For many of the social events on an undergraduate physicist's calendar - from Stat Mech. and Thermo. pset parties to science center lecture hall showings of The Princess Bride - a science t-shirt is the perfect casual attire. As 2 am rolls round and, after 10 pages of algebra, you find that the entropy of your closed system has decreased by a factor of 7 or, due to various projector issues, Westley is only just now fetching Buttercup her bucket, a science t-shirt with even the lamest pun is the perfect excuse for either hysterical laughter or at least an occasion to weep for the Life you once had.
Though my own collection took a sad hit when my "Not Only Space Time has Curves" and "Women Tunneling to Classically Forbidden Regions" t-shirts - both fundraisers for my college's physics club though I'm pretty sure we only managed to sell them to ourselves... - mysteriously disappeared in a laundry room in southern England, I remain the proud owner of a Drake equation t-shirt signed by Frank Drake, a t-shirt featuring my college's observatory, and a conference t-shirt a couple friends dared me to ask the author of my introductory physics textbook to sign. I was very tempted to wear the last one to a dinner with this author that was part of a recent graduate school visit, but at the last minute I came to my senses and wore a cardigan set instead.
Anyway, what about the rest of you? Is a science t-shirt (or several) What Not to Wear or a wardrobe essential?