3 ms·

Can anyone confirm the accuracy here? Sounds rather significant however I don't know the theoretical limit of how big a black hole can be - or the implications

Can anyone confirm the accuracy here? Sounds rather significant however I don't know the theoretical limit of how big a black hole can be - or the implications of that (haven't considered it). Seems like we are in an era of discovery in space - heady times!

ravi-delia 4y ago
There's no real limit, since you can just keep dumping stuff in forever. There is however a soft limit that the stuff has to be close enough to get dumped in, and this one is extremely old so we aren't sure where it got its mass from!
- taylodl 4y ago
  Au contraire! There's plenty of mass to feed such a black hole, the real question is "when you run things backward" in the lambda-CDM model why isn't the entire universe a black hole? Or why wouldn't it be the case that there wasn't a primordial mega star that quickly (in universal time) collapsed into a supermassive black hole and the remnants of the supernova is the mass of the remainder of the universe and form the CMB radiation?
  - michannne 4y ago
    This is a cool idea I've never heard before. The universe we're in is the result of a cosmically massive star going supernova.
xenadu02 4y ago
I don't know the number but the limit is the speed of light and expansion of the universe. In the modern phase of the universe a black hole would only be able to eat its own galactic cluster (or maybe supercluster). Hubble expansion means superclusters experience the expansion of spacetime so certainly any matter beyond a black hole's own supercluster will move away from the black hole faster than light and thus never be able to fall into it. In practice a black hole can't even get near that limit because angular momentum can't just vanish... much of the matter would (over a long time) end up in distant orbit around that super super massive black hole and never fall into it. In the early universe spacetime expansion was happening so quickly that it was difficult for large black holes to form at all. If that were not the case most matter in our universe would have collapsed due to gravity and ended up in black holes but we know it did not. Actually if gravity were that strong or expansion were slower/weaker then the universe would never have formed at all and stayed as a singularity. To get formation of super large black holes very early you'd need a knife-blade balancing act of gravity vs expansion to just barely form super super massive black holes without the "permanent singularity, no universe" scenario. We can see billions of stars, galaxies, etc so we know that scenario did not happen. Super super massive black holes are neat objects though. If this one really is as big as they say then it will be one of the last objects left in the universe. It would take trillions and trillions of years for it to evaporate due to Hawking radiation. I wonder if the last life left in the universe will end up gathered around this black hole, surviving on the Hawking Radiation energy gradient?
- kbelder 4y ago
  If the bulk of the universe was inside a black hole, including us, would we know it? My understanding was, not necessarily. Second question, if that's the case: Can singularities recurse? Could you have local blackholes inside a super-massive blackhole?
  - samus 4y ago
    We don't know what the inside of a black hole is like. My guess is that it's some esoteric state of matter. Like a neutron star, but up to eleven.

ravi-delia 4y ago

There's no real limit, since you can just keep dumping stuff in forever. There is however a soft limit that the stuff has to be close enough to get dumped in, and this one is extremely old so we aren't sure where it got its mass from!

taylodl 4y ago
Au contraire! There's plenty of mass to feed such a black hole, the real question is "when you run things backward" in the lambda-CDM model why isn't the entire universe a black hole? Or why wouldn't it be the case that there wasn't a primordial mega star that quickly (in universal time) collapsed into a supermassive black hole and the remnants of the supernova is the mass of the remainder of the universe and form the CMB radiation?
- michannne 4y ago
  This is a cool idea I've never heard before. The universe we're in is the result of a cosmically massive star going supernova.

xenadu02 4y ago

I don't know the number but the limit is the speed of light and expansion of the universe. In the modern phase of the universe a black hole would only be able to eat its own galactic cluster (or maybe supercluster). Hubble expansion means superclusters experience the expansion of spacetime so certainly any matter beyond a black hole's own supercluster will move away from the black hole faster than light and thus never be able to fall into it. In practice a black hole can't even get near that limit because angular momentum can't just vanish... much of the matter would (over a long time) end up in distant orbit around that super super massive black hole and never fall into it. In the early universe spacetime expansion was happening so quickly that it was difficult for large black holes to form at all. If that were not the case most matter in our universe would have collapsed due to gravity and ended up in black holes but we know it did not. Actually if gravity were that strong or expansion were slower/weaker then the universe would never have formed at all and stayed as a singularity. To get formation of super large black holes very early you'd need a knife-blade balancing act of gravity vs expansion to just barely form super super massive black holes without the "permanent singularity, no universe" scenario. We can see billions of stars, galaxies, etc so we know that scenario did not happen. Super super massive black holes are neat objects though. If this one really is as big as they say then it will be one of the last objects left in the universe. It would take trillions and trillions of years for it to evaporate due to Hawking radiation. I wonder if the last life left in the universe will end up gathered around this black hole, surviving on the Hawking Radiation energy gradient?

kbelder 4y ago
If the bulk of the universe was inside a black hole, including us, would we know it? My understanding was, not necessarily. Second question, if that's the case: Can singularities recurse? Could you have local blackholes inside a super-massive blackhole?
- samus 4y ago
  We don't know what the inside of a black hole is like. My guess is that it's some esoteric state of matter. Like a neutron star, but up to eleven.