Scientists May Get Best View Yet of a Black Hole in Action
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Re: Scientists May Get Best View Yet of a Black Hole in Action
#2[deleted]
Re: Scientists May Get Best View Yet of a Black Hole in Action
#3A question for the physicists on HN: I've heard that black holes emit radiation. But if nothing can go faster than the speed of light, and a black hole's gravity is so strong that not even light can escape, then how can a black hole emit anything?
Is there a kind of black hole which is so massive that not even that radiation can escape, or do all black holes emit some kind of radiation? (In fact, do they emit radiation proportional to their size?)
Re: Scientists May Get Best View Yet of a Black Hole in Action
#4A question for the physicists on HN: I've heard that black holes emit radiation. But if nothing can go faster than the speed of light, and a black hole's gravity is so strong that not even light can escape, then how can a black hole emit anything? Is there a kind of black hole which is so massive that not even that radiation can escape, or do all black holes emit some kind of radiation? (In fact, do they emit radiati…
Armchair Physicist here, not a real one.
There are two reasons why you'd say black holes emit radiation. An interesting one and a very interesting one (warning, other peoples scales may be calibrated differently to mine).
1) Black holes accelerate things massively, so they're travelling at an astonishing speed before they "enter". This can result in huge amounts of x-rays being emitted due to heating things to millions of degrees (well beyond white hot!). It's not the black hole itself, but the black hole is certainly to blame. http://hyperphysics.phy-astr.gsu.edu/hbase/astro/blkbin.html
2) The weirder one. Hawking radiation: http://en.wikipedia.org/wiki/Hawking_radiation
Hawking radiation happens when a pair of virtual particles "pop" into existence near the event horizon. Normally these pairs annihilate quickly, but if it happens near the event horizon it's possible for one of the particles to fall in and the other to escape. This results in a loss of mass of the black hole (told you it was weird) so could be considered to be the black hole emitting radiation.
Re: Scientists May Get Best View Yet of a Black Hole in Action
#5A question for the physicists on HN: I've heard that black holes emit radiation. But if nothing can go faster than the speed of light, and a black hole's gravity is so strong that not even light can escape, then how can a black hole emit anything? Is there a kind of black hole which is so massive that not even that radiation can escape, or do all black holes emit some kind of radiation? (In fact, do they emit radiati…
You may be referencing two different kind of radiations:
- the one emitted by the heated matter falling in / spinning around the black hole (the quasar referenced in the article [1])
- the Hawking radiation. Basically a pair of particle/antiparticle randomly appears near the black hole event horizon, one of the particle falls into the black hole while the other one escapes. The black hole would eventually evaporate if you waited long enough. [2]
[1] http://en.wikipedia.org/wiki/Quasar [2] http://en.wikipedia.org/wiki/Hawking_radiation
Re: Scientists May Get Best View Yet of a Black Hole in Action
#6A question for the physicists on HN: I've heard that black holes emit radiation. But if nothing can go faster than the speed of light, and a black hole's gravity is so strong that not even light can escape, then how can a black hole emit anything? Is there a kind of black hole which is so massive that not even that radiation can escape, or do all black holes emit some kind of radiation? (In fact, do they emit radiati…
[deleted]
Re: Scientists May Get Best View Yet of a Black Hole in Action
#7A question for the physicists on HN: I've heard that black holes emit radiation. But if nothing can go faster than the speed of light, and a black hole's gravity is so strong that not even light can escape, then how can a black hole emit anything? Is there a kind of black hole which is so massive that not even that radiation can escape, or do all black holes emit some kind of radiation? (In fact, do they emit radiati…
IanCal and blaze33 both gave good answers, but just to clarify one thing: the radiation we see coming from regions where there are black holes is of the first type: radiation emitted by objects like gas clouds that are falling into the holes, before those objects cross the event horizon. If we leave out quantum effects like Hawking radiation (see below), it's impossible for light, or any kind of radiation, or indeed anything at all, to escape from inside the event horizon of a black hole.
Hawking radiation is a quantum effect, which nobody has ever observed; the reasons for thinking that it exists are purely theoretical.
Re: Scientists May Get Best View Yet of a Black Hole in Action
#8If only black holes weren't illogical! [1] Any decent software developer (i.e. highly logical thinker) who knows basic info about black holes can look at the picture there to quickly see that black holes are inconsistent with the core postulate of general relativity, the equivalence principle. They're a bug! (which Einstein spent a decade trying to find, or some other way that nature could prevent black holes he thought didn't "smell right", and no that's not my blog) [2] is previous discussion showing no bona fide flaw in the argument. I've not seen anyone refute that simple picture, which should be easy if it's incorrect.
That black holes are a bug doesn't mean we can't explain observations. Gravitational redshift still exists to explain massive objects emitting no discernible light (might be only one photon every year, away from Earth).
Re: Scientists May Get Best View Yet of a Black Hole in Action
#9A question for the physicists on HN: I've heard that black holes emit radiation. But if nothing can go faster than the speed of light, and a black hole's gravity is so strong that not even light can escape, then how can a black hole emit anything? Is there a kind of black hole which is so massive that not even that radiation can escape, or do all black holes emit some kind of radiation? (In fact, do they emit radiati…
The simplest answer: it's the region immediately above the black hole that these reports refer to, not the black hole itself (its event horizon and below there).
Re: Scientists May Get Best View Yet of a Black Hole in Action
#10If only black holes weren't illogical! [1] Any decent software developer (i.e. highly logical thinker) who knows basic info about black holes can look at the picture there to quickly see that black holes are inconsistent with the core postulate of general relativity, the equivalence principle. They're a bug! (which Einstein spent a decade trying to find, or some other way that nature could prevent black holes he thou…
Here's another relevant discussion on HN that you conveniently forgot to link to, which does explain in detail the flaw in your argument (the discussion you did link to does too, but not in detail):
https://news.ycombinator.com/item?id=5233894
Click on "parent" to see the post of yours that I was responding to.