xkcd #2926: Doppler Effect ( imgs.xkcd.com )
Alt text:
The Doppler effect is a mysterious wavelength-shifting phenomenon which seems to primarily affect sirens, which is why the 🚨 emoji is red.
![](https://mbin.grits.dev/media/cache/resolve/entry_thumb/af/59/af5952fe472215e85d60c44d9661603dead4d3717a6a4126eb4f489ca45b9ada.png)
Alt text:
The Doppler effect is a mysterious wavelength-shifting phenomenon which seems to primarily affect sirens, which is why the 🚨 emoji is red.