Of Particular Significance

Galileo’s Winter

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 01/28/2014

While the eastern half of the United States is having a cold winter so far, the same has not been true in Italy. The days I spent teaching in Florence (Firenze), at the Galileo Galilei Institute (GGI), were somewhat warmer than is apparently the usual, with even low temperatures far above freezing almost every night. A couple of people there said to me that they “hadn’t seen any winter yet”. So I was amused to read, on U.S. news websites, yet more reports of Americans uselessly debating the climate change issue — as though either the recent cold in the eastern U.S. or the recent warmth in Europe can tell us anything relevant to that discussion. (Here’s why it can’t.) It does seem to be widely forgotten in the United States that our country occupies only about 2% percent of the area of the Earth.

Of course the warmer Italian weather made my visit more pleasant, especially since the GGI is 20 minutes up a long hill — the Arcetri hill, of particular significance in scientific history. [I am grateful to the GGI, and the scientist- organizers of the school at which I taught, especially Stefania de Curtis, for making my visit to Arcetri and its sites possible.] The University of Florence used to be located there, and there are a number of astronomical observatories on the hill. And for particle physics, there is significance too. The building where I was teaching, and that hosts the GGI, used to be the department of Physics and Astronomy of the university. There, in 1925, Enrico Fermi, one of the greatest physicists of the 20th century, had his first professorial position. And while serving in that position, he figured out the statistical and thermodynamic properties of a gas made from particles that, in his honor, we now call “fermions”.  [His paper was recently translated into English by A. Zannoni.]

All particles in our world — elementary particles such as electrons and photons, and more complex objects such as atoms — are either fermions or bosons; the classic example of a fermion is an electron. The essential property of fermions is that two identical fermions cannot do precisely the same thing at the same time. For electrons in atoms, this is known as the Pauli exclusion principle (due to Wolfgang Pauli in 1925, based on 1924 research by Edmund Stoner): no two electrons can occupy the same quantum state. All of atomic physics and chemistry, and the very stability of large chunks of matter made from atoms, are dependent upon this principle. The properties of fermions also are crucial to the stability and structure of atomic nuclei, the existence of neutron stars, the electrical properties of metals and insulators, and the properties of many materials at cold temperatures.

Plaque commemorating Fermi's work on what we now call `fermions'. [Credit: M. Strassler]
Plaque commemorating Fermi’s work on what we now call `fermions’. [Credit: M. Strassler]
Inside the building is a plaque commemorating Fermi’s great achievement. But Fermi did not remain long in Florence, or even in Italy. A mere 15 years later, in the midst of the Fascist crisis and war in Europe, and having won a Nobel Prize for his work on radioactive atoms, Fermi had taken a position in the United States. There he directly oversaw the design, building and operation of humanity’s first nuclear reactor, in a secret underground laboratory at the University of Chicago, paving the way for the nuclear age.

But the main reason the Arcetri hill is famous for science is, ironically, because of a place of religion.

Both of Galileo’s daughters had taken the veil, and in 1631 the aging scientist was prompted to rent a villa on a small farm, within sight and a short walk of their nunnery.  Unfortunately, what must have seemed like an idyllic place to grow old and do science soon turned into a nightmare. After years of coexistence with and even support from within the Catholic Church, he had pushed too hard; his publication in 1632 of a comparison of the old Ptolemaic view of the universe, with the Earth at the center, with the newer Copernican view (to which he had greatly contributed, through his astronomical discoveries, in the 1610s), engendered a powerful backlash from some who viewed it as heretical. He was forced to spend 1633 defending himself in Rome and then living in exile in Sienna. When he was allowed to return to Arcetri in 1634, he was under house arrest and not allowed to have any scientific visitors. Shortly after his return, his 33-year-old daughter, with whom he was very close, died of a sudden and severe illness. His vision failed him, due to unknown diseases, and he was blind by 1638. Unable to go to Florence, his home town, scarcely three miles away, and rarely able to meet visitors, he spent the rest of his time in Arcetri isolated and increasingly ill, finally dying there in 1642.

Yet despite this, or perhaps because of it, Galileo’s science did not come to a halt. (This was also partly because of the his support from the Grand Duke of Tuscany, who interceded on his behalf to allow him some scientific assistance after he went blind.) At Arcetri, Galileo discovered the moon did not always present exactly the same face toward the Earth; it appears, to us on Earth, to wobble slightly. The explanation for this so-called “lunar libration” awaited Issac Newton’s laws of motion and of gravity, just 50 years away. And he finished formulating laws of motion (which would also later be explained by Newton), showing that (on Earth) objects tossed into the air follow a trajectory that mathematicians call a parabola, until affected by what we now call “air resistance”, and showing that uniform motion cannot be detected — the first Principle of Relativity, authored 270 years before Einstein presented his revision of Galileo’s ideas.

Vaulted ceiling in the main entry hall of Galileo's rented villa in Arcetri. (No, the light fixture is not original.) [Credit: M. Strassler]
Vaulted ceiling in the main entry hall of Galileo’s rented villa in Arcetri. (No, the light fixture is not original.) [Credit: M. Strassler]
To step into Galileo’s villa, as I did a few days ago, is therefore to step into a place of intense personal tragedy and one of great scientific achievement. One can easily imagine him writing by the window, or walking in the garden, or discussing the laws of motion with his assistants, in such a setting. It is also to be reminded that Galileo was not a poor man, thanks to his inventions and to his scientific appointments. The ceilings of the main rooms on the lower floor of the villa are high and vaulted, with attractively carved supports. There is a substantial “loggia” on the upper floor — a balcony, with pillars supporting a wooden roof, that (facing south-east, south and west) would have been ideal, while Galileo could still see, for observing the Moon and planets.

While Galileo’s luck ran badly in his later years, he had an extraordinary string of luck, as a younger scientist, at the beginning of the 1600s. First, in 1604, there was a supernova, as bright as the planet Jupiter, that appeared in the sky as a very bright new star. (Humans haven’t seen a correspondingly close and bright supernova since then, not even supernova 1987a.  There is one you can see with a small telescope right now though.) Observing that the glowing object showed no signs of parallax (see here for a description of how parallax can be used to determine the distance to an object), Galileo concluded that it must be further away than the Moon — and thus served as additional evidence that the heavens are not unchanging. Of course, what was seen was actually an exploding star, one that was nearly a trillion times further from the Earth than is the Moon — but this Galileo could not know.

Next, just a few years later, came the invention of the telescope. Hearing of this device, Galileo quickly built his own and figured out how to improve it. In the following years, armed with telescopes that could provide just 20-times magnification (typical binoculars you can buy can provide 10-times, and with much better optical quality than Galileo’s assistants could manufacture) came his great string of astronomical discoveries and co-discoveries:

  • the craters on the Moon (proving the Moon has mountains and valleys like the Earth),
  • the moons of Jupiter (proving that not everything orbits the Earth),
  • the phases of Venus and its changing apparent size as Venus moves about the sky (proving that Venus orbits the Sun),
  • the rings of Saturn (demonstrating Saturn is not merely a simple sphere),
  • sunspots (proving the sun is imperfect, changeable, and rotating),
  • and the vast number of stars in the Milky Way that aren’t visible to the naked eye.

One often hears 1905 referred to as Einstein’s miracle year, when he explained Brownian motion and calculated the size of atoms, introduced the notion of quanta of light to explain the photoelectric effect, and wrote his first two papers on special relativity. Well, one could say that Galileo had a miracle decade, most of it concentrated in 1610-1612— playing the decisive role in destroying the previously dominant Ptolemaic view of the universe, in which the Sun, Moon, planets and stars orbit in a complex system of circles-within-circles around a stationary Earth.

We live in an era where so much more is known about the basic workings of the universe, and where a simple idea or invention is rarely enough to lead to a great change in our understanding of our world and of ourselves. And so I found myself, standing in Galileo’s courtyard, feeling a moment of nostalgia for that simpler time of the 17th century, cruel and dangerous as it was… a time when a brilliant scientist could stand on the balcony of his own home, looking through a telescope he’d designed himself, and change the world-view of a civilization.

Looking across the enclosed courtyard of the villa, at the second-floor loggia, suitable for telescopic observing.  It is not hard to imagine Galileo standing there and peering into the sky.  [Credit: M. Strassler]
Looking across the enclosed courtyard of the villa, at the second-floor loggia. It is not difficult to imagine Galileo standing there and peering into his telescope. [Credit: M. Strassler]

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13 Responses

  1. Wonderful comments.

    Looking back at Galileo, he was a great scientist who also experienced a great deal of good luck. Of course, he made the most of that luck with his ambition, his intelligence and his unbounded self-confidence.

    As for his run-in with the Catholic church—complicated is the only way to describe it, along a certain amount of straight-up bad luck and, not least, some overreaching on his part. For instance, I’ve never heard of anybody besides his most ardent and least critical supporters who ever believed his theory of the tides*, and yet at least according to some accounts that was what Galileo considered the “smoking gun” that would overthrow contemporary orthodoxy. If true, that was a major mistake on his part. He accidentally set up a straw man that could be used (incorrectly and illogically) to discredit his other ideas.

    *His theory of the tides was just straight-up wrong, and his contemporaries knew it. Even then, educated folk besides Galileo knew perfectly well the tides were related, in some complicated way, to the moon. The more independent ones asked him to please not use tides as evidence because it was so very wrong and just muddied the waters.

  2. BTW, Pauli’s Exclusion principle is also responsible for stopping the gravitational collapse of white dwarfs. This effect is called electron degeneracy pressure, but it can only work for stars smaller than 1.44 times the mass of our Sun. This is the Chandrasekhar limit.

    Stars larger than this limit will become either neutron stars or black holes.

    Kind regards, GEN

    1. … & Two students of Chandrasekhar and Fermi at the University of Chicago, Chen Ning Yang and the above mentioned Tsung-Dao Lee, won the Nobel Prize in 1957, for their work in particle physics. 🙂 Quoting Matt’s words: “As for Chinese science; in the previous generation, the three great contributors to our understanding of the weak nuclear force (Tsung-Dao Lee, Chen-Ning Yang, Chien-Shiung Wu) all chose to work in the United States”

  3. It is always good to remember that Galileo’s conceptions of motion, and especially of our place in the Universe, were so radical that he was made to suffer for them. It is the nature of “the establishment”—whether historical or modern—to resist change.

    Notice also that Galileo’s astronomical observations facilitated our understanding of gravity-induced motion OVER the surfaces of large bodies like the Earth and Sun. Whereas his suggestion to probe the nature of gravitational motion INSIDE gravitating bodies has never been taken up.

    In his famous “Dialogue” there are three instances (UC Press 2nd ed., pp. 22, 227, 236) in which Galileo suggested dropping a cannon ball through the center of Earth to observe how gravity works inside matter. A hole through Earth is impossible of course. But with a modified Cavendish balance or an orbiting satellite Galileo’s experiment could be done fairly easily with modern technology.

    For all we know “about the basic workings of the Universe,” our knowledge of how gravity works inside matter is still based on guesswork and extrapolation. Why not fill this gap in our knowledge with empirical evidence? Why not carry out Galileo’s experiment? (Small Low-Energy Non-Collider)?

    Resistance from the establishment?

  4. Wow! Prose from a scientist! I had a strong suspicion you guys weren’t all clinical number crunchers. Now I have proof! Great job of capturing the wonder, Matt.

  5. Yes, I meant the move to Florence from Padua. The loss of his eyesight and daughter were of course great tragedies. What I find interesting is that just like Oppenheimer Galileo wanted to both save the world and please the politicians. Both underestimated the vindictiveness of the politicians and their relish for holding on to power. And thus both became martyrs (certainly in the public imagination).

  6. Nice article! It was an intense tragedy indeed. However it was tragedy that he partly brought on to himself by becoming greedy for political power and influence. His friend Sagredo implored him to stick to science but he declined. In this sense Galileo was intriguingly similar to Oppenheimer; both men could have kept on doing great science, but both wanted more, and both got burnt by their ambition.

    1. Well, I don’t think the loss of his daughter or of his eyesight had much to do with greed. As for whether he was greedy for power and influence, I’m not sure; he certainly desired that the church change its teaching, and when one of his supporters became pope, he thought he could succeed in winning the day. But there he badly miscalculated. [In the long run, of course, he won — and I’m sure he knew he would win, because he had facts on his side.]

  7. If you could have read Brecht’s play Galileo while in Arcetri, your experience of the dilemmas of Galileo’s life would be beautifully highlighted. Great work by Brecht.

  8. What a beautiful article !!! Thank you from Italy 🙂 You know, in a famous church of the center of Rome there is a statue of Galileo designed by the Nobel laureate Tsung-Dao Lee… Thanks again for this nice post

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