Gravity wave finally discovered

Astronomers say they have finally found elusive gravitational waves, the mysterious ripples in the fabric of space. As these ripples pass the Earth, local space is alternately stretched and compressed

Gravitational waves: Concentric ripples that squeeze and stretch fabric of space-time, caused by movement of mass. Predicted by Albert Einstein in his 1916 General Theory of Relativity

U.S.

3,000km

Hanford, Washington

Livingston, Louisiana

LIGO sites

Two detectors help sift out terrestrial rumblings, such as traffic and earthquakes, from other faint vibrations within space

Effect of gravitational ripples, hugely exaggerated

LIGO – LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY

Laser beam fed into machine

Laser’s light split in two and sent down identical, perpendicular 4km tunnels

Beams bounce back and forth between mirrors

Two light paths recombined and sent to detector

Mirror

Light storage arm

4km

Laser

Beam  splitter

Light storage arm

4km

Mirror

Photodetector

By analysing light reflected off mirrors it is possible to detect tiny changes – fractions of width of
an atom – in distance between mirrors

Source: LIGO Caltech

Pictures: Associated Press, NASA