Isn't light speed faster than c?

After reading my own subject, I know how insane that sounds. But here’s my thought: Light behaves as a wave, and as a particle. We know the speed as measured from point A to point B is c. However, the light didn’t take the shortest route! It went up and down (or side to side) in its wave form. So didn’t it travel farther than we measured, and hence travel faster than c?

I know I’m not understanding quantum mechanics correctly. I’ll just wait to see why!

I’ll probably butcher this and be corrected by our resident physicists, but here goes.

Light is both a particle and a wave. A photon flying through space interacts with other photons and objects as if it were a wave, but it is not actually a particle tracing out a sine pattern through space.

Hopefully someone will correct me if I’m wrong, but when we say light is a “wave” we mean that it can be described using the mathematical model of a wave.

It’s not actually a bunch of squiggly lines undulating about.

That would explain it. I love GQ.

The speed of light is constant. Regardless of whether in a straight line or a wave the measurement taken at any one point will be equal to C or 182,000 miles per second.

The speed of a wave is not measured by “squiggles”, any more than the speed of sound depends on the speed of air molecules.

To be more precise, the speed of an EM wave in a vacuum is a constant, and is 299792458 meters/second.

You’re interpreting the idea of light being both a particle and a wave as meaning that it’s a tiny little particle that moves in a wave-shaped path. This is incorrect. An attempt to provide a better mental picture is beyond my ability.

The GIFin this wikipedia articleactually shows an em wave (packet) moving through a medium. Note the speed of the blue and the green dots representing the phase and group velocities can both exceed c. The red dot, representing the signal velocity may never exceed c and for an em wave in a vacuum must always be equal to c.

A “wave” is not something that moves in a wiggly line. It’s a disturbance that propagates. When you drop a rock in a pond, it doesn’t cause water molecules to travel in a wiggly pattern away from the rock. It causes a rise (or drop) of the water surface where the rock hit, which raises/lowers the water in a surrounding circle, which in turn causes the raising/lowering of the surface further out.

The speed of the wave is not the speed of any physical thing. It’s the speed at which the disturbance propagates.

Only in a vacuum. It is different in other mediums.

Another example is that sound is a compression wave. There are no air molecules moving up and down. Sound waves are composed of air molecules moving away from the place where the sound formed. When they hit other molecules, they bounce back to where they came from, while the molecules that they hit then move away from the center, etc. You need to learn the difference between the various types of waves. Can anyone suggest a website with a clear, simple explanation of the various sorts of waves?

The squiggly line that goes up and down or left and right is a mathematical graph showing the strength of the electric field (or magnetic field) as a function of position. It does not represent the position of a particle or anything else. The label on the axis perpendicular to the direction of propagation will not be calibrated in units of distance, rather it will be in units of electric or magnetic field strength.

So there is nothing traveling along a squiggly curve (sine wave).

This has appeared three times in this thread compelling the obsessive part of me to shout, NO! It’s 186,000 miles per second.

You mean that light travels faster than the speed of light which is 182 000 miles per second ? :confused::eek: :D;)

In other words, it’s the peak of the waveform that travels at c in a vacuum. The “particle aspect” is not a particle that traces along the wave, up and down.


.|<----|<----|*** c*** = 186,282 miles/s
.-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.
   '-'   '-'   '-'   '-'   '-'   '-'   '-'   '-'   '-'

Yes. Light that travels at 186,000 mps is faster than light that travels at 182,000 mps.

In that case, why didn’t you say 186,282 (and change) miles per second)? Do the last 282 (and change) miles per second mean nothing to you?

I like to think of it as the speed the *energy *(in the wave) is moving.

I dunno; it’s all relative to the way you look at it.