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BLACK HOLES
A black hole is a cosmic body of extremely intense gravity from which even light cannot escape. Black holes usually cannot be observed directly, but they can be “observed” by the effects of their enormous gravitational fields on nearby matter. It is a region of spacetime where gravity is so strong that nothing no particles or even electromagnetic radiation such as light can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. At the center of a black hole, it is often postulated there is something called a gravitational singularity, or singularity. This is where gravity and density are infinite and space-time extends into infinity. Just what the physics is like at this point in the black hole no one can say for sure. quantum mechanics could feasibly turn the event horizon into a giant wall of fire and anything coming into contact would burn in an instant. In that sense, black holes lead nowhere because nothing could ever get inside. This, however, violates Einstein's general theory of relativity. There are four types of black holes: stellar, intermediate, supermassive, and miniature. The most commonly known way a black hole forms is by stellar death. As stars reach the ends of their lives, most will inflate, lose mass, and then cool to form white dwarfs. Black holes are laboratories for testing fundamental theories that explain how the Universe works on the largest and the smallest scales eg quantum mechanics. A white hole is a black hole running backwards in time. Just as black holes swallow things irretrievably, so also do white holes spit them out. White holes cannot exist, since they violate the second law of thermodynamics. General Relativity is time symmetric. Near a black hole, the slowing of time is extreme. From the viewpoint of an observer outside the black hole, time stops. Inside the black hole, the flow of time itself draws falling objects into the center of the black hole. No force in the universe can stop this fall, any more than we can stop the flow of time. In 1971, Stephen Hawking(Astrophysicist) proposed the area theorem, which set off a series of fundamental insights about black hole mechanics. In astrophysics, spaghettification is the vertical stretching and horizontal compression of objects into long thin shapes in a very strong non-homogeneous gravitational field it is caused by extreme tidal forces. Spaghettification, also known as the “noodle effect,” is the stretching out of an object as it comes into contact with an extreme gravitational field, typically that of a black hole. Black holes have incredibly powerful tidal forces. The theorem predicts that the total area of a black hole's event horizon and all black holes in the universe, for that matter should never decrease. The birth of our universe may have come from a black hole. Most experts agree that the universe started as an infinitely hot and dense point called a singularity. To make a black hole, one must concentrate mass or energy sufficiently that the escape velocity from the region in which it is concentrated exceeds the speed of light. In such scenarios, black hole production could possibly be an important and observable effect at the Large Hadron Collider (LHC). When two black holes spiral around each other and ultimately collide, they send out gravitational waves - ripples in space and time that can be detected with extremely sensitive instruments on Earth. If confirmed, it would be the first known light flare from a pair of colliding black holes. Currently the largest known black hole, powering the quasar TON 618, has a mass of 66 billion solar masses. We know that many supermassive black holes formed early in the universe. For example, the quasar TON 618 is powered by a 66 billion solar mass black hole. Since its light travels nearly 11 billion years to reach us, TON 618 was already huge when the universe was just a few billion years old. TON 618 is now recognized as the 'accretion disc' of intensely hot gas swirling around a supermassive black hole in the centre of a galaxy in the Northern constellation of Canes Venatici. The distance is estimated to be 10.4 billion light years. NASA scientists have identified the lightest black hole yet, just 3.8 times the mass of the sun, in a binary star system in the Milky Way known as XTE J1650-500. The smallest possible Stellar black hole is set by the Tolman–Oppenheimer–Volkoff limit which is estimated at 2.17 solar masses. But actually it is less than that because the Neutron star will give off some mass as it collapses. The Unicorn black hole is about three times the mass of our sun – tiny for a black hole. Very few black holes of this mass have been found in the universe. This black hole is 1,500 light years away from Earth, still inside the Milky Way galaxy. And, until Jayasinghe started analyzing it, it was essentially hiding in plain sight. A Micro black holes, also called quantum mechanical black holes or mini black holes, are hypothetical tiny black holes, for which quantum mechanical effects play an important role. The concept that black holes may exist that are smaller than stellar mass was introduced in 1971 by Stephen Hawking. A black hole of 1 solar mass takes 1067 years to evaporate (much longer than the current age of the Universe), while a black hole of only 1011 kg will evaporate within 3 billion years. Black holes are detected by observing high-energy phenomena and the motions of nearby objects. Black holes have a finite lifetime due to the emission of Hawking radiation. However, for most known astrophysical black holes, the time it would take to completely evaporate and disappear is far longer than the current age of the universe. Black holes are freezing cold on the inside, but incredibly hot just outside. The internal temperature of a black hole with the mass of our Sun is around one-millionth of a degree above absolute zero. Hawking radiation is thermal radiation that is theorized to be released outside a black hole's event horizon because of relativistic quantum effects. It is named after the physicist Stephen Hawking, who developed a theoretical argument for its existence in 1974. According to quantum mechanics the black hole information paradox is a puzzle resulting from the combination of quantum mechanics and general relativity. However, this violates a core precept of both classical and quantum physics that, in principle, the state of a system at one point in time should determine its value at any other time. Once the black holes evaporate completely, in both cases, one will be left with a featureless gas of radiation. This gas cannot be used to distinguish between the two initial states, and therefore information of the objects which it had swallowed has been lost. In Hawking's original formulation of his radiation process, that radiation carried no information away with it. But as the black hole emits radiation, it evaporates, eventually disappearing altogether hence the so-called black hole information paradox. Hawking realized that black holes aren't static. Rather, they release their mass and energy back into the Universe particle by particle, until there is nothing left. If the information can be lost, that would mean that black holes can eventually delete the Universe. Any information drawn into a black hole has an unknown future, according to modern physics, so far. This idea suggests that Hawking radiation stops before the black hole reaches the Planck size. Since the black hole never evaporates, information about its initial state can remain inside the black hole and the paradox disappears.
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Data source - Google and Nasa
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