One day, astronauts might travel through
the solar system onboard spinning spaceships. Can human brains adapt?
by Patrick L Barry & Dr
Next time you go to
a playground, try this: Bring along a ball and a friend, and get
on the merry-go-round. Try throwing the ball to your friend across
the ride from you, or even just a few feet beside you, and see if
they can catch it on the first attempt.
They won't be able
to, guaranteed. In fact, your throw will be way off. You'll feel
your arm pulled strangely to one side as you make the throw, and
once in flight, the ball will veer wildly.
Physicists call this
the "Coriolis effect," and it happens on any spinning platform.
Hurricanes swirl because of the Coriolis effect, the spinning platform
being Earth itself. Contrary to popular belief, Coriolis forces
do not control your bathroom drains - Earth doesn't spin that fast.
But playing ball on a merry-go-round is definitely a Coriolis experience.
Space travel could
be a Coriolis experience, too.
Researchers have long
known that spinning spaceships like a merry-go-round could solve
a lot of problems: In weightlessness, astronaut's bones and muscles
weaken. It's tricky to eat and drink, and even use the bathroom.
Inside a spinning spaceship, on the other hand, there would be an
artificial gravity (due to centrifugal forces) that keeps bodies
strong and makes everyday living easier.
The problem is, spinning
spaceships also come with a strong Coriolis effect. Tossed objects
veer. Reach out to touch a button ... and your finger lands in the
wrong spot. Could astronauts adapt to this? And if so, could they
adapt well enough to perform dependably in the life-threatening
environment of space?
Credit: University of Illinois at Champagne-Urbana.
ball on a merry-go-round, beautifully illustrates the Coriolis
That's what researchers
James Lackner and Paul DiZio are trying to figure out. With support
from NASA's Office of Biological and Physical Research, these two
scientists are performing a series of experiments with people in
rotating chambers to learn how well astronauts might adjust to life
onboard spinning spaceships. They also hope to find training techniques
that could help ease the transition from non-spinning to spinning,
and back again.
"Experiments done in
the 1960s seemed to show that people did not adapt well to rotation,"
says Lackner, the Meshulam and Judith Riklis Professor of Physiology
at Brandeis University in Waltham, Massachusetts. "But in those
experiments, the subjects didn't have well-defined goals for their
movements. We've found that when a specific goal is given for the
motion, people adapt rather quickly."
Given specific motion
goals (such as reaching out to touch a target), people in their study
learned to move accurately after only 10 to 20 attempts. Such a rapid
adjustment surprised the researchers.
Says DiZio, an associate
professor of psychology at Brandeis, "we speculate that when a goal
is present, the brain dictates the desired motion to the muscles
more precisely. Deviations from that motion are detected more readily
by sensory feedback to the brain."
Why should people
have this natural ability to adapt to rotation?
Our bodies and brains
might have evolved, to a degree, to deal with the Coriolis effect.
Every time you turn and reach for something simultaneously, you
have a brief Coriolis experience. Turning atop an office chair.
Playing basketball. Spinning to see what made that strange noise
behind you! In each case, your brain makes on-the-fly Coriolis adjustments.
Other discoveries surprised
the researchers, too. For example, after rotating for a while, people
in their study no longer perceived the Coriolis effect.
The veering pull on their arms and legs seemed to vanish. Their
brains had compensated for it, so their minds no longer took notice
Credit: John Frassanito & Associates,
An artist's concept of a spinning spaceship.
Even stranger, when
test-subjects first return to a non-rotating environment, they report
feeling a Coriolis-pull in the opposite direction. It's
just a trick of the mind, notes DiZio. After another 10 to 20 attempts
at a goal-oriented motion, their brains readjust to the non-rotating
world, and the phantom effect goes away.
DiZio and Lackner have
found that people can adapt to rotational speeds as fast as a carnival-ride-like
25 rpm. That's about as fast as people turn their bodies during
day-to-day life. For comparison, a spinning spaceship would likely
rotate more slowly, perhaps 10 rpm, depending on the size and design
of the craft.
To exert more control
over the conditions of their experiment, the researchers have tried
something innovative: simulating the Coriolis effect with a robotic
arm. Seated subjects would try to make certain motions with their
arm while the robotic arm gently pulls on their wrist in a way that
mimics the Coriolis effect.
A rotating room used by Lackner and DiZio in their experiments
at the Ashton Graybiel Spatial Orientation Laboratory,
The advantage of this
approach is that the robotic arm can be reprogrammed to pull in
a variety of ways, thus testing how subjects respond to different
conditions. Using the arm, DiZio and Lackner have discovered that
people can adapt to a small, variable force even when it's masked
by a larger, constant force. So, for example, astronauts should
be able to adapt to a variable Coriolis effect in spite of some
constant background force, such as the steady push of a spacecraft's
Many questions remain
un-answered. Do results based on arm motions apply to the whole
body? Does carrying heavy tools make a difference? After adapting
once, can a person re-adapt more easily later? What's the best way
to train astronauts for life in a rotating home?
Lackner and DiZio plan
to tackle these questions and more as their research continues in
the months to come.