I'm reading a book by Lee Smolin, entitled The Trouble with Physics. It's an interesting book – one of those layman's accounts of all kinds of weird and interesting things about what's going these days in the world of theoretical physics. A "popularization" I guess it's called. Partially, it's a rant (though a largely courteous one) against the domination of string theorists in the current world of physics academia.
Anyway, I re-learned something I remember learning before, and for some reason it struck me as incredibly funny. The graviton (an as yet not-well-documented fundamental particle which is the "carrier" particle of gravitational force, much as a photon is a "carrier" for electromagnetism) is a necessarily massless particle. That's right – the graviton is massless. Isn't that… funny?