365DaysDate:  January 10, 2009


Title:  Galileo Discovers Jupiter’s Moons; Going to Disneyworld

Podcaster:  Davin Flateau, University of Cincinnati

Description:  Galileo’s discovery of the moons around Jupiter in 1610 was literally an earth shattering revelation.  But would it land him on the front of the Venetian Wheaties box?

Links:  Davin’s website:  The Perfect Silence

Bio: Davin Flateau has been a planetarium director, writer, educator, and large format producer for over 20 years.  He is currently an astrophysics student at the University of Cincinnati.  He hosts the radio show “The Planetarium” about astronomy on the Cincinnati, Ohio airwaves, and is the founder of Aural Moon internet radio, one of the internet’s first radio stations.  His homepage is, and welcomes new Friends at Facebook.


This is your 10th day of astronomy for January 10.  This is Davin Flateau from

Galileo Galilei.  You know him, you love him.  The celebrated Italian renaissance astronomer’s name seems to be on everything these days, from space probes to dog bones.  If Galileo were alive today, he’d be making endorsement money that would put Tiger Woods to shame.  But then again, Tiger Woods was never called the father of modern science.

Cue the obligatory renaissance chamber music!

399 years ago today on a Sunday, this 45 year old father of three ventured out under the bright stars of a cold Italian night.  He was planning, as he had for the last few nights, to look at the planet Jupiter, which was shining in the west as the brightest star in the sky.  Galileo had just discovered that Jupiter was the father of three himself, sporting, as he later wrote “three fixed stars, totally invisible by their smallness.”  that was near the planet from night to night.  The first night, two of these little stars were on the east side of the planet, with one on the west side, all lining up in a straight line. But the next night, all three of the stars were on the west side of Jupiter, implying that Jupiter  – — was moving in the opposite direction it was supposed to.

But wait.  The stars roving around  in sky in the 17th century was like watching someone walk through a wall.   Everyone knew how Jupiter moved through the sky – you can just look up every night and see that.  So, if there wasn’t anything wrong with Jupiter, there must be something wrong with the Universe!

With one casual observation, the Universe had been turned upside down.

Maybe tonight would be the night to make sense of it all.

Galileo readied his notebook and pen, then pointed his homemade meter long wooden telescope tube toward the king of the wandering stars.  It was this telescope that made all of this possible.   A relatively new invention, he had only been making telescopes for the past 6 or so months or so, each time improving the design and magnification until he’d produced one that magnified objects a whopping 20 times their apparent size.  Galileo knew that no one had studied the heavens with such a powerful instrument so methodically.  This made him the sole keeper of the secrets in the sky that were “invisible by their smallness” to everyone else.

Galileo squinted through his telescope, and spotted Jupiter shining brightly in his view.  And there were his sheep, still clustered around the shepherd like the nights before.  He started counting..  One, two…  and… that was it.

Just two?  There were supposed to be three. First Jupiter seemed to be moving in front of the stars like crazy, now one of them is just gone?

Well, it didn’t take long for Galileo to figure out that Jupiter’s missing toddler was hiding behind the planet, and that all of these little stars were somehow moving with Jupiter as it moved through the sky.

Inconceivable!  The heavens were supposed to perfect, beyond any unpredictable changes.  Everyone knew that the sun and all the planets moved around the earth, so that the earth was the center of all motion for the entire Universe… and that was that.  The planets, or wandering stars, did not have wandering stars of their own.  Such an observation would be heresy against the Catholic Church, like the Copernican theory that the sun was the center of the solar system.  These three, now two tiny lights in the tiny end of a homemade wooden tube with glass lenses, threatened to shake the foundations of natural philosophy, and challenge the authority of one of the greatest powers of the known world.

Tonight raised even more questions, instead of answering them.  So, Galileo he did what every good scientist did – he continued to gather more evidence.  Galileo kept his nightly appointments in his role as the world’s first planetary Peeping Tom.

Over the next several nights, Galileo’s pen filled up his notebook with sketches.  The missing star reappeared from behind Jupiter.  Not long after that, a fourth very faint star appeared. And by January 15, Galileo had it all figured out.  These weren’t background stars, these tiny lights were other planets in orbit around Jupiter.  It was, in essence, another miniature Universe going around our own.  The earth was not the only object to have a moon, and this was a huge boost to the idea that the earth, like Jupiter – was just another planet going around the sun.  Reality set in on Galileo – he was in big trouble – but for all the right reasons.  So was he crazy for revealing this?

Crazy like a fox!  He had been trying to get back to Tuscany where he grew up, and in a move reminiscent of awarding the naming rights for a new sports stadium today, Galileo named the new planets the “Medicean Stars” after his patrons in Florence.  Jupiter represented Grand Duke of the Medici family, and the four moons now represented the Grand Duke’s four sons.  And if that wasn’t enough, the eldest son that had just become the new Grand Duke, whom Galileo tutored as a child?  His name was Cosimo.

He laid out all of this and reported his findings in Sidereus Nuncius, or, the Starry Messenger, which was published in March of 1610, which described Jupiter’s new found moons, craters and seas on our own moon, where he argued that earth was just another wandering star around the sun, and an uncountable number of stars that Galileo had seen with his new telescope.

The Starry Messenger was a huge success, and made Galileo an instant celebrity.  It kick started a revolution in astronomy that continues to this day.  As more telescopes pointed skyward, the Universe, and our place in it – would quickly change dramatically.

And it got Galileo back to Tuscany, as the Grand Duke installed Galileo in his court in Florence in a matter of months.

And got him into a lot of trouble.

The Roman Inquisition, which unlike the Spanish Inquisition, was not armed with comfy pillows, declared the theory that the sun being the center of the Universe was heresy.  Galileo was not to discuss such theories.  Later he got permission to discuss the idea as a mathematical theory, but then he pushed the Church too far when he published Dialogue Concerning the Two Chief World Systems which pitted the two ideas against each other two ficticious characters.  He was convicted of heresey, and ordered to house arrest for the rest of his life.

So, the moral of the story?

Publish your science where they have the comfy pillows.

For the 365 Days of Astronomy, this is Davin Flateau from

365 Days of Astronomy
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