# Speed of Light, Photons or WaveSpeed?

The speed of light is almost 300 000 km/s.

The photons have a speed along the wave, and the wave have a speed straight forwards.

What is the speed of light? Is it the speed the photons have along the waveline, or is it the speed the wave travels in a straight line?

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This is absolutely fundamental: small enough particles or short (wavelength) enough waves can be described either as particle or as wave, but never as a mixture of both! This antinomy is the most basic thing in quantum mechanics. –  Georg Dec 5 '11 at 15:25
Know, we were just introduced to the subject at school. But our teacher didn't know the answer, so I asked it here... –  Friend of Kim Dec 5 '11 at 15:38
No problem, now You know! As an ointment to Your wounds: there are members with a physics degree here who slip on this point frequently. –  Georg Dec 5 '11 at 15:45
Thanks! It's really interesting this stuff, looking forward to learn more! –  Friend of Kim Dec 5 '11 at 15:53
The photons don't go forward in time--- there is no causal particle picture in relativity. –  Ron Maimon Aug 1 '12 at 8:35
However, it doesn't matter if you think of a wave or a photon or the complete quantum model, in vacuum the speed of light is $c=299792.458\,\mathrm{km}/\mathrm{s}$.