Silly physics humour

Two Hydrogen atoms are sitting at a bar.
The first says to the other, “Hey man, you look glum. What’s going on?”
The other replies, “I’ve been worried all week. I think I’ve lost my
electron.”
To which his sympathetic friend says, “Are you positive?”

While I’m on the topic, World of Physics is a really cool place to browse around (if you’re into that physics thing anyway)