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Posted by raattgift 13 hours ago

Black hole singularity is a surface not a point(arxiv.org)
216 points | 160 commentspage 2
ck2 13 hours ago|
what's really going to blow your mind is

while you probably assumed or knew spinning black holes move space around them

spinning black holes also move TIME around them

* https://www.science.org/doi/10.1126/sciadv.ady9068

so in theory a spinning black hole that's been around for billions of years has a time drag around it in a path that is billions of years old

(no we can't navigate it because yes that would be time travel to the past and violates causality)

black holes are just so weird with every new detail even more weird

oddly more interesting to me to try to grasp neutron stars (densest objects before black holes and are still visible, our entire solar system in a neutron star would be only 10km 6.2miles across)

My_Name 12 hours ago||
Another thing that may blow the minds of some is that M87* is less dense than air at 0.44kg/m³ so if you could bring it to sea level (in a large enough theoretical test area) it would float like a helium balloon (sea level air is 1.2kg/m³).

Of course if you did do that, the air itself would collapse into a black hole larger than M87*...

srean 12 hours ago|||
Consider the magnetar.

https://en.wikipedia.org/wiki/Magnetar

"A magnetar's 10^10 tesla field, by contrast, has an energy density of 4.0×1025 J/m3, with an E/c2 mass density more than 10,000 times that of lead."

1970-01-01 12 hours ago||
Yes, magnetars are considerably more rare than black holes and considerably more interesting to study in terms of raw horsepower. Imagine a type-2 civilization using them as engines or launchers for spacecraft to zip around the galaxy.
ck2 11 hours ago||
the radiation from a magnetar exceeds any other star, overcoming that would seem implausible

still trying to wrap my mind around kilonovas (colliding neutron stars)

ie. they can pop out earth-sized chunks of gold, in theory, and since they aren't black holes that would be VISIBLE, albeit also "in theory" lol

* https://www.nasa.gov/image-article/unfolding-story-of-kilono...

maybe Roman can spot one someday, that would be something

pfdietz 7 hours ago||
> they can pop out earth-sized chunks of gold

The can produce Earth masses of gold, but of course not in the form of "chunks". The gold starts as atoms in a highly ionized gas and only much later cools enough to form solids (dust).

mdavidn 10 hours ago|||
It blows my mind that, in the frame of an outside observer, time appears to stop at the event horizon. An observer falling through the horizon (who survived the radiation and tidal forces) would not perceive this.
inigyou 3 hours ago||
Assuming they do fall through it. Remember they're about to receive an entire universe lifetime's stellar radiation compressed into a microsecond.

(Which is another reason some people think we might be living inside a black hole. An entire universe of energy released in zero time is literally a Big Bang. It would form into stars and galaxies.)

SoftTalker 10 hours ago|||
> densest objects before black holes

Not quite, I think a (theoretical) quark star would be higher density?

aeve890 5 hours ago||
>what's really going to blow your mind is while you probably assumed or knew spinning black holes move space around them spinning black holes also move TIME around them

Well, isn't called space-time for nothing. You can't have one without the other. Like in electromagnetism. I thought it was kinda obvious since Einstein and Minkowsky.

throwawayffffas 8 hours ago||
Or you know there is no such thing as a singularity, and stars collapse to fuzzballs[1]

https://en.wikipedia.org/wiki/Fuzzball_(string_theory)

chendawenplus 5 hours ago||
is hole
metalman 9 hours ago||
treating a black hole as a point, or ;) pointicle,may be valid as matter may be condensed, to the, I mean ,in such a way that there is NO space left whatsoever, and therefor no room for physical dimensions to exist in, and the entire body functions as an undiferentiated body of stuff, or giant pointicle that destroys time and space. Hopefully very soon we will get news about our galaxys central black holes interaction with a star that is orbiting very close but at 8% light speed, which may reveal if our blackhole is spinning, and if that is the case the we would have proof of energy/information/gravity waves? escaping from a black hole, along with gravity which while apparently imune to its self, nothing else is so far.
542458 13 hours ago||
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helf 13 hours ago||
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Yiin 12 hours ago||
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dboreham 12 hours ago||
Isn't that how we're inside one.
neom 10 hours ago|
Good PBS spacetime episode that looks at this: https://www.youtube.com/watch?v=jeRgFqbBM5E ( Could The Universe Be Inside A Black Hole?) Also, this spacetime episode is interesting the context of the paper and your statement: https://www.youtube.com/watch?v=x4TdColoIu8 (We Thought Black Holes Created Event Horizons. It Might Be the Opposite)
Groxx 12 hours ago|
Well... yeah? That's describing the event horizon. It's a term roughly as widely used as "singularity".

Talking about the inside of a black hole is indeed rather pop-misunderstood though, yes. But it's not like physicists are especially confident about the details either. Theoretical astrophysics changes a lot as time goes on and our instruments improve, and it's a rather hard field to do experiments on to get better data quicker.

evanb 9 hours ago|
No, sorry, the singular surface in a Schwarzschild spacetime is not the event horizon. Nothing particularly interesting (from the GR point of view) happens at the event horizon.
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