Coffee Physics

NASA-supported researchers are working to develop such a theory through a combination of experimentation and mathematics. Jenkins, for example, is studying differential equations that describe molecular gases. It might be possible, he says, to adapt them for granular flows. He plans to test some of his ideas using a rotating chamber filled with beads; the device is slated for launch to the International Space Station (ISS) in 2007.

A sand column is compressed during an MGM experiment onboard shuttle flight STS-79. The speed of the movie is misleading; the complete sequence takes about an hour.

"We do this on the ISS," he explains, "because granular flows are affected by both gravity and internal collisions. We need to get Earth's gravity out of the picture to create a simpler system."

For the same reason, engineering professor Stein Sture of the University of Colorado is leading a series of experiments called "Mechanics of Granular Materials" (MGM) onboard the space shuttle. His device repeatedly squeezes a column of damp sand and records what happens. The goal, explains Sture, is to understand the liquid-like behaviour. of soil during some earthquakes. MGM has flown before on shuttle missions STS-79 and STS-89, and it's slated for another flight in 2003 onboard the shuttle Columbia (STS-107).

Earthquakes, avalanches, planetary rings, coal mines ... even bags of coffee. From the alien to the ordinary, we'll understand them all a little better when this research is done.

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