Stop It!

What if you could stop a falling drop or freeze a running child in his steps? What would you see?

That's what Harold “Doc” Edgerton wondered, so he invented a way to stop motion with his camera. By lighting a moving object for a fraction of a second with a specially designed flashing light called a stroboscope and then taking a picture, Doc was able to capture individual moments of movement on film. In doing so, he revealed an amazing and often beautiful world.

In the 1930s, in a darkened lab he called “Strobe Alley” at the Massachusetts Institute of Technology in Boston, Doc began taking pictures of anything that moved: water dripping, birds flying, balls bouncing. He created a way for his camera and strobe to work together so that when the strobe flashed, the camera took a picture. To time the picture accurately, Doc devised different ways to trigger the strobe, sometimes by sound and sometimes by the movement of the subject. To record a sequence of movements, such as the running boy above, Doc set his strobe to flash as fast as 300 times a second. At each flash, the camera took a picture.

To get the same effect, try this: Gaze at a turning wheel or fan and rapidly blink your eyes. See how each blink stops the action? If your eyes were strobe lights hooked to a camera, each time you opened them, a picture would be taken.

Doc's “motion pictures” show us many things human vision can't see. They help scientists study the way birds fly and the way people move. They picture what happens when one object strikes another, and how fast bullets and balls speed through the air. Strobe technology can even be used to examine fast-moving machinery, such as the moving parts of a car's engine. And Doc's inventions led the way to modern flash cameras.

Doc Edgerton's strobe photographs enabled us to see motion in a new way. Today, scientists rely on many kinds of photography to see things we can't see with our eyes alone. From the largest and most distant objects in the universe to the smallest and most ordinary ones, photography helps us picture our world.

Activity

  1. What can be learned about position and motion from Harold Edgerton's photographs? How is this different than what can be seen by the human eye?
    [anno: Harold Edgerton's photographs reveal motions that are too quick for the human eye to see. With his photographs, Edgerton reveals the position of an object through its motion, and the effect of that motion on an object.]
  2. Why might it be useful to see the position of the heated air around a match after the match has been lit? Who might find this information useful?
    [anno: Answers may vary but could include that it is useful to see the position of heated air around a match that has been struck to know the direction and shape of heated air after something is ignited or lit. A fireman might find it useful to know how heated air moves after something has been lit.]
  3. Why might it be useful to see the different positions of an insect's wings as it flies? Who might use this information?
    [anno: Answers may vary but could include that it is useful for scientists to see the different positions of an insect's wings as it flies so that they can understand the motion an insect uses to fly. Engineers who make different kinds of aircraft might find this information useful when designing new aircraft.]