Neil deGrasse Tyson Says Media Misled Over Speed Of Light Story

Steve Williams

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David Freeman, Huffington Post

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.
 

GaryProtein

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So how does this change affect the actual length of the meter, which is defined by the speed (velocity) of light? [one meter is by definition the distance light travels in exactly 1/299792458 seconds -- it isn't the old platinum/iridium bar in France]

and the second which is part of the units of velocity? [m/sec]
 

astrotoy

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The standard units of measure will not change, the definitions may, depending on what changes are found in the speed of light, if any. As an example, the origin of the foot was someone's foot. If that person's body is found with the foot intact and it measures something different from a foot, we wouldn't change the length of the foot. The person's foot would just be a little longer or shorter.

Similarly, what is actually happening is that the earth's rotation is slowing down. The length of the day is slightly more than 24 hours long (you may have read that from time to time we have to add a leap second to compensate for that). The hour or second is not getting longer, even though the original basis for the hour was 1/24th of the rotation period of the earth. (Tidal forces are slowing down the rotation of the earth. The same forces mean that the moon is slowly moving away from the earth. Eventually there will no longer be total eclipses of the sun, because the moon's apparent size will be smaller than the sun's, so the moon will not be able to completely cover the sun. More eventually, the earth and moon will be locked in a synchronous orbit, with the same side of the earth facing the moon - but that will take about 4 billion years).

This is part of my tides and time lecture in basic astronomy.

Larry

So how does this change affect the actual length of the meter, which is defined by the speed (velocity) of light? [one meter is by definition the distance light travels in exactly 1/299792458 seconds -- it isn't the old platinum/iridium bar in France]

and the second which is part of the units of velocity? [m/sec]
 

Speedskater

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......................................
. The same forces mean that the moon is slowly moving away from the earth. Eventually there will no longer be total eclipses of the sun, because the moon's apparent size will be smaller than the sun's, so the moon will not be able to completely cover the sun. More eventually, the earth and moon will be locked in a synchronous orbit, with the same side of the earth facing the moon - but that will take about 4 billion years).
This is part of my tides and time lecture in basic astronomy.
Larry
Will this happen before or after the Sun goes Super Nova?
Where do you do your lecture's?
 

astrotoy

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The tidal lock will take place about the time the sun expands to be a red giant star (and incinerates the inner planets of the solar system - probably including the earth and moon - so we don't have to worry about it). Whatmore is correct - it will eventually become a white dwarf, shedding its outer layers quite gently - no supernova.

Gave my last lectures in the late '90's after more than 25 years teaching astronomy. One of my college physics lab partners (Mike now known as Michio Kaku) still is active and does a nice job on the Discovery Channel.

Larry

Larry
 

Orb

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Larry,
when the sun expands to be a red giant star it still destroys the earth?
Just wondering if this is why it may get confused with going supernova.
....
OK Just read your brackets lol.
Cheers
Orb
 

astrotoy

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After their main life (called the main sequence) starts expand to many times their main sequence size. As a result their outer surfaces cool (becoming red giants). In the case of the sun this means it will expand to the size of the orbit of Mercury, maybe Venus and large enough to sterilize the surface of the Earth. The transition occurs when the sun exhausts the hydrogen at its core, having converted it to helium. The region just outside the core will still have hydrogen and become hot enough to ignite and fuse to helium (called the hydrogen shell). This provides enough pressure to expand the outer layers of the star, cooling them to become a red giant. That will really be global warming. It will be in about 4 Billion years, so no investing in extremely long term bonds.

Larry

PS. My PhD dissertation was on a specific kind of red giant star called a Mira variable.

Larry,
when the sun expands to be a red giant star it still destroys the earth?
Just wondering if this is why it may get confused with going supernova.
....
OK Just read your brackets lol.
Cheers
Orb
 

16hz lover

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I just discovered Neil deGrasse Tyson last month, what a fun guy to watch.
 

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