Create An Expanding Universe

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, 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
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