Is dark matter a candidate to fill void left by luminiferous ether as a medium for light travel?
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6$\begingroup$ no. the michelson morley experiment shows that there exists nothing with the attributes of ether and special relativity has made everything consistent. what void? $\endgroup$– anna vCommented Sep 1, 2014 at 13:10
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$\begingroup$ What is to prevent dark matter from being hypothesized as a medium of propagation? $\endgroup$– user56930Commented Sep 1, 2014 at 13:16
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7$\begingroup$ Are you saying that you don't believe light can propagate in a vacuum? $\endgroup$– DanuCommented Sep 1, 2014 at 13:20
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3$\begingroup$ @user56930 the fact that light propagates equally well in areas with very little DM as it does in areas with high concentrations of DM. That tends to indicate it has no role as a medium of propagation. Otherwise density changes would produce optical effects $\endgroup$– JimCommented Sep 1, 2014 at 19:56
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$\begingroup$ Thanks. Does sound travel at varying speeds through a bell jar as air is pumped out of it? $\endgroup$– user56930Commented Sep 1, 2014 at 19:59
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1 Answer
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No.
There is no void left by the lack of an aether. The very notion of aether should serve as a warning as to how catastrophically analogical reasoning can fail. "Water waves are in water, sound waves are in air, therefore there must be something in which light propagates." This is flawed logic, and decades of physics were arguably hindered by adhering to it.
In fact, any material medium for light would contradict the beautiful result of Michelson and Morley, showing that the speed of light does not depend on velocity with respect to some material's frame. This invariance is in fact now at the very heart of modern physics, and is the basis for relativity, which has been verified in innumerable experiments.
Dark matter is, according to the leading theories, some form of matter that is basically normal except that it essentially doesn't interact via the electromagnetic force. As such, it is actually a poor candidate for explaining anything to do with light, even if there were something that needed explaining.
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$\begingroup$ Thanks for your time. I'm sure the void I speak of is the void in my own. understanding. Suffice to ask only: is there anything to prevent the hypothesis that dark matter might propagate anything as a medium. Perhaps my question is not a fair question. $\endgroup$ Commented Sep 1, 2014 at 13:25
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3$\begingroup$ Things can only propagate stuff they interact with. Dark matter's sole reason for existing is that we see evidence of stuff that interacts via gravity and essentially nothing else. So it can have gravitational effects, but e.g. gravitational waves, like light, don't need a medium to propagate in. $\endgroup$– user10851Commented Sep 1, 2014 at 13:29
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$\begingroup$ "Water waves are in water, sound waves are in air, therefore there must be something in which light propagates." ... There is something in which light propagates: the electromagnetic field. It just happens to be a field that is Lorentz invariant. $\endgroup$– user1247Commented Sep 1, 2014 at 13:38
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1$\begingroup$ Dark matter may propagate sound, i.e. pressure waves of some type. In general it has been hypothesized to fit the gravitational orbits of galactic clusters, so dark matter is not something permeating all space uniformly. $\endgroup$– anna vCommented Sep 1, 2014 at 13:40
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1$\begingroup$ @user1247 the electromagnetic field is actually a varying electric and magnetic field with energy and momentum, not permeating all space either. $\endgroup$– anna vCommented Sep 1, 2014 at 13:42