Galileo Galilei was an Italian mathematician, astronomer, and philosopher.
In 1609, Galileo was in Venice to show the Doge his telescope when he encountered the First Doctor, Steven Taylor, and Vicki Pallister, who had come to Venice responding to a mysterious invitation. Since the Doctor required Galileo's assistance at the same time he was scheduled to demonstrate the invention, Steven had to impersonate Galileo by means of a holographic disguise. The Doctor also helped Galileo improve his telescope design. (PROSE: The Empire of Glass)
He told him he should remain quiet about some of his ideas that would be seen as heretical. (AUDIO: The Galileo Trap)
The Eighth Doctor met Galileo later in his life, in 1639, after he had lost his sight. (AUDIO: The Galileo Trap) Galileo later saw the effects of the Eleven's stellar manipulator on the sun, believing it to be the end of the world. (AUDIO: The Satanic Mill)
The only complete transcript of Galileo Galilei's trial was kept in the Library of St John the Beheaded. (PROSE: All-Consuming Fire)
References 
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Professor J. P. Kettlewell mentioned Galileo while speaking about unappreciated scientists with the Fourth Doctor. (TV: Robot)
In the late 15th century, the Fourth Doctor noted, while using Giuliano's telescope, that in another fifty years they could have used Galileo's. (TV: The Masque of Mandragora)
The Fourth Doctor thought Galileo would be impressed by in-station fusion satellites, devices used as artificial suns. (TV: The Sun Makers)
Sarah Jane Smith said that she didn't think that Galileo and Copernicus were carrying out experiments in the paranormal. (TV: The Lost Boy)
In the 23rd century of a parallel universe, a shuttlecraft attached to the USS Enterprise (NCC-1701) was named Galileo. (COMIC: Assimilation²)
Behind the scenes Edit
Galileo appeared in the Doctor Who Annual 1970 feature A Matter of Gravity, which described his 1589 experiments on gravity at the Leaning Tower of Pisa.
