It's from a discussion perhaps a year and a half(?) ago, about physics: How gravity (and/or other effects) near the surface of an infinitely long (but a few light-years will probably do, to fake it) and very thick and very rapidly spinning "rod" would make you travel backwards in time if you did a close fly-by. (Presumably in the correct direction, wrt the direction of spin.)
DrooK posted a helpful Google/Iwethey-EzBoard search hint somewhere else here only today.
HTH!