The Doppler effect is a mysterious wavelength-shifting phenomenon which seems to primarily affect sirens, which is why the 🚨 emoji is red.
Doppler Effect [Explained]
Transcript
[Miss Lenhart is pointing with a stick to a whiteboard with various scientific drawings and words, including but not only a graph.]
Miss Lenhart: The more distant a galaxy is, the redder its light.
Miss Lenhart: Why? Well, that's an interesting question.
[Zoom in on Miss Lenhart.]
Miss Lenhart: Ever notice how, when a siren is approaching, it sounds like Bweeeeeeeeee...
[Zoom in on Miss Lenhart with her arms raised.]
Miss Lenhart: ...but then it zooms past you and goes Nyeeeeooooowww?
Miss Lenhart: And sometimes they hit a button that makes it go Pyeew! Pyeew! really loud?
[Miss Lenhart with her finger raised is standing in front of the whiteboard and holding the stick down.]
Miss Lenhart: And in Europe they go Ooooeeeeooooeeee...
Off-panel voice: So why are galaxies red?
Miss Lenhart: Oh, no idea.
Miss Lenhart: Anyway, another siren I like is...
The Doppler effect is a mysterious wavelength-shifting phenomenon which seems to primarily affect sirens, which is why the 🚨 emoji is red.
Doppler Effect [Explained]
Transcript
[Miss Lenhart is pointing with a stick to a whiteboard with various scientific drawings and words, including but not only a graph.]
Miss Lenhart: The more distant a galaxy is, the redder its light.
Miss Lenhart: Why? Well, that's an interesting question.
[Zoom in on Miss Lenhart.]
Miss Lenhart: Ever notice how, when a siren is approaching, it sounds like Bweeeeeeeeee...
[Zoom in on Miss Lenhart with her arms raised.]
Miss Lenhart: ...but then it zooms past you and goes Nyeeeeooooowww?
Miss Lenhart: And sometimes they hit a button that makes it go Pyeew! Pyeew! really loud?
[Miss Lenhart with her finger raised is standing in front of the whiteboard and holding the stick down.]
Miss Lenhart: And in Europe they go Ooooeeeeooooeeee...
Off-panel voice: So why are galaxies red?
Miss Lenhart: Oh, no idea.
Miss Lenhart: Anyway, another siren I like is...