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The Law of Universal Gravitation


The Relativistic Explanation of Gravitation


The Search for Gravity Waves

Tantalizing evidence for the existence of gravity waves, which are predicted by Einstein's general theory of relativity and would be analogous to electromagnetic waves, comes from astronomical observations of a binary pulsar designated 1913 + 16. The rate at which the two neutron stars in the binary rotate around each other is changing in a manner that is consistent with the emission of gravity waves. A hypothetical particle, given the name graviton, has been suggested as the mediator of the gravitational force; it is analogous to the photon, the particle embodying the quantum properties of electromagnetic waves (see quantum theory). The search for gravity waves continues with the building of large interferometers that would be sensitive enough to detect the faint waves directly (see interference). Millions of dollars have already been spent on the Laser Interferometer Gravitational Wave Observatory (LIGO), supported by the National Science Foundation, and work is beginning on the even more ambitious Laser Interferometer Space Antenna (LISA).

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