How Fast Is Light?

[Iwikefactz]

According to the theory of reletivity, time dilates around the speed of light. How about if the point where time dilates is not as close to the speed of light, and it only seems like that light is 299 792 458 m/s because the light is going faster/close to the dilation point so that time slows down? So, relatively time seems faster than it really is!?!?

[Janus]

Time dilated at all relative speeds, it is just that it does not become easily measurable until you get up to significant fractions of c. For instance at 0.1 c time dilates at a rate of 0.995.

At 0.5c the rate is 0.866

At 0.8c, it is 0.6

At 0.9 c it is 0.436

At 0.99c it is 0.14

And the closer and closer you get to c from here, the greater the time dilation.

[swansont]

Time dilation has been measured in planes traveling several hundred km/hr, and has to be accounted for in a van traveling 100 km/hr, when they carry atomic clocks of sufficient precision. Tough to measure in these cases, but it's there at all speeds, just as Janus says.