What Left the Cold First

Muonium— electron plus antimuon— two microseconds of a neutral thing whose mass is almost all the heavier half.

In helium near absolute zero the liquid will not hold an impurity. At the surface the chemical potential turns into a launch: atoms leaving in a line, nearly the same speed, before they go to nothing.

Gravity has not been asked yet. The beam is the work so far. What left the cold left orderly and did not wait for the fall.