
#1
Nov310, 10:32 AM

P: 30

How we can prove the existence of black holes?
And how they are located in in the space as they can absorb light too? 



#2
Nov310, 10:41 AM

P: 474

Stuff falling into black holes is heated to very high temperatures as it collides with other stuff also being pulled into the blackhole  we don't see the blackhole directly but we do see a huge amount of xrays and other radiation from this material.
We can calculate the size of the object at the center of this and if it is small enough we know it is a blackhole. 



#3
Nov310, 01:24 PM

P: 113

some would say that, b/c we have yet to literally "see" the shadow of a BH (the event horizon) against the backdrop of stars and illuminated gas and dust, we do not have definitive proof of the existence of black holes. but if you ask me, the abundance of evidence  not proof, but evidence  of the existence of black holes is too convincing to possibly suggest that they don't exist.
we've observed and measured the motions of stars extremely close to the galactic center, and found that they orbit so fast within a radius so small, that the only way to explain their motions is if a mass of ~2.6 million suns is present. we know that any mass that causes a star to orbit it lies completely interior to the orbital path of the star itself. thus, the volume occupied by these ~2.6 million solar masses can be no larger than the volume contained within the radii of the orbits of the stars going around it. this is strong evidence that there may be a BH at the center of our galaxy... ...however this information alone is not enough to say definitively that the object is definitely a black hole (and not a huge conglomeration of burnedout white dwarfs or other massive, hardlyradiating objects). but we've studied the motions of other objects (gas, dust, etc.) much closer to the center of our galaxy than the actual stars that orbit it...this is what NobodySpecial is talking about. as gas and dust accretes around the BH and sink closer to the event horizon, its angular velocity (the speed at which it orbits) increases dramatically to appreciable fractions of the speed of light, and copious amounts of energy are released via compression and friction as the material orbits the BH. not only can we detect the highenergy radiation coming from this accretion process, but we can use spectroscopy to calculate red shifts and blue shifts caused by the motions of this orbiting gas and dust. if we were to view a BH edgeon or close to it (kind of like we view the possible BH at the center of our own galaxy), then the orbiting material would be more or less traveling away from us on one side of the BH, and toward us on the other side. we've found using spectroscopy that the red shifts and blue shifts induced by the gas and dust orbiting closest to the central object are significant, indicating that the velocities of the orbiting material is relativistic. this is more strong evidence that the central object is a black hole (and not a white dwarf or neutron star). these are just a few of the many pieces of evidence suggesting the existence of black holes. the relativistic jets of active galactic nuclei that stretch anywhere from thousands to millions of light years into space and are as straight as an arrow also suggest the existence of black holes. i haven't even scratched the surface now that i think about it. if you're seriously interested in learning about the all the evidence suggesting the existence of black holes, but don't want to deal with lots of technical jargon and math formulas, check out "The Black Hole At The Center Of Our Galaxy" and "The Edge Of Infinity: Super Massive Black Holes In The Universe," both by Fulvio Melia...they're both chalked full of information that is easily retained, yet aren't boring at all, and are quite easily understood by the layman. 



#4
Nov310, 02:12 PM

P: 3

Black Holes.
i was reading a brief history of time and i answers very clearly the very question you asked. Though black holes absorb all light(one way to detect anything) it does have a observable gravitational effect through which the have been proved to exist. they also release xrays which they don't suck in(this i couldn't understand why) which is another way to detect them




#5
Nov310, 02:33 PM

Mentor
P: 6,037

http://www.scientificamerican.com/ar...fablackhole http://arxiv.org/abs/astroph/0607279. 



#6
Nov310, 02:36 PM

P: 113





#7
Nov510, 02:49 AM

P: 3





#8
Nov510, 04:40 AM

P: 66

Quantum uncertainty allows for one of the particle pairs to escape at the event horizon boundary
You can view it as Quantum mechanics allowing the speed of one of the particle pairs to exceed the speed of light and therefore escape Some Big Relativistic Rule seems to be violated here 



#9
Nov510, 09:20 AM

P: 113





#10
Nov810, 01:20 PM

P: 70

I am not convinced by the mathematics of Hawking radiation. I believe it may be flawed.




#11
Nov810, 01:41 PM

P: 287

Source The Actual Paper 



#12
Nov910, 10:26 AM

P: 113

we know that quantum fluctuations occur in the magnetic field of a BH, and that those minute amounts of energy are used to bring particleantiparticle pairs into existence for infinitesimal time intervals. now i can understand that, if this occurs very near the BH's event horizon, it is entirely possible that one of the particles plunges through the event horizon never to return, while the other escapes to infinity, giving us the impression that the BH is radiating. i also understand that each particle must carry a fraction of the total energy that went into creating them. and so if the total energy taken from the BH's magnetic field in order to create a particleantiparticle pair is 10, then the sum of the particles' energies is 10...that is, each particle must carry an energy less than the total energy 10 (i left units out for simplicity's sake). so if a BHs' magnetic field gives up a specific amount of energy in creating a particleantiparticle pair, and the BH swallows one of the particles before the two can annihilate and return the energy to the vacuum, then the BH will have reacquired some, but not all, of the energy that went into creating the particleantiparticle pair. hence the result is a net loss of mass/energy for the BH. the things that make me unsure about the above scenario are the assumptions that have to be made in order for things to work out that way. what if we made some other initial assumptions? for instance, what if BOTH particles are swallowed by the BH before they can annihilate? then wouldn't the BH have reacquired ALL of the energy that its magnetic field gave up to create the pair in the first place? it would seem to me that this result has no net gain or loss of mass/energy for the BH, and therefore no evaporation (BH radiation) in this case. also, what about the instance in which the particleantiparticle pair is produced far enough from the event horizon that neither particle falls in? in this case, it would seem to me that the BH loses the entire amount of energy it put into making the pair in the first place, and is evaporating (radiating) at an increased rate. considering the above scenarios (and not knowing if all of them are even possible in reality), it would seem to me that in order for a BH to truly evaporate over time, the instances in which both particles of the particleantiparticle pairs escape the BH would have to occur at approx. the same rate at which the instances in which both particles of the particleantiparticle pairs fall into the BH occur, thus canceling each other's net effects of mass/energy gain and loss. this leaves only one other type of instance  the one in which one particle of the particleantiparticle pair falls into the BH, and the other escapes, which yields a net loss of BH mass/energy each time it occurs, and hence results in a BH that truly evaporates over time. perhaps i'm overanalyzing things  as i said somewhere above, i don't even know if its possible for both particles of an particleantiparticle pair to fall into a BH, or for both of them to escape it altogether for that matter. again, those were assumptions i made for a theoretical/mental exercise. if the scenarios i suggested are realistically impossible, then the only scenario left is the one in which one particle fall into the BH, and one escapes it, again yielding a net mass/energy loss for the BH. but i would need someone knowledgeable to show me that the alternative instances which i suggested either do not exist in reality, or do exist, but cancel each other's effects in order to convince me that Hawking Radiation in fact results in the evaporation of a BH over time... 



#13
Jan711, 03:00 AM

P: 604




#14
Jan1211, 06:43 PM

P: 4

One thing's for sure we cannot PROVE the existence of black holes.



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