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Dark Matter Grows Hair Around Stars and Planets (forbes.com)
StartsWithABang writes: Dark matter may make up 27% of the Universe's energy density, compared to just 5% of normal (atomic) matter, but in our Solar System, it's notoriously sparse. In particular, there's just a nanogram's worth per cubic kilometer, which makes the fact that we've never directly detected it seem inevitable. But recent work has demonstrated that Earth and all the planets leave a "wake" of dark matter where the density is enhanced by a billion times or more. Time to go put those dark matter detectors where they belong: in the path of these dark matter hairs.
Remember, when the facts don't match your theory
Correct. The facts don't match the theory. Galaxies could not hang together the way they do if all they consist of is the things we've already observed in the laboratory unless we change the law of gravity [to something enormously more complex - c.f. epicycles] or postulate the existence of something that interacts gravitationally but doesn't interact with light.
too bad for the facts
I don't get this. Nobody is ignoring the facts. That's why we need to change things. Dark matter is the heliocentric solution. No dark matter is the epicyclic solution.
The [difference between facts and] theory is easily explained
Don't know about easily. There's been a lot of "dark matter" theories that have fallen due to one or more inconsistencies with known physics.
by an abundant (making up 96% of the universe),
Necessary otherwise we have to change the theory of gravity
invisible,
If by invisible you mean doesn't interact with EM radiation then yes, this is required by the facts.
undetectable
It's not undetectable. If it were undetectable then we wouldn't need it. It's very detectable - its gravity is what makes galaxies hang together. Its gravity is what allows gravitational lensing to happen where there isn't any (visible) matter to make it happen.
magic
Definitely not magic. It has to agree with all the laws of physics. Conservation of momemtum, conservation of energy, speed of light etc.
"dark matter"
it's called dark matter because it doesn't interact with the EM spectrum. It neither emits EM radiation nor absorbs it.
that is everywhere and affects everything.
Actually, I think this is one of the great unknowns. Whether it's large numbers of light particles or smaller numbers of massive particles. Its primary interaction with the known universe is through gravity which yes, does affect everything, everywhere, at the speed of light.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
no they aren't. they have observations that don't match the math calculations and they are trying to account for it. just like right before the theory of relativity. they thought there was and extra planet due to unexplained observations in the orbit of the planets that didn't match the math
Dark matter isn't a case of "fact vs. theory", but "fact vs. fact". We have multiple methods of determining the mass of galaxies and galaxy clusters. One method - counting all the light-emitting stuff - gives a certain number, and all other methods (rotation curves, gas kinematics, gravitational lensing, large-scale structure analysis, and more) give a much higher number. Two possible conclusions: 1) Our understanding of gravity is wrong, or 2) There is a new component of the universe that does not interact with light. Option 1) fails a lot of tests: if you try to make solutions for gravity for certain systems, it doesn't work for others. Option 2) has a solution called "dark matter", a new weakly-interacting massive particle that explains almost all the observations (it's not 100% perfect, but it does much better than the changing-gravity option).
At the same time that all this was happening in cosmology, our particle physics friends were developing extensions to the Standard Model. In many theories they predicted new kinds of particle: ones that just happened to have a lot of the right kind of properties that the cosmologists needed for dark matter. Voila.
Dark matter is the simplest, most parsimonious, most elegant known solution that fits the observational data.
Source: I'm an astrophysicist and I do a podcast, and one of my first episodes was on exactly this.
You have that backwards. They're modifying theory to match the facts. They've tried to ignore darkmatter for nearly 100 years, but they can't get rid of it. The more information we get, the more real it becomes. It has reached a point in science where the numbers are slapping us in the face, saying, "STOP IGNORING ME!"