# Isn't light speed faster than c? **URL:** \ **Category:** Factual Questions\ **Created:** [September 10, 2011, 2:10pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821 "2011-09-10T14:10:26Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![CanTak3](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@CanTak3](https://boards.straightdope.com/u/CanTak3)\ **Post date:** [September 10, 2011, 2:10pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/1 "2011-09-10T14:10:26Z")
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! ---
**Author:** ![Silophant](https://avatars.discourse-cdn.com/v4/letter/s/a698b9/32.png) [@Silophant](https://boards.straightdope.com/u/Silophant)\ **Post date:** [September 10, 2011, 2:23pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/2 "2011-09-10T14:23:23Z")
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. ---
**Author:** ![Kinthalis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kinthalis/32/16084_2.png) [@Kinthalis](https://boards.straightdope.com/u/Kinthalis)\ **Post date:** [September 10, 2011, 2:28pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/3 "2011-09-10T14:28:43Z")
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. ---
**Author:** ![CanTak3](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@CanTak3](https://boards.straightdope.com/u/CanTak3)\ **Post date:** [September 10, 2011, 2:41pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/4 "2011-09-10T14:41:45Z")
That would explain it. I love GQ. ---
**Author:** ![NNN99](https://avatars.discourse-cdn.com/v4/letter/n/ac91a4/32.png) [@NNN99](https://boards.straightdope.com/u/NNN99)\ **Post date:** [September 10, 2011, 3:17pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/5 "2011-09-10T15:17:47Z")
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. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [September 10, 2011, 3:21pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/6 "2011-09-10T15:21:48Z")
The speed of a wave is not measured by “squiggles”, any more than the speed of sound depends on the speed of air molecules. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [September 10, 2011, 3:38pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/7 "2011-09-10T15:38:00Z")
> [@NNN99](#): > > 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. To be more precise, the speed of an EM wave in a vacuum is a constant, and is 299792458 meters/second. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [September 10, 2011, 4:33pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/8 "2011-09-10T16:33:10Z")
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. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [September 10, 2011, 5:01pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/9 "2011-09-10T17:01:33Z")
The GIF[in this wikipedia article](http://en.wikipedia.org/wiki/Speed_of_light#In_a_medium)actually 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. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [September 10, 2011, 5:11pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/10 "2011-09-10T17:11:31Z")
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. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [September 10, 2011, 5:16pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/11 "2011-09-10T17:16:38Z")
> [@NNN99](#): > > 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. Only in a vacuum. It is different in other mediums. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [September 10, 2011, 5:31pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/12 "2011-09-10T17:31:22Z")
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? ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [September 10, 2011, 6:30pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/13 "2011-09-10T18:30:09Z")
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). ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [September 10, 2011, 8:00pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/14 "2011-09-10T20:00:12Z")
> [@NNN99](#): > > The speed of light is . . . equal to C or 182,000 miles per second. This has appeared three times in this thread compelling the obsessive part of me to shout, NO! [It’s 186,000 miles per second](http://en.wikipedia.org/wiki/Speed_of_light). ---
**Author:** ![clairobscur](https://avatars.discourse-cdn.com/v4/letter/c/839c29/32.png) [@clairobscur](https://boards.straightdope.com/u/clairobscur)\ **Post date:** [September 10, 2011, 8:07pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/15 "2011-09-10T20:07:29Z")
> [@KarlGauss](#): > > This has appeared three times in this thread compelling the obsessive part of me to shout, NO! [It’s 186,000 miles per second](http://en.wikipedia.org/wiki/Speed_of_light). You mean that light travels faster than the speed of light which is 182 000 miles per second ? 😕:eek: :D;) ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [September 10, 2011, 8:35pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/16 "2011-09-10T20:35:21Z")
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. ```auto .|<----|<----| ***c*** = 186,282 miles/s .-. .-. .-. .-. .-. .-. .-. .-. .-. '-' '-' '-' '-' '-' '-' '-' '-' '-' ``` ---
**Author:** ![Chipacabra](https://avatars.discourse-cdn.com/v4/letter/c/e19b73/32.png) [@Chipacabra](https://boards.straightdope.com/u/Chipacabra)\ **Post date:** [September 10, 2011, 9:26pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/17 "2011-09-10T21:26:16Z")
> [@clairobscur](#): > > You mean that light travels faster than the speed of light which is 182 000 miles per second ? 😕:eek: :D;) Yes. Light that travels at 186,000 mps is faster than light that travels at 182,000 mps. ---
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [September 10, 2011, 9:30pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/18 "2011-09-10T21:30:31Z")
> [@Chipacabra](#): > > 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? ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [September 10, 2011, 10:03pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/19 "2011-09-10T22:03:48Z")
> [@scr4](#): > > The speed of the wave is not the speed of any physical thing. It’s the speed at which the disturbance propagates. I like to think of it as the speed the \*energy \*(in the wave) is moving. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [September 10, 2011, 10:14pm UTC](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821/20 "2011-09-10T22:14:53Z")
> [@Skald\_the\_Rhymer](#): > > 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 dunno; it’s all relative to the way you look at it. [Next page](https://boards.straightdope.com/t/isnt-light-speed-faster-than-c/595821.md?page=2)