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Figure 8.1 (also see Color Section). Potential methods to simulate the microgravity environment of low orbit
spaceflight. A. A classic two-dimension clinostat that rotates at 1 to 3 rpm in the direction indicated by the white
arrow. Petri dishes on the clinostat contain Arabidopsisseedlings. B. A three-dimensional clinostat, also known
as a random positioning machine. The sample is placed on the inner frame, and the randomization is controlled
by computer software. C. The free-fall phase (which lasts approximately 25 sec) of a parabolic flight on a
NASA airplane. (Note: the flight also contains a hypergravity phase after the free fall.) The methods in A and
B attempt to simulate microgravity but can be considered “omnilateral” gravity stimulation, whereas the para-
bolic flights (C) achieve the actual free-fall state of microgravity as noted by the orientation of the scientist.