Black Holes & Related Phenomena, What Is a Black Hole Options

[kallubhai4u]

hi
this is what Visuja had asked 4 & i m delivering it now. hope it'll satisfy his needs.

If a ball is thrown upwards from the surface of the Earth it reaches a certain height and then falls back. The harder it is thrown, the higher it goes. Laplace calculated the height it would reach for a given initial speed. He found that the height increased faster than the speed, so that the height became very large for a not very great speed. At a speed of 40000 km/h (25000 mph, only 20 times faster than Concorde) the height becomes very great indeed - it tends to infinity, as the mathematician would say. This speed is called the `escape velocity' from the surface of the Earth, and is the speed which must be achieved if a space craft is to reach the Moon or any of the planets. Being a mathematician, Laplace solved the problem for all round bodies, not just the Earth.

He found a very simple formula for the escape velocity. This formula says that small but massive objects have large escape velocities. For example if the Earth could be squeezed and made four times smaller, the escape velocity would need to be twice as large. This surprisingly simple derivation gives exactly the same answer as is obtained from the full theory of relativity.

Light travels at just over 1000 million km/h (670 million mph), and in 1905 Albert Einstein proved in the Special Theory of Relativity that nothing can travel faster than light. The above Laplace formula can be turned around to tell us what radius an object must have if the escape velocity from its surface is to be the speed of light. This particular radius is called the `Schwarzschild radius' in honour of the German astronomer who first derived it from Einstein's theory of gravity (General Theory of Relativity). The formula tells us that the Schwarzschild radius for the Earth is less than a centimetre, compared with its actual radius of 6357 km.

the source of this info is a site mentioned below:-
http://csep10.phys.utk.edu/guidry/violence/black2.html

some more coming up soon.

[kallubhai4u]

hi

dont u guys have some questions to ask me? if not then u can xpect me to write again & again.

this time i've collected an article frm http://csep10.phys.utk.edu/guidry/violence/black7.html and its anice one. so read it so that u can njoy it.
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How Might We See Black Holes?

Because black holes are small, and no signals escape from them, it might seem an impossible task to find them. However, the force of gravity remains, so if we detect gravity where there is no visible source of light then a black hole may be responsible. This type of argument, by itself, is not very convincing, and so we must look for other clues. If there is other material around a black hole which might fall into it, then it will. There is then a good chance that as it falls it will produce some detectable signal not from the black hole itself, but from just outside it.

Most stars are not single, like the Sun, but are found in pairs, small groups or large clusters. If a pair of stars have different masses then the more massive one will burn up its nuclear fuel and may become a black hole, whilst the other remains a normal star consuming its fuel more slowly. Gas can then be sucked from the star into the black hole. The gas becomes very hot, with a temperature of millions of degrees, and will shine not with visible light but with X-rays. These X-rays will have an observable effect on the light output from the ordinary star. Since the star and black hole go round each other every few days, we might expect to see regular variations in the brightness and X-ray output.

There are some X-ray sources which have all the properties described above. Unfortunately it is impossible to distinguish between a black hole and a neutron star unless we can prove that the mass of the unseen component is too great for a neutron star. Strong evidence was found by Royal Greenwich Observatory astronomers that one of these sources called Cyg X-1 (which means the first X-ray source discovered in the constellation of Cygnus) does indeed contain a black hole. Things are rather different if there is a massive black hole in the centre of a galaxy. It is possible there for a star to be swallowed by the black hole. The pull of gravity on such a star will be so strong as to break it up into its component atoms, and throw them out at high speed in all directions. Some of the fragments will fall into the hole, increasing its mass, whilst others could produce an outburst of radio waves, light and X-rays. Evidence for such behavior may be found in the section on Active Galaxies.

This is just the behaviour which is observed in galaxies of the type called `Quasars' and may well be happening in a milder way in the centre of our own Milky Way.

i m xpecting ur support. thats all 4 the time being...some more coming soon.