Comic Strips

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Doppler Effect (xkcd.com)

submitted 5 months ago by [email protected] to c/comicstrips

17 comments fedilink hide all child comments

The Doppler effect is a mysterious wavelength-shifting phenomenon which seems to primarily affect sirens, which is why the 🚨 emoji is red.

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[–] subtext 17 points 5 months ago (2 children)

This does not seem correct at all… as the comic states, it’s caused by the Doppler effect, not because red is the “fastest” light wavelength—it’s light it all travels at the same speed in a vacuum.

https://en.wikipedia.org/wiki/Redshift

I don’t know about lightning photography, I suppose it’s possible that different wavelengths have different speeds in air, so I can’t comment on that.

[–] kernelle 11 points 5 months ago

Yeah I'm no physicist but that ticked me off, the speed of light is the same for any wavelength. As for redshift:

a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light).

Speed of light isn't a factor in this, also when galaxy's move towards us (like the Andromeda galaxy) it is blueshifted, proving it's not the light that matters, but rather the direction of movement of the source. Proving the doppler effect.

[–] [email protected] 2 points 5 months ago

Could this be because space isn't a true vacuum? There's pockets of gas and crap, which could affect the speed of the light as it travels to us?