In the footsteps of Galileo

August 15, 2009


This year, 2009, is the International Year of Astronomy. IYA2009 celebrates the 400th anniversary of the first observations of the heavens with a telescope, by Galileo in 1609.

It’s staggering how much Galileo did. If you look at the stuff out there that can’t be seen with the naked eye, he discovered a vastly disproportionate amount of it. Let’s break it down:

Milky Way

GALILEO, 1609-1612
Sunspots (= sun not perfect)
Moon craters and mountains (= moon not perfect)
Venus phases (= Venus circles sun, not Earth)
Jupiter’s moons (= bodies circling Jupiter, not Earth)
Saturn “appendages”
“Star” next to Jupiter (later shown to be Neptune)
Milky Way composed of stars (stars vastly more numerous than previously suspected)
Other bright patches composed of stars (ditto)

Saturn “appendages” are rings – Huygens, 1655
Saturn’s moons – ditto
Uranus – Herschel, 1781
Ceres (first asteroid) – Piazzi, 1801
Neptune recognized as a planet – Galle, 1846
Asteroid belt – several, 1850s
Pluto – Tombaugh, 1930
Rings and moons of outer planets – Voyager probes, 1970s-1980s
dwarf planets beyond Pluto – Mike Brown, 1990s-2000s

Basically, the eras are “stuff everyone knew from when we lived in caves”, “Galileo figures out most of how the solar system works in the space of three years”, and “working out the details”.


It’s all the more impressive when you realize that he was stuck with a 1″ telescope with a field of view of perhaps 5 degrees and a maximum magnification of 20x that, in the memorable words of someone I’ve forgotten, “suffered from every aberration known to optics”. As much as amateur astronomers complain about “department store trash scopes”, the worst plastic monstrosities sold as ‘educational toys’ are still about a thousand times better than what Galileo had to work with for his entire life.

Galileo did more than any other single person before or since to give us a perspective on the universe and our place in it. It’s a perspective that most people have little or no firsthand experience of. In an age when satellite TV is more than a generation old, mobile phones and dashboard computers can guide you around the world using GPS, remote controlled robots explore the surface of Mars, and mankind’s orbital population never drops below 6 (on the International Space Station), average citizens are strikingly disconnected from the wonders of the night sky. Too many people assume that looking up is the exclusive domain of professional astronomers, or that it’s too expensive, or too time consuming, or impossible under the glare of city lights.

2009-04-27 lights at night

None of these assumptions is accurate.

My ambition for this blog is to invite you to be at home in the universe. During the day we see only the world around us, but when darkness falls we can look out, see firsthand, and really get a gut-level understanding of our place in the cosmos. You can learn your way around the sky without spending a dime, and you will never be lost again. An ordinary pair of binoculars, which you probably have stashed in the closet already, will show you most of the wonders that first excited Galileo four centuries ago. If you decide to get a telescope, they are better designed, easier to use, and less expensive than at any time in history.

The slogan of IYA2009 is “The universe, yours to discover.” It is yours to discover, and it doesn’t take a lot of time or money to learn your way around the night sky and see the best and brightest that the heavens have to offer. The journey begins whenever you go out at night and look up. If you’re not sure where to start, that’s okay–that’s what this blog is for. Let’s go!


  1. […] boy. So all of three days ago I started this blog with a post entitled, “In the footsteps of  Galileo”, about Galileo’s  achievements, IYA 2009, and starting out in astronomy (image above from […]

  2. “Pluto – Tombaugh, 1830”

    Shouldn’t that be 1930…?

  3. Whoops! Fixed now, thanks for the catch.

  4. […] part of IYA 2009, last spring astronomers around the world, both amateur and professional, hosted a weekend of […]

  5. […] in the Lunar II and Galileo clubs (although I was also interested in the latter simply because Galileo was The Man). Last year my interest shifted to the deep sky (i.e., objects beyond the solar system: nebulae, […]

  6. 7 years after starting your blog, I finally arrive and am so glad your still active.
    As a new astronomer (2yrs) I value your blog and hope you don’t go away for a long time.
    Your informative and entertaining and an enjoyable read. Keep up the good work.
    Sorry I’d love to chat more but got to go, need to get to reading more, got a longs ways to go to catch up.

    Thanks for sharing!
    (Looking up from the frozen tundra of Eastern Colorado.)

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