On Thursday, astronomers from around the world revealed that they had discovered the first evidence of a long-theorized type of gravitational wave that creates a “background hum” vibrating throughout the universe.
The discovery, made after years of work by hundreds of scientists utilising radio telescopes in North America, Europe, China, India, and Australia, was regarded as a huge milestone that opens a new window into the universe.
Gravitational waves are disturbances in the fabric of the universe that travel at the speed of light nearly fully clear as predicted by Albert Einstein more than a century ago. Their existence was only proven in 2015, when US and Italian observatories detected the first gravitational waves produced by two merging black holes. These “high-frequency” waves were caused by a single explosive event that sent a powerful, brief burst rippling towards Earth.
However, scientists have been looking for low-frequency gravitational waves, which are considered to be constantly rolling across space like background noise, for decades. Gravitational waves pinch and stretch everything they pass through as they travel through space. Astronomers examined pulsars, the dead cores of stars that erupted in a supernova explosion, for evidence of this squeezing and stretching at low frequencies.
Some spin hundreds of times per second, flashing radio wave beams at extraordinarily regular intervals, similar to cosmic lighthouses. This implies they can function as “a very, very precise clock,” according to Keith. Radio telescopes around the world were pointed at 115 pulsars scattered throughout the Milky Way for the new study.
Scientists then examined the exceedingly minuscule changes in pulse timing to look for traces of gravitational waves. According to Antoine Petiteau, a French astronomer, they were able to “detect changes of less than one millionth of a second over more than 20 years.” The early data was in line with science’s present knowledge of the world and Einstein’s theory of relativity, according to the experts.
However, they highlighted that they have not yet “detected” the waves with absolute certainty because they have not attained the gold-standard five sigma level of assurance. A statistical fluke has a one-in-million chance of occurring, according to the five sigma statistic. Keith remarked, “We’re frustratingly just shy of the mark,” adding that there is a 99.9% chance that the evidence supports gravitational waves.
Each nation or organisation in the collaboration independently published its study in a variety of journals.
The five sigma level may be reached in a year, according to Steve Taylor, director of North America’s NANOGrav gravitational wave observatory, once all the data had been compiled. But in the future, low-frequency gravitational waves might be able to throw additional light on this early expansion and possibly solve the riddle of dark matter, according to the researchers. They might learn more about the formation and development of galaxies and black holes as a result.