cosmic background radiation - alternative proposal

[zforgetaboutit]

I've had this idea for years but never had a forum.

How do we know we aren't merely measuring the energy emitted by our sun's Heliosphere (http://science.nasa.gov/ssl/pad/solar/images/heliosph.gif) ?

[russ_watters]

We see the background radiation in every direction - not just in the direction of the sun.

[zforgetaboutit]

The solar wind contents (heliosphere diagram) (http://science.nasa.gov/ssl/pad/solar/images/heliosph.gif) are also in every direction, relative to where we've been making CBR measurements.

The solar wind (http://science.nasa.gov/ssl/pad/solar/heliosph.htm) consists of particles, ionized atoms from the solar corona, and fields, in particular magnetic fields. (see web link for details - zforgetaboutit)

[russ_watters]

Solar wind and cosmological background radiation are completely unrelated concepts.

[Janus]

Originally posted by zforgetaboutit
The solar wind contents (heliosphere diagram) (http://science.nasa.gov/ssl/pad/solar/images/heliosph.gif) are also in every direction, relative to where we've been making CBR measurements.

But, the Solar wind becomes more concentrated as you near the Sun, so if it were the source of the CBR, then the radiation we measure would become stronger as we started pointing our detectors near the Sun. This doesn't happen.

[zforgetaboutit]

Originally posted by russ_watters
Solar wind and cosmological background radiation are completely unrelated concepts.

They are related inasmuch as they may both contribute to the perceived temperature of the night time sky.

If the dust of nebulas is illuminated by solar radiation, then the particles of the solar wind could also be lit up by radiation from our Sun. If the nebulas emit IR radiation then so could the solar wind, also consisting of particles, for the same reason.

[zforgetaboutit]

Originally posted by Janus
But, the Solar wind becomes more concentrated as you near the Sun, so if it were the source of the CBR, then the radiation we measure would become stronger as we started pointing our detectors near the Sun. This doesn't happen.

Fair enough. Do you happen to have a web link which mentions this lack of change when the detector is pointed closer to the Sun in a non-trivial way?

[Hurkyl]

Solar wind would also, I imagine, be much warmer than the CBR.

[UltraPi1]

The CBR could be the result of an ongoing process. I.E The universe is incomplete and new material is still being created.

[Nereid]

Originally posted by zforgetaboutit
*SNIP
If the dust of nebulas is illuminated by solar radiation, then the particles of the solar wind could also be lit up by radiation from our Sun. If the nebulas emit IR radiation then so could the solar wind, also consisting of particles, for the same reason. Before the COBE, WMAP, ACBAR, BOOMERANG, etc teams present results of their observations of the CMB, they must remove 'foreground' contributions to the microwave signal. For satellite observatories, there are two primary sources of such contributions (after purely instrumental effects are accounted for), the IR from solar system dust (which is also responsible for the 'zodiacal light'), and dust in the Milky Way.

Here's how the WMAP team dealt with the Milky Way sources (http://lambda.gsfc.nasa.gov/product/map/pub_papers/firstyear/foregrounds/wmap_galaxy.pdf).

Among the difficulties that zforgetaboutit's idea would have to deal with are:
- the CMB has a near-perfect black-body spectrum; as Hurkyl said, it's very difficult to see why 'solar wind particles' should be so cold (~2.73K)
- whatever solar wind particles are, they would have an emission spectrum that differed from a black-body; for example, silicate, carbon-compound, etc bands
- AFAIK, the 'solar wind particles' are ions, mostly atomic ions; how could they give rise to microwave radiation?
- quite a few other stars have 'solar winds' much stronger than the Sun's, yet AFAIK none have a spectrum resembling the CMB
- ditto zodiacal dust

[zforgetaboutit]

Originally posted by Nereid
- AFAIK, the 'solar wind particles' are ions, mostly atomic ions; how could they give rise to microwave radiation?


I didn't read about solar wind ions as a microwave source but I haven't finished the paper yet (~40 pages).

Reasonable replies, so far. The link is a good read (from what little I can grasp). I quote from it:

In addition to the thermal emission from dust, above, there are various other ways in which dust can radiate at microwave wavelengths. These include electric dipole emission from spinning dust grains and magnetic dipole emission from thermally fluctuating dust grains (Erickson 1957; Draine & Lazarian 1999, 1998a,b). Emission from spinning dust can produce   -2 from 20-40 GHz. The high-frequency cut-off of spinning dust emission is due to the limited speed at which a dust grain can spin.

So thermal emission from dust can emit microwaves. We already agree on a possible heat source (the Sun). As a source of dust, how about whatever ablates from comets as they are heated by the Sun? Comet dust may be spread about quite a bit from their orbital plane, due to eons of buffeting by the solar wind and may inhabit a spherical shell by now. We may be looking through this shell when making our measurements

[russ_watters]

Originally posted by zforgetaboutit
Fair enough. Do you happen to have a web link which mentions this lack of change when the detector is pointed closer to the Sun in a non-trivial way? [?] [?] Thats basic - its the reason we care about the cmb. Any single paragraph description of the cmb mentions its homogeneity. HERE (http://aether.lbl.gov/www/science/cmb.html) is a good description which includes a map of the sky. A map of the sky at microwave frequencies, showing that the CMB is almost completely the same in all directions.

[Nereid]

There's no doubt that comets 'shed' dust! That's what meteor showers are, the dust streams in the orbits of comets, intersecting the Earth. There's also no doubt that this - and other - dust can be detected; IRAS (http://dorothy.as.arizona.edu/DSN/IRAS/iras.html#i.3) may have given us the first 'all-sky' observation of this dust. As they journeyed out of the solar system, the Voyager (1 and 2) and Pioneer (10 and 11) spacecraft also measured dust.

IIRC, the IRAS etc results are all pretty clear - there's far too little dust in the outer reaches of the solar system to generate an 'undetected' zodiacal signal. Further, if there was enough dust to generate non-thermal microwaves at frequencies where the CMB is strong, a) it wouldn't have such a perfect black-body spectrum, b) the thermal signal from the dust - at considerably higher temperature than ~3K - would be very obvious, and c) there'd be significant anisotropy, near the shock-front of the heliosphere (and no, the CMB dipole is in quite a different direction from where the Sun is going).

[Loren Booda]

The CMB includes small changes in temperature: 2.735 [+/-] .0001 K across the sky. These fluctuations are thus some 20,000,000-fold less than the Sun's blackbody temperature at ~5800 K. The magnitude and variation of the Sun's radiation easily masks the CMB patterns; I believe this is the reason that COBE and similar explorers have been purposely hidden by the Earth from the Sun. The measured CMB has been used to calculate the age of the universe at 13.7 billion years, no solar artifact.

[zforgetaboutit]

As a lay person not trained in thermodynamics nor radio, my overall understanding of the paper's details is poor.

They performed an awful lot of statistical analysis and necessary (they claim) data smoothing to arrive at their results. Unfortunately I'm not qualified enough to referee this but am naturally wary of too much fudging.

However, you know how you can view some "microwave pictures" of this subject, and they purport to show the relative uniformity of the CMB?

Well I'm taken aback at the recent long exposure deep field Hubble pics that show a high number of galaxies having a non-trivial angular size inhabiting the picture. It's like increase the sensor exposure time enough and the entire frame would be occupied by pictorially visible galaxies.

What "background" would there then be ... the emissions from all these galaxies in our line of sight, barely leaving room for "empty black" space? By the time you removed all the pixels containing radiation from galaxies (the foreground anomalies) there might not be any pixels left!

I'm suggesting, without being educated in the subject, the temperature would not reasonably be ~3K. This is what I expect if COBE was to zoom in on, say, the Andromeda Galaxy as opposed to an empty piece of sky. I don't expect them to roughly be the same.

I'm thinking if COBE et al also had a much longer exposure time available, there might be no uniformity to its measurements.

Can anybody yet say COBE's uniformity results would not drastically change because its exposure times are already long enough to make final conclusions?

[Nereid]

Indeed, the WMAP team found ~200 point sources in their results, and they corresponded very closely with the ~200 that they expected to find, based on the known spectrum of (radio) galaxies, observed in different wavelength regions. Do other galaxies also emit microwaves? Certainly. Can at least some of these other galaxies also be detected in the wavelength bands at which WMAP (and later Planck) observes? Almost certainly. Is the combined contribution of all galaxies' microwave emission going to be detected any time soon? No; it's far, far too faint.

Interestingly there are other signatures which can be investigated, e.g. Sunyaev-Zel'dovich effect, Sachs-Wolfe effect.

Bottom line: COBE, WMAP, ACBAR, BOOMERANG, DASI, ... have observed the CMB. While there will always be fine tuning to be done, there's no evidence of 'local' contributions to the observed microwave sky, other than those already detected and analysed.

[kingofjazz]

how quickly is the Milky Way relative to the cosmic background radiation?

I mean not the rotation-speed !

thank you

[Nereid]

Welcome to Physics Forums kingofjazz!

This APOD (http://antwrp.gsfc.nasa.gov/apod/ap010128.html) has a good, if outdated, summary. Since this was written (in 2001), a lot of work has gone into understanding this ~600km/s motion; The Great Attractor (http://cow.physics.wisc.edu/~ogelman/guide/gr8a/) is the favourite fall guy. :smile:

[zforgetaboutit]

Next ideas ...

1) What if the CMB is emitted by some aspect, or possibly side-effect, of black holes situated in the center of galaxies?
Example: matter falling into the black hole, accelerates, emits radiation which is absorbed by something... which radiates to something else ... etc. which finally emits microwaves at CMB wavelength.

There are galaxies in every direction (observed) so that could account for the uniformity.

2. What if the solar wind loses velocity the further out it gets, and the particles slow down, exist as a particle cloud, and THEN are able to emit CMB because of interaction with cosmic rays, radiation from the Sun, or some other effect?

COBE would still be at the relative center of this weakly emitting soup, assuming the soup has, in its multi-billion year lifetime, expanded further than the Oort Cloud. We may not yet be able to "see" past the soup because our probes haven't gotten far enough yet.

Like, if you were underwater and you had a water detector, it would detect water in all directions! Cool water, to be sure, but evidence nonetheless of the "Big Sauna" which existed billions of years ago. :-)

Or your local solar system was inside a bright nebula. Everywhere you looked, you'd measure the radiation effects of local stars heating up the gas. That civilization might assume they were inside an illuminated cosmic "room" because everywhere they looked they saw this visible background haze. Having never left the nebula, instrumentation-wise, how could somebody propose, as an alternative idea worth exploring, that the nebula might be a local entity? The same objection would exist: "It's everywhere we've looked so obviously there is a 'room'". There's even a blue shift in the direction we are going (see APOD, below).

I looked at the APOD link - maybe it's Milky Way scale soup. That could account for the red shifts. I'd name the APOD pic the Great Yin-Yang.

Perhaps researchers could state "The uniformity of CMB measurement exists within our solar system - we don't know about further out, yet."

3) Sidebar: if a single "particle" (of the class attributed to CMB) was heated to "big bang" temperatures, how long would it take for it to cool down to < CMB temperature, without outside interference?

4) Sidebar: if the smallest collection of entities responsible for emitting the observed CMB were ideally contained in an isolation box, what does the current model predict about the long term (cosmological time scale, if necessary) observation of their emitted radiation? Asymptotically approaching some state, perhaps, but at what rate?

5. Sidebar: maybe the CMB comes from radiation emitted when small-enough particles (or whatever) decay, after enough time has passed. Why uniform CMB? Because very old stuff really really far away is decaying all over the place.

I've read here (http://www-personal.umich.edu/~jcv/imb/imb.html), for example, about a proposed, natural, proton decay mode of 10^31 years, which is somewhat older than current models of the universe's age.

We have the same chance of understanding the universe's origins as cartoon characters having the understanding that they were drawn by an artist.

But it's still interesting to try, and see how far we can get. Plus there's a lot of useful things we will discover on the way.

[jcsd]

The source of the CMBR must be very, very faraway (due to it's isotropy), certainly extragalactic; it also must be a single source of reasonably small size (due to it's homogenity), add to this the fact that ot is coming from all directions and the conventional big bang theory is really the only theory that can offer a reasonable explanation.

[Nereid]

Next ideas ...

1) What if the CMB is emitted by some aspect, or possibly side-effect, of black holes situated in the center of galaxies?
Example: matter falling into the black hole, accelerates, emits radiation which is absorbed by something... which radiates to something else ... etc. which finally emits microwaves at CMB wavelength.

There are galaxies in every direction (observed) so that could account for the uniformity.Wouldn't we then see much more of the CMB in the direction of the nearest BHs then (other than that at the centre of the Milky Way - too many other sources)? For example, a big increase towards the Andromeda nucleus, M87 and other big ellipticals in the Virgo cluster, ...

You would also have the problem of its spectrum - as I said earlier, it's a near-perfect black-body spectrum - how would something which gets emitted by galaxy nuclei at a wide range of distances make such a spectrum?2. What if the solar wind loses velocity the further out it gets, and the particles slow down, exist as a particle cloud, and THEN are able to emit CMB because of interaction with cosmic rays, radiation from the Sun, or some other effect?Yes, indeed ... can you describe such an effect? Can you show that it will have a 2.73 K black-body spectrum? That it will not show variation related to the solar cycle and known CMEs? (AFAIK, the CMBR does NOT show an 11-year cycle, nor the echos of past giant flares and CMEs; so, any alternative explanation involving the Sun would have to show why well-observed solar variability doesn't show up in the CMBR).COBE would still be at the relative center of this weakly emitting soup, assuming the soup has, in its multi-billion year lifetime, expanded further than the Oort Cloud. We may not yet be able to "see" past the soup because our probes haven't gotten far enough yet.

Like, if you were underwater and you had a water detector, it would detect water in all directions! Cool water, to be sure, but evidence nonetheless of the "Big Sauna" which existed billions of years ago. :-)If that were the case, then the obvious Milky Way emissions would surely be masked! Alternatively, since we know lots of stars have far, far more powerful 'stellar' winds than the Sun's, wouldn't we see lots of CMBR-like point sources at the positions of these active stars? If you propose the CMBR orginates beyond the Oort cloud, then the equivalent for Alpha Cen would be clearly visible (AFAIK, there's no enhancement of the CMBR in that direction).Or your local solar system was inside a bright nebula. Everywhere you looked, you'd measure the radiation effects of local stars heating up the gas. That civilization might assume they were inside an illuminated cosmic "room" because everywhere they looked they saw this visible background haze. Having never left the nebula, instrumentation-wise, how could somebody propose, as an alternative idea worth exploring, that the nebula might be a local entity? The same objection would exist: "It's everywhere we've looked so obviously there is a 'room'". There's even a blue shift in the direction we are going (see APOD, below).Well, we are near the edge of an interstellar bubble, and we can measure the density of all kinds of things between ourselves and the edge of the Milky Way halo. So, if we're inside and can't see out, what are all the objects that we *do* see in the same microwave bands as the CMBR? If we can see out of the room (and the CMBR is like a translucent curtain around us), why can't we see the equivalents around other stars?I looked at the APOD link - maybe it's Milky Way scale soup. That could account for the red shifts. I'd name the APOD pic the Great Yin-Yang.You would have the small problem of explaining the apparent motion of the solar system wrt this MW 'soup' ... no, perhaps it's a big problem, because you then have to 'un-explain' all the high quality proper motion and radial velocity observations of the hundreds of thousands of MW stars!Perhaps researchers could state "The uniformity of CMB measurement exists within our solar system - we don't know about further out, yet."

3) Sidebar: if a single "particle" (of the class attributed to CMB) was heated to "big bang" temperatures, how long would it take for it to cool down to < CMB temperature, without outside interference?Can you clarify? what is the 'BB temperature'? what do you mean by 'without outside interference'?4) Sidebar: if the smallest collection of entities responsible for emitting the observed CMB were ideally contained in an isolation box, what does the current model predict about the long term (cosmological time scale, if necessary) observation of their emitted radiation? Asymptotically approaching some state, perhaps, but at what rate?The CMBR, in today's concordance cosmological models, is the surface of last scattering - photons that decoupled from matter when hydrogen atoms formed. In a sense, it's like the photosphere of the Sun. Since the radiation has decoupled, it is moving through the universe essentially unhindered, and in the future we will see that it has become colder.

BTW, did you know there was a very good observation a year or so ago which showed that the CMBR was hotter in the past? While the observational constraints weren't all that tight (it was a pretty difficult observation), the inferred ancient temperature was just what the concordance model predicts!5. Sidebar: maybe the CMB comes from radiation emitted when small-enough particles (or whatever) decay, after enough time has passed. Why uniform CMB? Because very old stuff really really far away is decaying all over the place.Then why is the CMBR a black-body of temp ~2.73K? How do you explain the observed polarisation in the CMBR under this idea?I've read here (http://www-personal.umich.edu/~jcv/imb/imb.html), for example, about a proposed, natural, proton decay mode of 10^31 years, which is somewhat older than current models of the universe's age.IIRC, the current upper limit, from recent experiments, is ~1035 years, for a variety of proposed decay modes. Again, your challenge is to show that such decays can produce EM with the observed characteristics of the CMBR.We have the same chance of understanding the universe's origins as cartoon characters having the understanding that they were drawn by an artist. This may be so, but such speculation has nothing whatever to do with science :rolleyes:

[zforgetaboutit]

[QUOTE=Nereid]Wouldn't we then see much more of the CMB in the direction of the nearest BHs then (other than that at the centre of the Milky Way - too many other sources)? For example, a big increase towards the Andromeda nucleus, M87 and other big ellipticals in the Virgo cluster, ...

Let me address one rebuttal at a time.

As a result of your posting I just skimmed here (http://ernie.ecs.soton.ac.uk/opcit/cgi-bin/pdf?id=oai%3AarXiv%2Eorg%3Aastro%2Dph%2F9905257) as best I could and finally arrived at the Conclusions on page 27 where the authors state

With these handles on the cosmic signal, we find that the error bars on most cosmological parameters are degraded by less than a factor of two for our best-guess foreground model and by less than a factor of five in our most pessimistic scenario. (boldened characters by zforgetaboutit)

I was impressed with the paper's details, and the very difficult attempts to make sense of the apparently noisy data via COBE et al.

The sheer number of analytical assumptions that permit further progress is amazing, but you have to start some where.

So, as I (mis?)understand it, the results could be off by 2X or 5X, due to the complexities of foreground signal artifact removal. I realize the scope is cosmological here, but still - that's a lot of fudge factor, so far.

At the end of the parer they state

A large number of papers have now painted a rosy picture of the future of cosmology, with CMB experiments measuring cosmological parameters to unprecedented accuracy over the next decade. In this paper, we have tried quite hard to spoil this picture, using foreground models with hundreds of harmful parameters and pushing them to limits of physical plausibility and current constraints.

Although we have found that great care needs to be taken in the foreground removal phase of the data analysis to avoid potentially perilous pitfalls, we have failed to tarnish the overall picture with more than a few minor blemishes, degrading the accuracy on certain measurements by small factors. Although much work certainly remains to be done on the foreground problem, this is cause for cautious optimism.

Some other scientists think we should wait a little longer.

I'm prepared to accept I misunderstood this paper. Did I?

[zforgetaboutit]

AFAIK, the CMBR does NOT show an 11-year cycle, nor the echos of past giant flares and CMEs; so, any alternative explanation involving the Sun would have to show why well-observed solar variability doesn't show up in the CMBR

Maybe there is no correlation.

As for CME's (coronal mass ejections?) - maybe COBE et al weren't looking downwind at the CME's path, so there's no measurement one way or another? Did somebody actually try to do this during a CME?

There would be so much interference from the CME (as I understand from the aforementioned paper) that it would be a messy undertaking to subtract other CME artifacts from the observations.

[zforgetaboutit]

If we can see out of the room (and the CMBR is like a translucent curtain around us), why can't we see the equivalents around other stars?

Our local haze may prevent us from seeing more distant, and therefore less distinct, neighbor extrasolar hazes.

(speaking underwater) "Can you see any water over there a couple of Km away?"

"No, there's too much intervening water to know for sure."

[zforgetaboutit]

You would have the small problem of explaining the apparent motion of the solar system wrt this MW 'soup' ... no, perhaps it's a big problem, because you then have to 'un-explain' all the high quality proper motion and radial velocity observations of the hundreds of thousands of MW stars!

In my proposals, there could still be red shifts in the indicated directions; they would be from different causes (BH's, soups, etc.), not necessarily restricted to Big Bang theories.

[zforgetaboutit]

Can you clarify? what is the 'BB temperature'? what do you mean by 'without outside interference'?

What "BB" are you referring to? I meant the 2.72K temperature.

By interference I mean the ideal container has no effect on the CMB emitters we are studying (apologies to Heisenberg), and additionally shields them from perturbation by the rest of the universe.

[zforgetaboutit]

While the observational constraints weren't all that tight (it was a pretty difficult observation), the inferred ancient temperature was just what the concordance model predicts!

Inferred is the operational word here. I'll bet it was fudged just enough to agree with the concordance model.

Here (http://citebase.eprints.org/cgi-bin/citations?id=oai:arXiv.org:astro-ph/0306088) is an obvious example of concordance cosmological model fudging.

I'm not outright dismissing the results, but we have to be aware of the shadowy assumptions made to "make the data/theory fit".

I don't have a problem with this strategy, but I can't yet accept it as obvious fact either because of the fudging.

[zforgetaboutit]

Then why is the CMBR a black-body of temp ~2.73K? How do you explain the observed polarisation in the CMBR under this idea?

Help me here:

Black Body - An ideal body which would absorb all (and reflect none) of the radiation falling upon it. The spectral energy distribution of a black body is described by Planck's equation; the total rate of emission of radiant energy is proportional to the fourth power of the absolute temperature (Stefan-Boltzmann law).

I don't understand the claim of the CMBR being a black body in the first place.

If we heat a black body and measure the total rate of emission radiation and it fits the law (as above), fine.

How does this relate to CMB being heated, and emission measurements being made in accordance with the law? Radiation being heated? By what? How? I don't understand what you mean. Dumb it down for me. :confused:

[zforgetaboutit]

Again, your challenge is to show that such decays can produce EM with the observed characteristics of the CMBR.

I'm unable to comply. Maybe I could also fudge it into concordance.

My points are just thought experiments by me, after all, emitted by my semi-plausible shotgun theory-generator.

[zforgetaboutit]

This may be so, but such speculation has nothing whatever to do with science

Yes it does, because it's a statement made by me based on my study of the physical world and its manifestations. Maybe not so with your science, Horatio.

When was the last time you created a Big Bang in the lab and witnessed/published the resulting isotropic CBR? Where's your fudge-free experimental data? :tongue2:

I think mathematical theorems are fudge-free, as long as you accept the total set of axioms. :wink:

You, and everybody else, don't have any such experiments to relate, and that's why these grand concepts are in the realm of cosmology - nobody can and ever will know why these things are the way they are, because there will never be, and never can be, an experiment to prove them. It's too fundamental. I'm all for the continuation of observation/discussion about them, however, to improve upon their models.

[zforgetaboutit]

(various things)

Can anybody please explain the following statement from here (http://map.gsfc.nasa.gov/m_uni/uni_101shape.html)

The WMAP spacecraft can measure the basic parameters of the Big Bang theory including the geometry of the universe. If the universe were open, the brightest microwave background fluctuations (or "spots") would be about half a degree across. If the universe were flat, the spots would be about 1 degree across. While if the universe were closed, the brightest spots would be about 1.5 degrees across.

The website doesn't say (AFAIK) why these angular widths were expected nor how they relate to the proposed age of the universe since the claimed Big Bang.

[Nereid]

Let me address one rebuttal at a time.

As a result of your posting I just skimmed here (http://ernie.ecs.soton.ac.uk/opcit/cgi-bin/pdf?id=oai%3AarXiv%2Eorg%3Aastro%2Dph%2F9905257) as best I could and finally arrived at the Conclusions on page 27 where the authors state

I was impressed with the paper's details, and the very difficult attempts to make sense of the apparently noisy data via COBE et al.

The sheer number of analytical assumptions that permit further progress is amazing, but you have to start some where.Thanks for the link, it was a most enjoyable paper! You can see that the field has moved on a great deal by reading the early COBE papers, and how they analysed the data to characterise, and remove, the foregrounds (there were also a few subtleties and complexities that I hadn't been aware of).

One way to treat this paper is to think that Tegmark et al want to squeeze every last tiny bit of CMB data (actually, estimates of parameters in cosmological models) out of the experiments as they possibly can, and at the same time be able to robustly address any challenge to their analysis. It is quite possible to use much blunter instruments to make the data tell its CMB story - you could completely ignore all data from 20o either side of the galactic plane, for example, or remove only known radio and IR point sources.So, as I (mis?)understand it, the results could be off by 2X or 5X, due to the complexities of foreground signal artifact removal. I realize the scope is cosmological here, but still - that's a lot of fudge factor, so far.That's not quite what they're saying; more that the error bars on estimates of their favourite cosmology model parameters will be greater than if they could remove the foregrounds perfectly - so for example, if they estimate a model parameter (I'm making this up) to be 4.2 +/- 0.5 assuming they can characterise the foregrounds perfectly, the results from BOOMERANG, WMAP (as it's now called), or Planck could be 4.2 +/- 1.0 (or, worst case,4.2 +/- 2.5).At the end of the parer they state A large number of papers have now painted a rosy picture of the future of cosmology, with CMB experiments measuring cosmological parameters to unprecedented accuracy over the next decade. In this paper, we have tried quite hard to spoil this picture, using foreground models with hundreds of harmful parameters and pushing them to limits of physical plausibility and current constraints.

Although we have found that great care needs to be taken in the foreground removal phase of the data analysis to avoid potentially perilous pitfalls, we have failed to tarnish the overall picture with more than a few minor blemishes, degrading the accuracy on certain measurements by small factors. Although much work certainly remains to be done on the foreground problem, this is cause for cautious optimism.Some other scientists think we should wait a little longer.My interpretation is somewhat different (remember that Tegmark et al are regarded as among the leaders of observational cosmology) - unless there's something totally left-field, we can confidently expect that data from BOOMERANG, WMAP, and Planck will help to constrain cosmological models quite a great deal more than they were when the paper was written (we now have the first year of WMAP data in the public domain, as well as that from BOOMERANG). Why? Because the data can be analysed to characterise both the foregrounds and CMB quite closely.

[Nereid]

Maybe there is no correlation.

As for CME's (coronal mass ejections?) - maybe COBE et al weren't looking downwind at the CME's path, so there's no measurement one way or another? Did somebody actually try to do this during a CME?

There would be so much interference from the CME (as I understand from the aforementioned paper) that it would be a messy undertaking to subtract other CME artifacts from the observations.The beautiful thing about COBE and WMAP (and maybe BOOMERANG) is that the data is all in the public domain! Anyone with a broadband connection can download the many MB to their own computers, write their own cleaning and analysis software, and so on.

Specifically, if you think there might be such a signal in the data, you can do your own analysis!

Re CMEs (yes): IIRC, the COBE papers did say there were some residuals which they felt could be accounted for by solar flares ... however, these were in the zodiacal light, and due to the dust being a little brighter at the time of flares.

However, I think your first step - on a path to show that the 'CMBR' is quite local - might be to describe a physical process (or processes) which could generate the right sort of microwaves.

[Nereid]

Our local haze may prevent us from seeing more distant, and therefore less distinct, neighbor extrasolar hazes.

(speaking underwater) "Can you see any water over there a couple of Km away?"

"No, there's too much intervening water to know for sure."If we had no clear observations of distant microwave sources, this might be a reasonable counter; however, as the COBE maps show quite clearly, along the galactic plane, the signals in several microwave channels is dominated by galactic dust, synchrotron radiation, etc. Also, there are several radio sources - known to be galaxies (z < 0.5, IIRC) - which can be 'seen' in many of the CMBR experiments.

The universe is pretty transparent to microwaves :wink:

[Nereid]

In my proposals, there could still be red shifts in the indicated directions; they would be from different causes (BH's, soups, etc.), not necessarily restricted to Big Bang theories.Sorry I wasn't clear enough.

The CMBR dipole is interpreted as being motion of the solar system wrt the CMB. From the size and direction of the dipole, you can calculate how fast the solar system must be moving, and in what direction; it's several hundred km/sec. However, nearby MW stars appear to move with speeds of only ~km/sec, to ~tens of km/sec. So, if the CMBR were 'local' - nearby in the MW - all nearby stars would be moving quite fast wrt to it ... why?

If the CMBR were 'local' - in the Local Group, or nearby cluster or supercluster - why do we here in our solar system move with that velocity wrt to it?

[Nereid]

Inferred is the operational word here. I'll bet it was fudged just enough to agree with the concordance model.

Here (http://citebase.eprints.org/cgi-bin/citations?id=oai:arXiv.org:astro-ph/0306088) is an obvious example of concordance cosmological model fudging.

I'm not outright dismissing the results, but we have to be aware of the shadowy assumptions made to "make the data/theory fit".

I don't have a problem with this strategy, but I can't yet accept it as obvious fact either because of the fudging.I think it's important to distinguish between cosmology models and observational data.

For the CMBR, the data are now very good, and with the second year of WMAP results expected out soon (and Planck in a few years' time), will be much better. In summary, the CMBR:
- has a near perfect black-body spectrum, T ~= 2.725 K
- has a dipole, of 0.00335 K
- has smaller-scale temperature fluctuations, <~0.0005K
- has a detailed angular power spectrum, observed to +/-% to l~several hundred
- has specific, well constrained polarisation characteristics.

Any theory - cosmological or otherwise - needs to account for the observational data.

As to whether the observations I referred to were 'fudged', I'll let you read the PR (it has a reference to the paper) - once you've done so, please tell us how you think the conclusion is fudged. UVES Measures the Cosmic Temperature 12 Billion Years Ago (http://www.eso.org/outreach/press-rel/pr-2000/pr-27-00.html)

[Nereid]

Help me here:

Black Body - An ideal body which would absorb all (and reflect none) of the radiation falling upon it. The spectral energy distribution of a black body is described by Planck's equation; the total rate of emission of radiant energy is proportional to the fourth power of the absolute temperature (Stefan-Boltzmann law).

I don't understand the claim of the CMBR being a black body in the first place.

If we heat a black body and measure the total rate of emission radiation and it fits the law (as above), fine.

How does this relate to CMB being heated, and emission measurements being made in accordance with the law? Radiation being heated? By what? How? I don't understand what you mean. Dumb it down for me. :confused:
It's not that the CMBR *is* a black-body; it's that the observed spectrum of the CMBR is a black-body spectrum (i.e. 'described by Planck's equation').

IIRC, when the COBE results were announced, Smoot (or a co-worker) simply put up a slide like the one at the bottom of this page (http://farside.ph.utexas.edu/teaching/sm1/lectures/node83.html), with no comment .... the room broke into applause.

(in fact, the diagram is somewhat misleading; the error bars are smaller than the thickness of the line, not as big as the diamond-shaped data points! :surprised )

[Nereid]

We have the same chance of understanding the universe's origins as cartoon characters having the understanding that they were drawn by an artist.This may be so, but such speculation has nothing whatever to do with scienceYes it does, because it's a statement made by me based on my study of the physical world and its manifestations. Maybe not so with your science, Horatio.

When was the last time you created a Big Bang in the lab and witnessed/published the resulting isotropic CBR? Where's your fudge-free experimental data? :tongue2:

I think mathematical theorems are fudge-free, as long as you accept the total set of axioms. :wink:

You, and everybody else, don't have any such experiments to relate, and that's why these grand concepts are in the realm of cosmology - nobody can and ever will know why these things are the way they are, because there will never be, and never can be, an experiment to prove them. It's too fundamental. I'm all for the continuation of observation/discussion about them, however, to improve upon their models.So it comes down to what we each understand to be science ... how about: constructing theories and making observations and doing experiments, the theories which we keep are those which are a) internally consistent, b) consistent with theories that have passed experimental muster, and c) [the most important] consistent with observational and experimental results, within the theory's domain of applicability. In this sense, 'understanding' means little more than 'developing theories which fit the facts well'; one's interpretation of those theories is entirely beyond science itself. In this sense, cosmology is just a branch of science whose domain of applicability is the universe as a whole; cosmological theories are good if a) they are internally consistent, b) consistent with General Relativity (within its domain of experimentally verified applicability), and c) consistent with observational and experimental results.

[Chronos]

Well, zforgetaboutit, your cosmology is thoroughly refuted by observational evidence. Nereid tried, but, failed to guide you in the right direction. It was clearly a waste of her time. While I am tempted to remark upon your specious arguments, I decline. Believe what you like, ignore whatever evidence you choose to ignore and make up your own version of reality. Apologies to all, but, I still think 'crap=crap'.

[zforgetaboutit]

As to whether the observations I referred to were 'fudged', I'll let you read the PR (it has a reference to the paper) - once you've done so, please tell us how you think the conclusion is fudged. UVES Measures the Cosmic Temperature 12 Billion Years Ago (http://www.eso.org/outreach/press-rel/pr-2000/pr-27-00.html)

Well, first the paper declares
"Since the universe is expanding, it must have been denser in the past." A follow-up post will explore this idea.

I believe this with as much conviction as earlier papers that confidently stated the universe is steady-state. Others said contracting.

Back then they also had observational evidence. Yes, science continuosly observes and attempts to construct ever-changing models which rationally predict behavior. That's good. But I just don't see any rationalization happening on the cosmological scale. Too many flip-flops.

So this, therefore, is the first sufficient fudge that turns me off. :smile:

[zforgetaboutit]

The universe is pretty transparent to microwaves :wink:

I want to point out the analogy of visible light passing through water. Somebody measuring the blue wavelengths would say "water is transparent to light".

I would counter that with "yes, to a certain extent, but the red wavelengths are severely limited in the distance they travel before being absorbed".

So... maybe the microwaves from your mentioned radio sources can travel from there to here, but the CMBR-like ones are more distance limited before they are weakened below current detection. Or vice versa.

Is a plot of microwave "frequency attenuation in the typical interstellar vacuum" vs. distance, linear? "Typical" will have many interpretations, of course.

I would guess that the microwave frequencies that excite hydrogen would be weakened if they passed through sufficient clouds of hydrogen. Any current ideas about this?

Re COBE's maps of CMBR within particular viewing target regions, are they reproducible (within small limits) from day-to-day, or longer time-periods, ignoring CME's and other local phenomena?

[zforgetaboutit]

However, I think your first step - on a path to show that the 'CMBR' is quite local - might be to describe a physical process (or processes) which could generate the right sort of microwaves.

Alas, I cannot comply because of the many resources I don't have, the least of which are mental. :tongue2:

My intuition tells me that if dark matter exists, then CMBR might be caused by dark matter resonating due to

energies impinging it (dark matter)
energetic particles colliding with it


I find this proposal easier to accept, and simpler, than the universe having a beginning (or end).

[zforgetaboutit]

In this sense, cosmology is just a branch of science whose domain of applicability is the universe as a whole; cosmological theories are good if a) they are internally consistent, b) consistent with General Relativity (within its domain of experimentally verified applicability), and c) consistent with observational and experimental results.

No problem with that.

[zforgetaboutit]

Well, zforgetaboutit, your cosmology is thoroughly refuted by observational evidence. Nereid tried, but, failed to guide you in the right direction. It was clearly a waste of her time. While I am tempted to remark upon your specious arguments, I decline. Believe what you like, ignore whatever evidence you choose to ignore and make up your own version of reality. Apologies to all, but, I still think 'crap=crap'.

Wow - such jingoism from you. Is that a nice way to behave? You contributed nothing with your Cosmic Forum Posting Background fanboy noise.

Only daring speculation can lead us further, not accumulation of facts.

Albert Einstein
Letter to M. Besso, October 8 1952, Einstein, 1972

Apparently you feel you have the right to insult Einstein also.

I'm not here to refute anything.

My posts on this topic are not things I believe in - I'm just asking "have these alternatives been explored and dismissed?".

I certainly believe in the measurements cited, but not necessarily in the interpretations. I don't have any motivation to make sweeping statements.

Although I don't understand everything Neried writes, I sincerely appreciate the effort.

Anyways,

Cosmology-guiding = religion, and that is crap.

Cosmology-observation-stating = cool, and I embrace it.

[zforgetaboutit]

The CMBR dipole is interpreted as being motion of the solar system wrt the CMB. From the size and direction of the dipole, you can calculate how fast the solar system must be moving, and in what direction; it's several hundred km/sec. However, nearby MW stars appear to move with speeds of only ~km/sec, to ~tens of km/sec. So, if the CMBR were 'local' - nearby in the MW - all nearby stars would be moving quite fast wrt to it ... why?

This site (http://www.yfiles.com/4th.htm) quotes the velocity as being (just to mention a number)

In relation to the background heat of the Universe (our wall paper of the Universe for lack of a better term) called cosmic microwave background radiation (CBR) the Earth is moving at 872,400 Miles per Hour (~400 km/s)


This dipole you mention - is it the radio wave analogue to the doppler effect for light/sound? I don't know what you mean, yet.

I'm trying to imagine the resultant of all these motions and it's a necessarily complex path, like being on an amusement ride. If we wait a while, will the dipole observation look different, as we move aong the path?

I.E. While on an actual amusement ride, our perception of the frequency of a stationary static frequency tone emitter will change depending on exactly what part of the ride's path we are on. This may not pertain to your explanation, depending on what you mean by dipole.

[Chronos]

Wrong. Your 'static frequency emitter' only works in your reference frame.

[zforgetaboutit]

Wrong. Your 'static frequency emitter' only works in your reference frame.

My reference frame is the only one I care about.

[Nereid]

This site (http://www.yfiles.com/4th.htm) quotes the velocity as being (just to mention a number)

In relation to the background heat of the Universe (our wall paper of the Universe for lack of a better term) called cosmic microwave background radiation (CBR) the Earth is moving at 872,400 Miles per Hour (~400 km/s)


This dipole you mention - is it the radio wave analogue to the doppler effect for light/sound? I don't know what you mean, yet.'Dipole' in this case simply means 'has two poles' :smile: a hot pole and a cold pole - it's responsible for the 'yin/yang' appearance in the Aintoff projections - one part of the sky seems warmer, the other cooler, and the temperature varies between the two poles exactly as if the solar system were moving towards the warm pole at 369 km/sec (more details here (http://www.astro.ucla.edu/~wright/CMB-DT.html)). For comparison, this Hipparcos paper (http://astro.estec.esa.nl/Hipparcos/venice-proc/poster05_01.pdf) shows that stars nearby move at speeds of ~km/sec to ~tens of km/sec wrt the solar system (so if you seek an explanation for the CMBR that is local, you have a huge difference in the apparent speeds of neaby objects!)I'm trying to imagine the resultant of all these motions and it's a necessarily complex path, like being on an amusement ride. If we wait a while, will the dipole observation look different, as we move aong the path?Well, you have the satellites' motions (wrt the Earth), the Earth's (wrt the solar system barycentre), the solar system (wrt SagA*, the MW centre, mostly galactic rotation), the MW wrt the centre of the Local Group; that centre wrt the CMBR! The first two are so well known that the data is analysed to remove these; the third has been directly detected (e.g. long-baseline radio interferometry using quasars), but would take millions of years to show up in the CMBR signal; the last two are estimated based on other data - even LBI would take millenia to detect directly!

[Nereid]

Well, first the paper declares "Since the universe is expanding, it must have been denser in the past."
A follow-up post will explore this idea.
Here's the whole of the para: "Since the universe is expanding, it must have been denser in the past. A particular prediction of the Big Bang theory is also that the temperature of the CMBR must have been higher at earlier times. However, although quite a few attempts have been made, no clear observational confirmation of this has been possible so far. In fact, the best observations until now have only been able to establish upper limits to the cosmic temperature at earlier epochs."

So, what they are saying is IF the BB theory is right, THEN the CMBR must have been higher in the past ... and that's what they set out to look for, and that's what they found!

To repeat my challenge ... what 'fudge' was used in the observations?I believe this with as much conviction as earlier papers that confidently stated the universe is steady-state. Others said contracting.But the point about science isn't what you, or I, or Hawking, or even Einstein believe; it's about how consistent is the good observational data with any theory? So, are you saying that the observational results aren't consistent with the BB theory? If so, why do you say that?Back then they also had observational evidence. Yes, science continuosly observes and attempts to construct ever-changing models which rationally predict behavior. That's good. But I just don't see any rationalization happening on the cosmological scale. Too many flip-flops.

So this, therefore, is the first sufficient fudge that turns me off. :smile:Well, that's OK, you're entitled to your own opinions :smile:

However, if you wish to discuss science, don't you agree that you need to do so within its accepted framework? And that this means testing all theories on the wrack of experiment and observation?

[Nereid]

I want to point out the analogy of visible light passing through water. Somebody measuring the blue wavelengths would say "water is transparent to light".

I would counter that with "yes, to a certain extent, but the red wavelengths are severely limited in the distance they travel before being absorbed".

So... maybe the microwaves from your mentioned radio sources can travel from there to here, but the CMBR-like ones are more distance limited before they are weakened below current detection. Or vice versa.

Is a plot of microwave "frequency attenuation in the typical interstellar vacuum" vs. distance, linear? "Typical" will have many interpretations, of course.

I would guess that the microwave frequencies that excite hydrogen would be weakened if they passed through sufficient clouds of hydrogen. Any current ideas about this?OK, I'd like you to do some work now ... take some time with google and read some papers ... find out what observations have been made in the relevant microwave bands (the range of frequencies is not small!), by what kinds of telescopes, with what sorts of results. Pay particular attention to what absorption and emission process have been hypothesised and observed, and what the limits are to these. (Hint: the universe is pretty much transparent to microwaves; several processes are known to attenuate them, and several emission ones are known e.g. synchrotron, dust)Re COBE's maps of CMBR within particular viewing target regions, are they reproducible (within small limits) from day-to-day, or longer time-periods, ignoring CME's and other local phenomena?Yes; read the many CMBR papers on observations since COBE, with particular attention to parts of those papers which discuss consistency with earlier observations.

[Nereid]

Alas, I cannot comply because of the many resources I don't have, the least of which are mental. :tongue2:

My intuition tells me that if dark matter exists, then CMBR might be caused by dark matter resonating due to

energies impinging it (dark matter)
energetic particles colliding with it


I find this proposal easier to accept, and simpler, than the universe having a beginning (or end).Your intuition might be right :eek:

However, intuition is not science :surprised

Do you know of anyone who has made a proposal more or less in line with your intuition? Has such a paper been accepted for publication in a peer-reviewed journal? Have you worked out the details of your proposal (e.g. how those resonations give rise to a 2.73K black body spectrum, with a 369 km/sec dipole in the observed direction)?

You know, I personally find quantum mechanics downright spooky ... but no one has yet come up with an experiment which contradicts it! So, spooky-to-me or not, that seems to be the way the universe works :approve:

[zforgetaboutit]

Your intuition might be right :eek:

However, intuition is not science :surprised

Do you know of anyone who has made a proposal more or less in line with your intuition? Has such a paper been accepted for publication in a peer-reviewed journal? Have you worked out the details of your proposal (e.g. how those resonations give rise to a 2.73K black body spectrum, with a 369 km/sec dipole in the observed direction)?

You know, I personally find quantum mechanics downright spooky ... but no one has yet come up with an experiment which contradicts it! So, spooky-to-me or not, that seems to be the way the universe works :approve:

My motives are being misunderstood.

How about if you reconsider my postings as "Has anybody studied or proposed... (zforgetaboutit's musings)?"

When a prof suggests a research topic to the grad student, the grad student doesn't (usually) say "First you prove it then I'll consider it." or "That can't be right because nodbody else has published it."

Most of what I'm suggesting are directions in research for those who have the means to go down that road.

For no good reason one of the replies (not yours) was downright hostile.

[zforgetaboutit]

You know, I personally find quantum mechanics downright spooky ... but no one has yet come up with an experiment which contradicts it!

I'll be in that forum soon to ask about first principles of QED. Of all the explanations I've read to justify the first steps - they don't seem right to me. I'm missing too much formal background to go with the flow. I hope to improve my understanding in the other QED forum.

Some of you can hardly wait. :zzz:

[zforgetaboutit]

Pay particular attention to what absorption and emission process have been hypothesised and observed, and what the limits are to these.

I don't have enough fundamental background to judge their hypotheses, that ended up agreeing with their observations.

It would be so interesting for me to participate in recreations of all the classic experiments, discussing results, so I could better know the backgrounds of today's physics.

If I had the financial means I would gladly spend the rest of my life doing that.

[Nereid]

My motives are being misunderstood.

How about if you reconsider my postings as "Has anybody studied or proposed... (zforgetaboutit's musings)?"

When a prof suggests a research topic to the grad student, the grad student doesn't (usually) say "First you prove it then I'll consider it." or "That can't be right because nodbody else has published it."

Most of what I'm suggesting are directions in research for those who have the means to go down that road.

For no good reason one of the replies (not yours) was downright hostile.

I continue...Oops, sorry! :blushing:

Yes, I did misunderstand; the context of the sections here at PF has changed somewhat in the last month or so ... your good questions (if I may paraphrase, 'why is the CMBR considered to be a relict of the Big Bang? what foreground explanations have been ruled out and why?') deserve clear answers. If I may so however, sometimes I didn't fully understand some of those questions, rather interpreted some of them as "I've got an alternative proposal for the nature of the CMBR, it's {X}".

So, in a nutshell:
- AFAIK, no proposal other than that the CMBR is a highly redshifted 'image' of the surface of last scattering is consistent with the high quality observational data
- there are several well-understood foregrounds: the 'red tail' of thermal radiation from the solar system zodiacal light, 'free-free' emission, emission by (MW) galactic dust (both rotation - 'spinning' - and vibration), synchrotron emission, point sources (mostly beyond the MW), and the Suyaev-Zel'dovich effect (SZE)
- there are also some 'cosmological' footprints that are not 'just' the surface of last scattering, e.g. gravitational lensing of the CMBR, the late integrated Sachs-Wolfe effect, the Ostriker-Vishniac effect (aka 'the kinematic SZE'), and patchy re-ionisation
- AFAIK, all the 'well-understood' foregrounds have been unambiguously detected and well-characterised
- the Tegmark paper you provided a link to has a good discussion of each of these, as well as references to papers examining each in much more detail.

The SZE is a very interesting thing! I will do some digging to find what the status of the observational validation, in the microwave region. You will see there's an implication of the SZE for high energy cosmic rays - the inverse Compton scattering which give the microwave SZE footprint also produces high energy gammas (as also happens in supernova shockfronts) - in a few years' time (when CANGAROO and HESSI and VERITAS accumulate good data), and maybe after GLAST has been at work for a while, there should be independent data on the (distant) CMBR ... via UHE gammas!

[Nereid]

This set of slides from COBE (http://lambda.gsfc.nasa.gov/product/cobe/slide_captions.cfm) give a nice overview of how COBE worked, how foregrounds were measured and subtracted (and what they were), what the dipole is, etc.

Note that the microKelvin fluctuations detected by COBE may not all be 'real' - at that level the researchers could only be sure that there *were* statistically significant fluctuations in the (dipole-removed) residuals, of approximately the size and nature predicted by the \LambdaCDM cosmological models. The later CMBR observations - MAXIMA, DASI, ACBAR, CBI, FIRS, BOOMERANG, WMAP - were of higher precision, so any particular fluctuation has now be clearly re-observed (usual caveats apply, e.g. angular resolution).