BookWorm said:http://www.cnn.com/2004/TECH/space/04/02/einstein.satellite.ap/index.html
A satellite is used to gather data and perform experiments in space that can help confirm or disprove Einstein's theories, such as the theory of general relativity.
Satellites are primarily used to test two predictions of Einstein's theory of general relativity: the bending of light by massive objects and the gravitational redshift.
Satellites can observe distant stars and galaxies and measure how their light is bent as it passes near massive objects, such as planets or black holes. This bending of light is known as gravitational lensing and is a result of the curvature of space caused by these massive objects, as predicted by Einstein's theory.
A satellite can use precise instruments to measure the wavelengths of light emitted by atoms in space. As the light travels through a gravitational field, its wavelength is stretched or compressed, resulting in a shift in its measured wavelength. This shift is known as the gravitational redshift and is another confirmation of Einstein's theory of general relativity.
Multiple satellites have provided evidence supporting Einstein's predictions, particularly in the field of general relativity. For example, the Gravity Probe B mission in 2004 confirmed the theory of frame-dragging, which states that massive rotating objects, such as Earth, can drag and distort the fabric of space-time. Other satellites have also provided evidence for the bending of light and the gravitational redshift, further strengthening the validity of Einstein's theories.