How do high-wire artists balance on such a thin wire? Why do they carry such long poles?

Circus High Wire
How do tightrope walkers keep their balance?

Insights

Imagine yourself 20 meters (66 feet) above the ground on a platform, as thousands of faces watch and wait for you to style. Now imagine taking a step, with only a 1/2-inch metal wire between you and the ground. Welcome to the world of high wire.

High wire's roots are as old as ancient Egypt and first century China, where the art of "rope dancing" was performed over knives. In the 1850s, Jean Francois Gravelet received world acclaim for cooking and eating an omelette (complete with stove and neatly set table) on a high wire stretched over Niagara Falls.

Three different types of funambulism have evolved. Slack wire, where the rope or wire hangs a bit loose, is popular for juggling, clowning, and sword fights. Sloped wires are attached to the ground at one end and to a pole at the other, creating an angle of about 40 degrees. The most popular of all is the high-wire act, where a taut, springy wire is used to launch dizzying acrobatic tricks and phenomenal feats of balancing.

One way to view the high-wire act is to see the wire as an axis and the center of mass of the performer as having the potential to rotate about the axis. If the center of mass is not directly above the wire, gravity will cause the performer to begin to rotate about the wire. If this is not corrected, the performer will fall.
The artist often carries a balancing pole that may be as long as 12 meters (39 feet) and weighs up to 14 kilograms (31 pounds). This pole increases the rotational inertia of the artist, which allows more time to move his or her center of mass back to the desired position directly over the wire. This effect can be magnified by making the pole as long as possible and by weighting its ends.

The pole also helps balance the funambulist by lowering the center of gravity. High-wire artists use drooping, rather than rigid, balance poles. It's possible, in fact, to have such heavy weights attached to the ends of a long, drooping pole that the center of gravity of the performer/pole system is below the wire. In this case, the performer would require no more sense of balance than a person hanging from the wire.

Acrobats train for years and use mechanics to safely develop routines. Although a high-wire performance may seem like a combination of courage and magic, remember that there's a lot of work and good, old-fashioned physics thrown into the balance as well!

Connections

1. How would maintaining control over your center of balance change as you moved from a high wire to a slack wire to an angled wire?
2. Why do squirrels have long tails?

Key Words

center of mass the point at which the entire mass of a body can be considered to be concentrated
funambulism tightrope walking-from the Latin funis (rope) and ambulare (walk)
inertia tendency of an object in motion to remain in motion and an object at rest to remain at rest
mechanics circus term for the safety wire attached to a performer executing a difficult or dangerous trick or feat
riggers circus term for the people who hang the cable and wires for performers
static not moving
to style circus term for a performer's particular way of bowing and posing to acknowledge the audience
rotational inertia the resistance of a body to a change in its rotational motion

Resources

1. Antekeier, K. & Aunapu, G. (1989) Ringmaster! My year on the road with "The Greatest Show on Earth." New York: E.P. Dutton.

2. Burgess, H. (1976) Circus techniques: Juggling, equilibristics, vaulting. New York: Drama Book Specialists.

3. Collins, G. (1994, Dec 8) An inner light, a leap of faith. The New York Times, p. B1.

4. Cushman, K. & Miller, M. (1990) Circus dreams: The making of a circus artist. Boston: Little, Brown and Company.

5. Dubner, S.J. (1991, Apr 22) Four little girls that fold. New York,
   p. 28.

6. Moss, M. (1987) Fairs & circuses. New York: The Bookwright Press.

7. Rosenfeld, M. (1993, Oct 31) Body & Soleil. Washington Post, p. G1.

8. Vial, V. & Dufresne, H. (1993) Cirque du Soleil. New York: International Publications.

9. Wallenda, D. & DeVincentis-Hayes, N. (1993) The last of the Wallendas. Far Hills, NJ: New Horizon Press.

10. Wiley, J. (1974) Basic circus skills. Harrisburg, PA: Stackpole Books.

1. Encyclopedia Britannica: Circus! Videotape. (800) 621-3900.

1. Circus World Museum
   426 Water Street
   Baraboo, WI 53913-2597
   (608) 356-8341

Make your dreams of running away to join the circus come true-at least for a little while. In this activity, you'll construct a tightrope setup, learn the basics of tightrope walking, and understand a little more about the physics behind balancing! Get an adult to help you build the setup, as well as to double-check cushioning and spot you as you learn.

Materials

• one 8'-long two-by-four board
  
• two 4'-long two-by-four boards
  
• two smooth poles, one about 3' long, the other about 6' (The length doesn't have to be exact, so long as the two sticks have about 3' difference
  between them.)
  
• sandpaper
  
• hammer
  
• 3" nails
  
• soft, grassy area or cushioned mats
  
• 2 half-gallon plastic jugs filled
  with water
  
• broom
  
• 50 cm (20") of string or cord cut into two equal lengths

1. Place the two-by-fours on their thinner edges, forming an H (see illustration). Center and nail the shorter boards onto the ends of the longest two-by-four. Sand down the entire surface, making sure there are no rough edges or slivers.
   
2. Place your "tightrope" on the soft, grassy area. If you put it on cushioned mats, make sure there is enough padded area to protect your entire body if you fall.
   
3. First, try walking from end to end very slowly. Where do you find yourself holding your hands and arms? Try holding them still-first straight out from your body, then overhead, then stiff by your sides. How do these different positions affect your balance? Why? Try these same positions holding a filled plastic milk jug in each hand. Does the added weight make balancing easier or harder? Why?
   
4. Try walking your tightrope with your longer pole. Move your hands together until they touch in the middle of the pole and walk the tightrope holding the pole horizontally. Now spread your hands as far apart as possible on the pole and walk the tightrope again. Does your hand position affect your ability to balance? How? Why? Try the two hand positions again with a broom. Is there any difference? Why?
   
5. Using the hand position you found to be the best for balancing, try walking your tightrope first with your short pole, then with your long pole. Which length helps you balance better? Why?
   
6. Tie the filled plastic milk jugs to the ends of your long pole and walk the tightrope again. Do the weights affect your balancing ability? How? Why?
   
7. Using the short pole, walk across your tightrope. What happens to the pole when you start to lose your balance? What happens to your body? Can you use the pole to deliberately make yourself lose your balance?
   
8. Add some tricks to your repertoire. Try walking backwards from end to end, balancing on one foot, or turning around on one foot. Can you think of other tricks you can add with practice? (Here are a couple ideas-try stepping over your balancing pole, or playing with a hula hoop.)
   Question
   

Here's a simple model to help you understand how center of balance and counterbalances work: Take a piece of string about 30 cm (1') in length and form it into a circle. Take a ruler and a hammer and assemble them together as shown. Balance the end of the ruler against the edge of a table with the hammer hanging below. Where is the center of balance? Why does this look like it shouldn't work?

Hold a large book in your hands. Have a friend gently try to disturb your balance. Now hold the book in different locations. Which location makes it easiest for you to keep your balance? Why?

Stand on a pillow in a safe, open, soft area. Can you balance on one foot? Now put on a blindfold. How does that affect your sense of balance?

Newton's Apple is a production of KTCA Twin Cities Public Television.
Made possible by a grant from 3M.
Educational materials developed with the National Science Teachers Association.