They learned from books, Internet sources, university scientists and historians, and many other resources. As part of the project students performed experiments and built telescopes. They wrote poems about Galileo. The produced a newspaper that documented events of his time. They wrote books about Galileo's life and they shared those books and all they'd learned with K-2 students in the school.
Timelines are a great way to put the life of a famous historic figure in perspective.
But that's just one timeline application. Start with the everyday classroom resources. You might set an example this month by creating a timeline of events in the life of Martin Luther King. Read an encyclopedia account of his life and create a general timeline. To celebrate Presidents Day, create a timeline of events in the life of Abraham Lincoln or George Washington.