SUBJECT: Science
GRADE: 7,8,9
GROUP SIZE: Small or Large
TIME: 45 Minutes
TYPE OF ACTIVITY: Teacher Demonstration or Student Activity
CONCEPTS: Parabolic Reflector Radio waves Directionality of Radio waves
SKILLS: Observation Modeling Interpreting Data

Objectives: To see how a radio telescope works; to understand some of the reasons for using radio telescopes.

radio telescope demonstration setup 1

radio telescope demonstration setup 2

Materials: Radio; umbrella; heavy-duty aluminum foil (to line the inside of the umbrella).
Teacher Background Information:

“Our galaxy, the Milky Way, contains between 100 billion and 300 billion stars. One star out of every 18,000 has the potential for supporting a planet similar to Earth. Yet, even if we start with the lowest possible galactic number of 100 billion stars, this means that just within the Milky Way, some five million stars could meet the basic requirements for life. Beyond our own corner of the universe, the hundreds of billions of other galaxies might harbor millions of other suns supporting millions of other Earth-like planets, as well.

Most crucial to the question of extraterrestrial visitations is the problem of interstellar travel. The distance to even the nearest star is so great as to render space travel, by any means we now know, impossible within a human lifetime. A more likely form of contact with extraterrestrial intelligence (if it exists) may be through long-distance messages rather than actual visitations; radiowave transmissions now seem the most likely method of interstellar communication.”

Taken from, “Life in the Universe: an Introduction to the Search for Extra-terrestrial Intelligence,” a brochure from Harvard-Smithsonian Center for Astrophysics.


First, place the radio on the desk or a table in the classroom. Starting at one end, find weak stations on the radio and write down the dial numbers of five of them. Next, make a model radio telescope by opening the umbrella and lining the inside with sheets of aluminum foil. Now,

  1. Ask a student to rotate the radio until the best reception possible comes from one of the weak stations.
  2. Have the student hold the umbrella behind the radio with the aluminum foil facing the incoming waves as shown.
  3. Slowly move the umbrella closer to or farther from the radio until the position that best improves the strength of the radio waves is found.

With the class, repeat steps 1, 2 and 3 above for the other weak stations and put a check mark next to each station whose radio waves are strengthened by the radio telescope. Finally, place the radio telescope model between the radio and the incoming waves as shown

Notice what happens to the radio waves with the “telescope” in this position.

Discuss with the class such questions as:

  • Where did the radio waves that the radio received come from? (the station)
  • Where do radio waves that are picked up by actual radio telescopes come from? (Sun, other stars, quasars, pulsars)
  • What happened when the umbrella was put between the radio and the transmitting station? (Blocked the waves)
  • What is the function of the aluminum foil in this activity? (Acts as reflector for the waves.)
  • Why did the radio waves strengthen when they were reflected by the umbrella? (Concentrated all the waves captured by the parabolic arc and reflected them to one point.
  • Why do we listen to the sounds from space? (To “see” what stars are doing, to get beyond what visible light telescopes can see, to find new stars; to listen for the sounds of extraterrestrial life in space.)
  • If there are any extraterrestrials out there, what message might they be trying to get through to us?


  • Discuss the possibility of extraterrestrial life with the students and, just for fun, assume that the principles of bio-chemistry remain constant in the universe. What sorts of creatures might have evolved out there on other planets? Think about the environment of the planet and design a life form that “fits” the environment of choice. (Mars, for example, might have a very large, red, toad-like creature with enormous webbed feet for use as sand shoes, with very strong hind legs for magnificent leaps in the reduced gravity and huge deploy-able wings that he uses, along with those webbed feet, for sand surfing when the spirit moves him. He probably lives for frozen CO2!) Have students choose a planet or star that we know something about and draw a form of life they think would be appropriate for it.
  • Find information on the radio transmitter ET made in the movie. How is this similar to the radio telescope model made by the students?

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