Dark Matter/Dark Energy - just light we can't see?

[Bob G]

Maybe a naive question, but do the calculations that posit the existence of Dark Matter/Energy take into account light and other energy forms traveling through space that are NOT directed towards earth? When we see starlight, that same star light is traveling out basically in a "sphere", i.e., that light will be seen at any place in the universe. However, from our perspective, we can't see it because we only detect phenomena coming directly towards earth. Therefore there is a huge amount of light/energy filling space that we cannot see or detect directly.

Since it has been shown that light acts both as a wave and as a particle, it seems logical that all that light, with photons as mass, must exert some gravitational force. The same would hold true of cosmic rays and other forms of interstellar mass and energy. Since E=MC squared, all that energy is also likely to have some gravitational impact that we have not been able to measure because on an individual basis it is almost infinitesimal, but on a cosmic basis is huge.

It is not hard to believe that in the 13.8 billion years of the universe's existence that there is more light and other forms of matter/energy traveling through space than currently captured in stars.

Is anybody closely connected to the actual math and assumptions being used to calculate dark matter/energy?

 

[Helio]

Maybe a naive question, but do the calculations that posit the existence of Dark Matter/Energy take into account light and other energy forms traveling through space that are NOT directed towards earth? When we see starlight, that same star light is traveling out basically in a "sphere", i.e., that light will be seen at any place in the universe. However, from our perspective, we can't see it because we only detect phenomena coming directly towards earth. Therefore there is a huge amount of light/energy filling space that we cannot see or detect directly.

Yes, light does bend when it passes near gravitational "wells". DM is a form of matter that exhibits gravity so the use of this fact allows astronomers to detect and measure the amount of DM as light bends slightly around it.

DE (Dark Energy) howeve is deemed to be isotropic - no matter where you look it will appear the same.... if you could see it. So light will not alter its course.

Since it has been shown that light acts both as a wave and as a particle, it seems logical that all that light, with photons as mass, must exert some gravitational force. The same would hold true of cosmic rays and other forms of interstellar mass and energy. Since E=MC squared, all that energy is also likely to have some gravitational impact that we have not been able to measure because on an individual basis it is almost infinitesimal, but on a cosmic basis is huge.

Yes, but since the cosmos is huge then the density of light I assume is usually insignficant. Light flux density is very high near the Sun, but the mass of the Sun completely makes the light "mass" insignificant, and its density decreases using the inverse square law.

Is anybody closely connected to the actual math and assumptions being used to calculate dark matter/energy?

It would be interesting to see how the currently established mass ratios were determined.

 

[Bob G]

Yes, light does bend when it passes near gravitational "wells". DM is a form of matter that exhibits gravity so the use of this fact allows astronomers to detect and measure the amount of DM as light bends slightly around it.

DE (Dark Energy) howeve is deemed to be isotropic - no matter where you look it will appear the same.... if you could see it. So light will not alter its course.


Yes, but since the cosmos is huge then the density of light I assume is usually insignficant. Light flux density is very high near the Sun, but the mass of the Sun completely makes the light "mass" insignificant, and its density decreases using the inverse square law.

It would be interesting to see how the currently established mass ratios were determined.

Thanks for the feedback. I guess, ultimately, I would like to know, as you state in your last sentence - what factors are used to calculate mass ratios? I know I won't understand the math, but how are such things as cosmic rays, neutrinos, and energy such as gamma, radio and other waves factored in? I agree about the light density - but there are 13.8 billions years of photons, cosmic rays, radio waves, x-rays, etc., all "floating" out in interstellar space. How is that mass/energy calculated, even if only to discount it as a factor?

Thanks again for your reply.

 

[Catastrophe]

"all 'floating' out in interstellar space" My emphasis.

Please correct me, But I do not like the word 'floating'.
Passing by at c - that is fine. Floating, to me, suggests hanging around like grapes, waiting to be picked.

Also don't forget E = mc^2 is the rest mass only.

Cat

 

[Helio]

Thanks for the feedback. I guess, ultimately, I would like to know, as you state in your last sentence - what factors are used to calculate mass ratios? I know I won't understand the math, but how are such things as cosmic rays, neutrinos, and energy such as gamma, radio and other waves factored in? I agree about the light density - but there are 13.8 billions years of photons, cosmic rays, radio waves, x-rays, etc., all "floating" out in interstellar space. How is that mass/energy calculated, even if only to discount it as a factor?

Thanks again for your reply.

As Cat notes, E=mc^2 is for a rest mass, so when calculating energy for a photon, there are two ways, I think, that are valid. The full equation is actually:

E2 = p2c2 + m2restc4

So for a rest mass = 0, then E = pc, where p is momentum.

Also, E = hc/lambda, where lambda is wavelength.

Either should give you, let's call it "equivalent mass" though we see it only as photon energy.

But our retina will receive over 100,000 trillion photons per second when one foolishly looks at the Sun directly. The mass effect of that huge number isn't the viewer's problem.

Since a photon does have equivalent mass, albeit super tiny, it will alter its course when it gets near another mass. But this needs to be a significantly large mass because the photon's only go one speed - incredibly fast.

History....When Einstein derived is GR (General Relativity) equations, he wanted to have three separate objective tests as to its accuracy. The bending of light around the Sun during an eclipse is measurable. Interestingly, since we now recognize the photon has mass, then Newton's equations would also predict bending by a certain amount for a given distance from the Sun. Einstein's GR value was 2x, IIRC, the Newton value. Eddington's eclipse event measurements supported Einstein and the media quickly found out about making Einstein famous overnight.

The likely issue with a passing photon affecting the path of another becomes no big issues since at no time will they encounter one another at anything traveling less than c, so the "mass effect" that might cause it to alter course seems insignificant.

The CMBR, the most distant light known, seems unaffected, AFAIK.