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

I recall hearing this as "red shift",

[fixx.livejournal.com]

but I no longer recall if it works in both directions. If it does there is the potential for up to four bumper stickers of ever decreasing humor.

For example you could have:
1) a bumper sticker for the front of the car in red reading,
"If this bumper sticker appears blue, get the hell out of my way",
2) a bumper sticker for the front of the car in blue reading,
"If this bumper sticker appears red, call AAA",
3) an additional sticker for the rear of the car in blue reading,
"If this bumper sticker appears red, I've been abducted by aliens"

And that's on my first cup of coffee. :-)

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.