Signal from ‘dawn of time’ helps explain the birth of the universe
Discovery of gravity waves described as ‘equal to the detection of the Higgs boson’
The South Pole telescope and the Bicep2 telescope at the Amundsen-Scott South Pole Station is seen against the night sky with the Milky Way. Photograph: Keith Vanderlinde/National Science Foundation
It at once helps confirm theories of why the cosmos looks the way it does, and shows that gravity acts like other fundamental forces of nature at scales from atoms up to the entire universe.
It also confirms a prediction made by Albert Einstein almost a century ago, that the formation of the universe should have kicked off gravity waves that are still rippling across the cosmos 13.8 billion years later.
“It is pretty profound stuff,” said Prof Peter Gallagher, a physicist at Trinity College, when commenting on the US-based research. “It tells us about the very origins of our world and the universe we live in. It is a discovery that is very much worthy of a Nobel prize.”
Researchers from California, Massachusetts and Minnesota joined to search for evidence of gravity waves, but also for proof of a theory called “cosmic inflation”.
This theory would help cosmologists explain the homogeneity of the universe, with matter distributed evenly in all directions, explained Prof Tom Ray, an astronomer at the Dublin Institute for Advanced Studies.
The US-based researchers came up with the goods, finding the signature left behind by gravity waves as they sent ripples across space-time. These in turn provide evidence for cosmic inflation, which describes the instantaneous expansion of the universe immediately after the Big Bang.
Physicist Alan Guth proposed inflation in 1980 to help get a better match between theory and astronomical observations. He proposed that the universe began to expand exponentially a few trillion, trillion, trillionths of a second after the Big Bang.
Such a rapid expansion should have triggered a series of gravitational waves, given the violence of the process, but they could never be found – until now.
The Big Bang also produced intense heat, so hot that all matter was no more than a plasma of elemental subatomic particles. This cooled over billions of years, allowing galaxies to form, but a tiny amount of the original heat remains. It can still be seen today in the Cosmic Microwave Background, the faint glow that still exists from the Big Bang.
It is within this glow that the scientists found evidence for gravitational waves and hence support for cosmic inflation. They used the Antarctic-based deep space radio telescope called Bicep2 (Background Imaging of Cosmic Extragalactic Polarisation 2).
It is purpose-built to search the microwave glow for the telltale signs that gravity waves had passed through, an event that would have caused the glow to become polarised in a particular way.
“Our team hunted for a special type of polarisation called B-modes,” said Bicep2 co-leader Prof Jamie Bock of Caltech and the Jet Propulsion Laboratory. This showed up as a curling pattern in the polarised ancient light, delivering the first hard evidence for gravity waves.
In the end the signal was much stronger than expected. “This has been like looking for a needle in a haystack, but instead we found a crowbar,” said co-leader Prof Clem Pryke of University of Minnesota.
Physicists here are as impressed as they are around the world. “If what they have found can be confirmed there is no doubt it is a wonder leap forward in our understand of the very beginning of the universe,” said Prof Paul Callanan of the Department of Physics at University College Cork. “It seems to be a very significant result and so it is a very exciting time for cosmology.”
“I think it is a huge deal,” Prof Gallagher said. “We have been waiting for years for gravity waves and they are so faint and so difficult to measure. Now we have this amazing result saying they found evidence for these waves.”
The discovery was “certainly equal to the detection of the Higgs boson”, Prof Ray said. “Inflation was just a theory but this shows that it definitely occurred assuming the findings are verified. They also verify relativity and gravity waves. We have been looking for these for years and years.”
Finding primordial B-mode polarisation offered very strong evidence for inflation provided it was verified, said Prof John Womersley, head of UK funding body Science and Technology Facilities Council. The recent Higgs discovery and direct evidence for inflation made these “very exciting times to be a physicist”, he said.