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# Dark Matter explanation?

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A question to the scientific minds out there.

As gravity has an effect on light and other electromagnetic radiation could light and other EM radiation have an equal and opposite effect on its surroundings and thus account for all the excess gravity out there?

I'm sure this has been ruled out by more qualified people than me in the past, can anyone throw any light on this?

Thanks

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Radiation has an equation of state, under relativistic radiation.

http://en.m.wikipedia.org/wiki/Equation_of_state_(cosmology)

so your correct in that it does exert pressure. However it is already accounted for

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In addition to radiation pressure, light "attracts" matter, as any energy does, yes. (Relativity people wouldn't formulate it "attract").

Though, that won't by far suffice to replace dark matter.

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A question to the scientific minds out there.

As gravity has an effect on light and other electromagnetic radiation could light and other EM radiation have an equal and opposite effect on its surroundings and thus account for all the excess gravity out there?

I'm sure this has been ruled out by more qualified people than me in the past, can anyone throw any light on this?

Thanks

I think this is good conjecture. But like all conjecture it is a matter of opinion. As others have pointed out, EM radiation exerts pressure, and just as gravity "attracts" and bends light, so does light "attract" and gravitationally influence matter. Also as others have mentioned, the extent of both is small compared to the effect needed to explain the many supposed effects of dark matter including observed orbital velocities of spiral galaxies and clusters. This would be the standard-model answer and explanation for your query.

As to other possibilities there is an observed effect called the Tully-Fisher relationship where the Luminosity (intrinsic brightness) of a spiral galaxy is directly proportional to the maximum observed orbital velocity of the galaxy to the 4th power. In astronomy it can be written like this:

L (Vmax.) 4

This approximate relationship for orbital velocities of spiral galaxies means that there is a relationship between the brightness, the intensity of galaxy starlight, and a spiral galaxy's orbital velocity. This relationship is a factor in the MOND gravity formulation and some other formulations trying to provide an alternative explanation to dark matter.

MOND gravity, as well as other proposals, assert stronger gravity at galactic scales. The most well-known of these is MOND proposed in 1983 by Mordehai Milgrom, an Israeli Physicist. In 2004 Jacob Bekenstein, a Mexican-Israeli theoretical physicist, developed the first complete relativistic gravity formulation with MONDian behavior, called TeVeS. Still another proposal is called Scalar-tensor-vector gravity (STVG) which also proposes stronger "MOG" gravity. Other proposals not involving stronger gravity have been Metric Skew Tensor Gravity (MSTG) proposed by John Moffat, which proposes the additional gravity tensor influence of electro-magnetism. And a number of other lesser known or generally unknown proposals which propose such things as vortex mechanics at galactic scales, attempting to explain all venues that dark matter is presently thought to explain.

So your conjecture could be on target concerning the effect of radiation on the rotation velocities of spiral galaxies, at least indirectly IMO if any other model of gravity turns out to be correct in the absence of dark matter.

Edited by pantheory
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I think this is good conjecture. But like all conjecture it is a matter of opinion. As others have pointed out, EM radiation exerts pressure, and just as gravity "attracts" and bends light, so does light attract and gravitationally "attract" matter. Also as others have mentioned, the extent of both are small compared to the effect needed to explain the many supposed effects of dark matter and related orbital velocities. This would be the standard-model answer to your query.

Then it is NOT a "matter of opinion", is it. It is an idea (a hypothesis) which has been falsified by the evidence.

Edited by Strange

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