The god problem and the moons of Jupiter

A double digit number has just blown me away. Here’s why:

A few years ago, when I was working on a book entitled, Falling for Galileo: A Romance With History, I read Galileo’s monograph, Sidereus Nuncius (“The Starry Messenger”), in which he reported excitedly on his first telescopic explorations of the moon and Jupiter.

It’s thrilling writing, even today and even to a scientific ignoramus, i.e., me.

Galileo noticed some small radiant dots around Jupiter’s perimeter, dots he decided to call “stars.” Four of them.

Over subsequent nights peering into his telescope from his rooftop in Padua, he was surprised to see that each dot individually would seem to disappear but then reappear on the other side of the planet, from which he deduced they circled Jupiter. They moved.

His inscribed observation, that orbs circled planets–along with his delighted description of our moon as not a smooth silver ball, a/k/a god-created perfection, but with mountains and craters–were the small stirrings of his inadvertent career as a heretic.

Those four “stars,” the first of Jupiter’s moons ever seen and cited by a human being, Galileo named after and dedicated to the Medicis, Tuscany’s reigning dynasty.

So today you can imagine how my breath was taken away by this, in 538 Significant Digits:


Three astronomers spotted two additional moons of Jupiter in images they took looking beyond the planet into the Kuiper Belt. This would bring the number of moons of the gas giant to 69. [Scientific American]

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