3 ms·

There's a couple of things here. 1) Again, it cannot have this event horizon until it becomes a black hole. That is one of the defining features of a black hol

There's a couple of things here. 1) Again, it cannot have this event horizon until it becomes a black hole. That is one of the defining features of a black hole. We will be able to see photons escaping through the collapse period until it is a black hole, and once photons can't escape, it is already a black hole. 2) Time does not flow universally with a single reference frame. It appearing to take infinitely long for something to fall into the black hole from our point of view does not mean that it does so for the thing falling into the black hole or for the black hole itself. Time flows normally for the observer, and if they are falling into, say, a supermassive black hole with limited tidal forces, and in a spaceship that can protect from the radiation, etc. from the accretion disk and everything else, they will not notice anything particularly different about the low of time as they fall. In fact, for black holes of sufficient size and with sufficient charge or rotational velocity, there's actually a second event horizon past the first that could even potentially support stable orbits, even those of planets or entire solar systems. It's likely only a theoretical thing - we don't know a mechanism that would generate enough rotational velocity or charge for a black hole large enough for there to be enough room to push this second event horizon out far enough from the singularity to make this practical. But time flows differently for both parties, and the increase in mass in the black hole is immediate for the black hole itself, as is the increase in the event horizon's radius, as it would be for anything falling into it.

ars 4y ago
To your point #2 people say this a lot, but it's really not relevant. Because from my POV here on Earth, just like I can't see the final object fall in a make a black hole, the same way from my POV the black hole also doesn't exist. Keep in mind that from the POV of the infalling object they experience the entire lifetime of the universe! The two POV's are complimentary - just like it takes until the end of time to fall in (from the POV of the infalling object), it also means I never see the black hole form. i.e. from both POV's the black hole only forms at the end of time (which of course is never, since time never ends).
- cthalupa 4y ago
  You've got a whole lot of misconceptions here. >Because from my POV here on Earth, just like I can't see the final object fall in a make a black hole, the same way from my POV the black hole also doesn't exist. Again, until there is an event horizon it is not a black hole. Once it has the event horizon, it is a black hole. Once it at the point that you are concerned about this, it is already a black hole. If you are in a situation where your (misunderstood) scenario is occurring, it is already a black hole. (I am speaking purely of the gravitational event horizon here, not a causality event horizon a la the observable universe, etc.) >just like it takes until the end of time to fall in (from the POV of the infalling object) It does not take until the end of time to fall in. If you were to be launched into a black hole that lacked strong enough tidal forces to spaghettify you, you would go past the event horizon at basically the same speed you were going right before you crossed. If you are going straight towards the center of the black hole, you will be accelerating under the gravitational forces. >it also means I never see the black hole form. Again, even if what you were saying is true (and it isn't), by definition the black hole has already formed when it collapses into a singularity (or something closely approximating our understanding of the singularity) and gains this event horizon. Not one atom or quark or any other type of particle more needs to fall in past this point for the black hole to have formed, because it already has. If it somehow formed in some sort of theoretical vacuum where even virtual particles do not pop into existence and never even had a particle or anti-particle appear and fall in, it would still be a fully formed black hole. >which of course is never, since time never ends Not really related to the current discussion, but we don't actually know if this is the case or not, either from a philosophical or hard science perspective. There are plenty of cosmological models where time ends, or the emergent property we call time stops being an emerging property because of some other reason, etc.

ars 4y ago

To your point #2 people say this a lot, but it's really not relevant. Because from my POV here on Earth, just like I can't see the final object fall in a make a black hole, the same way from my POV the black hole also doesn't exist. Keep in mind that from the POV of the infalling object they experience the entire lifetime of the universe! The two POV's are complimentary - just like it takes until the end of time to fall in (from the POV of the infalling object), it also means I never see the black hole form. i.e. from both POV's the black hole only forms at the end of time (which of course is never, since time never ends).

cthalupa 4y ago
You've got a whole lot of misconceptions here. >Because from my POV here on Earth, just like I can't see the final object fall in a make a black hole, the same way from my POV the black hole also doesn't exist. Again, until there is an event horizon it is not a black hole. Once it has the event horizon, it is a black hole. Once it at the point that you are concerned about this, it is already a black hole. If you are in a situation where your (misunderstood) scenario is occurring, it is already a black hole. (I am speaking purely of the gravitational event horizon here, not a causality event horizon a la the observable universe, etc.) >just like it takes until the end of time to fall in (from the POV of the infalling object) It does not take until the end of time to fall in. If you were to be launched into a black hole that lacked strong enough tidal forces to spaghettify you, you would go past the event horizon at basically the same speed you were going right before you crossed. If you are going straight towards the center of the black hole, you will be accelerating under the gravitational forces. >it also means I never see the black hole form. Again, even if what you were saying is true (and it isn't), by definition the black hole has already formed when it collapses into a singularity (or something closely approximating our understanding of the singularity) and gains this event horizon. Not one atom or quark or any other type of particle more needs to fall in past this point for the black hole to have formed, because it already has. If it somehow formed in some sort of theoretical vacuum where even virtual particles do not pop into existence and never even had a particle or anti-particle appear and fall in, it would still be a fully formed black hole. >which of course is never, since time never ends Not really related to the current discussion, but we don't actually know if this is the case or not, either from a philosophical or hard science perspective. There are plenty of cosmological models where time ends, or the emergent property we call time stops being an emerging property because of some other reason, etc.