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Gravitational Relativistic Physics (GRP)
Low Temperature and Condensed Matter Physics
    PRESENT: Ongoing Research

Launch Date: Proposed Mission
Mission Duration: Several months
Principle Investigator: Dr. Melora Larson, JPL


EXACT image

Key Questions We Want to Answer:

Helium-3 and helium-4 atoms can be mixed together and cooled into a liquid. When they are cooled to very low temperature, they become a superfluid. However, when this mixture is further cooled there is a point where helium-3 and helium-4 act like oil and water and separate into two phases. The tricritical point is where a combination of precise mixture, pressure, and temperature levels bring these atoms to a remarkable spot where the transitions between the superfluid state and the two-phase state meet.

What We Already Know:

The mission Experiments Along Co-existence near Tricriticality (EXACT) will perform rigorous tests at the tricritical point, to further test the Renormalization Group theory-for which the Nobel prize was awarded in 1982. The theory allows predictions to be made of the critical properties of the mixture near the tricritical point.

While this experiment already has been conducted on Earth, it is expected to provide far more accurate data in the microgravity of space. When testing this phenomenon on the ground, gravity causes stratification of the mixture. This gradient in density makes it difficult to study the properties of the mixture because they vary through the sample.

What We Hope to Find Out:

By conducting this experiment in the absence of gravity, the separation of these atoms can be more easily studied, since they will not have gravity pulling the heavier atoms to the bottom. Observing this phase transition in a microgravity environment provides greater details to this phenomenon because the sample will remain uniform.

How We'll Conduct Our Experiment:

The experiment will be quite small, the size of a postage stamp. The purpose for the petite sample size is that, even in microgravity, a larger sample would tend to form layers, i.e., surface forces in nonuniform samples.

Better understanding this phenomenon will add a new facet to the investigation of current theories.

Additional information:

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