08/01/2014 03:06 pm ET | Updated Aug 01, 2014

Neil deGrasse Tyson Says Media Misled Over Speed Of Light Story


Were physicists all wrong about the speed of light? You might think so, given the stories posted recently about a new paper suggesting that light travels a bit more slowly than the 186,000-miles-a-second figure that's familiar to generations of science geeks.

The paper's author, University of Maryland, Baltimore County physicist Dr. James Franson, said his work had been "sensationalized" in some of the stories, including one entitled "Physicist Suggests Speed Of Light Might Be Slower Than Thought."

And Franson isn't the only physicist who takes a dim view of the coverage. So does celebrated astrophysicist Neil deGrasse Tyson.

"The speed of light has almost mythical significance in physics," Tyson told The Huffington Post in an email. "But to be honest, the headline in this case needs to say something like 'New Calculations Suggest that the Speed of Light May Be 0.0000003% Slower Than We Thought,' which then might not have garnered any headlines at all."

In the paper, Franson argues that a "corrected" value for the speed of light might help explain a puzzle stemming from observations of a supernova that exploded in 1987.

Following its explosion, astronomers observed photons (particles of light) and nearly massless particles known as neutrinos streaming from Supernova 1987a, Franson told The Huffington Post in an email, adding that photons and neutrinos have been thought to travel at roughly the same speed. But the first photons from the supernova, which was located in a small satellite galaxy of the Milky Way known as the Large Magellanic Cloud, were observed much later than the first neutrinos -- a discrepancy that astronomers were hard pressed to explain.

Franson's paper offers calculations suggesting a possible explanation for the anomaly, as he explained in the email:

What is new about my calculations is that they suggest that a gravitational field may slow light down slightly more than it does other particles, such as neutrinos. Neutrinos have extremely small masses and they travel very nearly at the speed of light as a result. My calculations suggest that the velocity of light may be slowed down by a few parts per billion more than the neutrinos.

So if we've been wrong about the speed of light, it's only by the tiniest bit. And Franson said that, in the absence of corroborating evidence, "we should be skeptical about these results."

Tyson, too, stressed the preliminary nature of the calculations. "If the author's calculations are correct," he said in his email, "then the speed of light may drop measurably... If true, this would be an important result for physics."

What's the takeaway? Maybe this: When it comes to accepting a new value for fastest speed in the universe, let's take it nice and slow.


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