himself even having renounced it 40 years ago.

Also, hopefully a clear-up point: If all the matter was concentrated at a point, isn't this a black hole?

Actually, that would be a singularity. The Schwarzschild black hole is one example of a solution to Einstein's equation that has a singularity and the Friedmann-Robertson-Walker metric (the metric most frequently used to describe the universe) is another.

 

[Chronos]

Correct, Tiger. Push that to the Planck mass and see what you have.

 

[Graviman]

Thanks guys - some good food for thought. I'm amazed that there is still so much debate on the subject! I imagine that the recent discovery of accelerating explansion has fuelled all sorts of ideas (Andreas Albrecht & Joao Magueijo had an interesting idea about variable speed of light).

The thing that that does bother me about "the" Big Bang: what was so special about that point in time? I appreciate that time as a concept only really exists with mass to "slow it down", so perhaps the concern of lack of symmetry here is misguided. Perhaps another way of saying this is what was so special about our Big Bang? This was my reasoning behind the possibility of even lower frequency CMB. ULF would be just an initial guess, since the actual time to any preceeding Big Bang might not be calculable.

Interesting that, despite the general acceptance of Big Bang, there are still alternate potential explanations for the 2.7K CMB radiation. I had wondered about zero point energy field, but don't feel qualified to question much further. To expand: i am currently studying physics as a second degree, already functioning as a dumb engineer .

Perhaps the steady_state/big_bang divide is too extreme: the universe clearly does change, but does it really need a beginning? Somehow continued creation and destruction (via black holes) makes sense, even if it was periodic. The distrubution of the elements is pretty hard evidence for some kind of "explosive" origin, but i had just wondered about alternatives...

Mart

 

[Chronos]

Steady state is dead in the water. It has no redeeming predictions for the moment. The CMB is one of the stakes in it's heart.

 

[SpaceTiger]

The thing that that does bother me about "the" Big Bang: what was so special about that point in time? I appreciate that time as a concept only really exists with mass to "slow it down", so perhaps the concern of lack of symmetry here is misguided. Perhaps another way of saying this is what was so special about our Big Bang?

Well, I'm not exactly sure what you're getting it, but if you're suggesting that the Big Bang as we know it may not have been the only "creation event", then I don't think you'll hear many objections from professional astronomers. There could have been other universes, other bubbles of our own universe, or "parallel" universes. In fact, there could even have been previous "Big Bang" events, the products of which were diluted to undetectability by inflation.

The problem is that this is mostly in the realm of philosophy. We can't currently put observational constraints on these ideas, so all I can tell you is that they're possible.

Interesting that, despite the general acceptance of Big Bang, there are still alternate potential explanations for the 2.7K CMB radiation.

I think many people have a natural resistance to the idea that there was a beginning and there will likely be an end (for the habitable universe, that is). Steady state models are appealing to folks who fancy some form of immortality, whether it be the literal human kind, the immortality of civilization, or perhaps just of the heavens themselves.

I don't know for sure, though, you'd have to ask them. You won't find a discussion of steady-state theory in any mainstream conference and I will tell you flat out that it's ruled out by the data.

I had wondered about zero point energy field, but don't feel qualified to question much further.

If you ask me, that's a sign of wisdom.

To expand: i am currently studying physics as a second degree, already functioning as a dumb engineer

Best of luck to you.

Perhaps the steady_state/big_bang divide is too extreme: the universe clearly does change, but does it really need a beginning? Somehow continued creation and destruction (via black holes) makes sense, even if it was periodic. The distrubution of the elements is pretty hard evidence for some kind of "explosive" origin, but i had just wondered about alternatives...

You might be interested in the "cyclic model" of the universe. It's discussed in this thread:

https://www.physicsforums.com/showthread.php?t=103866"

In it, you'll also find links to more information, if you so desire.

 

[Nereid]

And my belated welcome to PF, Graviman!

SpaceTiger, Garth, and Chronos have already addressed your questions, I feel; let me just add that Physics Forums is just the place for you to ask your questions, and you should never be shy about asking!

You've probably already 'got' this, but just in case ... there's a 'dirty secret' in modern physics - the two best theories (quantum theory and General Relativity) are not only mutually incompatible, but violently inconsistent in physical regimes such as 'the Planck era' (very dense, very hot, to put it simply). One implication of this incompatibility is that any statement concerning 'what goes on' in such regimes is, scientifically, essentially speculation (it can, of course, be immensely absorbing and fascinating speculation, and one can deploy vast armies of heavy duty math and physics in these speculative battles, but without the cold shower of good observational or experimental results, it remains speculation).

Regarding the CMBR, we don't need to concern ourselves too much with Planck era QM/GR inconsistencies; the relevant physics has been well-tested in our labs (and through observations of objects such as the recently discovered double pulsar).

You may have formed an opinion that there are viable 'alternative' explanations for the CMBR; in case you have, then I invite you to read up on some - nay, the best - of these; I feel it is quite a good learning exercise to see just how weak these 'alternatives' are (in terms of accounting for the good observational results).