Originally posted by RJHinds
As you know the earth is like a big magnet with a north and south pole.
It exerts an attractive force so that we can use a compass to tell direction.
These magnetic forces are really electrical forces and are related to
gravitation.
Newton's law of gravitation resembles Coulomb's law of electrical forces,
which is used to calculate the magnitude of el ...[text shortened]... his easier to understand by
putting it on graph paper rather than using the formulas.
Tell that to a black hole. Black holes have such warped space around them nothing can come out, gravity is so strong mass goes in and more stuff goes in and the mass of a big black hole can = millions of sol masses and space is curved around the black hole so severely light at one distance away from the 'center' can only orbit, and if it gets further in, can never escape.
Hawking says black holes can 'evaporate' due to virtual particles being created just at the surface of the event horizon, where one half of the pair shoots into the black hole and the other one can escape so it can slowly lose mass, a big one like in the center of the galaxy would take trillions of years to lose its mass but small ones lose their mass a lot quicker so don't last as long.
But the space around the black hole is extremely bent, it is like a 4 dimensional bathtub drain, except happening in all directions away from the black hole. This is a fundamental effect of nature.
Look at this link:
http://en.wikipedia.org/wiki/Tests_of_general_relativity
Scroll down to the 'perihelion Precession of Mercury'.
This is a perturbation in the orbit of mercury which was measured very precisely but classical physics had no answer for (Newtonian gravity and such).
There was this tiny left over perturbation of mercury's orbit that was figured out by Einstein due to space being curved slightly by the mass of the sun, a very small amount but Einstein used his theory of relativity to calculate it very precisely.
Because space curves. The entire universe is one big space curve. If you took a spacecraft out into the universe at very very very close to c, you would come back to the same place you left because traveling in space at galactic distances is like shooting around on a sphere, like the Earth.
A plane could fly forever over the surface of the Earth if it had enough fuel because there is no start or finish to the circumference of Earth. Just going straight into galactic space forces you to come back to where you started, just like that plane, say going around on the equator of Earth.
At some point, the plane revisits the same part of the equator every time it goes 360 degrees. Same with the space craft. Going straight means being on a gentle many billions of light year wide curve.
Age of the Universe
13 Aug '11 13:42
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