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The Universal Stretch!

Lab B Student Worksheet

Procedure

• Stretch the elastic band a small distance. Consider these locations as the Initial Distances. Measure the distances to each galaxy from the zero mark. Record the data in the table.
• Now slowly pull the elastic while counting approximate one-second intervals. You can count out the time or use a stopwatch or second hand on the room clock. Stretch for three seconds then stop. Now measure the distances to each sequin from the zero mark and record them in the date table as the Final Distances. Caution: do not pull the elastic band so much that you reach the elastic limit before the 3 seconds are up.

Galaxy #	Initial Distance (cm)	Final Distance (cm)	Change in Distance (cm)	Velocity (cm/s)
1
2
3
4
5

• Calculate the distance moved by each galaxy in one second by dividing the total distance moved by 3. This is the velocity (remember velocity is equal to distance divided by time). Enter this result in the final column of the data table.
• Plot the data points for each galaxy on the graph below. Connect the points for each galaxy with a straight line.

 



• Calculate the slope for each galaxy. Compare these results to the values you calculated for velocity in the data table. What do you notice?
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• Now do as American astronomer Edwin Hubble did: plot the velocity as the dependent (Y) variable and the Initial Distance as the independent (X) variable.

 



• What relationship do you see? Discuss.
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This is exactly what Edwin Hubble saw. He realized that the data he obtained by observing the apparent movement of galaxies were explained by the expansion of our Universe!