Variable speed of light in QED

[exponent137]

In QED calculations are made with variable c.
But Duff says that c does not exists, because it is only a transformation factor. So if we put c=1 how QED is changed at small distances?

 

[lugita15]

In QED calculations are made with variable c.
But Duff says that c does not exists, because it is only a transformation factor. So if we put c=1 how QED is changed at small distances?

This issue actually has nothing to do with quantum effects; it's just the way Special Relativity is interpreted. Some people like to think of the speed of light as a conversion factor between space and time. For instance, they would say that there is no difference between 1 year and 1 light-year. They do this because of the identity ds^2=dx^2+dy^2+dz^2-(cdt)^2. Note that the last quantity that gets squared is not dt, but cdt. So you can think of time as a fourth dimension w=ct. The authors who think along these lines often make the claim that everything in the universe is moving in the time direction with a constant speed c (although that's strange, because speed is distance over time).

Then you can say the only reason why w=t is not valid is that we chose a different unit for time than for space, and we can easily fix that mistake by measuring time in meters, which is equivalent to setting c=1.