Since moving photons have momentum, am I right to suppose that light from stars is able to interact with (and disperse, if intense enough) clusters of dark matter?
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1$\begingroup$ start with en.wikipedia.org/wiki/Dark_matter $\endgroup$– anna vCommented Sep 27, 2021 at 4:22
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3 Answers
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Dark matter can produce something called gravitational lensing. Therefore, depending on the distribution of the dark matter, it may cause some form of scattering of the light from galaxies. In fact, this process has been used in a recent survey.
answered Sep 27, 2021 at 7:20
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$\begingroup$ Gravity does not cause dispersion. Perhaps choose a different term. $\endgroup$– my2ctsCommented Sep 27, 2021 at 9:47
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Dark matter is totally transparent. A photon passing through dark matter will not deflect dark matter through collisions.
Dark matter only interacts with gravity. As my2cts pointed out, that means dark matter and light can interact. This usually would mean that light can be deflected when passing by a massive enough object, such as a galaxy or cluster of galaxies. This deflection is caused by the curvature of spacetime. Light is deflected in the sense that it follows a curved geodesic, not that it is deflected from a straight path by a force.
But for light to deflect dark matter through gravity, light would have to be a source of gravity. The sources of gravity are energy density, stress, and pressure. Starlight is far too dim for this to any measurable degree. It might have an impact in the interior of the brightest stars.
answered Sep 27, 2021 at 4:20
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$\begingroup$ This is not correct. Light and dark matter interact gravitationally. $\endgroup$– my2ctsCommented Sep 27, 2021 at 9:50
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$\begingroup$ @my2cts - You are right. I added a correction. $\endgroup$ Commented Sep 27, 2021 at 15:01
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$\begingroup$ I am realizing I put down my question in an improper form. What I actually wanted to achieve was an exploration of the subject of dispersing clusters of dark matter through light and heat. Can you expand on your statement that starlight is far too dim, and it requires the temperatures of the core of the hottest stars to achieve the slightest effect on dark matter? Thank you in advance $\endgroup$ Commented Sep 27, 2021 at 15:31
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$\begingroup$ Light and heat are not good ways to affect dark matter. Gravity is the only way. Rather than asking how to manupulate dark matter, you should be asking Is Dark Matter Real?. $\endgroup$ Commented Sep 28, 2021 at 0:24
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Light and dark matter interact gravitationally. The effect of light on dark matter should be utterly negligible. Conversely, dark matter affects light and causes dispersionless gravitational lensing.
