Joke check

[nancylebov]

I'll probably get bumper stickers printed in red that say "If this is blue, you're driving too fast."

It's occurred to me that I could add another twist to the joke by having them printed in blue, but I'm not sure whether that version of the joke would be either comprehensible or funny. What do you think?

If you and a source of waves are moving toward each other, the waves seem closer together. Blue light has shorter waves than red, so if something red looks blue, you're closing on that bumper much too fast.

Comments

Re: I recall hearing this as "red shift",

[nancylebov.livejournal.com]

It does work in both directions. It's just that everything that's fairly distant is moving away from us (do we have bad breath?), and the farther it is, the faster it's going, so the amount of red shift is really useful for astronomers who are trying to figure out how old/distant what we're seeing is.

Afaik, there's nothing in astronomy where blue shift matters.