(one example of why you might care whether moral patients in black holes “have experiences” is if you can influence what will happen in a black hole — for example, imagine a rocket with moral patients on board is headed for a black hole, and before it gets there, you get to influence how much suffering will happen on board after the rocket passes the event horizon)
Random aside:
I hear a ton of explanations of black holes that focus on the extreme cases of “literal light can’t literally escape”, sometime saying words like “you would experience X before getting squashed into spaghetti”. But the discussion always seems to be doing some kind of spherical cow abstraction over what actual happens to literal humans (or, at least, literal computronium running simulations of human) as they get near, and then cross over, the event horizon.
Your ship probably isn’t moving at literal lightspeed. According to this site a 10-solar-mass black hole has a 30 km radius (diameter?) event horizon. If you pass nearby at near-lightspeed with literal humans on board at distance of, say, 60 km are the humans already super F’d up? Are they basically fine as long as the ship doesn’t literally veer into the event horizon? Once they veer into the event horizon do they immediately start to get distorted by gravity forces before hitting the singularity at the center? Do they get to experience anything at all? Does the near-lightspeed ship spiral around the singularity once it crosses the event horizon or just sorta plunge right in? I assume it’s all basically over Very Very Fast at that point (my intuition is guessing less than a second and maybe orders of magnitude faster).
If you build a really robust robot designed specifically to survive black holes, with a really high clockspeed for observing/thinking, what’s the most conscious experience it would even hypothetically make sense to consider them having in the moments before and after crossing the event horizon at near-but-not-literal-lightspeed, before you start getting into ways that black hole physics is deeply weird?
The rubber-sheet analogy (img) for gravity is good for event horizon vs. spaghettification / tidal forces. The rubber sheet both has a slope (first derivative of height of the sheet as you go towards the center) and also has a curvature (second derivative). The event horizon is a point of a certain slope, and your atoms getting ripped apart by gravity is a point of a certain curvature. A really big black hole is “gentler”: at the event horizon, there’s less curvature, so space is locally flat and you feel like you’re on a normal free-fall trajectory—albeit one that will have a messy end. A small black hole has higher curvature at the event horizon—a black hole the size of an atom would be ripping other atoms apart before they crossed the event horizon (ignoring Hawking radiation).
Oh, huh, I just looked at wikipedia and it actually uses a 10 solar mass black hole as an example. In their example you basically have a steel cable that can hold 1 metric ton, and you put a 500 gram weight at each end. This weighted cable snaps due to the tidal forces well outside (300 km from the surface) of a 10-solar-mass black hole, but only snaps deep inside a supermassive black hole.
In terms of time, you can cheat a little, but basically yeah, you fall in really fast once you cross the event horizon—your maximum time is about 3⁄2 of the time it would take light to cross the distance of the Schwarzchild radius.
The largest known black hole has an event horizon of at least 3,900 AU, which is 22 light days. So you could maybe spend a month inside it before hitting the singularity.
Holy christ that is big. So, is that large enough that (according to the other claims about larger black holes having smoother event horizonal tidal forces), a fairly normal human ship could actually plunge in and experience some noticeable “normal” experiences for awhile before getting spaghettified? (or at least, “basic physics” says they have normal enough experience that it becomes an interesting question whether black holes have weird properties that might bring into question whether their experiences are morally relevant?)
I’m not a physicist but I believe the answer is yes, you could easily cross the event horizon of a supermassive BH without being spaghettified.
However, if the firewall solution to the black hole information paradox is true, then you’d be ripped apart at the moment you cross the event horizon. The firewall is super controversial in physics, because it violates Einstein’s equivalence principle. According to Einstein, there is nothing special about the moment you cross the event horizon; in principle, you could cross without even noticing. (Of course in reality you’d see such crazy shit that it’d be hard to be caught unawares.)
Outside of the black hole, its gravity acts essentially the same as any object with the same mass—the Schwarzchild metric is used for the external gravity of the earth and sun too.
Spaghettification happens when there is a significant difference in curvature over the space containing different parts of the body. For a big enough black hole, the curvature at the event horizon can be gentle enough to be survivable for a human. There might be quantum gravity effects that change things but as far as GR is concerned, there’s nothing locally special about the event horizon of a black hole.
while what you say is true for the gravitational event horizon of black holes, it doesn’t apply to the cryptographic event horizon of HECs or the expansion-of-the-universe event horizon of our ligth cone. so, yes, some cases of event horizons may not be livable, others might still matter — including potentially yet unknown unknown ones.
to you. i understand your comment as “this kind of thing wouldn’t really be a question with black holes” and i’m saying “maybe, sure, but there are other event horizons to which it might apply too”
Huh, I did not think of myself as at all making any positive claims about black holes (edit: and definitely did not mean to be making any claims at all about cryptographic event horizons one way or the other)
(maybe to clarify: my comment was definitely a digression that ignored the main part of your post, and I meant to flag it as such with the phrase “random aside.”)
Random aside:
I hear a ton of explanations of black holes that focus on the extreme cases of “literal light can’t literally escape”, sometime saying words like “you would experience X before getting squashed into spaghetti”. But the discussion always seems to be doing some kind of spherical cow abstraction over what actual happens to literal humans (or, at least, literal computronium running simulations of human) as they get near, and then cross over, the event horizon.
Your ship probably isn’t moving at literal lightspeed. According to this site a 10-solar-mass black hole has a 30 km radius (diameter?) event horizon. If you pass nearby at near-lightspeed with literal humans on board at distance of, say, 60 km are the humans already super F’d up? Are they basically fine as long as the ship doesn’t literally veer into the event horizon? Once they veer into the event horizon do they immediately start to get distorted by gravity forces before hitting the singularity at the center? Do they get to experience anything at all? Does the near-lightspeed ship spiral around the singularity once it crosses the event horizon or just sorta plunge right in? I assume it’s all basically over Very Very Fast at that point (my intuition is guessing less than a second and maybe orders of magnitude faster).
If you build a really robust robot designed specifically to survive black holes, with a really high clockspeed for observing/thinking, what’s the most conscious experience it would even hypothetically make sense to consider them having in the moments before and after crossing the event horizon at near-but-not-literal-lightspeed, before you start getting into ways that black hole physics is deeply weird?
The rubber-sheet analogy (img) for gravity is good for event horizon vs. spaghettification / tidal forces. The rubber sheet both has a slope (first derivative of height of the sheet as you go towards the center) and also has a curvature (second derivative). The event horizon is a point of a certain slope, and your atoms getting ripped apart by gravity is a point of a certain curvature. A really big black hole is “gentler”: at the event horizon, there’s less curvature, so space is locally flat and you feel like you’re on a normal free-fall trajectory—albeit one that will have a messy end. A small black hole has higher curvature at the event horizon—a black hole the size of an atom would be ripping other atoms apart before they crossed the event horizon (ignoring Hawking radiation).
Oh, huh, I just looked at wikipedia and it actually uses a 10 solar mass black hole as an example. In their example you basically have a steel cable that can hold 1 metric ton, and you put a 500 gram weight at each end. This weighted cable snaps due to the tidal forces well outside (300 km from the surface) of a 10-solar-mass black hole, but only snaps deep inside a supermassive black hole.
In terms of time, you can cheat a little, but basically yeah, you fall in really fast once you cross the event horizon—your maximum time is about 3⁄2 of the time it would take light to cross the distance of the Schwarzchild radius.
The largest known black hole has an event horizon of at least 3,900 AU, which is 22 light days. So you could maybe spend a month inside it before hitting the singularity.
Holy christ that is big. So, is that large enough that (according to the other claims about larger black holes having smoother event horizonal tidal forces), a fairly normal human ship could actually plunge in and experience some noticeable “normal” experiences for awhile before getting spaghettified? (or at least, “basic physics” says they have normal enough experience that it becomes an interesting question whether black holes have weird properties that might bring into question whether their experiences are morally relevant?)
I’m not a physicist but I believe the answer is yes, you could easily cross the event horizon of a supermassive BH without being spaghettified.
However, if the firewall solution to the black hole information paradox is true, then you’d be ripped apart at the moment you cross the event horizon. The firewall is super controversial in physics, because it violates Einstein’s equivalence principle. According to Einstein, there is nothing special about the moment you cross the event horizon; in principle, you could cross without even noticing. (Of course in reality you’d see such crazy shit that it’d be hard to be caught unawares.)
Outside of the black hole, its gravity acts essentially the same as any object with the same mass—the Schwarzchild metric is used for the external gravity of the earth and sun too.
Spaghettification happens when there is a significant difference in curvature over the space containing different parts of the body. For a big enough black hole, the curvature at the event horizon can be gentle enough to be survivable for a human. There might be quantum gravity effects that change things but as far as GR is concerned, there’s nothing locally special about the event horizon of a black hole.
Has the firewall concept been discarded?
That’s a speculative quantum gravity effect, still a live hypothesis.
while what you say is true for the gravitational event horizon of black holes, it doesn’t apply to the cryptographic event horizon of HECs or the expansion-of-the-universe event horizon of our ligth cone. so, yes, some cases of event horizons may not be livable, others might still matter — including potentially yet unknown unknown ones.
Was this meant to be a reply to me or one of the child comments?
to you. i understand your comment as “this kind of thing wouldn’t really be a question with black holes” and i’m saying “maybe, sure, but there are other event horizons to which it might apply too”
Huh, I did not think of myself as at all making any positive claims about black holes (edit: and definitely did not mean to be making any claims at all about cryptographic event horizons one way or the other)
(maybe to clarify: my comment was definitely a digression that ignored the main part of your post, and I meant to flag it as such with the phrase “random aside.”)
oops, i missed that flag. sorry.