Doppler effect in light

1. Nov 18, 2008

Combsbt

I do not fully understand the Doppler effect in light.
A theoretical question:

If I was traveling near the speed of light, towards a source of light. Would all the wavelengths in the visible spectrum be shortened and therefor, everything shifting towards red?

I thought the speed of light was supposedly constant, no matter the relative velocity of the observer.

2. Nov 18, 2008

Staff: Mentor

The observed wavelengths will be shorter, which means a shift towards blue.

The speed is constant. It's the observed wavelength that changes, not the speed.

3. Nov 18, 2008

Combsbt

Oh yeah, red is longer wavelength...

What I don't understand is how the speed of the wave propagation can remain constant relative to the observer. It seems that if you are moving towards the source, your relative velocity would be higher.

4. Nov 18, 2008

Staff: Mentor

That the speed of light is independent of the speed of the source or observer is counterintuitive. It requires special relativity to make sense of it all.

5. Nov 18, 2008

Combsbt

Oh I see, so that property is an assumption.

6. Nov 18, 2008

Staff Emeritus
No, it's an observation.

7. Nov 18, 2008

Combsbt

Einstein seemed to think differently.

8. Nov 18, 2008

Staff: Mentor

Einstein assumed the constancy of the speed of light in deriving the special theory of relativity. Since then it has been tested (observed) experimentally in various ways. The link below refers to many of them.

Experimental Basis of Special Relativity

9. Nov 18, 2008

ZapperZ

Staff Emeritus
Rather than playing word games and "quote the physicist", I think your time would be better spent understanding the physics, rather than the connotation of the word. There are already many sources (and many threads on here) on why the simple Galilean addition of velocities will not work at relativistic speeds.

Zz.

10. Dec 1, 2008

Combsbt

Found a video on youtube with a visual explanation of special relativity. Seemed to clear some things up for me with my original question. Here it is if anyone is interested.