相對論高深問題!!!麻煩大家幫忙

General Relativity is a piece of theoretical work. It is not based on any experimental results or observation. It's derivation are all based on mathematics.

Time dilation has already been given in Special Relativity (狹義相對論) which is formulated using the assumption that the speed of light in the universe is constant independent of the observer. A fast moving person observes that his clock runs slower than when he is at rest.

Generally Relativity deals with gravity. A massive object will distort the space surrounding it, making it to become curved. This phenomenon is known as "space warp". Gravity arises as a result of space warp. Since space and time are not separate entities, they are in fact tied together. The warpping of space also leads to the warpping of time. This is how time dilation comes out.
A simple explanation is that just imagine on a curved surface, the distance between two points is longer than if the surface is flat. When a traveller goes from one point to the other, he thought that he is going in a straight line. But the actual fact is that he is going along the curved surface (the warpped space), and thus takes a longer time than expected. That means the traveller feels his clock runs slower. A one hour journey, say, registered on the traveller's clock would be measured to be more than one hour by an outside observer. It is because of the curvature of space that make such difference, and it is because of mass that cause space wrap. The conclusion is mass produces gravity, which slow down the running of time.

A more detailed explanation is the application of the Principle of Equivalence postulated by Einstein. An accelerating system produces a force which cannot be differentiated with gravity. As Special Relativity has already shown that time dilation occurs in a moving system. This infers that an accelerating system also leads to time dilation....(contd).



2010-03-07 15:06:24 補充：
(contd)...A simple formula to calculate time dilation is given in the web-page quoted below (read the section on Gravitational Time Dilation):

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/gratim.html