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Galileo on Galileo, Part I
Color painting of a spacecraft approaching Jupiter.
An artist's concept of the Galileo spacecraft arriving at Jupiter.

Editor's Note:As the Galileo spacecraft approached Jupiter in 1995, Galileo science team member Jean Aichele imagined how Galileo the man might sum up the spectacular results of the machine that carried his name to Jupiter. The team members imagined a follow-up letter in October 2009 on the 20th anniversary of the historic mission's launch.

17th century Painting of Galileo Galilei
Galileo Galilei

A Communique From Somewhere in Outer Space -- Overheard on the World Wide Web

Galileo Project Science Group

Project Scientist Torrence Johnson
Probe Scientist Rich Young

To My Esteemed Fellow Scientists,

From my current perspective, I have been steadfastly observing the travels of your spacecraft and my namesake, Galileo. How fortunate you are to live at such a time of discovery and truth seeking. Yes, Copernicus and his followers understood the Sun to be the hub of the revolving planets. But many of my contemporaries who accepted the Ptolemaic system believed that the Earth must be stationary, for if it moved, the Moon would be left behind!

We needed knowledge--and thirsted for it. To better view the sky, it occurred to me that Hans Lippershey's Far Looker device, so useful on the battlefield, might aid me. I set to work grinding the necessary lenses and with my own telescope (now 30 power) soon beheld that magnificent celestial body--Jupiter. It was a January night in 1610, so long ago! Imagine my surprise at seeing star-like bodies in the planet's immediate vicinity. My surprise became amazement during subsequent viewing when I saw that they followed Jupiter across the sky. You no doubt have read my notebook describing the change in their relative position over the following few weeks.

Black and white image of Galileo's journal.
Galileo's journal entry detailing his discovery of four moons orbiting Jupiter.

Here was the proof we followers of the Copernican theory needed: celestial bodies that are in motion can themselves be centers of motion. Yes, it is possible for the Earth to orbit the Sun and for our Moon to orbit the Earth. I realized that Jupiter and its moons (now named Io, Europa, Ganymede, and Callisto) could serve as a model, a miniature solar system. As you know, I made many observations and was rewarded with seeing the Sun's spots, peaks and valleys on our Moon, and, over time, the phases of Venus. How I longed to see more....

Yes, that was a beginning of sorts, but you are the future. For you, the Pioneers and Voyagers have pointed the way. Soon the Galileo spacecraft will be arriving at Jupiter with its host of instruments, each a marvel in itself. What wonders they will reveal! But it will be up to you to interpret and explain the data they provide. This is the pleasure of discovery and its awesome responsibility.

For me, the truth was costly. At first, only the science community took much notice of my celestial discoveries as reported in The Starry Messenger (1610), but 22 years later, my Dialogue Concerning Two Chief World Systems, admittedly biting in its sarcasm, caused quite a commotion. The contrast I drew between the Copernican and Ptolemaic systems clearly showed the folly of the old view.

Unfortunately, my refusal to follow the Church's requirements on teaching of the world systems led to my house arrest; it devastated me at the time, though it did allow me to focus my energies on the development of the scientific method. It has been my great satisfaction to note how the discipline of science has grown from that seed, influencing endeavors such as yours. While imprisoned I also had my poetry and my music. Always an inspiring companion, the lute comforted me much in those final days of blindness.

The times are different now. You may have seen the commemorative coin struck in 1982 to honor the 350th anniversary of the Dialogue. Moreover, in 1992, Pope John Paul II concluded a retrial of my case, wherein the Church upheld the rightness of my world view. Surely, this event has done much to heal the disharmony between science and religion since my first trial over 350 years ago.

In December, the maneuver for placing the spacecraft into orbit and the data received will once again show the watching world the simplicity, the beauty, and the power of the sciences, especially physics and mathematics. Who knows what will be learned from this exploration--undoubtedly, something of the evolution of our solar system--and possibly, the universe itself? On to Jupiter!

I remain forever your humble servant,

Galileo Galilei

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Last Updated: 24 January 2011

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Last Updated: 24 Jan 2011