Amazing Facts About Black Holes

What would happen to our Solar System if the Sun were to suddenly become a black hole?

Not much! Other than getting very dark and very cold, nothing else would change. The planets would not be sucked into the black hole. Their orbits would not change since the mass of the Sun has not changed. Only the space the Sun occupies has changed. The gravity of a black hole is very powerful only when you are very close to it.

How much would a feather weigh on the "surface" of a black hole?

Several billion tons! The weight of an object is determined by the mass of an object and how much gravity is affecting the mass. The force of gravity near a black hole is extremely strong. Under this extremely strong gravitational pull, the object would weigh several billion tons.

What would happen to an astronaut if she tripped and fell into a black hole?

She would be stretched like a piece of spaghetti! The closer she got to the black hole, the stronger the force of gravity would be. In fact, the pull of gravity increases so fast, that the gravity tugs on her feet more than on her shoulders. With her feet being pulled into the black hole faster than her shoulders, she would be stretched out farther and farther, like a piece of spaghetti.

Could you watch this stretched out astronaut enter the black hole?

No! Einstein's theories of relativity tell us that as you approach an object that has a great deal of mass (like a black hole) time slows down. The closer the astronaut gets to the black hole, the more time slows down. When the astronaut reaches the event horizon time stops. To the astronaut however, time is normal, so they will see themselves enter the black hole, assuming of course they could survive the gravity.

Will black holes devour the universe?

Probably not. Black holes only severely affect the space within a few thousand miles of them. In the field of astronomy, a few thousand miles is considered a very small distance.

Could someone survive a trip through a black hole?

No! You would be killed by many things before you could enter the black hole. Gravity would pull you apart. X-rays and other forms of radiation would be lethal. Even though your lifeless form would appear to be suspended over the black hole forever, the atoms that make up your body could never be rescued from the black hole.

Black holes have no hair...

...or color, or light, or anything else we can use to identify them. This famous statement reminds us that once matter is inside a black hole, we can't tell what it was. As far as we could tell, or the black hole could tell, the matter inside could be made of elephants, cockroaches, toasters or anything else! The only things we can use to identify a black hole is its mass, electrical charge, and the amount of rotation it has.

Why are black holes black?

In order for a rocket to leave the surface of Earth, it must travel faster than 25,000 miles per hour (7 miles per second). This is called escape velocity. If the rocket has a speed less than the escape velocity of an object, the object's gravity will pull it back down. The escape velocity of a black hole is greater then 186,000 miles per second. That means a rocket would have to travel faster than 186,000 miles per second in order to leave the black hole. The speed of light is 186,000 miles per second, so light doesn't travel fast enough to leave the black hole, hence it is black.

According to Einstein's theories of relativity, nothing can travel faster than the speed of light. Therefore once an something is inside a black hole it can never get out.

Suggested References

The Cosmic Frontiers of General Relativity, William J.
Kaufmann, III, 1977.
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