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Scientists' Biggest Search For Dark Matter To Date Just Turned Up Nothing (sciencealert.com)
Peter Dockrill, reporting for ScienceAlert: For something that's hypothesised to make up more than 80 percent of the mass of the entire universe, it's no easy thing to detect the existence of dark matter. That's the conclusion the world is coming to today, after scientists announced that a massive $10 million experiment to find traces of elusive dark matter particles had failed after an exhaustive 20-month search. "We've probed previously unexplored regions of parameter space with the aim of making the first definitive discovery of dark matter," said physicist Cham Ghag from University College London in the UK, one of the scientists who took part in the Large Underground Xenon (LUX) project based in South Dakota. "Though a positive signal would have been welcome, nature was not so kind! Nonetheless, a null result is significant as it changes the landscape of the field by constraining models for what dark matter could be beyond anything that existed previously."Ars Technica has more details.
From Ars:
The LUX detector (Large Underground Xenon) is designed to pick up signs of weakly interacting massive particles, or WIMPs, when they engage in one of their rare interactions with normal matter.
There are indeed other candidates for dark matter, WIMPs being only one of those. This experiment searched specifically for WIMPs, which only rules them out, while of course the other remaining candidates remain to be explored.
nothing to do with string theory, it's the search for why the stars in even our own galaxy have the orbits they do, and why the cosmic microwave background has certain imprints in it
The orbital period of a star in a galaxy depends, to first order, on the amount of mass that is closer to the centre of the galaxy than the star. (That's a consequence of gravity being an inverse-square force.)
The distribution of stellar orbital velocities in a galaxy indicates that there is additional mass, not at the centre, but distributed amongst the stars in a galaxy. An inventory of the visible mass shows there is nowhere near enough to account for the velocity distributions. Therefore, it is inferred that there is invisible, or dark matter, that accounts for the discrepancy. It has nothing to do with mismeasuring the mass at the centre of the galaxy, whether it's a black hole or not.
>the dark matter explanation feels a bit hacky anyway.
Dark matter isn't the explanation, it's the question.
We observe things like: https://en.wikipedia.org/wiki/...
but we don't know what is causing them. "Dark matter" is just a short way of saying "whatever it is that is responsible for these things we are observing".
Right, a theory. But if you can't count it, can't measure it, does it really exist?
But we can measure it. Its gravity reveals its existence, its quantity, and its location. So yes it exists. We just don't know what it is, and the detector experiments are testing theories about what it may be.
We also have pretty good estimates of the density of dark matter in the solar neighborhood. It amounts to 0.49 ± 0.13 GeV cm3. This means, if you weight 70 kg, your body contains about 34 trillion electron-volts of dark matter (or 6*10^-20 grams).
Second class citizen of the New Gilded Age
They do not entertain the idea that maybe their laws are wrong, or that some other phenomenon might be affecting gravity.
Sure, MOND never happened.
Many people have spent a lot of time looking for ways to explain single like galaxy rotation curves, stellar velocities in globular clusters and elliptical galaxies, the structure of galaxy clustering and what-not without success. The simplest explanation has always turned out to be that there is some sort of extra matter that we cannot see. Dark matter requires the smallest number of assumptions out of all explanations that people have proposed so far. By Ocham's Razor it is probably the right solution. And by Grabthar's Hammer you shall be avenged.
Just because you are paranoid does not mean that no-one is out to get you.