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(Phys Org2)   For the first time, astronomers have measured the radius of a black hole, still can't calculate the number of digits in your mom's pi   (phys.org) divider line 39
    More: Interesting, black holes, supermassive black holes, Event Horizon, astronomers, radius, general relativity, extreme environment, Perimeter Institute  
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2827 clicks; posted to Geek » on 28 Sep 2012 at 1:10 PM (2 years ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2012-09-28 01:03:32 PM  
I laughed out loud and now my coworkers are all staring at me.

Thanks Subby.
 
2012-09-28 01:22:35 PM  
Would a fist count as five?
 
2012-09-28 01:22:59 PM  
HA, because our mom's fat! I GET IT!
 
2012-09-28 01:23:34 PM  
Both parts of the headline are farking funny.

Black holes are the space equivalent of CO2 induced greenhouse warming.
 
2012-09-28 01:26:27 PM  
Every time I try to wrap my head around the idea of black holes, I pull a brain muscle. Hell, space in general hurts my brain, when you think about size and distance and all that stuff.
 
2012-09-28 01:26:59 PM  
Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon. By definition though once you pass the event horizon you aren't escaping.

I was always confused about the hawking paradox (PBS special) as I thought matter did leave the black hole, negating his paradox. The 'some universe exists where matter didn't fall into a black hole' is a stupid cop out though.
 
2012-09-28 01:27:15 PM  
So what was the radius?
 
2012-09-28 01:41:33 PM  

whatshisname: So what was the radius?


12.
 
2012-09-28 01:51:06 PM  

TheGogmagog: Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon.


Yes, provided you were either infinitesimally small, or didn't mind having your head and toes pulled in opposite directions by tidal forces that would literally rip every molecule in your body apart.

I was always confused about the hawking paradox (PBS special) as I thought matter did leave the black hole, negating his paradox. The 'some universe exists where matter didn't fall into a black hole' is a stupid cop out though.

Not sure what you mean... The Hawking paradox always assumed that matter left the black hole, and in fact is why there's a paradox:
1. Stuff (like entangled particles carrying information about their quantum state) falls into a black hole and can never escape.
2. Black holes radiate (kinda) Hawking radiation, and as a result, eventually evaporate.
3. Thus, the information is apparently lost, which violates several symmetry laws.
 
2012-09-28 02:10:35 PM  
Link

I'll just leave this here enjoy.
 
2012-09-28 02:17:11 PM  

Theaetetus: TheGogmagog: Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon.

Yes, provided you were either infinitesimally small, or didn't mind having your head and toes pulled in opposite directions by tidal forces that would literally rip every molecule in your body apart.


Are you talking about gravitational gradients? Black holes at the centers of galaxies don't have those kind of gradients until well inside the event horizon. Granted, the black holes causing those jets are actively feasting on the galaxy around them, so you'd have quite a lot of other problems reaching it...
 
2012-09-28 02:21:37 PM  

JolobinSmokin: Link

I'll just leave this here enjoy.


Awesome. Loved it when MC Hawking kicked in with his mad skillz.

The universe is made of
12 particles of matter
4 forces of nature
doo-do dooby do-do
 
2012-09-28 02:21:51 PM  

hawcian: Theaetetus: TheGogmagog: Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon.

Yes, provided you were either infinitesimally small, or didn't mind having your head and toes pulled in opposite directions by tidal forces that would literally rip every molecule in your body apart.

Are you talking about gravitational gradients? Black holes at the centers of galaxies don't have those kind of gradients until well inside the event horizon. Granted, the black holes causing those jets are actively feasting on the galaxy around them, so you'd have quite a lot of other problems reaching it...


Nah, you'd have an easy time reaching it. Just a difficult time staying alive. ;)
 
2012-09-28 03:05:17 PM  
i was told there would be no math
 
2012-09-28 03:37:31 PM  
They've inferred the radius, they've measured the accretion disc.
 
2012-09-28 03:42:11 PM  

skodabunny: JolobinSmokin: Link

I'll just leave this here enjoy.

Awesome. Loved it when MC Hawking kicked in with his mad skillz.

The universe is made of
12 particles of matter
4 forces of nature
doo-do dooby do-do


It's a wonderful and significant story.

That cooked in the crucible that turned light elements into heavy elements.

doo-do dooby do-do :)
 
2012-09-28 03:50:00 PM  

whatshisname: So what was the radius?


Yeah I like when an article says, we know how big this black hole is and then won't actually get into what the number is. Seems like the kind of detail one would include doesn't it?
 
2012-09-28 04:01:55 PM  

whatshisname: So what was the radius?


19 billion kilometers, which is over three times the average distance from the Sun to Pluto. The mass of the black hole is 6.2 billion times that of the Sun.

However, the paper isn't about measuring the radius of the black hole. They got that figure from earlier research. Their new result is the radius of the accretion disk (5.5 times wider than the black hole).
 
2012-09-28 04:06:42 PM  

Extreme_Lukewarm: HA, because our mom's fat! I GET IT!


We're related??
 
2012-09-28 04:12:03 PM  

hawcian: Theaetetus: TheGogmagog: Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon.

Yes, provided you were either infinitesimally small, or didn't mind having your head and toes pulled in opposite directions by tidal forces that would literally rip every molecule in your body apart.

Are you talking about gravitational gradients? Black holes at the centers of galaxies don't have those kind of gradients until well inside the event horizon. Granted, the black holes causing those jets are actively feasting on the galaxy around them, so you'd have quite a lot of other problems reaching it...


If there was a black hole with the observable mass of a galaxy at the center of the galaxy... wouldn't the observable mass of the galaxy be doubled?
 
Xai
2012-09-28 05:06:32 PM  

Ambitwistor: whatshisname: So what was the radius?

19 billion kilometers, which is over three times the average distance from the Sun to Pluto. The mass of the black hole is 6.2 billion times that of the Sun.

However, the paper isn't about measuring the radius of the black hole. They got that figure from earlier research. Their new result is the radius of the accretion disk (5.5 times wider than the black hole).


that can't be right. At that size it is 8.54x10^13 times the volume of the sun, and at a mere 6.2b solar masses it would be 0.00007% the density of the sun. That cannot be right.
 
2012-09-28 05:11:46 PM  

Xai: that can't be right.


It is right. Helpful conversion: a black hole's radius is 3 km for every solar mass.

At that size it is 8.54x10^13 times the volume of the sun, and at a mere 6.2b solar masses it would be 0.00007% the density of the sun. That cannot be right.

Density calculations like that break down because they assume Euclidean geometry. Anyway, a black hole is virtually empty (pure vacuum, plus whatever may briefly may be passing through it), except for a point singularity at the center of infinite density.
 
ZAZ [TotalFark]
2012-09-28 05:47:32 PM  
As a comment on the article says, they measured the radius of the last stable orbit. To determine the size of the black hole itself from that figure you need to know its angular momentum.
 
2012-09-28 06:27:59 PM  

whatshisname: So what was the radius?


about tree fitty.
always about treeeeee fitty.
 
2012-09-28 07:53:20 PM  
I was gonna submit this story with a "your mom" reference, but subby did much better than I could have. Bravo, sir.
 
2012-09-28 07:54:41 PM  

Ambitwistor: Xai: that can't be right.

It is right. Helpful conversion: a black hole's radius is 3 km for every solar mass.

At that size it is 8.54x10^13 times the volume of the sun, and at a mere 6.2b solar masses it would be 0.00007% the density of the sun. That cannot be right.

Density calculations like that break down because they assume Euclidean geometry. Anyway, a black hole is virtually empty (pure vacuum, plus whatever may briefly may be passing through it), except for a point singularity at the center of infinite density.


Have either of you known the touch of a woman?

/I keed, I keed
 
2012-09-28 07:59:14 PM  
So just slightly larger than submitter's Mom?
 
2012-09-28 08:41:44 PM  
This is why I love Fark. We can have intelligent and scientific discussions from a headline about how many fingers fit in my mom's snatch. :)
 
2012-09-28 11:26:09 PM  
Pretty sure the radius of a black hole is undefined, since it by definition involves that pesky singularity. Maybe you can measure the circumference and divide it by 2π, but that would only give the true radius if the spacetime within were flat.
 
2012-09-29 12:02:53 AM  

Grither: whatshisname: So what was the radius?

12.


Big deal. I used to bulls-eye womp rats back home, and they're no bigger than two meters.
 
2012-09-29 01:06:29 AM  

TheGogmagog: Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon. By definition though once you pass the event horizon you aren't escaping.

I was always confused about the hawking paradox (PBS special) as I thought matter did leave the black hole, negating his paradox. The 'some universe exists where matter didn't fall into a black hole' is a stupid cop out though.


This is how I understoond Hawking's Radiation/shrinking black holes from reading ABHoT:

Quantum [mechanics? theory? something] says that in a vacuum, particles and their anti are endlessly popping into existence and annihilating themselves. (This is the basis for Zero Point Energy as well). Hawking Radiation is what happens when the Anti forms on the side of the event horizon with the singularity, and the particle forms on the other. The Anti falls into the singularity and annihilates one of those particles instead. This results in a slightly less massive black hole, while on the other side of the event horizon the original paired particle goes shooting off into the universe. This shows up on our telescopes as matter being ejected from the singularity.

If I remember, this is a dumbed down(and then dumbed down by me again because I haven't read the book since I was like 14) of an explanation that doesn't violate relativity in regards to how can something that light cannot travel fast enough to escape have things escaping it (since things escaping it would have to go faster than c)

/tired
//not drunk
/or maybe I am; that explanation didn't hurt my brain...
 
2012-09-29 06:57:07 AM  

Xai: Ambitwistor: whatshisname: So what was the radius?

19 billion kilometers, which is over three times the average distance from the Sun to Pluto. The mass of the black hole is 6.2 billion times that of the Sun.

However, the paper isn't about measuring the radius of the black hole. They got that figure from earlier research. Their new result is the radius of the accretion disk (5.5 times wider than the black hole).

that can't be right. At that size it is 8.54x10^13 times the volume of the sun, and at a mere 6.2b solar masses it would be 0.00007% the density of the sun. That cannot be right.


That`s the EVENT HORIZON, not the black hole itself. It`s an imaginary line where you are past the point of no return. No light gets out if it gets closer to the black hole than three times the distance from the sun to pluto but the hole itself is maybe a mile across or that sort of scale anyway, on the order of something measured in metres instead of AU.
 
2012-09-29 10:29:33 AM  
As a black hole shrinks, its gravity increases, so from the outside universe's perspective - ours - time slows down at the location of the black hole. So if we look at a black hole caused by a star collapse shouldn't we see it appear to stop collapsing at some point? From the black hole's point of view, it would still be collapsing at full speed.
 
2012-09-29 10:47:41 AM  

SwiftFox: As a black hole shrinks, its gravity increases, so from the outside universe's perspective - ours - time slows down at the location of the black hole. So if we look at a black hole caused by a star collapse shouldn't we see it appear to stop collapsing at some point? From the black hole's point of view, it would still be collapsing at full speed.


yes, as you said "if we look at a black hole" which implies the collapse into a black hole has already happened. This is the point we see it stop collapsing.

From the perspective of a black hole, it collapses, gains an event horizon, then instantly evaporates. To the rest of us, this takes a long long time.

This explains why it evaporates quite well. Due to the time dilation, it would appear to happen instantly from the viewpoint of the black hole itself.

Kurai Kage Ryu: TheGogmagog: Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon. By definition though once you pass the event horizon you aren't escaping.

I was always confused about the hawking paradox (PBS special) as I thought matter did leave the black hole, negating his paradox. The 'some universe exists where matter didn't fall into a black hole' is a stupid cop out though.

This is how I understoond Hawking's Radiation/shrinking black holes from reading ABHoT:

Quantum [mechanics? theory? something] says that in a vacuum, particles and their anti are endlessly popping into existence and annihilating themselves. (This is the basis for Zero Point Energy as well). Hawking Radiation is what happens when the Anti forms on the side of the event horizon with the singularity, and the particle forms on the other. The Anti falls into the singularity and annihilates one of those particles instead. This results in a slightly less massive black hole, while on the other side of the event horizon the original paired particle goes shooting off into the universe. This shows up on our telescopes as matter being ejected from the singularity.

If I remember, this is a dumbed down(and then dumbed down by me again because I haven't read the book since I was like 14) of an explanation that doesn't violate relativity in regards to how can something that light cannot travel fast enough to escape have things escaping it (since things escaping it would have to go faster than c)

/tired
//not drunk
/or maybe I am; that explanation didn't hurt my brain...

 
2012-09-29 01:24:17 PM  

Kurai Kage Ryu: Hawking Radiation is what happens when the Anti forms on the side of the event horizon with the singularity, and the particle forms on the other. The Anti falls into the singularity and annihilates one of those particles instead.


Close, but a few corrections:

Virtual matter-antimatter pairs form spontaneously in the quantum vacuum. One of the particles may escape the horizon while the other falls in. The one that falls in can be either the matter or the antimatter particle, with 50:50 odds. The one that escapes a real particle; the one that falls in is virtual and effectively has negative energy. It doesn't annihilate with anything (and it's unknown whether there's any matter or antimatter at the singularity, which is a breakdown in our description of spacetime).
 
2012-09-29 01:27:06 PM  

SwiftFox: So if we look at a black hole caused by a star collapse shouldn't we see it appear to stop collapsing at some point? From the black hole's point of view, it would still be collapsing at full speed.


The collapse happens rapidly from the perspective of an observe on the surface of the collapsing star. It appears to happen more slowly to an outsider observer. Technically, it happens infinitely slowly toward the end, which led to an old "frozen star" conception of a black hole in which black holes never finished forming. This is just an optical illusion, though, due to how long it takes light to escape to an outside observer. And due to quantum mechanics, there is a finite time at which the last photon escapes the collapsing star, so it appears to finish collapsing in finite time to an outside observer anyway.
 
2012-09-30 05:28:33 PM  

TheGogmagog: Interesting I always thought the extragalactic jets were from the black hole itself, but it's more matter ejected from the accretion disk's magnetic field. So you could get really close as long as the magnetic force ejecting you exceeded the pull toward the event horizon. By definition though once you pass the event horizon you aren't escaping.

I was always confused about the hawking paradox (PBS special) as I thought matter did leave the black hole, negating his paradox. The 'some universe exists where matter didn't fall into a black hole' is a stupid cop out though.


As I believe I understand it, Hawking radiation is a peculiar result of quantum properties of matter -- specifically, the property of certain kinds of matter to spontaneously appear in normal space (presumably from extra dimensions). In this case, an electron-positron pair will appear together. In most cases, they will quickly annihilate each other. But if they appear at the event horizon of a black hole, and the positron falls in while the electron escapes, then the positron that falls in will meet and annihilate an electron inside, resulting in a net reduction in the black hole's mass. Over time, this will cause the black hole to sort of 'evaporate'. Paradoxically, becasuse the radius and attraction of a black hole increases with its mass, this means that the bigger the black hole, the faster it evaportates. So according to the theory -- again, if I understand it correctly -- they do die, but it takes a very long time.
 
2012-10-01 12:58:26 AM  
You have all described Hawking radiation as well as I know it , but I was referring to the paradox that when matter enters a black hole its information is destroyed. That violates the second law. His solution is that there are parallel universes where the matter didn't get destroyed so all is good.
 
2012-10-01 09:14:23 PM  
The "a black hole has no hair" problem. I don't consider the entropy being reduced issue a real problem. The second law of thermo was never a cold, hard fact. Systems TEND to disorder in a positive energy system when treated probabilistically. But if the universe is headed for a black hole then that isn't positive energy system is it. Oh no, convergent dynamics!
 
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