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Burn, string theorists, burn December 8, 2006

Posted by dorigo in astronomy, books, humor, physics, science.

Just a few pages into chaper 2 of Lee Smolin’s quite nice new book “The Trouble with Physics”, I could not help laughing. He spends time in the introduction to explain that he does not mean to harm string theory with his book, and that he himself has worked on the field. And he explains that Giordano Bruno was burned on the stake by the roman inquisition for proposing that the stars are nothing but far-away copies of our sun.

In chapter 2 he deals with the subject of unification. And indeed, Bruno’s hypothesis is a nice unifying idea: sun and stars are one and the same, they just appear different but they aren’t: stars are just much more distant. And then Smolin writes:

“… Of course, this was an opportunity to make a novel prediction: if you could measure the distances to the stars, you would find they were in fact much farther away than the planets. Had it been possible to do this in Bruno’s day, he might have escaped the fire. But it was centuries before the distance to a star could be measured. What Bruno had done, in practical tests, was to make an assertion that was untestable, given the technology of the time. Bruno’s proposal conveniently put the stars at such a distance that no one could check his idea.”

Quite nicely put. Continuing the quote:

“So, sometimes the need to explain how things are unified forces you to posit new hypotheses you simply cannot test. This, as we have seen, does not mean you are wrong, but it does mean that originators of new unifications can easily find themselves on dangerous ground.”

Very witty understatement… I think it is about time we start setting up the stakes. Those who burned Bruno were wrong, but they died happily ignoring the fact. Would I prefer to be Bruno or the Archbishop who had him light up, and then went to sleep merrily in the knowledge he’d done his duty ? Hmmmmmm….

More seriously, indeed Bruno’s idea was not only untestable, but it plainly violated Occam’s razor. Stars had to be quite farther away than any other thing in the then known universe, to save a line in the list of heavenly bodies. Times were not right for his idea to be brought forward. So let it be with string theory.



1. Tony Smith - December 9, 2006

Tommaso Dorigo quoted Lee Smolin as saying in his book “The Trouble with Physics”:

“… Had it been possible to … measure the distances to the stars … in Bruno’s day, he might have escaped the fire. …
What Bruno had done, in practical tests, was to make an assertion that was untestable, given the technology of the time.
Bruno’s proposal conveniently put the stars at such a distance that no one could check his idea. …”.

Huygens DID “measure the distances to the stars” using “the technology of the time”.

According to Carl Sagan’s book Cosmos (Random House 1980, at pages 143 and 190):
“… In Italy, Galileo … and Giordano Bruno … had been made to suffer brutally. But in Holland, the astronomer Christian Huygens … was showered with honors. …
Huygens drilled small holes in a brass plate, held the plate up to the Sun and asked himself which hole seemed as bright as he remembered the bright star Sirius to have been the night before. The hole was effectively (Huygens actually used a glass bead to reduce the amount of light passed by the hole) 1/28,000 the apparent size of the sun. So Siriius, he reasoned, must be 28,000 times farther from us than the Sun, or about half a light year away. … If he had known that Sirius was intrinsically brighter than the Sun, he would have come up with almost exactly the right answer: Sirius is 8.8 light-years away. …”

So, maybe the obliviousness of the Roman Church to Huygen’s measurement and hostility to Bruno
corresponds to
the obliviousness of the present-day superstring theory establishment to experimental data supporting of the non-supersymmetric standard model and hostility to competing physics models.

Tony Smith

PS – Measurement by parallax was not done until 1838 (for Alpha Centauri, Vega, and 61 Cygni).

PPS – By “obliviousness” of the present-day superstring establishment to “experimental data supporting of the non-supersymmetric standard model” I do not mean that they are unaware of such data, only that they choose to ignore such data in the sense that they do not demand of their models that their models must predict or retrodict by calculation such data.

2. dorigo - December 9, 2006

Hi Tony,

thank you for mentioning Huygens’ contribution, which I had once read about and long since forgotten… As always, yours is valuable input.

Anyhow, the church was lighter-happy in the days of Bruno… I doubt that by showing stars “only” had to be 28000 times farther than the sun he’d be saved from the grill. I actually think they would have burned him regardless.


3. Markk - December 10, 2006

“Huygens DID “measure the distances to the stars” using “the technology of the time”.”

The time being a couple of generations after Bruno was killed. Bruno died in 1600 Huygens was born in 1629. Now I know things went slower back then, but there was a LOT of technological progress and growth of understanding in that time period.

4. Tony Smith - December 10, 2006

As Markk said, it is true that Huygens made his measurement of distance to Sirius after Bruno was killed.
Carl Sagan (in the book Cosmos referenced in my earlier comment here) described Huygen’s method of measuring that distance as a “… way to mesaure the distance to the stars which the Ionians were fully capable of discovering, although as far as we know, they did not employ it. …”.

So, Carl Sagan was of the opinion that the Huygen’s method did NOT depend on “technological progress and growth of understanding in that time period” between the life of Bruno and the measurement by Huygens.

Tony Smith

PS – Carl Sagan’s reference to “Ionians” was made in the context of his discussion of the facts that “Aristarchus suspected the stars to be distant suns”, and that “In the manuscript of his book, Copernicus mentioned Aristarchus’s priority, but he omitted the citation before the book saw print”.
(The last two quotes are from page 189 of Carl Sagan’s book Cosmos (Random House 1980).

5. dorigo - December 10, 2006

However, I insist – Huygens’ measuring the distance of stars involves assuming stars are suns farther away, which is exactly what was to be shown… So I guess it wouldn’t have saved Bruno…


6. Tony Smith - December 10, 2006

T. is correct in saying that the Roman inquisition “… would have burned him [Bruno] regardless …”.

Since Galileo was found guilty and sentenced to house arrest even though he had telescopic observation of the moons of Jupiter,
probably even a parallax measurement of stellar distance would not have prevented Bruno’s execution,
perhaps the more interesting questions are political.
For example,
Bruno was initially a Dominican from Naples, but left both the Dominicans and Naples due to their hostility to his ideas, moving to safety in Northern Europe.
Then some events happened in the Venetian Republic about which I wish I knew more details.
About all know is that Bruno and Galileo both applied for the same job at Padua.
Galileo got the job, but did not hold it long and moved (against the advice of his Venetian friends) to Tuscany and then even went to Rome, thus falling into the hands of the Roman inquisition.
Bruno, having lost the Padua job to Galileo, took a job in Venice tutoring Mocenigo. However, Mocenigo got mad at Bruno and denounced him to the Venetian inquistion, which transferred him to the Roman inquisition where he was convicted and executed.

If Bruno had gotten the Padua job, and avoided personal animosity of Mocenigo, would Bruno have been able to live out his life doing his work?

Tony Smith

7. dorigo - December 10, 2006

Hi Tony,

thank you for telling the story here. I will look into the details of the story if I find the time: my father had a library with scores of books on the history of Venice, which he himself helped writing, although he dealt mostly with the years before 1400: “Venetia Origini”, “Venezie Sepolte nelle terre del Piave”, “Venezia Romanica”, and things stopped there, while he was collecting material for a “Venezia Gotica”.

I think I have all the material in my father’s library. I just need energy and time…


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