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Buoyancy is just
one of the many
phenomena that
behave differently
in microgravity.
E D U C ATO R ’ S FA C T S H E E T : Physical Sciences
Our quest to understand gravity (and phenomena that depend
on gravity) began in ancient times. As early as 600 B.C.,
physicists and philosophers posed models to describe the world
around them and rules that might govern nature. Archimedes, a
prominent Greek scientist of the ancient world, supposedly ran
through the streets of Syracuse—naked—shouting, “Eureka!” when
he first discovered the nature of buoyancy. More than 2,000 years
later, buoyancy is just one of many phenomena that behave
differently in a microgravity (weightless) environment, allowing
modern scientists to do unique research aboard the International
Space Station.
Space effects on fluids and matter
With buoyancy effectively out of the picture, scientists can
study phenomena such as (1) diffusion, the movement of
molecules within a substance because of random motion
or unequal distribution of molecules, and (2) viscosity, the
resistance of a substance to flow (such as the way honey
pours out of a container, compared with water). Microgravity
unmasks the effects of such phenomena, which buoyancy
often overshadows in Earth-based studies. Thus, scientists can
more easily observe, study and describe these phenomena
in space-based experiments.
These microgravity effects also influence particle physics,
the study of the existence and interactions of small particles,
such as molecules. For example, because of changes in
fluid movement, particles in space behave differently within
fluids. Studying how particles move under different conditions
helps scientists better understand the fundamental rules that
govern these particles and their interactions. For example,
studying the way certain fluids move and behave in response
to a magnetic field may help scientists improve design of
consumer products such as brake systems, seat suspensions
and airplane landing gears.
The microgravity environment
How does space-based science help us understand
the physical sciences? Often by helping scientists study
phenomena that are masked on Earth. Aboard the space
station’s U.S. National Laboratory, scientists conduct long-term
experiments in a microgravity environment not achievable
on Earth. Gravity drastically affects many physical processes
on Earth, so in an environment without it, scientists can do
experiments in the physical sciences (such as fluid physics
and combustion) that would be difficult or even impossible
on the ground.
Because much of the physical sciences research in space
is theoretical or related to basic science, it has somewhat
less potential for commercial applications on Earth than, for
example, biomedical science or Earth observations. However,
findings from physical sciences research on the station add
to human knowledge and advance basic science fields and
materials science.
For example, buoyancy, a major cause of convection (the
movement of molecules within a fluid), depends on gravity.
Buoyancy is thus functionally absent in the microgravity
environment of the space station, so scientists can examine
movement in liquids to study subtler causes that buoyancy
masks (overshadows) in ground studies.
E D U C ATO R ’ S FA C T S H E E T : Physical Sciences
The combined study of fluid movement and the behavior
of particles within fluids helps scientists investigate the
fundamental internal structure of fluids. Such studies
advance basic science knowledge and are relevant to
materials science. (For more information on how fluid physics
influences the development of new materials for use on
Earth, see the Materials Science fact sheet.) Scientists are
also working on developing new techniques for electronics
cooling by studying the way fluids move in certain situations
on the station.
Effects on fluid movement also influence how substances
interact—for example, at the boundary between a liquid
and a solid. Certain aspects of interactions at these liquid–
solid boundaries are easier to study in space (because they
are unmasked, as described above). Results from the study
of these boundaries are important for several processes
on the ground. For example, bacteria in food-processing
industries often grow at such boundaries, so understanding
characteristics of these boundaries might help scientists
avoid bacterial contamination of food.
Other physical science experiments in space
In addition to fundamental physics, microgravity also
substantially affects combustion (burning). Certain types
of combustion studies performed in space are near
impossible on the ground, and studying combustion in this
altered environment helps scientists evaluate combustion
patterns and phenomena (such as flame structures and
soot formation). The results of combustion experiments
can help researchers make combustion on Earth more
efficient; for example during power generation or in internal
combustion engines in cars. Research results may also help
improve fire safety and reduce the environmental impacts
of combustion.
Finally, the space environment affords scientists greater
precision in their experiments. Research hardware aboard
the station can achieve and maintain extreme temperatures.
Thanks to these capabilities, along with other benefits of
microgravity, researchers can study certain fluids and gases
at very high and low temperatures, where substances start
to behave differently from traditional models of solids, liquids
and gases. Scientific measurements in space are often also
more precise because scientists can more easily control
experimental conditions.
CASIS, Center for the Advancement of Science in Space, and the CASIS Center for the Advancement of Science in Space logo are trademarks of the Center for the Advancement of Science in Space in the U.S. and/or other countries.CASIS, Center for the Advancement of Science in Space, and the CASIS Center for the Advancement of Science in Space logo are trademarks of the Center for the Advancement of Science in Space in the U.S. and/or other countries.
The Center for the Advancement of Science in Space (CASIS) manages
the International Space Station U.S. National Laboratory. This laboratory
supports basic and applied research across the range of physics, chemistry, engineering, materials science and
biology, as well as opportunities for technology development and education initiatives. CASIS is the gateway to
space-based research onboard this National Lab—and to all the excitement it offers to researchers and students.
For more information, visit www.iss-casis.org or scan the code to your left.
To learn more, contact CASIS: [email protected]
ISS photos courtesy of NASA.
The role of space science in education
The space station’s National Lab supports advanced research
that will ultimately improve human knowledge and quality of life
on Earth. The research aboard the space station is unique and
exciting, offering a new resource for project-based learning
and for using modern breakthroughs to illustrate traditional
science concepts. This new era in scientific discovery comes
just in time to inspire a new generation to continue the quest
for scientific exploration, educating the future leaders and
decision makers of our country and the world.
Note: NASA, not CASIS, manages some physics and combustion
experiments in space. Many of these experiments have to do with future
space exploration. To learn about these NASA-managed experiments,
visit www.nasa.gov/mission_pages/station/research/index.html.
E D U C ATO R ’ S FA C T S H E E T : Physical Sciences