Did light break its own speed limit?

Friday, January 6, 2017

Waterloo astrophysicist makes international news exploring the puzzle at the heart of the Big Bang.

iStock image of warp space travel faster than the speed of light.Niayesh Afshordi, a professor in the Department of Physics and Astronomy at the University of Waterloo, along with João Magueijo of Imperial College London, have proposed a novel theory in which  light traveled faster during the first critical moments after the Big Bang, explaining how the universe became so big and so uniform so fast.

Their model – and their proposed means of testing it – was highlighted last month in several  international news outlets, including  The Guardian, Motherboard, Forbes, and New Scientist.

Since the 1960s, the theory that the universe began with a single, cataclysmic expansion has dominated cosmology and particle physics. The Big Bang certainly explains  the existence of cosmic microwave background (CMB) radiation and other observations surrounding the early universe. But it can’t quite explain the size of the universe today or how uniform temperature, energy, and matter appear in whichever direction you look.

To resolve the enigma, cosmologists  introduced the theory of inflation – a rapid phase of accelerated cosmic expansion of the universe followed by an evening out of the cosmic temperature early on. But what if it was the reverse: what if light travelled faster than gravity, or anything else for that matter, in the initial moments of the expansion?

This idea, first proposed in the 1990s, would mean that light at one time broke its own speed limit– an absolute limit first proposed by Albert Einstein, that physicists never thought could be surpassed under theory of relativity.What’s new is that Afshordi and Magueijo have managed to turn this idea into a testable theory.

In their paper recently published as a rapid communication in the journal Physical Review D, Afshordi and Magueijo quantitatively describe how such a change in the speed of light could have occurred.

“In our theory, if you go back to the early universe, there’s a temperature around 1028 celsius when everything becomes faster. The speed of light goes to infinity and propagates much faster than gravity,” said Afshordi in an interview with The Guardian. “It’s a phase transition in the same way that water turns into steam.”

The duo propose to monitor the CMB spectral index, a measure of the initial density ripples of the universe. Their model predicts  this value to be exactly 0.96478,  within the margin of error of the observed  spectral index of 0.967 +/- 0.004.

According to Afshordi and Magueijo, cosmologists are continually improving the precision  of this number which means we could see the theory confirmed  or ruled out  within the next five to ten years.

Afshordi is also an associate faculty member of Perimeter Institute for Theoretical Physics.


Science in the MediaThe following news media outlets featured this story:

  • Theory challenging Einstein's view on speed of light could soon be tested. The Guardian, November 2016.
  • Gravity may have chased light in the early universe. New Scientist, November 23, 2016.
  • Physicists plan to test a new theory about the speed of light to explain what Einstein’s theory can’t. Quartz, November 27, 2016.
  • Could Einstein Have Been Wrong About The Speed Of Light? Forbes, November 28, 2016.
  • Scientists to Challenge Albert Einstein's 'Speed of Light is Constant' Theory. Nature World News, November 28, 2016.
  • Was the Speed of Light Even Faster in the Early Universe? Smithsonian Magazine, November 30, 2016.
  • Scientists Think the Speed of Light Has Slowed, and They're Trying to Prove It. Motherboard, December 6, 2016.
  • Was the speed of light faster at the beginning of the universe? Cosmos Magazine, December 5, 2016.
  • Was Einstein wrong? Controversial theory claims the speed of light is not a constant. Wired UK, December 13, 2016.