Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

JWST spots giant black holes all over the early universe

quantamagazine.org

Post reply on HN
Print view View original

141–150 of 186 posts

Re: JWST spots giant black holes all over the early universe

#141

Post by codethief »

zycon wrote: post #123
micw wrote: post #121

Earlier quoted context omitted.

What exactly is the "density" of a black hole? As I understand, a BH is a singularity, so all mass is at one point which means all BHs have the same (infinite) density. Is it a kind of "virtual density", e.g. the mass of the singularity devided by the schwarzschild radius or the event horizon?

Density is mass divided by volume. Volume of BH is defined by event horizon. Singularity is a result of applying a theory of relativity in a case where we know relativity doesn't work, so it's unlikely it's real.

> Volume of BH is defined by event horizon.

The event horizon is a three-dimensional null hypersurface, though, encompassing a four-dimensional spacetime "volume". You are probably referring to the two-dimensional apparent horizon, which depends on the spatial slicing.

Re: JWST spots giant black holes all over the early universe

#142

Post by AnimalMuppet »

sebzim4500 wrote: post #122
kune wrote: post #112

The density of black hole decrease by the inverse square of the mass of the black hole. That means massive black holes have a much lower density that small black holes. So they are more likely to form than small black holes. Dark matter will have played an important role in the creation of those early black holes. If there is no dark matter and some form of MOND theory of gravity is correct, the Schwarzschild formula…

>So they are more likely to form than small black holes. This certainly does not follow from the rest of your comment. I'm pretty sure it's false.

I think the claim is like this: You have the primordial universe, shortly after the big bang, with fluctuations in density. But the whole density is very high. A fluctuation over a large region could put the region over the threshold to become a black hole, because the density required for that to happen is lower than for a small region.

Mind you, I don't know if this actually works. What was the density of the early universe, compared to the density required to form a black hole? How large were the fluctuations? Is this scenario plausible at all?

I suppose that if you go back close enough to the big bang, then you can get a density high enough. But then, if you go back not much farther, shouldn't the whole universe have formed a black hole? And if it didn't, can we trust the logic that says that the situation should have led to the formation of giant black holes?

Re: JWST spots giant black holes all over the early universe

#143

Post by AnimalMuppet »

JumpCrisscross wrote: post #22
r2_pilot wrote: post #12

Earlier quoted context omitted.

Not the original author but my first interpretation is that this means, if it were in a video game, it would be a way to self-reinforce "fog of war" where you can only have extremely local information and you don't want extra information to leak to the players.

Has anyone re-written a classic RTSG with a slower speed of light? Like, Red Alert, but with time dilation.

I don't know about an RTSG, but I have seen it in a novel: Redshift Rendezvous.

Re: JWST spots giant black holes all over the early universe

#144

Post by AnimalMuppet »

andrewflnr wrote: post #134
_8j50 wrote: post #71

I've wondered how blackholes have a similar 2d shape as with hurricanes and whirlpools where the center is empty. What if the inside of a blackhole is devoid of all things including spacetime, although that doesn't make good scifi.

I believe this actually is one of the hypotheses about black hole interiors, though I forget the name. Nothing to do with terrestrial storms or vortices, though; a black hole doesn't have to have any rotation at all.

There are rotating black holes (https://en.wikipedia.org/wiki/Rotating_black_hole).

Re: JWST spots giant black holes all over the early universe

#145

Post by dotnet00 »

Moldoteck wrote: post #105
dotnet00 wrote: post #61

Earlier quoted context omitted.

It is worth considering that a black hole's hold on its galaxy is not as strong as a sun-like star's on its accretion disk. Our Sun is 99% of the mass of the solar system, our Sagittarius A* is ~4 million solar masses, while our Milky Way is 800 billion solar masses. On top of that, black hole growth rate slows to nearly a stop at ~270 billion solar masses, so even if a black hole manages to meet the rare conditions…

Is the upper limit due to hawking radiation?

Something to do with the spin rate and the stability of the accretion disk. I don't fully understand it, just something I picked up off wikipedia.

Re: JWST spots giant black holes all over the early universe

#146

Post by dtgriscom »

sinuhe69 wrote: post #98

Maybe I’m a bit naive here, but I thought finding of many supermassive back holes in the very early universe should be expected, and not a surprise. My chain of thoughts is following: - Blackholes are collapsed masses. In our phase of the universe, they are normally the results of supernovae but only because today stars are the only source of dense masses. - Because the total mass of the universe is constant and the…

What do you mean by "many" black holes being "expected"? What's "many"?

You have to be specific, and to do that you model, and then validate through observation. The article states that more black holes are being observed than the models predict, which is their definition of "many".

Re: JWST spots giant black holes all over the early universe

#147

Post by blueprint »

jpk wrote: post #124
blueprint wrote: post #93

Earlier quoted context omitted.

photons dont exist, dude, except in connection with and at the site of the detector. study some qft and then you can go talk about it on the internet with authority. and yes direct observation exists. that's what measurement is. and that's all you can ever "observe" unless you incorporate the wavefunction, which also doesn't "exist".

This comment is needlessly hostile. It's ok to correct someone if you think they're wrong, but this tone isn't conducive to curious conversation.

so it's the tone of my textual words? i think you're mistaking my laughter at their blatant and willful ignorance for hostility, and quite honestly it sounds like you're projecting that hostility. from the start I've been incorrectly downvoted and critiqued while being the primary commenter in this child thread providing a semblance of correct view. to be quite frank i deserve an apology, not some nitpick that comes from your personal assumption about my tone. but i know i won't get one because it's not hostility you care about at all. a lot of you commenters here are pretty hilarious. but not in a good way.

Re: JWST spots giant black holes all over the early universe

#148

Post by antonvs »

somat wrote: post #135
antonvs wrote: post #127

Earlier quoted context omitted.

That doesn't follow. A galaxy is not like a star system that orbits a single massive object in a single plane. Objects orbit the center of mass of the galaxy, which is made of of an enormous mass of stars and clouds of dust and gas. For example, the central molecular zone (CMZ) is an asymmetrical roughly spherical region, about 1600-1900 light years in diameter, that contains about 60 million solar masses of gas and…

An excellent reply, far better than my idle musings warranted, however a point was missed. At some point in solar system formation the mass of the not quite yet a sun was only 6% of the mass of the entire system. At some very early point I assume the distribution of mass in the proto solar dust cloud would be the same as the distribution of mass in the galaxy. I hesitate to reinforce my idea because really, it is ill…

> the mass of the not quite yet a sun was only 6% of the mass of the entire system.

That seems like an arbitrary division of the mass of the system. More than 99% of the mass of the system was going to become a star, so on what basis are you identifying a small subset of that as being significant? Gravity involves the net effect of the forces between every particle in a system.

> At some very early point I assume the distribution of mass in the proto solar dust cloud would be the same as the distribution of mass in the galaxy. [...] would galaxy sized objects eventually coalesce into the same proportion of objects.

No and no, because of the inverse square law. Galaxies don't look like large solar systems because they're much bigger. The Sun has a big effect on all the planets in the solar system, but it doesn't have much of an effect on Alpha or Proxima Centauri, even though that's our nearest neighbor.

Re: JWST spots giant black holes all over the early universe

#149

Post by throwuwu »

vagab0nd wrote: post #73
throwuwu wrote: post #58

Earlier quoted context omitted.

Partition them by velocity

Velocity relative to what?

If it’s a simulation then there is a fixed point. Any proper game developer would also fake it for the most part e.g. culling things the players aren’t looking at, making distant objects static billboards and they’d also fudge the numbers with something like the cosmological constant.

Re: JWST spots giant black holes all over the early universe

#150

Post by d1sxeyes »

blueprint wrote: post #147
jpk wrote: post #124

Earlier quoted context omitted.

This comment is needlessly hostile. It's ok to correct someone if you think they're wrong, but this tone isn't conducive to curious conversation.

so it's the tone of my textual words? i think you're mistaking my laughter at their blatant and willful ignorance for hostility, and quite honestly it sounds like you're projecting that hostility. from the start I've been incorrectly downvoted and critiqued while being the primary commenter in this child thread providing a semblance of correct view. to be quite frank i deserve an apology, not some nitpick that comes…

At this point anyone who is as certain about the nature of light as you seem to be may well be right, but is demonstrating a level of confidence the literature does not yet seem to support.

Although there are those who believe that photons only exist at source and at the detector, there is some experimental evidence which contradicts that (for example, this 2013 paper in which researchers 'read' information from a photon without destroying it, which implies its continued existence between creation and observation: https://doi.org/10.1126/science.1246164).

For what it's worth, I am also of the opinion that your tone was hostile, and yes, 'textual words' can and do have a (metaphorical) tone. Regarding downvoting and critiquing, there's an old adage about if you walk into a room and it smells of dog shit, maybe someone in the room stepped in something on the way in, but if every room you walk into all day stinks, well maybe you should check your own shoes.

Post reply on HN