4 ms·
Well, in normal waves, particles don't travel either. Water waves move up and down while the wave moves forward. Compression waves like sound move air particles
by leecho0 17y ago
Well, in normal waves, particles don't travel either. Water waves move up and down while the wave moves forward. Compression waves like sound move air particles back and forth, but in general they go back to where they started from. Light is weird because it's both a wave and a particle.
But you're right, this is just a trick to make something look like a wave that's travelling faster than light. It takes the same amount of time for it to get to you, but when it does, it looks like it's travelling faster.
- teilo 17y agoI understand wave-particle duality, thank you. Irrelevant, really. We're talking separate photons, not the same photon moving across the moon. If it was actually moving across the moon, you would never see it, because it would not be traveling back to your eyes
- leecho0 17y agoI think the example of the moon kinda sucks, I agree. but it doesn't mean that this is totally irrelevant. To measure the speed of a wave, you find the length between peaks, the wavelength, and then the time it takes to go from peak to peak, the period. Wavelength / period = speed, which has nothing to do with the motion of the particle. But the interesting thing about waves is that it can stack without disturbing each other, and if you can stack different waves just right, you can make create something that looks periodic, but travels faster than any of the combined waves. Shining light on the moon or motion on a LCD screen uses a similar idea where the peak intensity is moving much faster than the components (pixels don't move at all in lcd screens). If this is periodic, you can call it a wave, whether it makes sense or not to call it as such.