What did the Hubble Space Telescope reveal?

The answer

Since its launch in 1990, the Hubble Space Telescope has revolutionized our understanding of the cosmos. The Hubble Deep Field, created by pointing the telescope at a seemingly empty patch of sky for 10 consecutive days, revealed over 3,000 galaxies in an area the size of a tennis ball held at arm's length. Later deep fields found over 10,000 galaxies. Hubble determined the age of the universe (13.8 billion years), proved that supermassive black holes exist in most galaxies, confirmed dark energy's existence, and captured some of the most iconic images in science history.