Name _____________________
Honors Physical Science
20.E.2 (Models)
Astronomers believe that the universe is expanding –that all points in the universe are
getting farther apart all the time. It’s not that stars and galaxies are getting bigger; rather,
the space between all objects is expanding with time.
Making a model: Scientists often use models to help them understand what is happening
on a larger scale. Today you are going to make a model of the universe to show how this
expansion works. The universe is too big for us to observe on a small scale, so a model can
help us observe how it is working.
In what ways are models helpful?
Procedure:
You will need a balloon, permanent marker, string, and a ruler
1. With the permanent marker, make 6 small dots on one side of the balloon. Number
the dots 1-6. Don’t put all the dots in a straight line. Make sure the dots are spread
out a little. Each dot represents a galaxy.
2. Define galaxy: ______________________________________________________________________________
3. Now, blow the balloon up slowly. Write your observations below:
What happens to the dots as you slowly blow up the balloon?
4. Let the air out of the balloon. This time, blow the balloon up half way.
5. Keep the balloon filled halfway and circle one of the outmost dots (the ones farthest
to the left or right). This dot represents the Milky Way.
6. Measure the distance from “The Milky Way” to the other galaxies. Record this in
your data table.
7. Blow up the balloon all the way and measure the distance from “The Milky Way” to
the other galaxies. Record your data.
Name _____________________
Honors Physical Science
20.E.2 (Models)
Data Table: Create your own data table. You should have two columns of data: the distance
to each galaxy the first time and the distance to each galaxy the second time. Make sure to
include all labels and units for your table. Give your table a title.
Calculations: Calculate the “average speed” of each dot on the balloon with respect to the
Milky Way dot. Subtract the distance (first time) from the last distance (d2-d1). Divide this
amount by the time it took you to blow up the balloon.
Galaxy
D2- D1 (cm)
Graphing: Create a graph that shows the second
distance on the x-axis and the speed on the y axis
Time (seconds)
Speed (cm/s)
Estimate how many seconds
it took you to blow up the
balloon from half way to all
the way. This is your time.
Name _____________________
Honors Physical Science
20.E.2 (Models)
1. Which of the following best represents what we showed using this model? (more
than one)
a. how the galaxies are getting larger
b. how the universe is expanding
c. how the space between galaxies is increasing
d. how the universe is gaining more stars
For questions 2-5, use complete sentences.
2. Look at your graph. What pattern do you see?
3. What can you conclude about the speed of galaxies based on this model?
4. Models are helpful in science, but there are limitations. Describe 1-2 limitations of
this model.
5. Describe another way you could model the universe. Example: Bake chocolate chip
cookie dough and measure how the distance between chips changes.