Yesterday, the Library of Congress digitized a treasure trove of materials from Carl Sagan’s life—including early Cosmos drafts, NASA proposals, correspondences with Neil deGrasse Tyson, audio recordings, and over 30 minutes of home movie footage.

In lieu of this momentous occasion, they’ve also created a showcase of over 300 historic items exploring connections between the legacies of Carl, Galileo, H.G. Wells, and many others.

Discover “Our Place in the Cosmos

Message From the Moon

At first glance, these probably come across as little more than hastily painted watercolor sketches of the moon. That’s precisely what they are, actually. Attractive, yes, but certainly not high art.  

But hiding in their shadows lies a greater significance. The squiggled edges of that bleeding ink bear an observation that altered the heavens themselves. Or at the very least, our view of them.

The hand that traced these orbs belonged to none other than Galileo Galilei. They were included in his 1610 work Sidereus Nuncius (“The Sidereal Message”, which would make a great band name), the first scientific text based on telescope observations. To understand the significance of his illustrations, it helps to understand the world in which he drew them.

In 1610, cosmology, not that it had much to show for itself as a science, was still based on the ideas of Aristotle, who by this time had been dead for 18 centuries. So current! Copernicus’ observation that the Earth orbited the sun, first published in 1543, had begun to challenge Aristotelian supremacy, it wasn’t exactly a popular idea. 

Aristotle’s cosmological beliefs were based on the idea that the heavens were made of a perfect substance called “aether”, and therefore the circular motions and spherical shapes of heavenly bodies were also perfect. Earth, he claimed, was inherently imperfect, as were all the things that existed upon it. Everything in the heavens was awesome, and Earthly matter was inherently “just okay”, even if its name was Aristotle. This was one of the reasons people found Copernicus’ claims so hard to swallow. The imperfect Earth among the perfect heavens? Heresy!

Enter Galileo and his humble 20x telescope, in 1609. At the time, in Aristotelian fashion, the moon, being of the heavens, was assumed to be a perfect sphere, its dark and light areas just splotches upon the billiard-ball-smooth lunar surface. I imagine it took Galileo about 7 seconds of lunar observation to realize that was not the case.

The terminator, that line that separates the moon’s illuminated face from its dark one, is jagged as a crocodile’s smile. I’ve seen it myself through modern telescopes, and I must say, it’s really something to witness how light and shadow break over a distant crater’s edge. Galileo painted this in his sketches above, inferring that the moon in fact had a rough and crater-marked face. This meant that not only was Earth not the center of the universe, as Copernicus had shown, but the heavens themselves were imperfect, just like Earth.

Scientists would go on to realize that the orbits of heavenly bodies were not perfect circles, nor were the bodies perfect spheres, and that everything up there is made of the same stuff as everything down here. It was either a huge demotion for the heavens, or a great promotion for Earth, I’m not sure.

Galileo’s Sidereus Nuncius also included newly detailed maps of the constellations and the mention of four moons of Jupiter (although detailed observations of those were still centuries away), but it was his drawings of our moon that bore the most impact on future astronomical science, realigning the heavens with a single stroke of the brush.

Keep on drawing, and keep on looking up.

(You can read an English translation of Sidereus Nuncius here. If you’re hungry for more selenology, tour through these historical maps of the moon. Tip of the telescope to Steve Silberman for tweeting these sketches.)

On January 7, 1610, Galileo first observed the moons of Jupiter – his most significant contribution to modern science – through a homemade telescope and recorded what he saw in his journal. This seminal observation was pivotal evidence that everything did not revolve around the Earth.

Galileo would go on to spend a lifetime, and risk his life, defending this centerpiece of modern science against the church.

Happy Birthday, Galileo Galilei, born February 15, 1564.  

On the nights of January 7/8, 1610, Galileo Galilei noted in his notebooks the discovery of the first 4 Jovian moons, which he named after the powerful Medici family, naming them Medicean I, II and III.  The name Europa (second from right) comes from Greek mythology-Europa was abducted by Zeus (the Greek name for Jupiter) in the form of a bull and bore him many children.  Io (the yellow moon on the left) is also named for a child of Zeus (Jupiter) the daughter of Inachus, who was raped by Jupiter. Jupiter, in an effort to hide his crime from his wife, Juno, transformed Io into a heifer.  Calllisto (on the far right) was named for another seduction of Jupiter.  Callisto was the daughter of Lycaon, who was a follower of Artemis, famous as goddess of the hunt and for her chastity.  To punish Callisto for lying with Jupiter, Artemis banished her.  Without protection, Jupiter was forced to change Callisto and her son into bears to hide them from his wife Hera’s fury.  Eventually, Jupiter placed them both in the sky as the Ursa Major and Minor, the Big and Little Bears (known today as the Big and Little Dippers).  Ganymede (largest moon pictured here, third from right) was the fourth moon discovered by Galileo, named for the shepherd boy known for his incredible beauty and kidnapped by Jupiter.  These names would not become common for several hundred years.  Today, Jupiter has fifty named moons:

1. Io  2. Europa 

3. Ganymede 
4. Callisto 
5. Amalthea 
6. Himalia 
7. Elara 
8. Pasiphae 
9. Sinope 
10. Lysithea 
11. Carme 
12. Ananke 
13. Leda 
14. Thebe 
15. Adrastea 
16. Metis 
17. Callirrhoe 
18. Themisto 
19. Megaclite 
20. Taygete 
21. Chaldene 
22. Harpalyke 
23. Kalyke 
24. Iocaste 
25. Erinome 
26. Isonoe 
27. Praxidike 
28. Autonoe 
29. Thyone 
30. Hermippe 
31. Aitne 
32. Eurydome 
33. Euanthe 
34. Euporie 
35. Orthosie 
36. Sponde 
37. Kale 
38. Pasithee 
39. Hegemone 
40. Mneme 
41. Aoede 
42. Thelxinoe 
43. Arche 
44. Kallichore 
45. Helike 
46. Carpo 
47. Eukelade 
48. Cyllene 
49. Kore 
50. Herse 

and an additional 16 provisional moons:

1. S/2003 J2 
2. S/2003 J3 
3. S/2003 J4 
4. S/2003 J5 
5. S/2003 J9 
6. S/2003 J10 
7. S/2003 J12 
8. S/2003 J15 
9. S/2003 J16 
10. S/2003 J18 
11. S/2003 J19 
12. S/2003 J23 
13. S/2010 J 1 
14. S/2010 J 2 
15. S/2011 J1 
16. S/2011 J2 

All images courtesy NASA.  Thanks also to NASA for additional historical background

In 1610 Galileo looked through a telescope and sketched the first detailed map of the moon. Here it is compared with a photograph of the same view. .


Galileo’s moon sketch from Sidereus Nuncius, the first published scientific work based on observations made through a telescope.