The Expanding Universe
Galaxy Number 
Distance 1 (cm) 
Distance 2 (cm) 
Difference (cm) 
"Velocity" (cm/s) 


















































 Plot the velocity versus the second measurement to get the "Hubble Law for Balloons". Label the units on your axes.
 Draw a 'bestfit' straight line through your points. The line should go through (0,0) on your graph. Why?
 Find the slope.
 Find the age of your balloon universe from this slope.
 How does this age compare to the time it took to blow up the balloon the second time?
 What assumptions do you make about your balloon universe when you find it's age by this method? Are these sensible assumptions?
 How would your results change if you used a different reference "galaxy" on the balloon? If you are not sure, try it!