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: info@iss-casis.org

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