Scientists from multiple countries, including the United States, India, Australia, and China, have made a groundbreaking discovery regarding gravitational waves. They have confirmed the existence of a cosmic "background hum," a long-theorised form of gravitational waves that permeate the universe. This significant achievement comes after years of collaborative work by hundreds of scientists utilising radio telescopes across North America, Europe, China, India, and Australia. The findings have been hailed as a crucial breakthrough that opens up new possibilities for exploring the universe.
Gravitational waves, which were predicted by Albert Einstein over a century ago as ripples in the fabric of spacetime, have now been observed at low frequencies, creating a cosmic background hum. These gravitational waves oscillate over long periods, stretching and compressing everything in the universe. Objects like pairs of supermassive black holes spiraling together and merging are primarily responsible for generating these waves.
The detection of gravitational waves was made possible through the use of pulsars, highly dense cores of exploded stars that emit regular beams of radio waves. By analyzing the arrival time of pulses from an array of pulsars in our galaxy, scientists were able to observe changes caused by the passage of gravitational waves.
Very Large Array radio telescope in New Mexico. This and several other telescopes around the world were used to observe the slow gravitational waves faint ripples made by massive black holes that are constantly stretching and squeezing everything in the universe ever so slightly | via AP
“We now know that the universe is awash with gravitational waves,” Michael Keith of the European Pulsar Timing Array told the AFP.
The evidence for the existence of gravitational waves comes from 15 years' worth of data collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Physics Frontiers Center, a collaboration involving over 190 scientists from the United States and Canada. The researchers liken the gravitational wave background to the hum of a large group of people talking at a party, without being able to distinguish individual voices. This discovery represents a significant advancement in our ability to study the universe, providing insights that were previously unattainable through traditional methods of observation.
The detection of these low-frequency gravitational waves follows the momentous confirmation of high-frequency gravitational waves generated by the collision of black holes, which was achieved in 2015 through the Laser Interferometer Gravitational-Wave Observatory (LIGO). The recent discovery sheds light on a new band of the gravitational wave spectrum, with frequencies that are orders of magnitude smaller than those detected by LIGO.
According to Jeff Hazboun, an astrophysicist from Oregon State University and a member of the scientific collaboration behind the research, the most plausible explanation for these gravitational waves is an ensemble of supermassive black hole binaries in our cosmic neighborhood. However, other explanations involving new physics from the early universe, near the Big Bang, are also being considered.
Max Planck Institute for Radio Astronomy's Radio Telescope Effelsberg near Bad Munstereifel
The detection of low-frequency gravitational waves not only confirms a long-held theoretical prediction but also opens up avenues for further exploration. These waves have wavelengths that stretch across light years, offering a unique perspective on the universe and the potential to unravel mysteries such as the nature of dark matter, the formation and evolution of black holes and galaxies, and the early expansion of the universe during cosmic inflation. While the evidence is highly compelling, researchers are working towards reaching the gold-standard level of certainty in the coming years.
