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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.
Ockham's razor: The facts suggest that gravitational force without visible source is being exerted.
Since the only known source of gravity we know is matter, we assume that gravitational source comes from some invisible matter, but we don't currently have any solid proofs for this specific assertion (although neither do we have any to the contrary, nor alternate viable theories).
It may yet appear that it does not. It may be some form of existence different than matter or energy; some wrinkles of spacetime or some sourceless gravity clusters. Since we don't know anything like that, "dark matter" is a convenient shorthand to describe that effect.
It's a bit like both with Rutheford's atom model and with Planck's quantization of spectrum.
The first - assuming that atom structure is a kind of "dough" with electrons being "raisins" fit the knowledge of that time explaining the "solid" nature of solids. It was blatantly wrong, proven by later experiments that found tiny nuclei in huge empty space. It was still a convenient shorthand for a time, to describe several observed phenomena and fit some observations - and for lack of better alternatives, it was accepted until disproven.
The latter sounded so incredible at first, that it was used strictly as a *hack* to obtain results that fit the experimental data, with belief that the underlying mechanism is vastly different, but undiscovered as of yet - so the "hack" was again a shorthand used to explain given phenomena, out of convenience, because again, we didn't know any better way to explain the behavior of photon emissions, or the stability of atom - even though practically nobody believed it to be true, just a conveniently close approximation. And then, surprise-surprise, more and more experiments confirmed - that "hack" was actually how the reality worked, that was not a mistake but a very unlikely - though ultimately true - description of the nature of atom.
Whether Dark Matter is another Rutheford's Atom, or another Planck's Quantum distribution, is to be determined and it will either be confirmed or invalidated. Currently, as a shorthand explaining the observed phenomena, it's doing pretty well.