Are black holes really black?
920733
Steven Hawking has recently changed his view that no "information" could escape a black hole.  Current thinking is that as matter falls into a black hole, some radiation / information escapes across the event horizon.  So according to current thinking black holes are not completely "black"
373282
We haven't actually had a black hole close enough to experiment with, at least not that we know about--although there are theories about dryers having a black hole that eats socks, see earlier response!!--so most of the work on black holes is done with theory, prediciting what a black hole might do, and then seeing if something out there is doing it.\n\nNow, the best data seems to be based on the orbital velocities of stars in galaxies: the velocity distributions demand a truly massive central mass in a lot of the galaxies, one that is best viewed as a black hole.\n\nSome very nice data exists with observations of events predicted to happen with "near misses" with black holes--particles that get into the titanic gravity well of the black hole, but decay into two particles, one escaping the black hole.\n\nBut no one has actually seen a black hole do anything, directly..
330944
A black hole is a very large star, many times more massive than our Sun, that has collapsed under its own gravity (Usually, the star doesnt collapse because the nuclear reactions occuring in its core counter the gravitational force) The gravitational field around a black hole is so strong that not even light can escape
357992
i dont believe so, from watching many episodes on nova , i understand black holes to be tinny[ in size] particles of compressed matter , so compressed as to create an astronomical gravitational force so strong that even light cannot escape. i believe most scientist believe it is a large compressed star; a star the size of our sun compressed to the area of a marble or tennis ball which because of its great gravitational force act like a celestial vacuum cleaner... its real esoteric b.s.
600386
You don't need a black hole to be able hold itself together through gravity. Just look at the earth or the moon for example. They are nowhere near as dense as a black hole, yet they support themselves gravitationally.
775784
Black holes as mentioned above are a singularity.  Nobody really knows what happens once you cross the event horizon ( the edge of the black hole).  These are very strange events in that they pull everything including light towards them, which contradicts Newtons second law with mass being proportional inversely proportional to mass ( as light has no mass) and Einstein's theory of relativity and the conservation of mass and energy.  All theory we have breaks down when we encounter black holes.\n\nAn interesting theory is that black holes are a link to another universe, matter passing through a black hole and appearing through a white hole in another universe.  This theory has the assumption that there is more than one universe and that they are all linked.  Stephen Hawking's "A Brief history of time" gives many interesting insights.  \n\nHe has recently changed some of his views however with a new theory that a Universe is created by the bumping of one universe into another with black holes becoming the remanents of the reaction, and thus there is no begining or end to time.  He is publishing his ideas soon.  In short however nobody really knows what happens in a black hole.
943076
You can spin a black hole?   Well aren't you talented...  actually the whole known physical universe is first and foremost a gigantic black hole, and it is in motion.  Before the first star formed the dark spacial universe existed and on the smallest scale there is no empty space, everything is connected.  It has been said that darkness is merely the absence of light, but there's no such thing as nothing, everything is made of something, even the ordinary everyday nighttime darkness, on some immeasurable scale even your shadow is made of something?  Black holes are a different more massive type of darkness comprised of dark physical matter.   There's a theory that every galaxy has one at the center and without it the stars that form a galaxy couldn't exist, and it's probable that it is already spinning, nothing is actually sitting still.  It's estimated the output of light from all the stars should be enough to light up the whole universe, but it doesn't.  Then where does it go, what happens to it, we know on a sub atomic scale it doesn't simply dissipate?  Where does the darkness go when you switch on a light?  When you turn off the light, obviously it's still there, so wasn't it there the whole time?   Well, there are still more questions than answers, and maybe you should be a physicist, perhaps you could find an answer to the enigmas of the infinite machine.
325445
White holes were initially hypothesized by Stephen Hawking (who wrote a Brief History of Time), based on quantum mechanics.  Quantum mechanics theory states that for everything, there is an opposite.  So there is matter and ant-matter, for example.  That means if black holes exist, there must be white holes, regions from which particles are emitted but no particle can ever enter.  However, in a momentous physics finding, Mr. Hawking later proved that black holes actually DO emit certain types of radiation.  Apparently, once matter goes into a black hole, it is transferred to energy and is emitted by radiation, making use of Einstein's E=MC^2 rule.  So, since black holes are not really black, many believe that white holes do not exist.  In addition, we have "seen" black holes in space (areas of matter that swirl into blackness), but have seen nothing like a white hole.
127702
Black holes are full of electrons.They are not capable of any expansion or constriction. Time also does not expand.
5155
Because a "black hole" has a gravitational field so strong, light cannot escape.  Therefore, all we can see is that nothing is there, which appears like "blackness" to us, and since light "falls" into it, it's a "hole".\n\nThus, black hole.
1098294
no. The definition of black hole is that what comes in, never comes out anymore.\n\n"What goes in must come out?" is a saying, not a law of physics
6001
yes!!\n\nBlack holes are predictions of Albert Einstein's theory of general relativity. In particular, they occur in the Schwarzschild metric, one of the earliest and simplest solutions to Einstein's equations, found by Karl Schwarzschild in 1915. This solution describes the curvature of spacetime in the vicinity of a static and spherically symmetric object, where the metric is\n\n    ds^2 = - c^2 &#92;left( 1 - {2Gm &#92;over c^2 r} &#92;right) dt^2 + &#92;left( 1 - {2Gm &#92;over c^2 r} &#92;right)^{-1} dr^2 + r^2 d&#92;Omega^2,\n\nwhere d&#92;Omega^2 = d&#92;theta^2 + &#92;sin^2&#92;theta&#92;; d&#92;phi^2 is a standard element of solid angle.\n\nAccording to Schwarzschild's solution, a gravitating object will collapse into a black hole if its radius is smaller than a characteristic distance, known as the Schwarzschild radius. Below this radius, spacetime is so strongly curved that any light ray emitted in this region, regardless of the direction in which it is emitted, will travel towards the center of the system. Because relativity forbids anything from travelling faster than light, anything below the Schwarzschild radius – including the constituent particles of the gravitating object – will collapse into the center. A gravitational singularity, a region of theoretically infinite density, forms at this point. Because not even light can escape from within the Schwarzschild radius, a classical black hole would truly appear black.\n\nThe Schwarzschild radius is given by\n\n    r_s = {2&#92;,Gm &#92;over c^2}\n\nwhere G is the gravitational constant, m is the mass of the object, and c is the speed of light. For an object with the mass of the Earth, the Schwarzschild radius is a mere 9 millimeters — about the size of a marble.\n\nThe mean density inside the Schwarzschild radius decreases as the mass of the black hole increases, so while an earth-mass black hole would have a density of 2 × 1030 kg/m3, a supermassive black hole of 109 solar masses has a density of around 20 kg/m3, less than water! The mean density is given by\n\n    &#92;rho=&#92;frac{3&#92;,c^6}{32&#92;pi m^2G^3}\n\nSince the Earth has a mean radius of 6371 km, its volume would have to be reduced 4 × 1026 times to collapse into a black hole. For an object with the mass of the Sun, the Schwarzschild radius is approximately 3 km, much smaller than the Sun's current radius of about 700,000 km. It is also significantly smaller than the radius to which the Sun will ultimately shrink after exhausting its nuclear fuel, which is several thousand kilometers. More massive stars can collapse into black holes at the end of their lifetimes.\n\nMore general black holes are also predicted by other solutions to Einstein's equations, such as the Kerr metric for a rotating black hole, which possesses a ring singularity. Then we have the Reissner-Nordström metric for charged black holes. Last the Kerr-Newman metric is for the case of a charged and rotating black hole.\n\nThere is also the Black Hole Entropy formula:\n\nS = &#92;frac{Akc^3}{4&#92;hbar G}\n\nWhere A is the area of the event horizon of the black hole, &#92;hbar is Dirac's constant (the "reduced Planck constant"), k is the Boltzmann constant, G is the gravitational constant, c is the speed of light and S is the entropy.
67663
*puts on cokebottle glasses*\nTechnically, black holes haven't been proven to exist, their existence is just extremely well supported, like the theory of plate tectonics.\n\nAlso, black holes don't actually move faster than the speed of light.  Nothing can move faster than the speed of light in a vaccuum. What you're probably thinking of is their gravitational pull is so intense that their escape velocity (the speed you have to be traveling at to break free of their gravitational pull) is faster than the speed of light.\n\nI think it's awesome in the biblical sense.  Black holes have always intrigued me- something that you can get stuck in and never, ever escape.  The way they distort light also is very interesting.\n\nI sometimes pretend that the inside of the event horizon of a black hole is where Hell is.  You can't escape it so you would be stuck there for eternity (the slow Hawking radiation notwithstanding) and you would be ripped up into your individual subatomic particles.  Plus, the rules of Classical Physics don't work in the way you would expect them to.\n\nCloyvin.
762962
no, but i can tell you what we think it is:\n\nit is a star whose gravity is too great for the nuclear fusion in its core to negate.  it collapses in on itself and goes supernova.  then it is a neutron star.  if the gravity is still too great, it collapses some more and becomes a black hole.  its gravity is so strong that light itself cannot escape it (thus it is 'black').  they are suspected to be at the center of many galaxies, especially quasars and other active galaxies.  one is believed to be at the center of our own galaxy, the milky way.\n\nonce again, no one has really seen one, just the indirect evidence that one exists (strange star orbits, gas being sucked into nothing, strange bursts of some kind of rays (can't remember what kind) coming out of the poles, etc.\n\neverybody is pretty convinced that they exist.  its just kinda hard to prove.\n\nps the idiot down there who said black holes are dead galaxies has no clue what he is talking about. please ignore him.  and its not the size of an atom, its an infinitely small point, the swartzchild point.
481008
Yes, they have gravitational pull strong enough to pull in light, but there is one known thing that can escape, thermal radiation. Steven Hawking's book a brief history of Time. There are many theories about black holes, but yes they exist.
314939
there is no 'color' they are black. If u look through a telescope you will see the 'white' stars and then this giant lack of space (the black hole) and then back to stars
295074
Things that enter a black hole do not "implode," and black holes and the big bang are two uttern non-connected things.\n\nshort answer day!