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Big Picture

Water, Water Everywhere...

Aliens Have Landed

New Energy Age

Paper Personality

Healing Touch

Viewer Challenge
in the classroom


Imagine tapping into the energy believed to exist in the vacuum of space (called zero-point energy). Scientists we meet in this episode believe they are on the verge of harnessing this zero-point energy to power the world. But zero-point energy is scientifically very controversial. Scientists agree that it exists, but many, like Nobel Prize-winning physicist Steven Weinberg, say the amount that exists in our universe is too small to be useful.

Curriculum Links
Related Frontiers Shows and Activities
The Quest For Perpetual Motion
Activity 1: Waste Not, Want Not!
Activity 2: Think More About It



energy, machines





engineering, inventions


In earlier times, long before the concept of zero-point energy was introduced, inventors dreamt of building a perpetual motion machine that would run forever without any input of energy. Such a machine fits the definition of pseudoscience because the concept is based on faulty science.

Early inventors didn't know enough about physics to understand why their perpetual motion machines could not work. By the 1850s, scientists discovered the first and second laws of thermodynamics. The first law states that energy cannot be created or destroyed (also known as the law of conservation of energy). Later, Scottish physicist James Maxwell observed that a perpetual motion machine violates the second law of thermodynamics, which states that heat cannot flow from a colder body to a hotter one without adding more energy than is produced. To keep running, an engine must continually be supplied with energy. So far, no one has ever been able to build a machine that runs forever.


It's your turn to be an inventor. For this challenge, things will be easy. You won't have to invent a zero-point energy or perpetual motion machine. Instead, you'll re-design a basic machine so that its observable motion lasts for the longest possible period. Think you can do it? Good luck!

The basic machine is a water wheel. The wheel's spin is powered by drops of water that fall onto its paddles. Let's see how this basic machine works.


Design and build a machine, then participate in a competition.

  • large funnel
  • ring stand with 2 rings or alternate support
  • sheet of thin, clear plastic (like a report cover)
  • ruler
  • wooden dowel or bamboo skewer
  • scissors
  • rubber bands
  • empty spool from large spool of thread
  • 1 cup of water
  • large bowl
  • small cork or piece of clay
  1. Cut four rectangular pieces of the plastic. Each piece should be about 4 cm long and about the same width as the spool.

  2. Trim off two corners producing a shape like the one on the right.

  3. Crease and fold the shape along the dotted line.

  4. Wrap the base of one "paddle" along the spool. Secure the base with two rubber bands - one placed along each edge of the spool.

  5. Slip the other three paddles under the rubber bands. Make sure that they are spaced evenly at one-quarter distances around the spool.

  6. Set up the ring stand and rings as shown.

  7. Slip the dowel through the center of the spool. Position the dowel in the center of the bottom ring so that the spool can spin freely. Use tape to secure the ends of the dowel to the ring.

  8. Position the large funnel in the upper ring so that the water stream is directed at the paddles. Position the bowl beneath the water wheel assembly.

  9. Place a small cork or plug of clay into the funnel spout.

  10. Pour one cup of water into the funnel. Begin timing when the plug is removed. Stop timing when the wheel no longer turns.

Redesign this machine so that the wheel spins for the longest time. You can change the size, shape and placement of any of the components. You can add objects or take them away. Change the machine in any way. Variations might include different sizes and shapes of paddles or different sizes of spools, but you must follow these two rules:
  1. You may use only one cup of water, which must be entirely poured into the funnel before you start.

  2. The height of the fall (measured from bottom of the funnel spout to the top of the dowel) must be less than one foot (30 cm).


Perhaps you've seen ads in science or novelty catalogs for toys that seem to be powered by unknown energy sources, tapping into the idea of a perpetual motion machine. Examine the ad below and address the questions that follow.


Apply critical analysis to an advertisement.

  1. If perpetual motion were possible, would its commercial application be limited to toys?

  2. Why might this device require several batteries?

  3. Why might the ad mention Roswell, UFOs, military scientists, pyramids and crystals?

Design a scientific experiment that would test whether this toy uses a perpetual motion engine.


Each year the U.S. Patent Office receives about 100 applications to patent perpetual motion machines. Today, each application must be accompanied by a working model. The office doesn't test the inventions to see if they perform as claimed.

The patent office maintains that its responsibility is to ensure that the machine designs are original -- not to test whether the claims are true. What do you think? Should a patent office be responsible for testing perpetual motion devices (or other inventions)? Does a patent convey endorsement of a product and suggest that the product works according to its claim?


Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.