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I apologize in advance for the dumb question. How is an earth mass black hole formed? I thought they form from collapsing large stars.
by rapsey 7y ago
I apologize in advance for the dumb question. How is an earth mass black hole formed? I thought they form from collapsing large stars.
- opmac 7y agoPrimordial black holes were formed during the big bang. That's the only way we think such objects could form.
- dr_dshiv 7y agoWhat mechanism could create them? By the time there was matter, I thought the only pressure forces were ambient light and baryonic acoustic waves, neither of which should be strong enough...
- knzhou 7y agoYou're right that there is no mechanism to make primordial black holes in the standard theory. That's because they're new, separate things, so to have them, you of course need to add in new ingredients. They can be created by the collision of topological defects in the early universe, which in turn can be created in phase transitions during the cooling of the universe, like imperfections in quickly frozen ice. Or they can be created by simple collapse following inflation, if inflation is modified to create large inhomogeneities.
- ben_w 7y agoYou don’t need to matter to create a black hole, a Kugelblitz black hole is made entirely of light.
- dr_dshiv 7y agoFascinating! But, if that's the case, the densities of light after the big bang would have created endless numbers of these?
- Simon_says 7y agoThat's the idea.
- dr_dshiv 7y agoMy understanding is that things were incredibly homogeneous until the time in which baryonic acoustic waves started creating compressed and expanded areas. If there were black holes in that homogeneous soup, when things were so dense, it seems like everything would turn into a black hole or get sucked it. Assuming light going into a black hole adds to its mass? But assuming some light and matter didn't get sucked in and that's what remains, then I can understand why black holes are proposed as a possible answer to the mystery of dark matter.
- ben_w 7y agoWolfram Alpha says that the Schwarzschild radius for the mass of the visible universe is bigger than the visible universe, so all I can say is something is missing from my understanding (but I already knew that). http://www.wolframalpha.com/input/?i=schwartzchild%20radius%20for%20mass%20of%20universe http://www.wolframalpha.com/input/?i=schwartzchild%20radius%...
- hnuser123456 7y agoWhat you might be missing is that the radius of a black hole is proportional to its mass, so in fact, two half-visible-universe-mass-BHs would take much less volume than a vis-universe-mass one, moreso for four quarters, etc. Additionally, it's been proposed this universe is a 4d-spatial black hole. In this case, you can re-consider aggregating the entire 3d-spatial universe as a 4d black hole, and the Schwarzschild radius calculation works again. https://www.nature.com/news/did-a-hyper-black-hole-spawn-the-universe-1.13743 https://www.nature.com/news/did-a-hyper-black-hole-spawn-the...
- ben_w 7y agoThat’s isn't something I missed, as it happens. Given some of the answers on the Physics StackExchange, I think my error is using a static approximation like the Schwarzschild solution for a dynamic situation — given my grasp of the Einstein field equations is “ooh pretty symbols” this isn’t a huge surprise, though my lack of detailed understanding is a personal frustration.