3.1 What are gravitational waves?

Gravitational waves are waves in space-time that are caused by an accelerated masses. The term itself was first introduced by Henri Poincaré in 1905. According to Einsteins theory of relativity, nothing can move faster than the speed of light. Local changes in the gravitational field can therefore only affect distant locations after a finite amount of time. From this, Albert Einstein concluded the existence of gravitational waves in 1916. As they pass through a region of space, they temporarily compress and stretch distances within this region. This can be seen as the compression and stretching of space itself. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation.

On February 11th, 2016, the LIGO collaboration announced the first observation of gravitational waves. They found out that it came from a signal detected at 09:50:45 GMT on September 14th, 2015. As the source two black holes with masses of 29 and 36 solar masses merging about 1.3 billion light-years away were figured out.

Task 3.1

Use the following videos to inform yourself about the role Michelson interferometers play in the detection of gravitational waves.

https://www.ligo.org/detections/GW150914.php (English)