Check out our The Universe CD-ROM which includes similar activities.
Big Bang Balloon
An activity you can use in the classroom

In the 1920s astronomer Edwin Hubble used the red shift of the spectra of stars to determine that the universe was expanding. By carefully observing the light from galaxies at different distances from Earth, he determined that the farther something was from Earth, the faster it seemed to be moving away. This relationship has become known as Hubble's Law, and it's just one piece of a bigger puzzle known as the Big Bang theory.

Developed over many years and by many people, the theory states that about 15 billion years ago the universe was compressed into an infinitely small space, known as the primordial atom. It exploded in a sudden burst of energy and created a small, superdense, extremely hot universe that began to expand in all directions. Over time things cooled, and tiny bits of matter clumped together to form stars and galaxies. As a result of this explosion, all of these objects are still moving away from each other. In this experiment, you'll create a simple model to learn how the universe expands over time.

• 12-inch (30-cm) round latex balloon
• a permanent felt-tip marking pen
• 24-inch (60-cm) piece of string
• metric ruler
1. Inflate your balloon until it is about 4 inches (10 cm) in diameter, but do not tie the end.
2. Using the felt-tip marker, make six dots on the balloon in widely scattered locations. Label one dot "home" and the others A-E. The home dot represents the Milky Way galaxy, and the others represent galaxies formed in the early universe.
3. Without letting air out of the balloon, use the string and ruler to measure the distance from home to each dot. Record the distances in the worksheet table under the heading "Time 1."
4. Inflate the balloon so that its diameter is about 2 inches (5 cm) bigger. Again measure the distances to each of the dots, and record the distances under "Time 2" on the worksheet.
5. Inflate the balloon in 2-inch (5-cm) increments three more times. After each inflation, measure and record the distances on the worksheet (pg. 2 of the printable PDF).
6. Answer the follow-up questions on the worksheet.