Barany Chair Demo on the Planetarium Stage

March 2006

Brief Summary

The Barany [BARE-uh-knee] Chair looks like a barber chair that swivels. It is used to train pilots and astronauts about the illusions of motion that can cause fatal accidents when pilots do not trust their instruments. This demo calls for a volunteer from the audience to come up and sit in the Barany Chair and get spun gently. After putting earmuffs and a blindfold on the volunteer from the audience, the demonstrator asks thevolunteer to indicate the perceiveddirection of motion by pointing with his or her thumbs. The audience discovers that two illusions can occur: 1) Feeling that no motion is occurring when it is, and 2) the opposite, feeling that motion is occurring when it is not.

Equipment Required

SAFETY POINT: Always keep the Barany Chair locked up with the cable and padlock firmly in place when you are not physically present. This means getting out a computer and the microphonesfrom the Demo Storage Room before you go to the Planetarium Stage.

What you need:

  1. One handheld and one headphone microphone.
  2. A laptop computer. (Enter Planetarium backstage area through sliding door. Open stage door from the inside. Bring computer up ramp onto stage.)
  3. On the Portal, go to Exhibit Resources/Barany Chair. Boot up the Barany Chair PowerPoint from the dock on the computer. This contains all the images you will need for the demo.
  4. The earmuffs, blindfold goggles, physical model of the mechanism of balance, and a bucket. These are stored backstage.
  5. The unlocked Barany Chair


The Barany chair /
The physical model of motion sensors cells in the inner ear /

The screen images of the ear used in the demo (see final page of manual for labels)

Educational Strategies

  • Because this demo is necessarily short, (7-10 minutes) a specific sequence is recommended, rather than trying out alternatives.
  • Everything in this demonstration relates in one way or another to the semicircular canals. Be sure to keep this through line clear.

Main Teaching Points

  • The semicircular canals, the organs of balance and motion detection, are located in the inner ear.
  • The semicircular canals contain a liquid that moves around inside them as the head moves. Tiny hair-like nerve fibers inside the semicircular canalsrespond to motion in the fluid, but when the head stops moving, the liquid continues to move, creating the illusion of motion which isn’t really happening.
  • If pilots and astronauts rely only on their sense of motion and not their instruments, they can make fatal errors and crash.

Procedure

  1. Ask, “Have you ever ridden on a merry-go-round?” and “When you got off did you feel like you were still moving?” This was an illusion of motion, similar to an optical illusion, when you see something that isn’t really there. In this came you sense motion that isn’t really there.
  2. Mention that pilots and astronauts can experience the same thing, and are trained on how to deal with it using the Barany Chair.
  3. Briefly introduce the Barany Chair and say that in a minute, you’re going to have a volunteer from the audience come up and assist you by going for a spin in it.
  4. Mention that we can perceive motion by means of the semi-circular canals, the organ of motion and balance located in our inner ear. Remind visitors that the ear not only hears, but also helps us balance and perceive motion.
  5. Put up the images of the inner ear on screen and use the cursor to point out the semi-circular canals, not your finger because there are three screens.
  6. Explain, using body motion, “pitch”, “yaw”, and “roll.” If time permits, and particularly with school group audiences, have the whole crowd move through these motions along with you.
  7. Use the image to show what you’re going to explain next: the interior of the semi-circular canal.
  8. Take out the physical model of the interior of the semi-circular canal and explain the bobbers and what they relate to in the inner ear.
  9. Demonstrate three facts about the effect of motion: 1) When the liquid is still, the bobbers point upwards, indicating “no movement” to your brain. 2) When motion begins, the bobbers tilt so that they point opposite to the direction of motion, indicating “I’m moving” to your brain. 3) After about 10 turns, they become upright even though the canister is still moving, and because they are upright, your brain thinks you are not moving. 4) When the canister is abruptly stopped, the bobbers tilt in the opposite direction of movement, indicating to your brain that you are moving again (in the opposite direction to previous movement).
  10. Now call for a volunteer and strap him/her into the chair (IMPORTANT: see “Operating Tips” for specifics on how to do this).
  11. Give the volunteer the blindfold goggles to put on, and say that it is also important to close his/her eyes.
  12. Give the volunteer the earmuffs, and ask him/her to adjust it so it fits well.
  13. Tell the volunteer that you will spin the chair. Tell the volunteer to put his/her hands on his/her knees and use the thumbs to indicate the direction of perceived motion, and to point thumbs up again when (s)he thinks the chair has stopped. Then, if (s)he thinks the chair is moving again, to point the thumbs in that direction.
  14. Ask the audience to be quiet so as not to give audio clues to the volunteer.
  15. Give the chair a brisk shove so that it turns about once per second.
  16. While the chair is moving, do not say anything, but use your own thumbs to mimic those of the volunteer.
  17. If the volunteer forgets to point his or her thumbs, ask them to remember to do it, then try again.
  18. If, for whatever reason, the experiment does not work, do not try it a third time with the same person (since (s)he may get sick). If there is time, you can have a different volunteer try it.
  19. Summarize the main points of the demo, and if time permits, call for questions about the demo.

Operating tips

  • After unlocking the chair, wrap the cable around the base to keep it from becoming a tripping hazard.
  • Have the earmuffs, blind fold and model close at hand so there is no dead time while you locate them.

Specifics on Getting the Volunteer into the Barany Chair

  • When performing for a school group, ask a chaperone or teacher to assist you in belting the kid in. In all cases, while you should be the one attaching the straps, be sensitive to how you do this. Ask the volunteer to reach for the strap between his/her legs rather than grabbing it yourself.
  • To assemble the buckle parts, begin with #1 and add buckle parts one by one up to #5. Then attach to the buckle release lever.


The buckle assemble has five parts that assemble into one mechanism.
  • As you belt the volunteer in, make sure you remain engaged with the audience, by explaining what you’re doing. Humor here is important too. “OK Kids, I’m almost finished strapping your teacher in. Get your water balloons ready.”


Jim before spinning /
Jim after spinning

Take Down Procedure

  • Put props back into proper place backstage.
  • “Return Space To Normal” on the OCC and return computer and microphones to Space Odyssey storeroom.
  • Turn Barany Chair toward the wall and lock it up with the cable and padlock.

Parts of the Ear

Background materials (websites, videos, articles, digital collections links)