Top Eleven: Galileo Galilei

The first and oldest of the experiments in the Top Eleven is actually a two-fer: Galileo Galilei is nominated both for the discovery of the moons of Jupiter, and for his experiments on the motion of falling objects.

Who: Galileo Galilei (1564-1642), the great Italian physicist, astronomer, and general Renaissance man.

When: He’s known to have made the first observations of the moons of Jupiter around 1610. The dates of the experiments on accelerated objects are fuzzier, but around the same time.

What: Shortly after obtaining a telescope (after its invention by Dutch astronomers), Galileo began observing just about everything there was to observe. He discovered the mountains of the Moon and the phases of Venus, made early measurements of sunspots, determined that the Milky Way was made of stars, and may or may not have spotted Neptune without realizing the significance.

The most significant of his astronomical discoveries was the observation of the four largest moons of Jupiter. Using his telescope, he notices a set of small bright objects associated with Jupiter, and observed that they moved in and out of view. He correctly attributed this to their orbiting the planet, and occasionally moving behind it. This turned out to be a discovery that would cause a great deal of trouble for a great many people.

As for the motion of objects, the legend of Galileo dropping balls of different masses off the Leaning Tower of Pisa is almost certainly not true, and anyway, he wouldn’t’ve had the timing accuracy to do much with actual falling objects. He did, however, realize that similar information could be gained by rolling objects of different masses down ramps. This slows their motion down to a level that could be accurately timed with the technology of the 1600′s, and allowed him to observe that the distance moved by an accelerating object in a given time scales as the time squared.

Why It’s Important: The discovery of the moons of Jupiter turned out to be a huge point in support of the heliocentric model of the Solar System, that is, the idea that the Sun is stationary and the planets revolve around it. This directly contradicts the accepted model of the time, that held (on the basis of Scripture and Aristotle) that the Earth was stationary, with the Sun, Moon, stars, and planets revolving around it.

If Jupiter had its own set of moons, then that was a major blow to the theory that the Earth was unique. If Jupiter can have satellites, there’s no reason why other bodies can’t orbit the Sun, and thus the heliocentric model gains some credence. This got him into a world of trouble with the Church, which had a great deal invested in the geocentric model at the time.

The experiments on the motion of objects were less splashy, but are arguably some of the very first experiments recognizable as science in the modern sense. He set out to measure a physical phenomenon, devised an experiment that would let him do what he wanted, and came up with a mathematical relationship to describe the results.

His results and his experimental approach would lead in time to the work of Isaac Newton (famously born in the year of Galileo’s death), whose Principia Mathematica was deemed the Greatest Physics Paper by the folks at Cosmic Variance.

Reasons to Vote for Him:: More or less the first modern scientist, put a thumb in the eye of the Catholic Church, inspired a pretty good Indigo Girls song.

Reasons to Vote Against Him: Cited by every crackpot with a Theory of Everything and a persecution complex, inspired an Indigo Girls song.

Comments

  1. #1 Scott Spiegelberg
    January 24, 2006

    Most importantly, Galileo’s father was Vincenzo Galilei, an important Renaissance musician who helped usher in the Seconda Practica.

  2. #2 Roman Werpachowski
    January 25, 2006

    Reasons to Vote for Him:: More or less the first modern scientist
    What about Copernicus?
    put a thumb in the eye of the Catholic Church
    Now that’s pure politics. How about voting for Fritz Haber? He “irritated” a lot of people, too.

  3. #3 Chad Orzel
    January 25, 2006

    Reasons to Vote for Him:: More or less the first modern scientist

    What about Copernicus?

    These reasons aren’t entirely serious. And anyway, I said “more or less”…

    put a thumb in the eye of the Catholic Church

    Now that’s pure politics.

    Sure.
    But taking cheap shots at the Church seems to get PZ a lot of traffic, so I figured, what the hell?

    And really, they were way off base on the whole geocentric model thing. They needed to be poked in order to make the modern world possible.

  4. #4 Roman Werpachowski
    January 26, 2006

    Who’s PZ?

  5. #5 Roman Werpachowski
    January 26, 2006

    And really, they were way off base on the whole geocentric model thing.
    AFAIR, their main grudge with Galileo was not about that only about some theological issues.

  6. #6 Bob Oldendorf
    January 28, 2006

    Roman: “PZ” = “PZ Myers”, a biologist and a blogger who’s been at the forefront of America’s fight to keep religion out of science education.

    Chad: One thing I’ve never understood about Galileo’s “discovery” of the moons of Jupiter is that – under ideal conditions – they are naked-eye objects. I mean, I’ve seen them (with my eyeglasses), and I’m as blind as a bat, and I’m watching under modern conditions (presumably through more light polution and haze than in pre-Edison/pre-Ford centuries).

    What’s up with that? did the entire ancient world need glasses?

  7. #7 Chad Orzel
    January 29, 2006

    Chad: One thing I’ve never understood about Galileo’s “discovery” of the moons of Jupiter is that – under ideal conditions – they are naked-eye objects. I mean, I’ve seen them (with my eyeglasses), and I’m as blind as a bat, and I’m watching under modern conditions (presumably through more light polution and haze than in pre-Edison/pre-Ford centuries).

    I suspect that it’s a matter of making repeated observations over a period of weeks or months, to establish that the moons are always near Jupiter, but change positions (and sometimes vanish behind Jupiter) in a way that indicates they’re orbiting. With the naked eye, it may be hard to sort out which things are moons and which are faint background stars.

    You’d have to ask an astronomer for a real answer, though.

  8. #8 Torris
    January 29, 2006

    Chad – I think PZ gets his high traffic for reasons other than “cheap shots”. It might have something to do with humor, writing style and knowledge about a lot of topics.

  9. #9 Peter Lund
    January 29, 2006

    “More or less the first modern scientist”

    Eratosthenes (size of the Earth)
    Aristarchus (sizes and distances of the Sun/Moon)
    Hipparchus (sizes and distances of the Sun/Moon)

  10. #10 Anonymous
    January 29, 2006

    With the naked eye, it may be hard to sort out which things are moons and which are faint background stars.

    I assume that’s it. It’s just remarkable that – for all the naked-eye astronomy that got done, in so many places — nobody before Galileo tried it. I mean, it’s not like millenia of astronomers weren’t closely watching Jupiter.

  11. #11 Bob Oldendorf
    January 29, 2006

    (Oh – that last (9:17pm) was me, the “remember me” box came unchecked))

    So it’s not strictly that Galileo “discovered” the moons of Jupiter — it’s that he realized that Jupiter’s just-visible companions WERE moons, in regular, predictable orbits around their primary.

    That’s not how it’s usually presented, but that’s an even more impressive discovery.

  12. #12 Joe Longtin
    February 20, 2006

    Galileo gets high marks and my vote for the degree of privation and suffering he endured as a result of his scientific work.

  13. #13 Joe Longtin
    February 20, 2006

    Galileo gets high marks and my vote for the degree of privation and suffering he endured as a result of his scientific work.

  14. #14 Zelah
    February 23, 2006

    Galileo is a shoein right?

    That is where my vote is going!

  15. #15 Gustavo Richmond
    February 27, 2006

    Galileo is the One, and The Men

  16. #16 katoey
    May 23, 2006

    Galileo did not discover any planets.. its now well documented that the mayans from Peru knew about every planet and moon in our solar system over 5000 years ago, even as a Thai ladyboy I know that

The site is currently under maintenance and will be back shortly. New comments have been disabled during this time, please check back soon.