� The purpose of this lab is to model the uniform expansion of the universe and how the Doppler effect has contributed to its discovery.
I think that the Doppler effect contributed to the discovery that the universe is expanding because…
1. Use a sharpie to draw four dots in a row, 1 cm apart, on the surface of an un-‐inflated balloon. Label the dots 1, 2, 3, and 4. Draw a wavy line through the dots so that ½ of a wavelength goes through each dot.
2. Blow one large breath into the balloon and hold it closed so that no air can escape.
3. Using a piece of string and a ruler, measure the distance from dot 1 to each of the other dots. Record your measurements in Data Table 1.
4. Add another large breath into the balloon so that there are now two large breaths in the balloon; repeat step 3.
5. Add a third large breath into the balloon; repeat step 3.
Data Table 1: Distances from Dot 1 to Dots 2, 3 and 4. Distance in cm
from Dot 1 to Dot 2
Distance in cm from Dot 1 to Dot 3
Distance in cm from Dot 1 to Dot 4
Breath 1
Breath 2
Breath 3
1. Are the dots still separated from each other by equal distances? Explain.
2. What happened to the waves as you added breaths to the balloon?
3. How does this activity model the Doppler effect?