Key concepts
Geometric shapes
Have you ever seen a geodesic dome? Geodesic domes are spherelike structures made up of interconnected triangles. A famous geodesic dome is Walt Disney World’s Spaceship Earth at Epcot, but geodesic domes are also commonly found as climbing domes at playgrounds. In this science activity you will get to build a simple geodesic dome using gumdrops and toothpicks. Get ready to do some tasty engineering!
A geodesic dome is a structure made of struts that are connected to one another to approximate the shape of a sphere (or part of a sphere). Richard Buckminster "Bucky" Fuller, an American inventor, architect, author, engineer, designer and futurist, patented the geodesic dome in the 1940s and made it popular. Spaceship Earth at Epcot is a geodesic dome that is a complete sphere shape, but many other geodesic domes, such as climbing domes at playgrounds and some greenhouses, are often only part of a sphere.
Typically, the struts or ridges of a geodesic dome are joined together in triangles, with the points of the triangles creating the sphere's "surface." The edges of the triangles form great circlelike shapes, or geodesics, over the dome’s surface. The struts form a rigid network that transmits stress forces throughout the structure, allowing geodesic domes to support a surprisingly large amount of mass compared with the mass of the structure itself.

  • 11 gumdrops (Alternatively, jelly beans or other semifirm, chewy candies may be used.)
  • 25 toothpicks
  • Gather the 11 gumdrops and 25 toothpicks that you will use to make your geodesic dome.
  • Attach five toothpicks together using the gumdrops to form a flat pentagon (five-pointed) shape. You should have a gumdrop at each point and a toothpick along each edge.
  • Poke two more toothpicks into each gumdrop, arranging the new toothpicks so that they are pointing up.
  • Take five new gumdrops and attach them to the top of the new toothpicks, putting two toothpicks into each gumdrop, to form triangles. (The pentagon should form the base of the triangle, and the new gumdrops should form the top point.) You should end up with five triangles this way. Why do you think the geodesic dome is made out of triangular shapes?
  • Attach a toothpick between the top points of the triangles you just made, connecting the triangles together. This uses five toothpicks, and will create another pentagon, this time at the top of the dome.
  • Take five more toothpicks and poke one into each of the five gumdrops that make up the top pentagon. Arrange the new toothpicks so that they are pointing up. Then poke all five toothpicks into a gumdrop in the middle, and at the top, of the dome. Your geodesic dome is complete!
  • Gently press down on the top of your geodesic dome. If it does not break, try carefully pressing down on it a little more. How strong is your dome? Are you surprised by how well it can support your hand as you press down on it?
  • Extra: Try doing this activity again, but this time use long, wooden skewers instead of toothpicks. Is one geodesic dome stronger than the other? If so, which one is stronger and why do you think this might be?
  • Extra: Try adding some mass on the top of your dome, such as heavy envelopes. How much mass can your dome support before it fails? Are you surprised by how strong it is? When the dome fails, how does it fail? Can you figure out a way to make it even stronger?
  • Extra: The geodesic dome you made in this activity uses a relatively simple design. You could try making a more complicated  or larger one by looking at the resources in the "More to explore" section. Can you build a much larger geodesic dome? What about one that uses multiple different strut lengths? How does a more complicated design compare with the one used in this activity?

Observations and results
Could your geodesic dome easily support your hand as you pressed it down on the dome, even when you increased the pressure?
A geodesic dome's design allows it to support a surprisingly large amount of mass compared with the structure's mass itself. Because of this you should have seen that the geodesic dome could easily support your hand as you pressed down on the top of the dome, even when you increased the pressure a little. You would need to apply a lot of pressure before the dome would fail. The struts of a geodesic dome—made here by toothpicks—are arranged to make triangles, which overall create a rigid network that disperses any stress forces applied to the top of the dome through the rest of the structure.
Because the geodesic dome approximates a sphere, it has a relatively low surface-area-to-volume ratio (that is, its volume is relatively large compared with its surface area) and it can enclose a large amount of volume when compared with the mass of the structure itself.
More to explore
Chapter 9: Mathematics, Geodesic Dome, from Science Toys
Dome Basics, from Building Big, PBS Online
Fun, Science Activities for You and Your Family, from Science Buddies
Dome Sweet Dome, from Science Buddies

This activity brought to you in partnership with Science Buddies