The Hubble Law tells us that our Universe is expanding. We observe galaxies, find their distances and their velocities, and find that they are all moving away from us. The more distant the galaxy, the faster it is moving away. From this information, we can estimate the age of our Universe. We assume that the Universe has always been expanding at the same rate, then we know how long distant galaxies have been travelling in order to get where they are today!
In this lesson we will use a balloon to simulate the expanding universe, and take measurements between "galaxies" to determine the time of expansion of our balloon universe.