Science Focus - the home of BBC Science Focus Magazine
Does the speed of light ever change? © Getty Images

Does the speed of light ever change?

Published: 02nd December, 2016 at 14:00
Subscribe to BBC Science Focus Magazine and get 6 issues for just £9.99

The more pertinent question is as to whether this affects Superman's top speed.

Asked by: Jackie Taunton, Reading


Light has long been known to slow down whenever it passes through a medium such as air or glass.

Light also interacts with the molecules in its surroundings.

But over the years, some theorists have proposed that the speed of light in a vacuum may have been far higher during the Big Bang. While this would solve some of the technical problems concerning the early Universe, there’s no compelling evidence that this is the case.


Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.


Robert is a science writer and visiting professor of science at Aston University.


Sponsored content