[sketchers356]

Will,

Liquid hydrogen is colder than most any thing with a boiling point of approx 20K but helium has the lowest boiling point at 4K, significantly colder in this domain. Helium will not freeze at 0K, it has to be pressurized to do so (26 atms to freeze at 1K). A couple of years ago the nobel prize went to a team that supercooled helium with lasers so that it was superfluid, it would not stay in a container, instead defying gravity and crawling up the sides!!