There are few famous plays about famous scientists. Bertolt Brecht's Life of Galileo, written from 1937 to 1939, is one. The opportunity to get Galileo's views on the play, which he has just seen, is a unique and poignant occasion. I started by asking him whether he had enjoyed the play.
Galileo Galilei: Of course I didn't enjoy it. I was mildly flattered that someone would write a play about me and was curious to see how I was represented. Do I really eat in so gross a manner? No, this is not an accurate reflection of what happened, the author simply used my life to promote his own ideas. That is wrong. If one uses real people in a play there is some obligation to depict them accurately. I find even the title annoying - Life of Galileo, as if my whole life was a battle with the church...
Lewis Wolpert: We'll return to that later. Can we first explore how you became interested in science.
GG: My father wanted me to study medicine and I started at the University of Pisa. But after hearing lectures on Euclid's geometry, I developed a passion for mathematics. My father insisted I must finish my medical studies but I left without a degree.
LW: But what made you want to apply mathematics to problems in physics?
GG: Ironically my father influenced me, he was a musician with an interest in mathematics. He investigated the tensions of musical strings and discovered a mathematical law. I also read Archimedes and was influenced by his studies on floating bodies and levers.
But I must return to the play. Brecht shows no understanding of science. In the first scene, he has me gabbling about a new age, with everyone questioning old certainties. What nonsense. Then there is a line where someone says, "we shouldn't have tried what is in the books, but should have looked for ourselves." Again, nonsense. If you look, it seems obvious that the earth stands still and the sun moves around it each day. No, science requires a sound knowledge of mathematics and a special mode of thought. To deal with matters scientifically, it is necessary to make abstractions from the concepts of weight and speed, which are infinitely variable. Brecht just wants to see our new science overthrowing the established political order. But the common man will never make contributions to science. It goes, unfortunately, against common sense. Even Aristotle understood this.
LW: Did the church object to your views on motion?
GG: No. My true enemies were the philosophers at that time, yet they do not get a mention in the play. The great Aristotle would weep to see what the philosophers have done with his philosophy. Have you interviewed him yet? I do not believe that he wished his ideas turned into irrefutable dogma.
LW: Why were the philosophers so against you?
GG: Because I exposed their ideas as empty dogma. Their aim was not to search for new understanding, but the preservation of Aristotle, virgo intacta. They were not interested in mechanism, but causes - by which they meant the ultimate purpose behind all events in nature. Following Aristotle, they thought in terms of the natural place for objects and this determined that stones fell, while steam rose. They were not interested in measurement, or laws, which describe in a quantitative way the motion of objects. They also believed that the heavens were quite different from the earth and that heavenly bodies were perfectly round and moved only in perfect circles. They were not the least interested in whether or not this was true. This is illustrated by their teaching that heavy bodies fall faster than light ones.
LW: Did you really drop weights from Pisa's tower?
GG: Yes. But of course I already knew the result. In fact there is evidence that Philoponus in the 6th century dropped weights and showed that Aristotle was wrong. And it is possible to prove by argument that a heavier body does not move more rapidly than a lighter one, provided both are of the same material.
LW: Why did it take so long for the falsity of Aristotle's views to be recognised?
GG: The philosophers were not interested in trying to describe nature or in discovering the laws of motion. They were interested in maintaining their own authority, as I have said. There is another point. If you carry out the speed-of-bodies experiment with a 100-pound ball and a one-pound ball, you do indeed find that the larger, when dropped from a height, arrives by two finger-breadths before the smaller. According to Aristotle, the difference in time of arrival should be very great. The two-finger breadth requires explanation and I did not provide it, but that does not save Aristotle. One has to live with uncertainties. Copernicus had difficulty explaining the phases of Venus, yet he put this to one side. With reason as his guide, he continued to affirm what experience seemed to contradict.
LW: You have said, "There is not a single effect in nature, not even the least that exists, such that the most ingenious theorists can ever arrive at a complete understanding of it."
GG: That is true. Full understanding can never come. True understanding is reserved for the intellect of the Divine. We can approach it, but never arrive. The closest we ever get is in mathematics.
LW: Were you convinced by Copernicus when you first heard his ideas?
GG: It completely changed my views of the heavens. It provided a much more elegant account of the motion of the planets than the Ptolemaic system. No, not convinced, startled and impressed.
LW: Brecht has you confirming the Copernican system with your telescope.
GG: That is again wrong. What I showed with my telescope was that heavenly bodies lacked the perfection ascribed to them by the philosophers. The moon is not a perfect sphere, but pitted with craters and mountains; there are satellites around Jupiter. The philosophers were enraged-the Aristotelians thought that celestial bodies were incorruptible, invariable, eternal and absolutely perfect.
LW: When did you first defend Copernican astronomy in public and why?
GG: The only time in print that I came out unequivocally in favour of Copernicus was in 1613 in my Letters on Sunspots. What clinched it was the discovery of the eclipses of the satellites of Jupiter. To predict such eclipses, one had to introduce a correction into the sun's motion, but if the earth moved round the sun no such correction was necessary and it was easy to predict the eclipses.
LW: Why did you only back Copernicus once?
GG: I had no incontrovertible evidence. There were still unsolved problems. I struggled to explain the tides. But I was convinced that the earth moved.
LW: Are you religious?
GG: Yes. I am a deeply committed Catholic. I am committed to the Catholic church because I believe it provides us with the rules for moral behaviour. I never wanted to come into conflict with the church and, on the contrary, it was my aim to protect it from a disastrous path.
LW: How do you mean?
GG: The church was setting itself up as the judge on the nature of the world. It was getting into an absurd position where it might have to defend views about motion that were contrary to the truth. That is not its function. It worried me that the church might find scientific ideas unacceptable. I did not care about the philosophers, but I cared about the church. St Augustine and St Thomas Aquinas had wisely tried to prevent faith from being in conflict with science. The Bible should not be used to make scientific judgements. To do so is to undermine its authority. The Bible, on scientific matters, has to be interpreted metaphorically. Aquinas foresaw this when he tried to deal with Averro?s, an Arab philosopher in Spain, who separated religious knowledge from scientific knowledge. Aquinas, by making religion compatible with Aristotelian science, resolved the problem only temporarily.
LW: Did you want the church to adopt the Copernican system?
GG: No! You have completely missed my point. I didn't want the church to take any position on such matters. It was outside its competence and irrelevant to its authority.
LW: Were you shocked when the works of Copernicus were banned?
GG: Shocked but not totally surprised. I had argued my case for the freedom of scientific enquiry in my Letter to Castelli. The Church made no objection to that view. However, Cardinal Bellarmine made it clear that I should tread cautiously and treat the earth's motion hypothetically. Again in my Letter to the Grand Duchess Christina (of the Medici family) I argued my case for separation: there should be no conflict between science and religion. But Pope Paul V was not sympathetic to intellectuals and decided on Bellarmine's advice to put the issue to the theological qualifiers.
LW: What did they say?
GG: They considered the proposition that the sun is the centre of the world and immovable. Then they censured this unanimously, saying that the said proposition is heretical since it contradicts the scriptures.
LW: What happened then? Did the inquisition proceed against you?
GG: Bellarmine informed me that the Pope had said that I was not to defend the propositions which had been censured. If I submitted without protest, then no further action would be taken. A member of the inquisition also present forbade me to teach such ideas. Bellarmine told me to ignore him.
LW: What did you do?
GG: I had no choice. I accepted. And I continued to work. I published The Assayer in 1623, in which I promoted scientific reasoning in contrast to the prevailing philosophy. I also spoke of the book of nature being written in the language of mathematics. I struGGled with the problem of the tides and presented the ideas to Pope Urban VIII several times. I made it clear to him that this required hypothesising that the earth moved. He seemed content with my approach although he refused to rescind the earlier edict. I wrote my book Dialogue Concerning the Two Chief World Systems - Ptolemaic and Copernican. I analysed the two systems and put forward my ideas on the tides. Incidentally, Brecht is confused-he has me investigating sunspots which I had done years earlier. The book was published in 1632. But then the inquisition stopped all sales.
LW: Why? You had a licence.
GG: It's hard to know. I was summoned to Rome where I was confident I could defend myself as I had obeyed the Pope's edict. But then I learned that the Pope's fury was based on the assumption that I had received an injunction not to teach Copernican ideas. I denied this and claimed I had conscientiously stuck to Bellarmine's injunction. I produced Bellarmine's signed edict, but it was no use. I was charged with heresy. They said that there was no chance of acquittal but that if I admitted to wrongdoing I would be treated leniently. I was condemned to indefinite imprisonment. I was devastated.
LW: Why did you recant?
GG: Not to have done so would have been too terrible. I would almost certainly have been tortured until I did recant. Here Brecht was correct. I was afraid of pain. Reconciliation also offered me the hope of continuing to do science.
LW: Were you ashamed of your behaviour?
GG: It is no shame to be afraid of torture and to save one's life. I could see no point in being a martyr. My whole life had been devoted to reason.
LW: But was not recantation a betrayal of science?
GG: Yes and no. Confessions made under duress cannot be taken as valid. But more important, science is never dependent on a single individual. It is a collective activity. I knew that scientific ideas could not be suppressed for any length of time. The church would, sooner or later, come round to my view.
LW: But at the end of the play, Brecht has you saying that the sole aim of science is to lighten the burden of human existence. That scientific knowledge must be used solely for mankind's benefit. Do you agree?
GG: How can one not agree that one should lighten burdens? But that is not the aim of science. The aim of science is to understand the world, not change it. Scientific ideas are neutral, free of value. How they are used is another matter. They can be applied to both war and peace. Ethics are not for the scientists.
LW: You exonerate scientists from moral responsibility for the results of their work?
GG: Without doubt. They are merely telling us how the world works, not how it should work.
LW: Are you impressed with science's progress?
GG: It is almost unbelievable; in fact, much of quantum physics still is for me. I never imagined that the heavens would be so large, that distance would be measured in light years, that there would be other galaxies. I remain amazed that there are 100,000 million suns in each galaxy and 100,000 million galaxies. If each star were a grain of sand then the heavens could be represented by a pile of sand five miles high and five miles long. The structure of the sun and nebulae are truly amazing, as are quasars which seem to be remnants of the big bang-a wonderful idea, although what existed before it is still a mystery.
LW: Are you surprised that so many physicists are religious?
GG: Not at all. I can see that it is a temptation to suGGest God's hand plays a key role.
LW: Did you find the new discoveries hard to grasp?
GG: Yes. You must realise there have been big advances in mathematics, like the invention of the calculus by Newton and Leibniz. I was amused by their battle over who got there first-we did not have problems like that as there were so few of us.
LW: What would you like to be remembered for?
GG: My physics. First, my contributions to understanding motion, then the strength of bodies, and finally my studies of the planets. But perhaps most of all for restoring Archimedes's approach by applying mathematics to understanding nature. Of course, Newton really made an even greater step with his mathematical formulation of the laws of motion, then Einstein's later contribution was miraculous.
LW: When Newton spoke of standing on the shoulders of giants he was undoubtedly referring to you.
GG: I can think of no greater compliment.
