2023-07-10 15:43:52
For a long time it was gravitational wave background as a mere theoretical entity pointing to a “hum” of gravitational waves penetrating the entire universe. Such waves result from a number of different sources such as black hole mergers, neutron star mergers, supernovae, and possibly also events that occurred in the early Universe, including the inflation just after the Big Bang. In much the same way that the cosmic microwave background noise represents a reverberation of Big Bang energy, the gravitational-wave background could be viewed as an echo of massive cosmic events. This concept is now being transferred from theory to application for the first time.
Gravitational wave background discovered
In a groundbreaking discovery, an international research consortium has picked up this cosmic hum that reverberates throughout the universe. This hum, emanating from the Very Large Array in New Mexico, is thought to be a collective echo from supermassive black holes located in ancient galaxies, some as much as 10 billion light-years away.
Xavier Siemens, a physicist involved in the collaboration with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), compared this phenomenon in the New York Times with an orchestral symphony. Each pair of merging supermassive black holes creates a unique note, culminating in an expansive cosmic melody. This revelation was highly anticipated as it came 15 years after the NANOGrav began collecting data. She supports Albert Einsteins general theory of relativity and suggests the existence of exotic matter thought to have formed from the Big Bang around 13.7 billion years ago.
The groundbreaking discovery, says Yale University astrophysicist Chiara Mingarelli and member of NANOGrav, marks the beginning of a new approach to observing the Universe. Previous signals detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) were mainly in the frequency range of a few hundred Hertz. The researchers behind this Study However, they were looking for a collective hum at much lower frequencies — one billionth of a hertz — radiating simultaneously from all corners of the universe.
There is no absolute security
At these extraordinarily low frequencies, the hum is so intense it could be due to the historic cosmic merger of possibly a million supermassive black holes. This was discovered by studying the behavior of pulsars, fast-spinning stars, using a Nobel Prize-winning study Method from 1993, which is used to indirectly measure the effects of gravitational waves. The pulsars, also known as the cosmic clocks due to their periodic emission of radio waves, were crucial to the signal’s detection.
The Very Large Array, the Green Bank Telescope in West Virginia, and the now-defunct Arecibo Observatory in Puerto Rico were instrumental in collecting observational data for the NANOGrav team. These contributions enabled a global collaboration within the International Pulsar Timing Array that led to the unveiling of the gravitational-wave background. Currently, the results have a confidence level of 3.5 to 4 sigma, which is just below the desired 5 sigma standard that physicists typically use to make a discovery. “One day we’ll make it,” Mingarelli is certain. It’s enough for her.
From the microwave to the gravitational wave background
Analysis of the gravitational-wave background could shed light on the evolutionary history of supermassive black holes and their surrounding galaxies. This could also allow for a deeper understanding of the expansion of the universe and the nature of dark matter, potentially leading to the discovery of previously unknown particles or forces. The NANOGrav team and its international partners are analyzing measurements from 115 pulsars spanning more than two decades in hopes of deciphering the origin of the gravitational-wave background.
University of Michigan astrophysicist Marcelle Soares-Santos compares the potential importance of these gravitational waves to the groundbreaking discovery of the cosmic microwave background in the 1960s. It too reshaped our understanding of the early universe. Indeed, this could be the beginning of a new chapter in our understanding of gravitational waves. As we come closer to understanding this cosmic hum, we may witness the writing of a new chapter in the history of gravitational waves.
For comparison: The microwave background allows us to look back some 380,000 years after the Big Bang. The gravitational-wave background, on the other hand, gives us a glimpse of what happened just seconds after the Big Bang. It is not only the key to a hitherto unknown type of physics, but could also clarify the all-important question once and for all: Why is there something and not nothing?
Great importance for future research
Specifically, the discovery of this “hum” in the universe forms the basis for five other astronomical breakthroughs:
Confirmation of the inflation theory: The inflation theory, which states that the universe went through an extremely rapid expansion phase in the first fractions of a second after the Big Bang, is further confirmed by the discovery of the gravitational wave background. These waves are an expected product of this inflationary process and their detection is strong evidence for this theory.
Exploration of the early Universe: Gravitational waves allow science to see “beyond” the cosmic background radiation and gain information about the very early phases of the Universe that we have not been able to reach until now.
Testing the general theory of relativity: Gravitational waves are a direct prediction of General Relativity. While we already have evidence for the existence of gravitational waves, the discovery of the gravitational-wave background provides further data points for testing and improving this theory.
Insights into the nature of gravity: If we are able to measure and analyze gravitational waves in more detail, we could learn more about the nature of gravity itself, especially on cosmological scales.
Quantengravitation: The discovery could also have implications for the theory of quantum gravity, which aims to unify gravity with the other three fundamental forces.
also dr Soares-Santos believes the find “could lead to something really groundbreaking.”
Sources: New York Times; “The Basis of the General Theory of Relativity” (Annalen der Physik, 1916); “Focus on NANOGrav’s 15 yr Data Set and the Gravitational Wave Background” (The Astrophysical Journal Letters, 2023); The Nobel Prize; own research
War has been raging in Ukraine since February 24, 2022. You can help those affected here.
1689022245
#Gravitational #Wave #Background #means #discovery