# Thread: speed of light not constant?

1. http://www.livescience.com/29111-spe...-constant.html

Could someone clarify what it means in ignorant people language for me?

Is this new stuff or just new spin on scientific knowledge that has been around for a while? I have observed where the media likes to have their way with the words of scientists in order to appeal to their non-scientifically inclined readers, usually distorting the facts as they go.

2.

3. Yet another example of piss poor journalism.

It's been covered how when light interacts with matter, hits an electron cloud, the electron changes energy state because a photon has momentum, energy must be conserved, electron drops down energy state and emits a photon- DELAY.
Ok, that was abbreviated.
I gave Sculptor an analogy of a car a while back, that always moves at 100mph. There is no acceleration, it goes 0mph to 100mph instantly.
If you drive it on a long country road for an hour, you will go 100 miles.
But drive it in the city where traffic lights delay you and you will cover less ground at the same speed due to delays. Your average speed would be affected, but your actual speed would always be 100mph.

In this article, astronomers were conducting experiments to see whether the large empty spaces out in space were literally nothing... or if something was there, including 'virtual particles' which would interact with light and cause a series of delays.
The further out, the more space must be crossed, the more interactions would delay light and so the greater discrepancy we would see.
Which is what they saw.

The constant is still a constant. Light still always moves at 'c' and that journalist is an idiot.

4. Originally Posted by Neverfly
Yet another example of piss poor journalism.

It's been covered how when light interacts with matter, hits an electron cloud, the electron changes energy state because a photon has momentum, energy must be conserved, electron drops down energy state and emits a photon- DELAY.
Ok, that was abbreviated.
I gave Sculptor an analogy of a car a while back, that always moves at 100mph. There is no acceleration, it goes 0mph to 100mph instantly.
If you drive it on a long country road for an hour, you will go 100 miles.
But drive it in the city where traffic lights delay you and you will cover less ground at the same speed due to delays. Your average speed would be affected, but your actual speed would always be 100mph.

In this article, astronomers were conducting experiments to see whether the large empty spaces out in space were literally nothing... or if something was there, including 'virtual particles' which would interact with light and cause a series of delays.
The further out, the more space must be crossed, the more interactions would delay light and so the greater discrepancy we would see.
Which is what they saw.

The constant is still a constant. Light still always moves at 'c' and that journalist is an idiot.
I read the article and I'm a bit baffled. It seems to be, in effect, about what the true refractive index is of the vacuum of space. But don't we say that the speed of light in vacuo is c by definition, and define the refractive index of the vacuum to be 1?

I mean, how could we determine the speed of light in a vacuum without the effect of these virtual particles? It's not as if we have any way to suppress them, in any measurement we make.

Or is it that what this is really about is the possibility of a tiny discrepancy between the theoretically calculated speed of propagation of an EM wave - done without taking these virtual particles into account, vs. a measurement in the real world of space where they are present?

Or am I being thick?

5. Originally Posted by exchemist
I read the article and I'm a bit baffled. It seems to be, in effect, about what the true refractive index is of the vacuum of space. But don't we say that the speed of light in vacuum is c by definition, and define the refractive index of the vacuum to be 1?

I mean, how could we determine the speed of light in a vacuum without the effect of these virtual particles? It's not as if we have any way to suppress them, in any measurement we make.

Or is it that what this is really about is the possibility of a tiny discrepancy between the theoretically calculated speed of propagation of an EM wave - done without taking these virtual particles into account, vs. a measurement in the real world of space where they are present?

Or am I being thick?
Not being thick at all.

The speed of light is calculated more than measured since getting a truly accurate measurement here is pretty difficult.
Speed of light - Wikipedia, the free encyclopedia

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