Faster than the speed of light

DaleSpam

Hi Mr.GaGa, welcome to PF.

Yes, there are in fact many quantities with units of speed and values > c. None of them can be used for superluminal travel or superluminal communication.

epenguin

Quote by Antymattar

Funny thing is that the speed of light has been observed to be slowing down.
The speed of light is calculated using atomic clocks. Scientists have observed that, in fact, either the atomic orbits are slowing down, or the speed of light is slowing down because every once in a while you have to change the calculations to accurately fit the atomic clocks.

Is that true and accepted? Sounds like a big thing for a throwaway comment.

Anyone else?

Also it seems to me that nothing can be faster than the speed of light, although I know there was a book of that name which I have even read. Also that nothing can be slower than the speed of light. Not for physical reasons but for grammatical ones.

JesseM

Quote by epenguin

Is that true and accepted? Sounds like a big thing for a throwaway comment.

No, it's a completely silly claim that Antymattar seems to have picked up from a creationist source:

With respect to the fact that measurements made after 1960 do not show any decrease in the speed of light, Walt Brown has concocted his own misinformed "explanation" based on the assumption of two different systems of time:

By way of background, scientists found that it was necessary to revise the length of a "standard" second. The standard second is equal to the number of vibrations of a cesium atom that correspond to a second based on the time required (in seconds) for the earth to orbit the sun.

The cesium atom vibration frequency is extremely constant. Scientists have constructed instruments which can count these vibrations. By assigning a specific number of vibrations to a standard second, a super-accurate clock can be constructed. However, the cesium clock must be calibrated in order to correspond to the average period of revolution of the earth around the sun. In order to make the standard second (as defined by the cesium clock) precisely equal to the length of a second based on new and more accurate astronomical measurements, it was necessary to revise the previously selected number of vibrations corresponding to the standard second. The change was extremely minute.

The CSC web site speaks of "orbital" time versus "atomic" time as if they were two different systems of time measurement. Because of the necessity to re-calibrate the cesium clock, Brown mistakenly concludes that "atomic" time is "slowing." He states: "If atomic frequencies are decreasing, then both the measured quantity (the speed of light) and the measuring tool (atomic clocks) are changing at the same rate. Naturally, no relative change would be detected, and the speed of light would be constant in atomic time-but not orbital time." Of course, this is complete nonsense.

(many creationists like the idea that light is slowing down because they want to believe the universe was created only a few thousand years ago, but this leads to the obvious problem of explaining how we can see galaxies and supernovas and such that are millions or billions of light-years away)

DrGreg

Quote by epenguin

Quote by Antymattar

Funny thing is that the speed of light has been observed to be slowing down.
The speed of light is calculated using atomic clocks. Scientists have observed that, in fact, either the atomic orbits are slowing down, or the speed of light is slowing down because every once in a while you have to change the calculations to accurately fit the atomic clocks.

Is that true and accepted? Sounds like a big thing for a throwaway comment.

I'm guessing that Antymattar is getting confused with the leap second which we need to occasionally add to compensate for the fact that the Earth's rotation is very gradually slowing down. The second is defined using atomic clocks, not the Earth's rotation which is no longer reliable enough for accurate timing, which is why we have to add leap seconds to compensate.

Technically it's impossible for the speed of light to slow down since 1983, when the new definition of the metre fixed the speed of light at 299,792,458 m/s precisely.

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DaleSpam Mentor	Faster than the speed of light Hi Mr.GaGa, welcome to PF. Yes, there are in fact many quantities with units of speed and values > c. None of them can be used for superluminal travel or superluminal communication.