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

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The folks at Newton's Apple wrote the following!
Circus High Wire

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.