  The speed of gravity is an important universal constant. But, it has not been
directly known with experiment or observation. The explanations for it are
contradicted with each other. Here, it is presented that the interaction and
propagation of the gravitational field could be tested and understood by
comparing the measured speed of gravitational force with the measured speed of
Coulomb force. A design to measure the speeds of gravitational and Coulomb
force is presented. From satellite motions, it is observed that the speed of
gravitational force is larger than the speed of light in a vacuum. From this
observation and the recent experiments, the structure of electric and
gravitational fields is studied. A line to indirectly test the wavelengths of
gravitational waves is presented.
