In this clip from Genius by Stephen Hawking, learn how many galaxies there are in the visible universe. The three volunteers are presented with an ultra-deep field image taken by the Hubble Space telescope. This square foot images states there are 10,000 galaxies in the image. Using a telescope and a surveyor's wheel, the volunteers must get the image to scale with the viewfinder of the telescope and calculate the distance between the image and the telescope. This will give the volunteers the radius needed for an equation to work out how many Hubble Images it would take to calculate the surface area of a sphere. When the volunteers have worked this out they will be able to work out how many galaxies are in the observable universe.