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Photographing Physics: Critical Research in Space

On a quiet March afternoon in Cleveland, Ohio, Bill Meyer browsed the 
second floor of a Department Store. He was just about to buy a pair of 
shoes at 70 percent off when his cell phone rang.

Sighing, he lifted the phone to his ear and said, "Hello?"

"Is this William Meyer?" the voice on the other end inquired.

"Yes, it is," he replied.

"This is CapCom at the Johnson Space Center," the voice said. "Can you 
get to a land line? You have a phone call from the International Space 

 Astronaut Leroy Chiao examines BCAT-3 samples on space station The 
normally mild-mannered scientist rushed to the customer-service counter. 
Astronaut Leroy Chiao had a question about an important space station 
experiment, and he could only take the call from a land line.

Store employees were more than happy to help. "They were so excited that 
they were jumping up and down," said Meyer, who works at NASA's Glenn 
Research Center. "I wouldn't be surprised if their heads knocked out 
some of the ceiling tiles."

Just before he called, Chiao had been photographing the Binary Colloidal 
Alloy Test-3 (BCAT-3). This book-sized container holds ten sample cells 
filled with colloids, or tiny particles suspended in fluid. A hundred 
times smaller than a fine human hair, colloids are everywhere. Milk, 
paint, makeup and smoke are just a few examples.

On Earth, the BCAT-3 colloids aren't very surprising -- they just sink 
to the bottom of the container. But in the absence of gravity, they 
behave like slow atoms, allowing scientists to model all sorts of atomic 

According to the BCAT-3 scientists, studying colloids in space could 
lead to revolutionary advances in technology, such as computers that 
operate on light, new pharmaceuticals, clean power sources and unique 
propellants for rocket engines.

BCAT-3 focuses on two frontiers of science: critical points and 

Critical Point Research

In a pot of boiling water, bubbles of vapor begin to form at the bottom 
of the pot and grow until they escape into the atmosphere. The water 
exists simultaneously in two states -- liquid and gas. If you could 
increase the temperature and pressure much higher than the average stove 
and pot allow, the water would reach its critical point, where the 
liquid and vapor cannot be distinguished.
 Critical point samples in space - the colloids appear blue and the 
solvent appears nearly black. Just above that is the supercritical 
region, where the liquid and gas are no longer distinct states, but 
rather form a homogeneous supercritical fluid. Like gases, supercritical 
fluids flow easily, but they also can transport dissolved materials and 
thermal energy, like liquids do.
Photos of two of the BCAT-3 critical point samples on the International 
Space Station show the colloids (blue) and solvent (dark) separating 
after seven days (left) and eleven days (right). The colloids represent 
liquid, and the solvent represents gas. Credit: NASA (See all six samples.)

Supercritical carbon dioxide is used to extract molecules from plants 
for pharmaceuticals. Supercritical water is used to remove toxic waste 
from contaminated soil. And some scientists believe supercritical fluids 
could be used to extract magnesium from rocks on Mars to make rocket fuel.

Six of the BCAT-3 experiment samples were created by David Weitz and 
Peter Lu at Harvard University to study atomic behavior near the 
critical point.

Crystallization Research

Scientists also study colloids because they are the right size to 
manipulate light. Over time, they form crystals that can split up light 
and send it in different directions.

By enhancing our ability to control light, scientists hope to improve 
fiber-optic communication systems and build computers that operate on 
light instead of electricity. Because cosmic rays degrade electronic 
circuits in space, these technologies are essential to fulfilling the 
Vision for Space Exploration with journeys to the moon, Mars and beyond.

The optical properties of a crystal vary depending on its size and 
shape. So scientists Peter Pusey and Andrew Schofield at the University 
of Edinburgh are studying BCAT-3 samples to see how changing the size 
and proportion of colloids affects the crystals. Meanwhile, University 
of Pennsylvania researchers Arjun Yodh and Jian Zhang are trying to 
determine how crystals form on the surface of a container in microgravity.

Catching Colloids in Action

Since the BCAT-3 scientists can't join their experiments on the 
International Space Station, they depend on the station crew to 
photograph the samples and collect data for them.
Hoffman, Lu and Foale examining BCAT-3 training samples at JohnsonImage 
. NASA Glenn project manager Monica Hoffman and Harvard grad student 
Peter Lu train Astronaut Michael Foale to photograph BCAT-3 samples at 
the Johnson Space Center before he takes off on Expedition 8. A 
flashlight positioned at a high angle behind the experiment illuminates 
the samples.

Because colloids behave differently in space than they do on Earth, the 
researchers are seeing some surprising results -- so surprising that 
NASA has agreed to keep the project on the space station for another 
year. In October, Expedition 12 Commander William McArthur will pick up 
the project where Chiao left it.

If only Meyer can get McArthur to call him while he's shopping. The 
employees at the store were so happy to hear from Chiao that when Meyer 
checked out they gave him a scratch-off coupon -- another 10 percent off 
that pair of shoes.
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