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The Development Team

Recreating Galileo’s Discovery: 400 Years Later

January 7, 2010 —
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Four hundred years ago, on January 7, 1610, Galileo pointed his telescope at the planet Jupiter and discovered that it had its own moons. This discovery changed our perspective on the universe.

Prior to Galileo’s discovery, the Earth-centric Ptolemaic system was the standard view of the cosmos where Earth was the center–heaven was above and Earth was below. Copernicus had proposed a heliocentric model, but it was a mental exercise meant to simplify the complicated Ptolemaic system. Galileo’s discovery was the first one that showed evidence that something was orbiting a body other than Earth. If Jupiter had things in orbit around it, why couldn’t other bodies?

At the time telescopes were cutting-edge, and only a few people had them. What Galileo did was an instructive example on how to combine technology and curiosity.

Today you can recreate the moment with today’s technology by typing “Jupiter” into Wolfram|Alpha.

Among the pods about Jupiter, there is a graphic showing the current configuration of the so-called “Galilean moons”, the ones Galileo saw 400 years ago: Io, Europa, Ganymede, and Callisto.

Type “Galilean moons” to find out more about them. Or for historical curiosity, try “January 7, 1610” and find out more about that day.

You can even virtually recreate Galileo’s observations for yourself. Here’s how he depicted what he saw 400 years ago on the night of January 7:


And here is what he saw a few days later:


In Galileo’s diagrams, the circle represents Jupiter, and the asterisks represent the moons he observed. He didn’t know they were moons until the second observation, when they had changed position.

Here’s what the venerable scientist would see tonight from Padua, courtesy of the input “Jupiter from Padua January 7 10pm” in Wolfram|Alpha:


Galilean moon configuration on January 7

Using the same input construct for the two following nights, our virtual discoverers would see the following:


Galilean moon configuration on January 8


Galilean moon configuration on January 9

Of course, when it comes to discovering things with new technology, we have our own big story. Our company founder, Stephen Wolfram, has spent the past 30 years exploring the computational universe… and in 1984 he made what he considers his greatest single discovery when he pointed not a telescope, but a computer, at the computational universe, and discovered the “rule 30” cellular automaton.

For Stephen Wolfram, that discovery launched what became his A New Kind of Science, provided part of the foundation that made Wolfram|Alpha possible, and is steadily expanding in influence across science, technology, and the arts.

Where will Stephen Wolfram’s discovery lead in 400 years? Galileo’s discovery of 1610 in many ways launched modern exact science, and led to the technology of today. Stephen Wolfram’s discovery seems to be leading us to a new kind of science—and new kinds of technology, like Wolfram|Alpha.


I don’t wanna sound mean, but I think it’s somewhat ballsy to compare yourself to Galileo.
Though I will admit, you might be the next big scientist.

Posted by BlockJuice January 7, 2010 at 8:34 am

“If I have seen further it is by standing on the shoulders of Giants.”
Sir Isaac Newton

Posted by Johann Rosario January 7, 2010 at 9:46 am

Amazing article. I especially like the two drawings of Galileo and his subsequent realization that what he was observing were in fact moons.

Let us hope you can lead us even a fraction of where Galileo took mankind. For that would truly be a worthy accomplishment for any man.

Posted by Adam777T January 7, 2010 at 6:56 pm

Great info. I think it is wonderful to look at how people who redefined the world thought. By adopting the same ways of thinking, we can do the same.

Posted by George January 7, 2010 at 9:34 pm

Another thing that Galileo did with his telescope was measure the approximate height of the mountains on the earth’s moon.
He did it using some fairly simple mathematics, and I have described his calculations in a blog post:

Posted by curiousCharacter January 9, 2010 at 2:52 pm

I wonder what Wolfram considers to be the simplest program he has looked at to exhibit complex behavior? Would it be a cellular automata, or might he for example consider say, some turing machine or perhaps a cyclic tag machine to be simpler?

Posted by Eric Parfitt January 9, 2010 at 10:53 pm

This blog entry by a veritable Braggadocio, “The Development Team”, is such painful reading. Apart from the hubris, it should have been edited more closely. The description of the tripartite Ptolemaic system has “Earth” as two of the three parts, and ‘today’ is repeated in “Today you can recreate the moment with today’s technology.” By the way, John of Salisbury ascribes the wisdom on nanos gigantum umeris insidentes to Bernard of Chartres. Newton was merely quoting it.

Posted by Christian January 14, 2010 at 2:22 pm

Thank you for this contribution! But my question is: can i generate this configuration scheme with Mathematica, V7.0 (maybe by the help of “AstronomicalData”)?

Kind regards from Germany,

Posted by Armin January 19, 2010 at 6:31 pm