Galileo’s Telescope: the 400th Anniversary, August 25, 1609

August 25, 1609, Galileo presented a telescope identical to this one to the Doge of Venice. First thought to be primarily of military value, very soon Galileo pointed his scope at the moon over Venice. Modern astronomy was born, and by 1610, he had proven the Copernican model of the sun-centered universe relegating the Ptolemaic geocentric model to history. He was hailed as a genius and a hero.

Galileo's Telescope, 1609. The objective lens was only about 2" with 2-3X magnification. He soon made improvements and bigger scopes up to 20X.

And what of the conviction for heresy in 1633? The mantra repeated by astronomers and scientists alike is Galileo was convicted of heresy for believing in the Copernican model, where the Sun is the center of the universe (it would take some more time for astronomers to properly define the Solar System). That is not historically accurate. Wade Rowland, in his book, Galileo’s Mistake shows quite convincingly by analyzing the letters and transcripts of the trial, that, in one very real respect, Galileo’s ego got him into trouble. When Galileo published his apology for Copernicanism, Dialogue on the Two Chief World Systems, Ptolemaic and Copernican, commonly referred to as The Dialogue, he went much further than just presenting the arguments for both theories. He challenged the authority of the Church. Rowland writes,

The problem was that as Galileo framed the dispute, its resolution demanded nothing less than the Church’s acquiescence in the dismembering of philosophy into two separate disciplines, moral and natural. And it demanded religion’s complete withdrawal from the field of science and the interpretation of scientific knowledge. Here was the ultimate challenge to the Church’s authority, beside which all others paled (p. 258).

The photo below gives a good sense of scale when the telescope was put on display at the Franklin Institute in Philadelphia in April 2009:

: Show is Galileo Galilei’s telescope, during a press preview for the Galileo, the Medici and the Age of Astronomy exhibition at The Franklin Institute in Philadelphia, Thursday, April 2, 2009. (AP Photo/Matt Rourke)

And here I am in the backyard in January 2008 with my “small” Orion Apex 90mm (3 1/2″) Maksutov-Cassagrain telescope (freezing my a— off, by the way; the temp was 28 degrees F.), that has the ability to see details that Galileo could only dream about, with a magnification range, depending on which eyepiece I use, from 48-160X. He would have been stunned. And my 90mm is a mere toy compared to the scopes that are available to amateurs, with refracting telescope lens up to 6 inches in diameter, and mirrors for reflecting telescopes up to 18, even 24 inches if you have the cash. (If you go to my link “About Extreme Thinkover” there is a picture of me with my Meade 6″ Newtonian reflector.)

David in the Backyard Observing with his Orion Apex 90mm Maksutov-Cassagrain Telescope

Finally…How far we have come in 400 years:

Galileo's Telescope & the Hubble Space Telescope. Photo: Institute and Museum on the History of Science. A replica of the telescope was launched aboard Space Shuttle STS 125 in May 2009.

For information about the Galileo Telescope aboard STS-125, click here.

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