Dark matter does not radiate

[Aki]

I find it hard to believe that dark matter does not radiate. Everything radiates, including icwe caps in the north pole. It is believed that dark matter is made up of WIMPs, and since it is a particle, it should radiate. Well I was thinking maybe dark matter does radiate waves, but the range is outside of the electromagnetic spectrum we know and it is beyond detection with the equipement we have. Is that possible?

[Tormod]

Aki,

 

Do all particles radiate? I thought radiation in the electromagnetic spectrum at least *is* particles...

[pgrmdave]

Is it possible that they radiate in an entirely different spectrum, one that we haven't discovered because our area of the universe doesn't have much of it?

[lindagarrette]

If dark matter radiated, we would be able to find it. So I say no, it does not.

[GAHD]

I suppose if it was a different state of matter it could radiate beyond known wavelengths....

 

Still it could be anything. Heck it could even be forces of another dimension acting on our 'brane.

 

:shrug:Who knows?

[maddog]

Well, I'm baack! Skiing in Steamboat was wonderfull!

 

Aki -- The theory of Dark Matter being WIMPs is out because theory of WIMPs is out of

---> favor... Best way to check is do a google search with both criteria and "dark matter"

---> in quotes. :cup:

 

Tormod -- Yes, Radiation in the context discussed here are EM (both wave or particle

---> description).

 

All -- Dark Matter as defined as dark because no evidence for radiation has yet been

---> found. Such a concept was found by gravitational lensing of a distant object when

---> nothing was found closer in the field of view. There are now numerous cases. A

---> recent sky survey has shown matter to be composed of 5% matter (we do see),

---> 25-30% of Dark Matter (we don't see), and 65-70% of Dark Energy (haven't figured

---> out how this percentage is verified). There are 3 flavors of Nuetrinos that all are

---> weakly interacting with other particles including photons. There are still a bunch of

---> particles yet to find as the superpartners of the normal particles, if you go by

---> Supersymmetry.

 

Maddog

[GAHD]

ugh, I still wonder if dark matter couldn't be two-dimentional, now there'd be a twist.

[BlameTheEx]

Perhaps dark matter does not radiate, or radiates very little. Why should it radiate? Consider the possible reasons:

 

1) Radiating heat left over from the big bang. - Unless it almost a perfect insulator or in very large chunks (say star sized) the heat should have all dissipated.

 

2) Re-radiating energy absorbed from starlight, cosmic background radiation, and the like. - Not an option if dark matter is a poor absorber. If it is not made with charged components (i.e. orbiting electrons) it won't be. Think of a perfect glass. If it is in largish chunks (say asteroid to planet sized) of ordinary matter there won't be enough surface area to count.

 

3) Decay. - But dark matter may be stable.

[Tormod]

Well, I'm baack! Skiing in Steamboat was wonderfull!

 

Good to see you back! Too bad you lost our chat yesterday...make sure you make it to the next one. Skiing is a bad, bad excuse. :)

 

Tormod -- Yes, Radiation in the context discussed here are EM (both wave or particle

---> description).

 

Okay, I stand corrected.

[Tormod]

Wait - Maddog - hang on. I thought particles are wavelike in nature except when interacting with other particles. So radiation = particles, no?

[C1ay]

If dark matter radiated, we would be able to find it.

 

That is not necessarily true. There are many discoveries to be made in the future that we do not yet have the technology for. If dark matter radiates it may be millennia before we even have the technology to detect it. To be honest to ourselves we must acknowlege at least this much.

[maddog]

Wait - Maddog - hang on. I thought particles are wavelike in nature except when interacting with other particles. So radiation = particles, no?

Tormod,

 

In QM there is this duality notion for both Fermion of spin 1/2 (matter like) and Bosons of integral spin

(force like) where either can be seen as wave and or particles depending on the situation. For example,

the Photoelectric Effect discovered by Einstein showed light could behave as a particle (1921). He won

his only Nobel prize for that. And later De Broglie discovered Electrons could be made to behave as waves

with De Broglie waves (1925) in a variation of the multiple slit experiment. It was this dual nature that had

everyone baffled until Heisenberg came up with using Spinors to do matrix mechanics (1927) and later

formalized by Dirac (1929). So and the answer is a qualified yes (depending on how you are looking).

Really, radiation can be both perceived as particles and waves. However, you can definitely think of light

as radiation (unless you consider Nuclear radiation; then you are dealing with a different critter)... :(

 

So a Photon being a Boson is a packetized version of light. It would still adhere to Maxwell's equations for

EM as photons are one in the same -- just quantized.

 

If you wish to discern when to either class as wave or particle, thes depends are where each is dominant.

Waves dominate in the aggregate (lots of particles) or systems or beams. Particles dominate when the

population is small. It is for this reason why discovering a quantum description for gravity is so difficult.

Gravity as a force is so weak that even when the population is large the actual local field potential is so

small that even with todays devices it is theorized we are at least 6 orders of magnitude away from

measuring gravity waves. So when you see if the population were small how much harder to detect a

Graviton would be. For a typical laser beam the population of photons would be around 10^15 or so.

For gravity we don't know how many theoretical gravitons would be needed to express a 1 G field.

 

An so it goes... :(

 

Maddog

[maddog]

At the moment it is hard to determine whether dark matter radiates or not. Yes, true it being doesn't

bear as proof it doesn't, only we don't observe the effect. Without knowing much of what the material is

speculation of whether it does radiate is of little value. :(

 

Maddog