What is Black Hole ?

The gravitational waves spotted by LIGO came from merging stellar black holes.

Black holes are the only objects in the Universe that can trap light by sheer gravitational force. Scientists believe they are formed when the corpse of a massive star collapses in on itself, becoming so dense that it warps the fabric of space and time.

A black hole refers to the region in space in which the singularity’s gravitational force is so strong that not even light can escape its pull.

Black holes do not "suck." Suction is caused by pulling something into a vacuum, which the massive black hole definitely is not. Instead, objects fall into them.

If you fell into a black hole, theory has long suggested that gravity would stretch you out like spaghetti, though your death would come before you reached singularity.

Some think that black holes are like cosmic vacuums that suck in the space around them when, in fact, black holes are like any other object in space, albeit with a very strong gravitational field.

The singularity at the core of a black hole may shrink to a size smaller than an atom, and eventually become an infinitely small point in space containing infinite mass. Here the gravitational force is so strong that the spacetime surrounding the singularity is bent to infinite curvature, and scientists are left searching for a good quantum theory of gravity to explain what is truly going on inside these incredibly dense objects.

But a 2012 study in Nature suggests that quantum effects would cause the event horizon to act much like a wall of fire, instantly burning anyone to death.

If you replaced the Sun with a black hole of equal mass, Earth would not get sucked in – it would continue orbiting the black hole as it orbits the Sun, today.

The mass of a black hole is so dense and the gravity of its singularity so strong that, in accordance with Einstein’s theory of general relativity, it actually distorts the space-time around it and not even light can escape.

Black holes look like they're sucking in matter from all around, but that's a common misconception. Companion stars shed some of their mass in the form of stellar wind, and the material in that wind then falls into the grip of its hungry neighbour, a black hole.

If a star passes too close to a black hole, it can be torn apart.

an object passing the event horizon will appear to slow down then “freeze” in time without ever seeming to pass through the event horizon. This is because the light takes longer to escape the black hole’s gravitational pull and light signals won’t reach the viewer for an infinitely long time

Einstein didn't discover the existence of black holes – though his theory of relativity does predict their formation. Instead, Karl Schwarzschild was the first to use Einstein's revolutionary equations and show that black holes could indeed form.

Astronomers estimate there are anywhere from 10 million to a billion stellar black holes, with masses roughly three times that of the sun, in the Milky Way.

If a person was able to survive long enough to describe falling into a black hole, he would at first experience weightless as he goes into free fall, but then feel intense “tidal” gravitational forces as he got closer to the center of the black hole. In other words, if his feet were closer to the centre than his head, then they would feel a stronger pull until he eventually is stretched and then ripped apart.

It is important to realize that a black hole’s gravitational field is the same as that of any other object in space of the same mass. In other words, it won’t “suck” objects in any more than any other normal star, with things being more likely to just fall into them if they got too close to the event horizon. If our Sun was replaced with a black hole of equal mass

Cygnus X-1 was the subject of a 1974 friendly wager between Stephen Hawking and a fellow physicist Kip Thorne, with Hawking betting that the source was not a black hole.

He accomplished this the same year that Einstein released his theory of general relativity in 1915. From Schwarzschild's work came a term called the Schwarzschild radius, a measurement of how small you'd have to compress any object to create a black hole.

In 1990, he conceded defeat. [VIDEO: Final Nail in Stephen Hawking's Cygnus X-1 Bet?]

the Earth would continue experiencing the same gravitational force as before. Only when objects get too close to the black hole would the stronger gravitational force become apparent.

Long before this, British polymath John Michell predicted the existence of 'dark stars' so massive or so compressed that they could possess gravitational pulls so strong not even light could escape; black holes didn't get their universal name until 1967.

Black holes have this incredible ability to literally stretch you into a long spaghetti-like strand. Appropriately, this phenomenon is called 'spaghettification'. Look it up.

A traversable wormhole, known alternatively as a Lorentzian wormhole, Schwarzschild wormhole or Einstein-Rosen bridge, is a theoretical opening in space-time allowing a “shortcut” through intervening space to another location in the Universe.

The way it works has to do with how gravity behaves over distance. Right now, your feet are closer to the centre of Earth and are therefore more strongly attracted than your head. Under extreme gravity, say, near a black hole, that difference in attraction will actually start working against you.