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A wobble from Mars could be sign of dark matter
- venusenvy47 2y agoWould a primordial black hole have a small accretion disk? If so, it seems like that disk would give off radiation.
- mystified5016 2y agoProbably not. Accretion disks are temporary, they only exist for a few thousands/millions of years after a capture event. Something has to get really close, and the smaller your object is, the more unlikely it is for something to come close enough to be consumed. Plus the rate at which a black hole can consume mass is proportional to mass/radius. If it's too small, it can only consume matter very slowly, which means the accretion disk would be cold and quiet.
- jalapenos 2y ago"Dark matter" sounds a lot like "we've run out of ideas so we're going back in the direction of 'the ether' and chariots pulling the sun across the sky and the like".
- MathMonkeyMan 2y agoThere are a bunch of good reasons to believe there really is matter there that we can't detect aside from its gravity. Here's a talk: <https://www.youtube.com/watch?v=h8KV9Ht5o_M https://www.youtube.com/watch?v=h8KV9Ht5o_M>.
- smolder 2y agoDark matter is an observed discrepancy between measurements. There appears to be a lot of unaccounted-for mass, based on many experimental results. There are several theories as to what that observed discrepancy could be caused by. This is a well-covered topic, anywhere you could hope to learn about astrophysics. What it may sound like to you is not what it is. I'd recommend watching a video from PBS Spacetime if you want to learn about it. They have several.
- throwawaymaths 2y agoThe original dark matter turned out to be Neptune. The second dark matter was planet Vulcan (which turned out to not exist) Dark matter has a roughly 50/50 track record.
- jalapenos 2y agoYeah I just feel like they're talking about a problem they've been unable to solve, rather than a solution. Einstein and Planck just solved stuff, with a fraction of the talk and resources. Now Physics seems to be so stagnant it's mostly an exercise in making descriptions for the things it's failing at, as though a problem can somehow match the value of a solution if you give it a cool name and talk about it enough.
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- Supermancho 2y ago> Einstein and Planck just solved stuff, Their ideas, solutions, and problems didn't come about from magic.
- smolder 2y ago> Yeah I just feel like they're talking about a problem they've been unable to solve, rather than a solution. That's right. There is not yet a definitive answer on what dark matter is, just several theories. WIMPs, MOND, primordial black holes... > Now Physics seems to be so stagnant Crapping on modern physics for a lack of progress seems a popular thing amongst us lay people, but despite all the credit you give them (and that they deserve,) I doubt Einstein or Planck would have just intuited the right solution to dark matter.
- tekla 2y agoShitting on all of science ever is easy. Actually doing it is hard.
- throwawaymaths 2y ago
- lordloki 2y agoYeah. What if space/time is just noisy?!?
- klyrs 2y agoThat "noise" would be called dark energy until we understand its source.
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- mystified5016 2y agoGalaxies don't behave how they should with our understanding of gravitational mechanics. The only thing that fixes the model is the addition of a lot of mass that we can't see. That would be easy enough to explain away as an incomplete model, except we have observed galaxies which do fit our models. The only way to explain that is if those galaxies are missing this invisible mass. There's no other way to reconcile these observations. How would you square these observations? Under our models of gravity, most galaxies behave as though they contain much more mass than what we observe. However, some behave exactly as Newton would predict. The misbehaving galaxies can be made to fit the model by adding mass in very particular locations, mainly as a halo or shell around the outside. We can show how much mass and where it must be to make galaxies behave as expected. These calculations are the same for most galaxies with dark matter, and galaxies without dark matter require no correction. At this point we have two explanations: either gravity behaves radically differently in different places in the universe, or there's a new type of massive particle that we haven't discovered. We know already that the standard model of particle physics is incomplete, and there are more particles to be discovered. We are also very confident that the laws of physics are the same throughout space and time, and we are very confident that our models of gravity are correct on large scales. The simplest explanation that fits all available data is dark matter. Positing that there's a new type of massive particle that we haven't discovered isn't really a shocking revelation.
- moi2388 2y agoWith our calculations. Which we know use wrong distance, don’t take spin direction into account, and use newton instead of Einstein. And use things like pi=3=1 and a whole bunch of other simplifications. It’s a miracle it predicts anything at all.
- mystified5016 2y agoUh, no. None of that explains the fact that the large structure of the galaxies we observe is not possible without extra mass. This has nothing to do with observational error or rounded calculations. The shape of the galaxies and their internal structures are clearly wrong. Besides, this also ignores the fact that we observe galaxies both with and without dark matter. These galaixes have very different structures that cannot arise from the same physics unless we consider dark matter.
- Already__Taken 2y agoso wouldn't small black holes since the dawn of the universe be very fast by now? 13 billion years of bouncing past particles must add up.
- dctoedt 2y agoStupid question, posed but apparently not answered in TFA: What if a small black hole approached a person, or even came into contact? Would we see it as, say, someone's arm suddenly falling off for no apparent reason? Or would the size of the black hole be so infinitesimal that for practical purposes it wouldn't matter? FTA: "'I think someone asked me what would happen if a primordial black hole passed through a human body,' recalls Tung, who did a quick pencil-and-paper calculation to find that if such a black hole zinged within 1 meter of a person, the force of the black hole would push the person 6 meters, or about 20 feet away in a single second. Tung also found that the odds were astronomically unlikely that a primordial black hole would pass anywhere near a person on Earth."
- kadonoishi 2y agoHere's another answer to the Fermi Paradox, that while life is normal and abundant, there are lots of random possibilities for destruction such as a primordial black hole coming by. The apparent rarity of intelligent life might be a statistical matter of there being lots of opportunities for such life to arise, but also lots of hazards of random destruction. ... on reflection, while this might be intellectually satisfying, it's not particularly nice to contemplate.
- valiant55 2y agoThat sounds like a variation of the Great Filter[0] [0]: https://en.wikipedia.org/wiki/Great_Filter?wprov=sfla1 https://en.wikipedia.org/wiki/Great_Filter?wprov=sfla1
- Ancalagon 2y agoWouldn’t a black hole that small evaporate pretty quickly?
- ithkuil 2y agoIirc a black hole with the mass of an asteroid (whose event horizon would be very small indeed) would have a hawking temperature smaller than the cosmic microwave radiation so there wouldn't be any net evaporation.
- okasaki 2y agoMust be from the Gods on Olympos QTing around.