Scientists have formed a new kind of molecule out of two atoms that don’t normally form play well together, sodium and potassium, by cooling them to less than a millionth of a degree above absolute zero, colder than any molecule that’s ever been witnessed. The team of MIT physicists led by Martin Zwierlein managed to get the sodium-potassium molecule to hold together for 2.5 seconds, which may sound short but is actually pretty surprising for a molecule that textbook chemistry tells us shouldn’t even exist. Temperature is hard to conceptualize close to 0 kelvin When you’re talking about extreme temperatures…