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]

this time i've collected something called Gravitational Lensing. so read & njoy( the source beinghttp://csep10.phys.utk.edu/guidry/violence/black4.html ).

Another consequence of the influence of Einstein's gravitation on light is that gravitational masses can alter the direction of light and cause lensing effects. The adjacent Hubble Space Telescope image shows a spectacular example of such a Gravitational Lens. Click on the image for an enlarged view and a more detailed discussion. The arc-like pattern spread across the picture like a spider web is an illusion caused by the gravitational field of the cluster. The arcs are actually distorted images of very distant galaxies that are being imaged by the gravitational lens: The cluster is so massive and compact that light rays passing through it are deflected by its enormous gravitational field, much as an optical lens bends light to form an image. The figure also reveals multiple imaging, a rarer lensing event that happens when the distortion is large enough to produce more than one image of the same galaxy.