Key Questions We Want to Answer:
The most readily observable result of entering the critical region
of a material's liquid-gas phase transition is the appearance of a
cloudiness, a sign that the density fluctuations are scattering light.
In the Critical Fluid Light-Scattering Experiment (ZENO), scientists
looked for this light- scattering phenomenon in xenon. Their goals
were to measure the size of the density fluctuations and to determine
the length of time the density fluctuations existed. There are several
theories as to why this light scattering occurs and how these
fluctuations relax - ZENO endeavored to test them.
What We Already Know:
By getting a uniform sample, which is possible only in the microgravity
of Earth orbit, ZENO's data were 100 times better than similar observations
made on the ground.
How We'll Conduct Our Experiment:
The experiment was conducted in 1991 and again in a 1994 reflight on the
Shuttle. The first time researchers ran into problems because the transition
temperature couldn't be located well enough. A new strategy was devised in
the way the experiment temperature was controlled before the experiment
flew a second time. ZENO's experience illustrates that these experiments
are complex and will not always work the first time. Making adjustments
in the experimental process and continuing to attempt ground-breaking
investigations is crucial to the scientific method.
The sample region of the experiment was approximately one cubic inch
in size, with a larger container of the optical elements and the thermal
control devices needed to make it work. Overall the experimental apparatus
was about 5 feet by 3 feet by 2 feet in size.