Galileo Galilei discovered phases in Venus -- pretty much proof of a heliocentric solar system -- in 1610 September.
By looking into space with the telescope.
Galileo
Galileo
The popular answer to this question would be Galileo. However, contrary to popular belief Galileo did not invent the telescope. He built his own telescope about a year after their initial creation and later made significant improvements.
By 1609 Galileo had a telescope that magnified 20x
Galileo saw in his telescope when it was 1995
Galileo
what is the comparison between Hubble telescope and Galileo telescope
galileo galilie improved the telescope
Why, the telescope, of course! Using his telescope, Galileo was able to make observations of the heavens in a way no one else was able to before.
galileo galileo
Galileo is credited with the invention of the Telescope. Galileo was Italian.