Gravity Waves

Theoretical Discovery of Gravitational Waves

When Einstein developed Special Relativity in 1905, it immediately became clear that Newtonian Gravity was wrong. This was because Special Relativity showed that no signal can travel faster than light, but Newtonian Gravity contains no propagation time or wave speed. This problem was solved in 1916 by General Relativity which predicted that gravitational effects would also propagate with the speed of light. According to General Relativity, if the sun were suddenly to cease to exist, we would see its light vanish eight minutes later, and the earth would also be released from the sun's pull eight minutes later. Newtonian Gravity on the other hand predicted that the earth would be immediately released from the sun's pull eight minutes BEFORE the light ceased.

Although Gravitational Waves were predicted in 1916, they have never been directly detected because their effect is so tiny. When a Gravitational Wave passes an observer, space is alternately stretched and compressed. Any dynamical system, for example a binary star pair, emits gravitational waves; but for normal binaries the effect is so small as to be undetectable even today.

Detectable Sources

There are astrophysical events, however, which emit Gravitational Waves strong enough to be detected with present technology. Examples are: supernovas, binary neutron star pairs, binary black-hole pairs, the coalescence of a binary neutron star pair or a black-hole binary pair, accretion onto Massive Black Holes, etc.