Whats the best website to find info on Black Holes?

Question

I have a 2 page report on black holes due tomorrow and was wondering where online could I find info about it.

Answer 1

Basically, Black holes suck up on everything and destroy anything they come into contact with. There's speculation about such a thing as White holes, but nobody has ever found one. Only the Black holes seem actually to exist.

What kind of class is it that tells you to write a two-page report on Black holes without teaching you general relativity first? If you're only expected to write down the gee-whiz stuff, then you could get your information from a popular science magazine, or just write down stuff from a science documentary on TV.

Answer 2

Wikipedia is a good starting place to find information and leads to more serious material.

I know many teachers (and others) still preach that wikipedia is not reliable, but the science journal "Nature" did a study and came to the conclusion that, when dealing with science topics, it was as reliable as the Encyclopedia Britannica on-line.

The good people at Britannica did not like the comparison (their service, unlike wiki, is not free). But Nature had documented their study and were able to substantiate their conclusion.

I know that on subjects dealing with astronomy, physics, chemistry and subatomic particles, the information is generally reliable (even if sometimes it is difficult to understand).

Plus they often have links to other interesting sites.

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In summary, a black hole is an object that is so compact that the escape speed is greater than the speed of light. Therefore, nothing can leave a black hole (not even light).

The idea that such an object could exist began as early as astronomers understood two concepts:

1) escape speed: from each body (planet, satellite, whatever else), if you shoot something upwards it should fall back down, unless you shoot it fast enough that gravity will be insufficient to slow it down to zero. Then the object cannot fall back down and will continue to move away forever. It has "escaped". On Earth, escape speed is 11.2 km/s (approx. 25,000 mph).
A more massive body (same size) would have a greater escape speed. A smaller body (same mass) would have a greater escape speed.

2) Light has a finite speed. After Galileo's discovery of satellites around Jupiter, astronomers found that a periodic error in predicting their positions depended directly on our distance from Jupiter. This showed that light took some time to reach us and tht, therefore, light had a speed (it was not instantaneous). The first acceptable estimates of the speed of light came around 1725 when it was found that astronomers had to "tilt" their telescopes in the direction of Earths's movement (this was a very tiny correction, but it could be calculated -- see the second reference).

Putting both together:

The escape speed from the "surface" of the Sun is 617.5 km/s. If you could compress the Sun (make it smaller) while keeping the same mass, the escape speed would get higher and higher. If you could get the Sun down to 3 km across, then the escape speed at this new surface would be 300,000 km/s (the speed of light).

Astronomers understood this concept before Einstein's theory of Relativity. What Einstein did was to confirm that nothing could go faster than the speed of light in a vacuum. Therefore, if a black hole existed, then nothing (light, heat, magnetism...) could escape its surface.

Answer 3

Wikipedia, but don't just copy and paste because your teacher knows Wikipedia too.

This one looks like a good one too -

http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html

Answer 4

go under the website that i have put

Answer 5

try:
www.wikipedia.org