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BLACK HOLE.....AND SPACE SCIENCE

BLACK HOLE B lack holes are some of the most interesting pathologies in space and time delivered by Einstein's general theory of relativity. They form when matter collapses gravitationally onto itself, such as when massive stars burn out. They are a region of space where the gravitational pull is so strong that nothing--not even light--can escape. Hence John Wheeler called them "black holes." There is more. They incorporate singularities in spacetime structure: points where Einstein's theory breaks down, since the curvature of spacetime becomes infinite. And they can supply bridges to new universes. S uch a star may become a white dwarf or a neutron star, but if the  star  is sufficiently massive then it may continue shrinking eventually to the size of a tiny atom, known as a gravitational singularity. 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.
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BLACK HOLE.....AND SPACE SCIENCE


BLACK HOLE



Black holes are some of the most interesting pathologies in space and time delivered by Einstein's general theory of relativity. They form when matter collapses gravitationally onto itself, such as when massive stars burn out. They are a region of space where the gravitational pull is so strong that nothing--not even light--can escape. Hence John Wheeler called them "black holes." There is more. They incorporate singularities in spacetime structure: points where Einstein's theory breaks down, since the curvature of spacetime becomes infinite. And they can supply bridges to new universes.
Such a star may become a white dwarf or a neutron star, but if the star is sufficiently massive then it may continue shrinking eventually to the size of a tiny atom, known as a gravitational singularity. 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.






LET US KNOW SOME FACTS ABOUT BLACK HOLE:
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. The boundary beyond which light cannot escape the black hole’s gravity well is known as the event horizon, while its radius is called the Schwarzschild radius. Once particles and light-rays go past the event horizon their light cones “tip over” and point to the singularity, which now represents all future-directed paths with no escape possible.







Person falling black hole
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. As he falls in he may observe distorted images as the light bends around him and he will also still be able to see beyond the black hole as light continues to reach him from the outside.


Freezing of  time
To an outside observer with a telescope, 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. As time elapses, the light subsequently becomes red shifted and dimmer as its wavelength becomes longer, eventually disappearing from the sight of the observer as it becomes infrared radiation, then radio waves.


Wormhole
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. However, from the outside wormholes may exhibit many of the characteristics usually associated with a black hole and be virtually impossible to tell apart.
Hawking Radiation
Physicists now believe that black holes actually radiate small numbers of mainly photon particles and so can lose mass, shrink then ultimately vanish over time. This unverified evaporation process is known as “”, after Professor Stephen Hawking who theorized its existence in 1974. However, it is a staggeringly slow process and only the smallest black holes would have had time to evaporate significantly during the 14 billion years the Universe has existed.
It is now thought that most galaxies are held together by supermassive black holes at their centers, which cluster hundreds of solar systems around them. In fact, 30,000 light years away at the centre of our own Milky Way galaxy is a black hole with 30 million times the mass of our own sun.

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