Create An Expanding Universe | The Schools' Observatory

You have likely heard about the Universe expanding. Or that redshift can tell us about the movements of galaxies. Both are difficult ideas to imagine and understand.

In this activity, you will use a balloon to explore the expanding Universe. As part of your exploration, you will investigate the relationship between the distance to galaxies and the speed at which they move.

By the end of this activity you will:

Have worked scientifically to carry out an investigation
Have calculated speed using distance and time measurements
Have plotted and interpreted a distance-speed graph
Have looked at, and replicated, the evidence for the expanding Universe
Have investigated the relationship between distance and redshift

To complete this activity you will need:

To watch the 'How do we know the Universe is expanding?' video
To read the instructions on this page
The worksheet below, or to create your own table of results
A round balloon (do not use a long, thin one)
At least 5 stick-on dots (make sure each is a different colour)
A ruler
A piece of string about 50cm long
A stopwatch or other timer

Files or Documents

Expanding-Universe-Worksheet-update.pdf (175.79 KB)

Expanding-Universe-Worksheet-Answers-update.pdf (208.44 KB)

A photo of the NASA deep field, a patch of space filled with hundreds of small galaxies — This image from the James Webb Space Telescope shows the galaxy cluster SMACS 0723 teeming with thousands of galaxies.
Credit: NASA, ESA, CSA, and STScI

Approx Duration

15 - 30 mins

Have a go

Before you start:

Download the 'Create an Expanding Universe' worksheet above.
Assemble your equipment
Follow the instructions in the worksheets to fill in your table of results

Now follow the instructions on the worksheet:

Select your “Milky Way” colour sticker. Fill the colours of your stickers into the table
Blow the balloon up at little bit, and stick your dots all over the balloon
Use the string and ruler to measure the distances from the Milky Way dot to each of the other dots
Now blow the same balloon up fully while timing how long it takes to expand
Repeat your measurements for each dot
Calculate the speed at which your coloured dots have moved
Plot a graph of the speed and distance of each coloured dot
Add a line of best fit to the points on your graph
Answer the questions on the worksheet

If you liked this, why not try

How is the Universe Expanding?

Make Your Own Spectroscope

Have a go

About Us