Polystyrene spherical particles were used to trace the fluid motion in
an experiment of crystal growth from aqueous solutions in space. This
paper presents the particle motion derived from the images reconstruc
ted from holograms taken in the space experiment. The particle mechani
cs is also discussed. It was observed that some particles can independ
ently move in different directions; some particles can move much faste
r than the others, and some small particles may have the same speed as
large ones. Particles may individually have the behavior of the inert
ial random walk. But more importantly, there are non-random motion so
that particles may keep moving in certain directions. It becomes diffi
cult to estimate g and g-jitter from these particle motions as expecte
d. This also leads to a doubt that the particles in the fluid experime
nt system are subjected to g and g-jitter, which have been considered
as only a function of time.