If there’s nothing around to block our view, 5 kilometres (3.1 miles) is the furthest we can see. Atmospheric moisture, dust or smoke can reduce our visibility, but for the most part, everything we can see happens within an area of just 80 square kilometres. The higher up we go, the further we will be able to see. So how much of the Earth can we actually see at once? This video from Vsauce explains.