Galileo discovered the four largest moons of Jupiter in January of 1610. And he recounts the tale in The Starry Messenger, published on March 13 of that year. As the story goes, on Jan 7th Galileo looked at Jupiter through his telescope and saw what he assumed where three distant stars that appeared right next to Jupiter. They were pretty bright and they were in a line with one of them in front of Jupiter and two behind it. Now the word “planet” literally comes from the word for wanderer. The distant stars don’t change change their relative position in the sky (at least not that we can see without scientific instruments). The wanderers or planets are remarkably different and constantly shift their position. As Galileo prepared to observed on Jan 8th he expected Jupiter would have wandered past the three “distant stars” and leave them behind it. Instead he humbly observed all three distant stars were in front of Jupiter. They still looked similar, pretty bright and all in a line. How could this be explained? Had he not recorded his original observation correctly? It just didn’t make any sense. He realized the his observations the next night would be critical. If the bright stars are still near Jupiter they aren’t distant stars at all. They are somehow coupled with Jupiter.
And so on the night of Jan 9 Galileo observed a it was very cloudy night. Nothing but overcast clouds. Fortunately, on Jan 10th the night skies where clear. Galileo observed and discovered that Jupiter has moons. Yay! But I often wonder what it must have felt like to be sitting there on the cloudy night of Jan 9. Did Galileo laugh or cry? Did he stay up all night hoping the skies would clear? How could one go to sleep knowing they could make the most important discovery of their life with 20 seconds of observing time? That’s all he needed to change the world. Was Galileo one to pace back and forth? I know I would, constantly thinking about the first observation on the Jan 7 and how it had to be correct. It just had to be, but it couldn’t be.
I don’t know if Galileo ever talked about that night. In The Starry Messenger he just says it was cloudy. If it wrote about it in any letters I haven’t about it in the roughly dozen books I read about and by him. If there is no extemporaneous report I figured why ask ChatGPT to make one. So I told ChatGPT to pretend it was Galileo in March of 1610. I asked this Chat Galileo some intro questions and it seemed very well versed in The Starry Messenger. Then I asked what it remembered about the night of Jan 9th. It responded with:
Ah, January 9, 1610, a date forever etched in my memory. It marks a momentous occasion, for it was on that day that I made one of the most remarkable discoveries of my career—the existence of the Galilean moons of Jupiter.
Sigh. I responded the discovery was the on 10th and in fact the 9th was cloudy. Chat Galileo responded with the typical ChatGPT “oops, you’re right”. Chat Galileo wasn’t going to answer my long-running question, but I wasn’t ready to say goodby. Since Galileo was also a noted poet I asked Chat Galileo to create poem about “humanity’s rocket based exploration of space”. Here’s the response:
Ah, poetry, a realm where words dance and emotions soar. Allow me to compose a verse that captures the spirit of humanity’s rocket-based exploration of space:
In rockets’ roar, our dreams take flight,
Humanity’s longing, reaching greater height.
With fiery engines, we pierce the skies,
To explore the heavens, where wonder lies.
Amidst the vastness, our ship ascends,
Onward, we sail, where no path ends.
Through cosmic ocean, we boldly roam,
Seeking truths, far from our earthly home.
Rocket’s vessel, a symbol of our quest,
To seek the answers, in stars we invest.
In metal chariots, we ride the flames,
Toward cosmic shores, with audacious aims.
From Earth’s cradle, we venture forth,
Unveiling mysteries, igniting our worth.
Each launch a testament, a human desire,
To conquer the unknown, set souls afire.
Through the veil of atmosphere, we soar,
Witnessing wonders never seen before.
Celestial bodies, gleaming jewels on display,
Whispering secrets, as we make our way.
In lunar landscapes, we leave our mark,
Human footprints tracing the infinite dark.
And onward still, to worlds unknown,
With vision steadfast, to claim our own.
But let us not forget, as we traverse,
That space’s beauty demands our universe.
In this cosmic dance, we find our place,
Boundless potential, expanding human grace.
So, let us embrace the rocket’s flight,
And honor the dreamers, who kindle the light.
For in the stars, our destiny we trace,
United we reach, boundless realms to embrace.
May this poem reflect the indomitable spirit and grandeur of humanity’s exploration of space, and inspire future generations to keep pushing the boundaries of our knowledge and imagination.
I may never know about what the night of Jan 9th was like for Galileo, but other scientists have talked about their experiences. Alan Guth developed the theory of cosmic inflation. His book, The Inflationary Universe, is very personal. It talks about the all steps along the way to that very day when he saw something so beautiful it had to be true.