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from the still-might-be-made-of-missing-socks dept.
Arthur T Knackerbracket has found the following story:
For one brief shining moment after the 2015 detection of gravitational waves from colliding black holes, astronomers held out hope that the universe's mysterious dark matter might consist of a plenitude of black holes sprinkled throughout the universe.
UC Berkeley physicists have dashed those hopes.
A supernova (bright spot at lower left) and its host galaxy (upper center), as they would appear if gravitationally lensed by an intervening black hole (center). The gravitational field of the black hole distorts and magnifies the image and makes both the galaxy and the supernova shine brighter. Gravitationally magnified supernovas would occur rather frequently if black holes were the dominant form of matter in the universe. The lack of such findings can be used to set limits on the mass and abundance of black holes. (Miguel Zumalacárregui image)
Based on a statistical analysis of 740 of the brightest supernovas discovered as of 2014, and the fact that none of them appear to be magnified or brightened by hidden black hole "gravitational lenses," the researchers concluded that primordial black holes can make up no more than about 40 percent of the dark matter in the universe. Primordial black holes could only have been created within the first milliseconds of the Big Bang as regions of the universe with a concentrated mass tens or hundreds of times that of the sun collapsed into objects a hundred kilometers across.
The results suggest that none of the universe's dark matter consists of heavy black holes, or any similar object, including massive compact halo objects, so-called MACHOs.
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(Score: 0) by Anonymous Coward on Wednesday October 10 2018, @11:40PM
No. The planck mass is a little under 2.2*10^-8 kg, on the order of a speck of dust. So you're off by 20 orders of magnitude. A Planck mass black hole wouldn't cause any more gravitational lensing than a speck of dust would.
A black hole of Planck mass would have a Schwarzschild radius of the Planck length, and would no longer be able to evaporate by Hawking radiation. It also would not interact by any of the other fundamental forces, and would be so small that it could pass not only right through an atom, but right through a proton, without interacting. It is a perfect WIMP dark matter candidate. Some scientists think it will still evaporate, and others think it will remain as an essentially stable particle. Wikipedia acts like it is settled and it would just evaporate, and the majority opinion is that it would probably be unstable somehow, but no one actually knows. The question cannot be answered without a theory of quantum gravity. A theory of quantum gravity would allow meaningful predictions about such objects, and conversely, the detection of such an object would tell us a tremendous amount about quantum gravity. There is, unfortunately, no chance of creating one of these in any technologically plausible particle accelerator.
But please, go on talking down to me. That's always a totally awesome thing to do, especially when you have completely missed the point and gotten all your science wrong (the risk of relying on unsourced Wikipedia articles!).