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Measure For Measure (Not By Shakespeare)


You and Your Students!

Script By

Vicki Cobb, Education World Science Editor


You can tell a person's shoe size without looking at his or her foot!


Human Body, Measurement

Props Required

  • rulers
  • string
  • three bowls of water -- 1) hot, 2) iced, and 3) room temperature

Setting the Scene (Background)

Measurement is an important part of science, but try to teach measurement and you often hear groans from students. In these easy- and fun-to-teach activities, the human body offers some surprising proportions that can ease you into the subject.

Stage Direction

  • Choose one student and do this activity as a demonstration first, then have everyone try it.
  • Or have kids work with a partner so each student has the measuring experience.

The Plot

Act I:
Use a ruler or a piece of string to measure the distance from the elbow to the wrist. Then measure the length of the foot. (Flexible kids can put a bare foot against their forearm with the heel at the elbow.) What do students learn? (Surprise! Both measurements are the same length!)

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Act II:
The body has some other surprising proportions:

  • The distance around a closed fist is the same as the length of that person's foot. Ask: How can that help you shop for socks?
  • The distance between outstretched arms held parallel to the floor with fingers extended is the same as your height.

The human body has served as a measuring stick for centuries because it is a portable measuring device. Over history, the first knuckle of the thumb was equated to an inch, the length of a foot was equated to the measurement of the same name, the distance from the fingertip of an outstretched arm to the tip of the nose was equated to a yard, and the width of the palm is the four-inch "hand," which is used for measuring the height of horses.

Act III:
How reliable is the human body when it comes to measuring other some other variables? Not very! Here are some things you can try:

  • To measure temperature, place one hand in ice water and the other hand in very warm water for one minute. Then plunge both hands into water at room temperature (about 70 degrees F). The tepid water will feel warm to the hand that's been in the ice water and will feel cool to the hand that's been in hot water.
  • Test your ability to measure weight: Put two quarters in one envelope and one quarter in another. Seal the envelopes. Hold an envelope in each hand. Can you tell which envelope has two quarters and which envelope has one? Piece of cake! Now take off your shoes. Put an envelope in each of your shoes. Hold a shoe in each hand. Can you tell which shoe has the envelope with two quarters? Not likely. Each shoe weighs so much more than the envelopes with the quarters that you can't tell the difference in the weight of one quarter. With lots of practice you can learn to tell small differences in weight. Experienced deli workers can slice almost exactly the amount you ask for without putting it on a scale.

The End

Measurement is a way of knowing what's real. Ren Descartes (1596-1650), the French mathematician and philosopher, concluded that trusting your senses was not the way to know reality. What do your students think on this subject? Why is it important to have measurement standards?

Article By Vicki Cobb
Education World®
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