Now reading: Might Einstein have been wrong about the speed of light?

Might Einstein have been wrong about the speed of light?

It has long been considered a non-negotiable law of physics: the speed of light is a constant. But is it true?

Speed of light

New research co-authored by Perimeter Institute Faculty member Niayesh Afshordi suggests the speed of light might not always have been the same.

Afshordi and João Magueijo, a professor at Imperial College London, proposed nearly two decades ago that there may have been a time, immediately after the big bang, when the speed of light was slower than it is now.

In a paper published this week in Physical Review D, they propose a new (and testable) version of the idea. They suggest that in the early universe, light and gravity propagated at different speeds.

In their model, some details about the cosmic microwave background — the afterglow radiation of the big bang — reflect the way the speed of light and the speed of gravity vary as the temperature of the universe changes. They saw an abrupt change at a certain point, when the ratio of the speeds of light and gravity quickly went to infinity.

Read more in New Scientist and Forbes.



In celebration of the International Year of Light, Perimeter Institute presents 20 fascinating factoids about photons.

/Jan 28, 2015

Theorists from Perimeter and experimentalists from the Institute for Quantum Computing have found a new way to test whether the universe is quantum, a test that will have widespread applicability: they’ve proven the failure of noncontextuality in the lab.

/Aug 16, 2016

Correlation does not imply causation – unless it’s quantum. That’s the message of surprising new work from Perimeter Institute and the Institute for Quantum Computing.

/Mar 23, 2015