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Offline Vern

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Can dark matter be a simple thing?
« on: 30/03/2009 15:34:00 »
While reading the recent dark matter thread, an idea came to me. So since this section is for fun stuff, here's the thought:

Is it possible that the dark matter we see affecting galaxies could simply be electromagnetic radiation? At first thought, this seems preposterous; but after I dwell upon it some, I see a possibility.

If this were true, the radiation would be at a frequency we could not detect via common methods. It would either be too low in frequency, or too high in frequency for our current detectors. We detect high end radiation all the way through gamma radiation and notice that at about .511 MeV two gamma photons can interact to produce a positron and electron. So, it is probably not the high end of the spectrum.

What about the low end? We are not usually interested in radiation below the radio spectrum; but we know there's a bunch of it at those lower frequencies. We don't know how much. I don't think there's ever been an attempt to measure it. The frequency would need to be less than about 10 cycles per second or we would pick up a buzz. Suppose it is on the order of one cycle per second or less.

Now, there's so much of that stuff out there, and probably right here, if we had a perfectly tuned receiver maybe we could harness some of that energy and convert it to usable power.

Edit: Oops; wrong section; but since the referenced thread is in this section, maybe it will work.
« Last Edit: 31/03/2009 13:00:13 by Vern »


 

Offline lightarrow

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Re: Can dark matter be a simple thing?
« Reply #1 on: 30/03/2009 16:00:55 »
While reading the recent dark matter thread, an idea came to me. So since this section is for fun stuff, here's the thought:

Is it possible that the dark matter we see affecting galaxies could simply be electromagnetic radiation? At first thought, this seems preposterous; but after I dwell upon it some, I see a possibility.

If this were true, the radiation would be at a frequency we could not detect via common methods. It would either be too low in frequency, or too high in frequency for our current detectors. We detect high end radiation all the way through gamma radiation and notice that at about .511 MeV two gamma photons can interact to produce a positron and electron. So, it is probably not the high end of the spectrum.

What about the low end? We are not usually interested in radiation below the radio spectrum; but we know there's a bunch of it at those lower frequencies. We don't know how much. I don't think there's ever been an attempt to measure it. The frequency would need to be less than about 10 cycles per second or we would pick up a buzz. Suppose it is on the order of one cycle per second or less.

Now, there's so much of that stuff out there, and probably right here, if we had a perfectly tuned receiver maybe we could harness some of that energy and convert it to usable power.

Edit: Oops; wrong section; but since the referenced thread in in this section, maybe it will work.
High energy photons have to be excluded because they would be detected; very low frequency EM radiation is a possibility, even considered that we still haven't experimentally proved the fact that radiation is made of photons (or, however, it's not easy to detect a radiation at those frequencies, in general).
 

Offline Vern

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Re: Can dark matter be a simple thing?
« Reply #2 on: 30/03/2009 17:37:41 »
It might be noticed as a gradual fluctuation in electrostatic or magnetic fields if we could figure how to detect it.
 

Offline lightarrow

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Re: Can dark matter be a simple thing?
« Reply #3 on: 30/03/2009 20:23:13 »
Anyway, I wonder if someone has made a simple computation of the mass of CMBR and of visible light (I presume it has already done and that the result is negligible, but I actually don't know).
 

Offline Vern

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Re: Can dark matter be a simple thing?
« Reply #4 on: 30/03/2009 22:07:27 »
Yes; one of the reasons I began to wonder about the electromagnetic field contributions to the massiveness of galaxies is the billions of years that galaxies have been generating a wide spectrum and flinging it out into their spacial area. It must tug a little on the source galaxy. I don't remember ever coming across a serious study of that.

Edit: Also, there would be lots of electrons, protons, and alpha particles that might be slung out a few light years only to slow down and eventually return.
« Last Edit: 30/03/2009 22:09:43 by Vern »
 

Offline Maze

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Re: Can dark matter be a simple thing?
« Reply #5 on: 30/03/2009 22:30:24 »
Quote from lightarrow
Quote
even considered that we still haven't experimentally proved the fact that radiation is made of photons

I had thought that all electromagnetic radiation was photons. What are photons considered to be?
 

Offline Vern

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Re: Can dark matter be a simple thing?
« Reply #6 on: 30/03/2009 22:52:59 »
We do consider all electromagnetic radiation to exist as photons each of which contains one quanta of energy-time. We have no way to prove that, however, as lightarrow suggested.
 

Offline astrobabe

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Re: Can dark matter be a simple thing?
« Reply #7 on: 31/03/2009 01:34:54 »
My main concern for you theory is that extreemly long wavelength radiation has very little energy (since energy is proportional to frequency) and as "dark matter" seems to have many times the mass of "light matter" within our galaxy that would require a huge huge huge source of these low frequency photons. Also if so much of such long wavelength light existed then there would be a noticeable effect of the photons up-scattering off electrons in the galaxy and halo (known as the inverse Compton effect).

Also if it were electrons or any other type of matter we know about it we would be able to detect the absorption of distant light by them.

I think we just don't understand gravity yet but am hoping the dark matter people will finally find something to prove their theory right....
 

Offline lightarrow

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Re: Can dark matter be a simple thing?
« Reply #8 on: 31/03/2009 09:22:30 »
Quote from lightarrow
Quote
even considered that we still haven't experimentally proved the fact that radiation is made of photons

I had thought that all electromagnetic radiation was photons. What are photons considered to be?
Quantums of electromagnetic field's energy: when you measure EM energy with a detector (for example a photomultiplier) the energy detected comes in "packets". This is an *experimental* result and has been showed for visible light and other frequencies, but not for very low frequencies, yet.
« Last Edit: 31/03/2009 09:24:54 by lightarrow »
 

Offline Vern

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Re: Can dark matter be a simple thing?
« Reply #9 on: 31/03/2009 12:47:04 »
Quote from: astrobabe
My main concern for you theory is that extreemly long wavelength radiation has very little energy (since energy is proportional to frequency) and as "dark matter" seems to have many times the mass of "light matter" within our galaxy that would require a huge huge huge source of these low frequency photons. Also if so much of such long wavelength light existed then there would be a noticeable effect of the photons up-scattering off electrons in the galaxy and halo (known as the inverse Compton effect).
Yes; it's true that low frequency photons would have little energy, however, every photon has the same amount of energy-time that we call action. All of the action of a single photon seems to happen at a very small point. Very low frequencies wouldn't interact with matter except gravitationally. So, your point is valid, but I don't think it conclusive enough to dismiss the concept.

BTW, not a theory; wild guess, and probably wrong. :)
 

Offline yor_on

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Can dark matter be a simple thing?
« Reply #10 on: 31/03/2009 14:41:02 »
Vern?
Would those low frequencies contain more 'gravity' the lower they became?ŽAnd if so, wouldn't those lower frequencies become 'quenched' at some point? Would they then become 'infinitely' 'gravitational', if that is a property relating to frequency?
 

Offline Vern

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Can dark matter be a simple thing?
« Reply #11 on: 31/03/2009 14:57:46 »
Hi; yor_on.

I haven't seen a theory that equates photon gravitational attraction with frequency. If my speculative guess about the cause of gravity is correct, each photon would have equal gravitational attraction. The cause would be that photons have points of saturation. The points tend to reach saturation toward increasing field strength of residual fields. Low frequency photons would contribute to the strength of the residual fields. But that is highly speculative and only pondered by a very few.

Edit:
Another curious thing about gravity is that it diminishes as the square of distance away from its source. The volume of a sphere increases as the cube of distance. So, does gravity occupy a sphere? The area of a flat disk increases as the square of distance. The force of gravity seems to convey as flat disks of force.
« Last Edit: 31/03/2009 15:45:21 by Vern »
 

Offline Soul Surfer

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Can dark matter be a simple thing?
« Reply #12 on: 31/03/2009 20:51:28 »
An interesting concept but I think we would have to be talking about frequencies of cycles per thousand years or so and the fields would probably have to be enormous and coherent. what are essentially fixed electric and magnetic fields do have an effect on light and other particles which would also be detected they would also show in structural regularities.
 

Offline Vern

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Can dark matter be a simple thing?
« Reply #13 on: 31/03/2009 21:07:31 »
The field of a single photon could not be detected easily. A jumble of long wave photons would not be coherent and so would not be detected as well. So we still need a conclusive reason that low frequency photons could not produce the gravitational anomaly seen in galaxies.

But, I can't think of anything that might produce such low frequency beasties. :) It seems it would need be common to every star; or maybe a galactic phenomena that increases with age. This would explain the absence of the anomaly in some galaxies; I've read that the anomaly is not present in all galaxies.

The absence of the anomaly is mentioned in this paper.

Quote from: the link
When Newton's or Einstein's gravitational theory is applied on galactic and cosmological scales, various anomalies are found: most famously, the orbital speed of stars far from the centre of a galaxy is roughly constant, where the theory predicts that it should fall off with radius r as 1/√r (which, furthermore, appears to happen for at least one galaxy); this is called the anomalous rotation of galaxies. This has traditionally been accounted for by postulating the existence of "dark matter", which we are unable to identify other than by its effect, via gravity, at galactic scales.
« Last Edit: 31/03/2009 21:22:48 by Vern »
 

Offline yor_on

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Can dark matter be a simple thing?
« Reply #14 on: 01/04/2009 14:38:30 »
Vern, you write "The force of gravity seems to convey as flat disks of force." and I agree if seen two dimensionally. But, if seeing it three dimensional, then it seems more like you might expect gravity to work in more dimensions, as it decreases by the square of its distance instead of 'increase' as you 'juggled' those comparisons :) More dimensions as if it was a 'mirror' of those examples and we assume spacetime to be 3+1 then I would expect it to mirror "The volume of a sphere increases as the cube of distance" but here as an gravitational decrease by that cube of distance. As it doesn't it leaves me no choice then but assume that gravity 'spills' in more dimensions than 3+1 :)
« Last Edit: 01/04/2009 14:58:31 by yor_on »
 

Offline Vern

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Can dark matter be a simple thing?
« Reply #15 on: 01/04/2009 14:52:02 »
I guess you could assume that gravity spills to other dimensions. But, to me, that seems a further stretch than the notion that gravity propagates in planes rather than volumes. It could affect the 3 + 1 space of a volume but propagate in 2 + 1 space of a plane. All of this is wild speculation and has no basis in theory, but it is interesting.:)

Edit: We have another force that is mediated by a critter that seems to exist as planes of electric and magnetic force, one plane being perpendicular to the other. And we have no trouble visualizing this in 3 + 1 space.
« Last Edit: 01/04/2009 15:02:45 by Vern »
 

Offline Soul Surfer

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Can dark matter be a simple thing?
« Reply #16 on: 01/04/2009 15:50:42 »
incoherent low frequency electromagnetic effects could not produce anyeffects but coherent ones could.  I would not expect these fields to have been generated now but are very much expanded relics of very early stages of the big bang.  Astronomers are just beginning to detect and measure magnetic fields on a galactic scale and finding them larger than they expected.  They could be large enough to affect the structure of galaxies but I do not think they could produce effects large Eng to cancel out the missing mass associated with expected dark matter. 

There are also good theoretical reasons for expecting the mass of the universe to be large enough to result in substantially flat space time
 

Offline Vern

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Can dark matter be a simple thing?
« Reply #17 on: 01/04/2009 16:43:13 »
incoherent low frequency electromagnetic effects could not produce any effects but coherent ones could.
I don't see how that assumption, which would be true for some effects, can be extended to gravity. We don't know the mechanism of gravity. It seems to me that the only requirement would be that the effects be in place.
 

Offline lightarrow

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Can dark matter be a simple thing?
« Reply #18 on: 02/04/2009 08:54:54 »
In Scientific American of this month there is an article on dark energy. According to a new theory, the effect of d.e. can be reproduced also assuming that our galaxy and some others could be at the centre of a gigantic "void", a vast region of space with lower density of matter than the rest of the universe; then there is lower gravitational "pull" and this would be perceived as a greater space expansion.
 

Offline Vern

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Can dark matter be a simple thing?
« Reply #19 on: 02/04/2009 12:41:40 »
I saw something similar a couple of years ago; but I think the one I saw had the Milky Way on the edge of the void. The quote below has the void repulsing the Milky Way. But further into the article it explains that the repulsing is only an effect due to the presence of matter in other directions.

From Astronomy on-line Magazine

Quote from: the link
June 12, 2007
Our Milky Way galaxy lies at the edge of a huge void and is being repulsed by the void at high speed. This observation provides astronomers with fundamental insights into how dark matter is distributed and the process of galaxy formation. Brent Tully of the University of Hawaii discussed this discovery at the meeting of the American Astronomical Society in Honolulu, Hawaii.
« Last Edit: 02/04/2009 12:44:24 by Vern »
 

Offline lightarrow

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Can dark matter be a simple thing?
« Reply #20 on: 02/04/2009 16:18:08 »
This is the article in Scientific American:
http://www.sciam.com/article.cfm?id=does-dark-energy-exist
 

Offline Vern

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Can dark matter be a simple thing?
« Reply #21 on: 02/04/2009 17:10:19 »
Thanks for the link; it is a very interesting concept. It is an attempt to explain dark energy, I don't think it would apply to the dark matter problem. :)
 

Offline astrobabe

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Can dark matter be a simple thing?
« Reply #22 on: 02/04/2009 19:14:49 »
E = mc2 meaning longer wavelength light (ie lower energy) must have less gravity than higher energy light.
 

Offline Vern

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Can dark matter be a simple thing?
« Reply #23 on: 02/04/2009 20:29:37 »
E = mc2 meaning longer wavelength light (ie lower energy) must have less gravity than higher energy light.
Each photon is less energetic but the energy-time is the same. It seems that the gravitational attraction between high frequency photons should be greater than between low frequency ones, however, there could be any number of the low frequency critters. Since we can't detect them, we can't count them. :) Maybe a good solid theory will develop and we can stop guessing. :)

 

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