3 ms·

> There isn’t. This is the most common _conclusion_, based on the math. It’s not a starting assumption. How? Time doesn't work inside black holes, we have no c

> There isn’t. This is the most common _conclusion_, based on the math. It’s not a starting assumption. How? Time doesn't work inside black holes, we have no clue how that even works or if things are frozen or if it happens instantly. Math can't answer what happens when time doesn't work. This isn't just the time paradox of near light travel, the math says that inside black holes you have an entire different dimension of time instead of our regular one, nothing can be said at all about what it looks like from our point of view since there is no concept of shared time between us and what is inside of black holes. So either the formulas are wrong, or we can't say anything about what is inside.

codethief 2y ago
> Time doesn't work inside black holes, we have no clue how that even works or if things are frozen or if it happens instantly. […] This isn't just the time paradox of near light travel, the math says that inside black holes you have an entire different dimension of time instead of our regular one There is no such thing inside a black hole as "an entire different dimension of time." Yes, by the very definition of an event horizon, the coordinate chart of an observer at infinity cannot extend inside a black hole. Needing multiple coordinate charts is not really unusual, though. The two-dimensional sphere S² also requires at least two charts. All in all, time inside a black hole locally works the way it does outside a black hole. Yes, there might be interesting non-local effects like closed timelike curves but you can also have those outside.
- Jensson 2y ago
  > time inside a black hole locally works the way it does outside a black hole That doesn't mean that it actually runs though, you can interpret the lack of possible shared reference of time as the black holes time either happens instantly, but also that it never ever happens and everything in it is stuck and time is frozen from our perspective. In the time frozen perspective the singularity would never form, all objects are frozen and never reach it.
  - db48x 2y ago
    Time doesn’t magically freeze inside of a black hole. That is a misunderstanding of what happens to light rays carrying the image of the infalling diver as they approach the event horizon. From the perspective of an outside observer, those light rays are slowed down more and more and light from the instant of crossing the event horizon never actually arrives; it appears to take an infinite amount of time to do so. The mistake is to think that the object is still there, hovering at the event horizon, for an infinite amount of time. The reality is that the diver notices nothing unusual as they cross the event horizon; they may not even be able to tell exactly when it happens. They certainly do not freeze in place forever.
    - Jensson 2y ago
      > The reality is that the diver notices nothing unusual as they cross the event horizon That doesn't mean that he actually crosses it from our reference frame. Relativity is all about understanding that time is relative, that applies here as well, except that there is no connection between the two reference frame unlike regular space, so we can't say anything about how time flows inside of a black hole from our perspective. Basically what I am saying is, you can't say whether the singularity has actually formed, since your reference frame is just as connected to the instant anything fell into the black hole as it is connected to the end state of the singularity. That makes it just as valid to say that things freeze the instant they touch the black hole as to say that they merge with the singularity the instant they touch it, since both are equally valid viewpoints from our perspective.
      - db48x 2y ago
        There is no disconnection between the interior of the black hole and the exterior. They are smoothly and continuously connected, and the “normal” axis of time blends seamlessly with the “bent” axis of time inside the black hole. That’s why orbits are so weird outside the black hole. You’re simply wrong about this.
        Jensson 2y ago
db48x 2y ago
> Time doesn't work inside black holes… Time and space work exactly the same inside the black hole as outside, they just swap places. One dimension that was spacelike is bent into becoming timelike. Closer to the center becomes further in the future, and outside the event horizon becomes part of the past. The singularity at the center of the black hole is now the literal end of time. Nothing exists past the end of time; you hit that singularity and you cease to exist. From the outside, all that we can detect is the mass of the black hole. Or rather, all we can detect is some gravity pulling us in, as if there were mass inside. Einstein proved that all gravity is just the curvature of spacetime. Your body is bending the fabric of spacetime right now!¹ When you dive into a black hole, the curvature you are causing is added to that of the black hole, so that the black hole grows exactly as if your mass still existed inside of it. But really you ceased to exist when you hit the end of time at the singularity. But of course that is how we _used_ to think of it, up until a decade or two ago. As Susskind would say, ER=EPR. Spatial connectivity (which Einstein and Rosen wrote a paper about) is exactly the same thing as quantum entanglement (which Einstein, Podolsky, and Rosen wrote a completely different paper about in the same year). I won’t try to recapitulate one of his lectures (since you can just watch one; see <https://www.youtube.com/watch?v=31fVea8_OAw https://www.youtube.com/watch?v=31fVea8_OAw> for a recent example, but there are others), but the result is that the spacetime inside the black hole grows without bound, and you never actually reach the end of time. You cannot go back, but neither do you go splat. The matter that was once a star is somewhere ahead of you in that growing region of spacetime, forever in your future. ¹ Note all possible “yo mamma” jokes for future reference.
- Jensson 2y ago
  Let me rephrase: The time we measure with our clocks from the outside doesn't apply inside of black holes. There is no way to say whether any singularity has ever formed or ever will form even according to the math, since time inside of them isn't the kind of time we can measure from the outside. If you go inside of it the math says that now your clock inside of the black hole can still function, but that also means you are no longer connected to time outside of the black hole, so you can't say whether anything actually happens inside of them from our perspective, all the math says is what it would be like for someone inside. You need to make extra assumptions about what it means to have a disconnected time reference frame to say anything.

codethief 2y ago

> Time doesn't work inside black holes, we have no clue how that even works or if things are frozen or if it happens instantly. […] This isn't just the time paradox of near light travel, the math says that inside black holes you have an entire different dimension of time instead of our regular one There is no such thing inside a black hole as "an entire different dimension of time." Yes, by the very definition of an event horizon, the coordinate chart of an observer at infinity cannot extend inside a black hole. Needing multiple coordinate charts is not really unusual, though. The two-dimensional sphere S² also requires at least two charts. All in all, time inside a black hole locally works the way it does outside a black hole. Yes, there might be interesting non-local effects like closed timelike curves but you can also have those outside.

Jensson 2y ago
> time inside a black hole locally works the way it does outside a black hole That doesn't mean that it actually runs though, you can interpret the lack of possible shared reference of time as the black holes time either happens instantly, but also that it never ever happens and everything in it is stuck and time is frozen from our perspective. In the time frozen perspective the singularity would never form, all objects are frozen and never reach it.
- db48x 2y ago
  Time doesn’t magically freeze inside of a black hole. That is a misunderstanding of what happens to light rays carrying the image of the infalling diver as they approach the event horizon. From the perspective of an outside observer, those light rays are slowed down more and more and light from the instant of crossing the event horizon never actually arrives; it appears to take an infinite amount of time to do so. The mistake is to think that the object is still there, hovering at the event horizon, for an infinite amount of time. The reality is that the diver notices nothing unusual as they cross the event horizon; they may not even be able to tell exactly when it happens. They certainly do not freeze in place forever.
  - Jensson 2y ago
    > The reality is that the diver notices nothing unusual as they cross the event horizon That doesn't mean that he actually crosses it from our reference frame. Relativity is all about understanding that time is relative, that applies here as well, except that there is no connection between the two reference frame unlike regular space, so we can't say anything about how time flows inside of a black hole from our perspective. Basically what I am saying is, you can't say whether the singularity has actually formed, since your reference frame is just as connected to the instant anything fell into the black hole as it is connected to the end state of the singularity. That makes it just as valid to say that things freeze the instant they touch the black hole as to say that they merge with the singularity the instant they touch it, since both are equally valid viewpoints from our perspective.
    - db48x 2y ago
      There is no disconnection between the interior of the black hole and the exterior. They are smoothly and continuously connected, and the “normal” axis of time blends seamlessly with the “bent” axis of time inside the black hole. That’s why orbits are so weird outside the black hole. You’re simply wrong about this.
      - Jensson 2y ago

db48x 2y ago

> Time doesn't work inside black holes… Time and space work exactly the same inside the black hole as outside, they just swap places. One dimension that was spacelike is bent into becoming timelike. Closer to the center becomes further in the future, and outside the event horizon becomes part of the past. The singularity at the center of the black hole is now the literal end of time. Nothing exists past the end of time; you hit that singularity and you cease to exist. From the outside, all that we can detect is the mass of the black hole. Or rather, all we can detect is some gravity pulling us in, as if there were mass inside. Einstein proved that all gravity is just the curvature of spacetime. Your body is bending the fabric of spacetime right now!¹ When you dive into a black hole, the curvature you are causing is added to that of the black hole, so that the black hole grows exactly as if your mass still existed inside of it. But really you ceased to exist when you hit the end of time at the singularity. But of course that is how we _used_ to think of it, up until a decade or two ago. As Susskind would say, ER=EPR. Spatial connectivity (which Einstein and Rosen wrote a paper about) is exactly the same thing as quantum entanglement (which Einstein, Podolsky, and Rosen wrote a completely different paper about in the same year). I won’t try to recapitulate one of his lectures (since you can just watch one; see <https://www.youtube.com/watch?v=31fVea8_OAw https://www.youtube.com/watch?v=31fVea8_OAw> for a recent example, but there are others), but the result is that the spacetime inside the black hole grows without bound, and you never actually reach the end of time. You cannot go back, but neither do you go splat. The matter that was once a star is somewhere ahead of you in that growing region of spacetime, forever in your future. ¹ Note all possible “yo mamma” jokes for future reference.

Jensson 2y ago
Let me rephrase: The time we measure with our clocks from the outside doesn't apply inside of black holes. There is no way to say whether any singularity has ever formed or ever will form even according to the math, since time inside of them isn't the kind of time we can measure from the outside. If you go inside of it the math says that now your clock inside of the black hole can still function, but that also means you are no longer connected to time outside of the black hole, so you can't say whether anything actually happens inside of them from our perspective, all the math says is what it would be like for someone inside. You need to make extra assumptions about what it means to have a disconnected time reference frame to say anything.