On February 11, 2016, the whole world learned about the scientific discovery, for the first time gravitational waves (“ripples” in the fabric of space-time) were discovered, the existence of which Albert Einstein predicted back in 1916. These waves were recorded as a result of the collision of two black holes using the upgraded interferometer of the LIGO laser-interferometric gravitational-wave observatory.
One LIGO detector is located in Washington State on the West Coast and the other is located in Louisiana at Livingston. These are two laser interferometers with arms approximately 4.5 km each. A powerful laser sends a beam that splits in two mutually perpendicular directions (arms of the interferometer). Mirrors are hung at the end of the shoulders, specially isolated from various noises. These mirrors play the role of test masses. When a gravitational wave passes, these mirrors begin to oscillate slightly in a certain phase. The light is reflected from these mirrors, then again collected at the separator and interfered at the detector. When the mirrors are hanging freely (that is, they are not affected by a gravitational wave), the light arrives at the detector in a certain phase, and when the mirrors begin to move, the interference pattern is disturbed. By changes in this interference pattern, one can judge the movement of mirrors – test masses. This is the main idea of this detector.
Why is this discovery so important? And what will happen next, after the existence of “elusive” waves is finally confirmed? First of all, the collision of two black holes is an exciting discovery in itself – no one knew for sure if black holes could really merge to create an even more massive black hole, but now there is evidence. And, of course, the confirmation of a phenomenon predicted 100 years ago is an exciting event in the scientific world.
Gravitational waves and Einstein’s general theory of relativity
Gravitational waves were first predicted by Einstein’s general theory of relativity, which was published in 1916. This theory has withstood all physical tests, but some aspects scientists have not yet been able to study in the real world, because they require extremely extreme conditions. Everything changed on September 14, 2015, when LIGO first recorded the collision and merger of two black holes, which caused a storm in the fabric of space-time. These observations are excellent confirmation of Einstein’s general theory of relativity.
The study of gravitational waves is far from complete. Questions remain about the nature of the graviton – a particle that is a carrier of gravitational interaction without an electric charge (for example, a photon is a particle that carries electromagnetic radiation). And scientists have many questions about the interior of black holes that gravitational waves can help answer. However, this information will be released gradually as LIGO and related tools collect data on various events.