Expanding Universe
a simple model for determining the Hubble constant
and age of the universe


print the worksheet

1.  Using the compass and a blank sheet of paper, draw a smallish circle in the middle of the page, making sure to leave a mark at the center.

2.  Mark a home “galaxy” and 10 other numbered “galaxies” randomly spaced around the circumference of the circle.

3.  Measure and record on the worksheet the distance of each galaxy from the home galaxy.

4.  Now draw a large circle (as large as the page will hold) using the center mark.

5.  Use a ruler pivoting on the center mark to find the new position of each galaxy.

6.  Record the new distance of each galaxy from the home galaxy.

7.  Determine difference in the distances between time 1 and 2 (the two circles), and calculate the velocity that the galaxies have moved away from the home galaxy between times 1 and 2.  Use 10 minutes for the time.

8.  Plot the velocity versus the second distance measurement on the graph.

9.  Draw a best-fit line from the origin (0, 0) through the plotted points.

10.  Determine the slope of the line.  This is the Hubble constant for our imaginary paper universe.

11.  Take the inverse of the Hubble constant.  This is the age of our paper universe.