What are black holes -In short, a black hole is an imploded star. star. When a massive star undergoes a supernova explosion, it may leave behind burned our stellar remnant. With no outward forces on these remnant, the star collapses on itself, to a point with no volume and innite density. density. - The gravitational force from this point is so vast that light itself cannot escape the gravitational eld, and therefore gets sucked up into the mass itself. itself. Thus creating a black hole. Spacetime curvature -The theory of general relativity predicts that a suciently compact mass will deform spacetime to form a black hole. Foramtion of a black hole -When a gigantic star reaches the nal stage of its life and is about to go supernova !which normally takes billions of years", it spends all the nuclear fuel by then. #o it stops burning and heating up and cannot create the nuclear energy re$uired to feed the star and let it make a pivotal balance to support its own gravitational draw against the intense pressures pressures brewing inside. -Its stability cracks under its own gravity. -The radius of the star shrinks to a critical si%e, called the #chwar%schild radius . -The outer shells of the star explode into the space. They may even fall into the already dense black hole making it even heavier and denser. denser. &nd that's how you get a stellar mass black hole. STRUCTURE OF A BLAC !OLE -The #ingularity( #ingularity( This is the region of the black hole where all the mass of the black hole has been compressed compressed down to nearly %ero %ero volume. &s a result the singularity singularity has almost innite density and creates an enormous gravitational force -The )vent *ori%on( *ori%on( This is the +point of no return+. return+. &ny obect, even light, that is within within this radius cannot escape the gravitational pull of the black hole -The #chwar%schild adius( This is the event hori%ons radius. It is the radius at which the escape velocity is e$ual to the speed of light -The &ccretion &ccretion /isk( This is a disk composed of stellar material that is spiraling towards that black hole -The )rgosphere( If the black hole is rotating, then as it spins, its mass causes the space time around the black black hole to rotate as as well. This region is called called the ergosphere. ergosphere. -0ets of 1as( 2or some black holes high intensity magnetic elds are emitted perpendicular to the accretion accretion disk. This causes charged charged particles to circle circle these magnetic eld lines and creates ets of gas perpendicular to the acceleration disk. Si"es of black holes -#upermassive black holes( They are those who have masses of several million solar masses. They are at the heart of many galaxies . &re formed in the same process that gives rise to spherical components of galaxies. -#tellar-mass -#tellar-mass black holes ( They are formed when a star of mass 3.4 times that of the #un goes supernova and explodes. Its nucleus is concentrated in a very small volume is reduced whenever more . This is the type of black hole for the rst time goes into the theory of general relativity. -5icro black holes ( They are hypothetical obects , somewhat smaller than stellar . If they
are small enough, they can get to evaporate in a relatively short period through emission of *awking radiation . This type of physical entities is postulated in some approaches to $uantum gravity, but can not be generated by a conventional process of gravitational collapse , which re$uires higher mass to the #un . Fallin# into a black hole -It would look $uite di6erent depending on your perspective. If you were safely away from the black hole watching someone else fall in, you would see them speed up as they fell towards it, but then slow down again as they approached the event hori%on. -)instein's theory of general relativity says that in very high gravitational elds, time slows down as observed by someone outside the gravitational eld. &t the event hori%on, time would stop. #o you would see them get closer and closer to the event hori%on, but never actually reach it. They would seem to stay in suspended animation for ever. -7ut it wouldn't seem like that from the perspective of the person falling in. The person falling in would see themselves falling faster and faster towards the event hori%on, then plunging straight through it without any slowing down. 8ike everything else that fell through the event hori%on, they would fall straight to the singularity at the centre of the black hole. -)verything in the black hole would be concentrated in the centre at the singularity. It would take only a fraction of a second after falling though the event hori%on to reach the singularity and be s$uashed to %ero si%e. -If the person were able to look back as they fell through the event hori%on, though, they would see the whole future of the universe unfold before their eyes, albeit rather dimly. -That's hypothetical, though .In actual fact the person would be spaghettied before they reached the event hori%on. !a$kin# ra%ioation -adiation theoretically emitted from ust outside the event hori%on of a black hole. #tephen W. *awking proposed in 9:;< that subatomic particle pairs !photons, neutrinos, and some massive particles" arising naturally near the event hori%on may result in one particle's escaping the vicinity of the black hole while the other particle, of negative energy, disappears into it. The =ow of particles of negative energy into the black hole reduces its mass until it disappears completely in a nal burst of radiation. &nformation para%o' -7ecause a black hole has only a few internal parameters, most of the information about the matter that went into forming the black hole is lost. egardless of the type of matter which goes into a black hole, it appears that only information concerning the total mass, charge, and angular momentum are conserved. &s long as black holes were thought to persist forever this information loss is not that problematic, as the information can be thought of as existing inside the black hole, inaccessible from the outside. *owever, black holes slowly evaporate by emitting *awking radiation. This radiation does not appear to carry any additional information about the matter that formed the black hole, meaning that this information appears to be gone forever. $ormhole -& wormhole, also known as an )instein>osen bridge, is a hypothetical topological feature of spacetime that would fundamentally be a +shortcut+ through spacetime.
-?err showed that a spinning black hole would collapse not into a point, but to a @ring of re.A 7ecause the ring was spinning rapidly, centrifugal forces would keep it from collapsing. emarkably, a space probe red directly through the ring would not be crushed into oblivion, but might actually emerge unscratched on the other side of the )instein-osen bridge, in a parallel universe. This @wormholeA may connect two parallel universes, or even distant parts of the same universe.
