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Dark Matter/Energy

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Jenny
53509.  Mon Feb 20, 2006 11:08 am Reply with quote

I hesitate, ignoramus that I am, to join in a technical conversation, but what is radiation if it's not a form of energy, and how would that energy differ from the energy released in nuclear fission and changed to matter in nuclear fusion? Or have I got totally the wrong end of the stick (quite likely)?

 
Tas
53511.  Mon Feb 20, 2006 11:18 am Reply with quote

Quote:
I assume that by refering to matter=energy that Tas is refering to the E=MC2. Matter can be changed into energy and back again through the processes of nuclear fussion and nuclear fission. It is not radiation itself that changes into matter. So it isn't a candidate for the missing matter in the universe, neither is background radiation much of a candidate for the missing dark energy. Dark energy needs to be causing the force that is causing the expansion of the universe to accelerate and I don't believe radiation is a candidate for this.


Hmmm.....so, radiation (caused by fission/fusion) is not the missing matter?
I have never liked the 'dark matter' theory, anyways, as it does seem to be a bit like a black hole in someones accounting.
"Well, we think there should be....but well....errr....we can't find it. Sorry"

:-)

Tas

 
gerontius grumpus
53517.  Mon Feb 20, 2006 11:28 am Reply with quote

It's a shame darkmatter/dark energy is so dark. If it could be made a bit brighter we might be able to find it more easily.

 
grizzly
53522.  Mon Feb 20, 2006 11:35 am Reply with quote

Jenny wrote:
I hesitate, ignoramus that I am, to join in a technical conversation, but what is radiation if it's not a form of energy, and how would that energy differ from the energy released in nuclear fission and changed to matter in nuclear fusion? Or have I got totally the wrong end of the stick (quite likely)?


It does depend upon the type of radiation (alpha beta or gamma). I am not an expert but I do believe that the energy that changes to matter in nuclear fussion is not radiation because it is extreme heat which is the form of energy that is necessary in nuclear fusion. Of course I am not an expert so I am liable to get these sort of details wrong.

The existence of dark energy is infered from the fact (disputed by a minority) that the rate that the universe is expanding is increasing. That acceleration implies a force is exerting itself on all matter in the universe. Whether radiation could create that force I don't know but it is probably unlikely to cause a sufficient force to cause the accelerating expansion of the universe.

 
Kevino7
53534.  Mon Feb 20, 2006 11:44 am Reply with quote

It can't be alpha or beta radiation as they are particles and would disprove the fact that Space is a vacuum.

 
Tas
53544.  Mon Feb 20, 2006 11:49 am Reply with quote

I thought it was fairly well known that space was not, in fact, a vaccum. It is filled with cosmic dust, stellar particles (solar wind, no doubt brought on by large amounts of solar baked beans!), and so on...

:-)

Tas

 
Kevino7
53551.  Mon Feb 20, 2006 11:54 am Reply with quote

My mistake, chances are though it is Gamma radiation.

 
dr.bob
53572.  Mon Feb 20, 2006 12:04 pm Reply with quote

grizzly wrote:
I assume that by refering to matter=energy that Tas is refering to the E=MC2. Matter can be changed into energy and back again through the processes of nuclear fussion and nuclear fission. It is not radiation itself that changes into matter.


Radiation certainly can, and does, convert into matter and back again. I can't find a decent link anywhere, but check out http://sol.sci.uop.edu/~jfalward/elementaryparticles/elementaryparticles.html and scroll down to the bit with a picture of Paul Dirac looking particularly dorky. It shows a cloud chamber track where a gamma ray photon converts into an electron and a positron.

Indeed, Stephen Hawking theorised that black holes may shine with the egotistically named "Hawking radiation" whereby photons near the even horizon turn into a particle and an anti-particle. One of them is then sucked into the black hole, which means the other (heading in the opposite direction) can't recombine and annihilate them both, so it just heads away from the black hole into space.

 
grizzly
53577.  Mon Feb 20, 2006 12:05 pm Reply with quote

Kevino7 wrote:
It can't be alpha or beta radiation as they are particles and would disprove the fact that Space is a vacuum.


Space isn't a complete vacuum, at least not the space inside the solar system. Anything from the solar wind to charged particles that form the magnetosphere of the planets. Beyond the solar system is the interstellar wind which fills the space beyond our solar system. Plus many theories exist of quantum particles popping in and out of existence even in a complete vacuum.

 
Kevino7
53579.  Mon Feb 20, 2006 12:05 pm Reply with quote

Mkaes sense. After all Energy cannot be created or destroyed.

 
Kevino7
53598.  Mon Feb 20, 2006 12:15 pm Reply with quote

A major question would be: Why are they mining miles underneath the surface for it?

 
grizzly
53603.  Mon Feb 20, 2006 12:19 pm Reply with quote

dr.bob wrote:
grizzly wrote:
I assume that by refering to matter=energy that Tas is refering to the E=MC2. Matter can be changed into energy and back again through the processes of nuclear fussion and nuclear fission. It is not radiation itself that changes into matter.


Radiation certainly can, and does, convert into matter and back again. I can't find a decent link anywhere, but check out http://sol.sci.uop.edu/~jfalward/elementaryparticles/elementaryparticles.html and scroll down to the bit with a picture of Paul Dirac looking particularly dorky. It shows a cloud chamber track where a gamma ray photon converts into an electron and a positron.

Indeed, Stephen Hawking theorised that black holes may shine with the egotistically named "Hawking radiation" whereby photons near the even horizon turn into a particle and an anti-particle. One of them is then sucked into the black hole, which means the other (heading in the opposite direction) can't recombine and annihilate them both, so it just heads away from the black hole into space.


In neither case is nuclear fusion taking place, nor . In any case using the word radiation is not completely correct in this sense. Electromagnetic radiation (i.e. gamma rays) are only photons which in the exceptional circumstances above only have a mass because they are moving.

Besides in all of these cases of radiation they are effectively only conventional particles and are probably part of what is included when we talk about the "normal matter". They are not what explain the dark matter.

 
Celebaelin
53622.  Mon Feb 20, 2006 12:37 pm Reply with quote

If photons are massless and energy and mass are interconvertable but not equivalent/in equilibrium i) why can't light escape the gravitational attraction of a black hole and, if I'm allowed a follow up question, ii) how does light exhibit both particle and wave properties?

 
Kevino7
53625.  Mon Feb 20, 2006 12:40 pm Reply with quote

light is an electromagnetic wave and carries energy (That would help explain the second question).

For question 1, i dunno when it moves it has a mass?

 
tetsabb
53632.  Mon Feb 20, 2006 12:47 pm Reply with quote

Quote:
Just sweep the excess 4% under the carpet. Nobody will notice.


Quote:
I have never liked the 'dark matter' theory, anyways, as it does seem to be a bit like a black hole in someones accounting.
"Well, we think there should be....but well....errr....we can't find it. Sorry"


Management (named Wendy!) and I have similar feelings about all this. Somewhere we have failed to observe something, or Enron rules the Universe

 

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