Most images of black holes are illustrations. Here’s what our telescopes capture • Hacker News Board

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#151

Post by IntronExon » Thu, Mar 01, 2018, 12:51 AM UTC

pdonis wrote: post #146

qubex wrote: post #69

Earlier quoted context omitted.

First and foremost: GR guarantees that an event horizon will form. Oddball exotic states of matter (quark stars, fuzz balls, whatever) might form in proper time within the event horizon, halting collapse before it reaches the singularity state of infinite compaction. (Since time freezes at the event horizon, these states would occur infinitely far in the future from the perspective of any external observer and might…

> Oddball exotic states of matter (quark stars, fuzz balls, whatever) might form in proper time within the event horizon, halting collapse before it reaches the singularity state of infinite compaction. No, this is not correct. Once an event horizon forms, everything inside the horizon will hit the singularity, because the singularity is not a place in space, it's a moment of time, which is in the future (and the not…

While I’m totally in agreement with the second part of your comment, the first part may not be true.

No, this is not correct. Once an event horizon forms, everything inside the horizon will hit the singularity, because the singularity is not a place in space, it's a moment of time, which is in the future (and the not too distant future for holes of reasonable size--the time from horizon to singularity for a black hole of 10 solar masses is about 100 microseconds) for everything inside the horizon.

We don’t actually know if there’s a singularity within the event horizon. GTR predicts it, but that’s in the context of the breakdown of the predictive power of the theory. Until/Unless we have a viable theory of quantum gravity what is inside an EH is speculative. Quark stars or any form of conventional matter are right out obviously, but Fuzzballs or some other novel “structure” can’t be ruled out yet.

Having said that, I’m not a string theory adherent, I’m just pointing out that within the event horizon we need a complementary theory to augment GTR and QM.

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#152

Post by pdonis » Thu, Mar 01, 2018, 1:18 AM UTC

IntronExon wrote: post #151

pdonis wrote: post #146

Earlier quoted context omitted.

> Oddball exotic states of matter (quark stars, fuzz balls, whatever) might form in proper time within the event horizon, halting collapse before it reaches the singularity state of infinite compaction. No, this is not correct. Once an event horizon forms, everything inside the horizon will hit the singularity, because the singularity is not a place in space, it's a moment of time, which is in the future (and the not…

While I’m totally in agreement with the second part of your comment, the first part may not be true. No, this is not correct. Once an event horizon forms, everything inside the horizon will hit the singularity, because the singularity is not a place in space, it's a moment of time, which is in the future (and the not too distant future for holes of reasonable size--the time from horizon to singularity for a black hol…

> We don’t actually know if there’s a singularity within the event horizon.

Not if we take quantum effects into account, no. I was describing what classical GR predicts. I agree that GR also predicts that it should break down in the regime close to the singularity.

It's also worth noting that there is a school of thought among physicists that says that quantum effects are non-negligible even at the horizon of a black hole of stellar mass or larger. This is the "firewall" debate that is currently ongoing. I personally don't find the arguments in favor of a "firewall" convincing, but it is an area of ongoing debate.

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#153

Post by IntronExon » Thu, Mar 01, 2018, 1:19 AM UTC

pdonis wrote: post #152

IntronExon wrote: post #151

Earlier quoted context omitted.

While I’m totally in agreement with the second part of your comment, the first part may not be true. No, this is not correct. Once an event horizon forms, everything inside the horizon will hit the singularity, because the singularity is not a place in space, it's a moment of time, which is in the future (and the not too distant future for holes of reasonable size--the time from horizon to singularity for a black hol…

> We don’t actually know if there’s a singularity within the event horizon. Not if we take quantum effects into account, no. I was describing what classical GR predicts. I agree that GR also predicts that it should break down in the regime close to the singularity. It's also worth noting that there is a school of thought among physicists that says that quantum effects are non-negligible even at the horizon of a black…

Agreed on all points, and the firewall is interesting, but I can’t see how it doesn’t somehow create a privileged frame of reference. It’s still very cool/terrifying, even in the already notoriously cool/terrifying realm of black holes.

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#154

Post by matte_black » Thu, Mar 01, 2018, 1:31 AM UTC

AnimalMuppet wrote: post #139

clarkmoody wrote: post #130

Earlier quoted context omitted.

In the Death's End by Cixin Liu, there is a speed of light weapon that lowers the local speed of light to almost nothing, effectively taking an enemy out of the game until the end of the universe.

In Redshift Rendesvous (don't recall the author), there was an environment where the speed of light was just above running speed - maybe 15 m/s. You observed relativistic effects just walking around.

There was a game like this, I wonder if such a universe can be simulated in VR? Perhaps it would allow for a better understanding of relativity?

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#155

Post by Retra » Thu, Mar 01, 2018, 3:19 AM UTC

InclinedPlane wrote: post #143

coryfklein wrote: post #140

Earlier quoted context omitted.

> escaping a black hole is impossible Except for Hawking Radiation [1] "black holes that do not gain mass through other means are expected to shrink and ultimately vanish. Micro black holes are predicted to be larger emitters of radiation than larger black holes and should shrink and dissipate faster." [1] https://en.wikipedia.org/wiki/Hawking_radiation

Hawking Radiation comes from outside the event horizon.

Hawking radiation takes energy away from the inside of a black hole.

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#156

Post by Retra » Thu, Mar 01, 2018, 3:29 AM UTC

Sir_Cmpwn wrote: post #75

blackrock wrote: post #38

Earlier quoted context omitted.

I would prefer if black holes were called "Dark Stars". Because that really is what they are. A weird star that is so massive, its gravitational field distorted the fabric of its local space, that not even light can escape it. It is theoretically possible that the black hole is still performing fusion, and emitting light and heat, like a regular star. But its gravitational field is so intense, that even light cannot…

It's a lot more complicated than this and a lot of your assumptions are not true. So far as our universe is concerned, the inside of a black hole literally doesn't exist and events in there literally don't happen. Once you get inside, spacetime is warped so severely that a lot of our fundamental assumptions about how space and time work change. It's not reasonable to assume that normal processes observed outside of t…

Obviously the inside of a black hole does exist on account of the fact that it is able to warp spacetime in an externally detectable manner. If the interiors of black holes didn't exist they would be indistinguishable from empty space, and not seem so remarkable as to be called "black holes."

Either way, we do not know what processes occur inside because we lack any theory which could describe it. This certainly doesn't mean nothing happens in there or nothing exists in there.

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#157

Post by Retra » Thu, Mar 01, 2018, 3:30 AM UTC

chopin wrote: post #53

JumpCrisscross wrote: post #39

Earlier quoted context omitted.

> then you will only see the star as pitch black, since light can't even escape it Would it be black? Right above the event horizon is flaming relativistic matter.

That's true but afaik time dilation makes it rather dim infrared radiation.

On the inner-most layer, yes. But outside of that, it will be less dim and less infrared.

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#158

Post by Sir_Cmpwn » Thu, Mar 01, 2018, 3:39 AM UTC

Retra wrote: post #156

Sir_Cmpwn wrote: post #75

Earlier quoted context omitted.

It's a lot more complicated than this and a lot of your assumptions are not true. So far as our universe is concerned, the inside of a black hole literally doesn't exist and events in there literally don't happen. Once you get inside, spacetime is warped so severely that a lot of our fundamental assumptions about how space and time work change. It's not reasonable to assume that normal processes observed outside of t…

Obviously the inside of a black hole does exist on account of the fact that it is able to warp spacetime in an externally detectable manner. If the interiors of black holes didn't exist they would be indistinguishable from empty space, and not seem so remarkable as to be called "black holes." Either way, we do not know what processes occur inside because we lack any theory which could describe it. This certainly does…

From my earlier comment:

>So far as our universe is concerned, the inside of a black hole literally doesn't exist and events in there literally don't happen.

It would probably be easier to get this across if I substituted "So far as our universe is concerned" with "From our perspective outside of the event horizon". Remember that a singularity doesn't just "pull" light so hard that it can't escape - they warp spacetime around them, so much so that the space and time within the event horizon ceases to be meaningful from our reference frame. The only way to go is down - literally. If you turn 360 degrees in a black hole you will never face the outside.

Also, we definitely have theories that describe what could happen inside an event horizon. General relativity, for example. It's from these that we can establish that space and time "switch" within, for example. We can solve general relativity for the conditions within an event horizon and make some pretty strong predictions about it (it's from these predictions that I conclude elsewhre in this discussion that fusion is unlikely).

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#159

Post by InclinedPlane » Thu, Mar 01, 2018, 5:36 AM UTC

Retra wrote: post #155

InclinedPlane wrote: post #143

Earlier quoted context omitted.

Hawking Radiation comes from outside the event horizon.

Hawking radiation takes energy away from the inside of a black hole.

Certainly, but the radiation still comes from outside the event horizon.

Re: Most images of black holes are illustrations. Here’s what our telescopes capture

#160

Post by qubex » Thu, Mar 01, 2018, 8:58 AM UTC

Retra wrote: post #156

Sir_Cmpwn wrote: post #75

Earlier quoted context omitted.

It's a lot more complicated than this and a lot of your assumptions are not true. So far as our universe is concerned, the inside of a black hole literally doesn't exist and events in there literally don't happen. Once you get inside, spacetime is warped so severely that a lot of our fundamental assumptions about how space and time work change. It's not reasonable to assume that normal processes observed outside of t…

Obviously the inside of a black hole does exist on account of the fact that it is able to warp spacetime in an externally detectable manner. If the interiors of black holes didn't exist they would be indistinguishable from empty space, and not seem so remarkable as to be called "black holes." Either way, we do not know what processes occur inside because we lack any theory which could describe it. This certainly does…

The inside of a black hole doesn’t exist as far as our universe is concerned. Even the ‘gravity’ isn’t ‘emanated’ by the mass ‘inside’ the event horizon; rather it is a ‘recursively’ generated field (remember: gravity is generated by mass-energy curving space-time, gravity is a form of energy, and so gravity begets gravity in an entirely self-sustaining manner).