#2926: Doppler Effect explain

[Miss Lenhart is pointing with a stick to a whiteboard. There is an unreadable heading and two lines of unreadable text above a drawing of a spiral galaxy, this is what she points at. Below that there is a graph with a curve that looks like it is increasing exponentially. The line is going through a cloud of points, scattered on either side of the curve. Beneath the graph there is another unreadable line of text.]

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…

[Same setting but Miss Lenhart has raised her arms.]

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?

[Back to the original view with Miss Lenhart in front of the whiteboard. She is now raising a finger in the air while holding the stick down with her other hand. A student ask a question from off-panel.]

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…