Lesson Plan #26 http://www.phy6.org/stargaze/Lmass.htm . A qualitative discussion of the distinction between weight and mass, followed by a description of astronaut mass measurements in a zero-g environment, conducted in 1973. ... Mass Aboard Skylab" section #17a: . ... Learn that in oscillations of a mass against an elastic spring--in the absence of gravity, or in horizontal motion--the length of the oscillation period is proportional to the square root of the mass. ... Weight causes motion. ...