Science, Science and Tech

Gravitational ‘smoke’ from the big bang

In a landmark new study, astronomers have found strong evidence of the exponential inflation widely believed to have occurred during the first fleeting moments of the universe following the big bang. Unveiling their work, they also showed the first direct evidence of the gravitational waves that accompanied this inflation: the last untested prediction of Einstein’s general theory of relativity.


When the universe began 14 billion years ago, it expanded by 100 trillion times in a small fraction of a second. This left an afterglow known as the cosmic microwave background (CMB). It was also predicted that such an expansion would produce gravitational waves – ripples in space-time, much like the waves on the surface of water following a disturbance.

The Bicep2 project was established to search for these ripples. Gravitational waves, which are also produced by celestial systems in the present-day universe, leave behind them a polarisation pattern known as B-mode polarisation. Primordial gravitational waves – those predicted by inflation – would leave such a pattern in the CMB. It is evidence of this polarisation that makes Bicep2’s results exciting.

“Detecting this signal is one of the most important goals in cosmology today,” said John Kovac, who led the experiments and is one of four principal investigators on the Bicep2 collaboration. He and his international team travelled to the South Pole to conduct their experiments. “It’s one of the driest and clearest locations on Earth, perfect for observing the faint microwaves from the big bang,” he said.

The work will now be scrutinised carefully by cosmologists in order to confirm the results. If the work is proved to be correct, it is likely to lead to a Nobel prize. Initial reactions from physicists are full of cautious optimism, with the Bicep2 team themselves amazed at their apparent success.

“This has been like looking for a needle in a haystack, but instead we found a crowbar,” said Clem Pryke, one of the principal investigators.

“Gravitational waves are a new frontier in astrophysics and cosmology,” said Ed Daw from the University of Sheffield after the discovery was announced. “If today’s findings are accurate then it will further strengthen our understanding of how the universe formed.”

The theoretical physicist Andrei Linde helped to establish inflation theory in the 1980s. “It’s amazing because many great intellectual discoveries are never confirmed at the time when the authors are still alive,” he told science journal, Nature. “I’m not dead yet, and they are already seeing this gravitational wave signal.”


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July 2021
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