Therefore, if all thought is either practical or productive or theoretical, physics must be a theoretical science, but it will theorize about such being as admits of being moved, and about substance-as-defined for the most part only as not separable from matter.
– Aristotle, Metaphysics Book VI.
– Aristotle, Metaphysics Book VI.
Philosophy is written in this grand book – I mean the universe – which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics.
– Galileo Galilei, Il Saggiatore (Assayer).
– Galileo Galilei, Il Saggiatore (Assayer).
J’ai aussi composé et imprimé un livre dans lequel je traite de cette doctrine condamnée et avance en sa faveur de forts arguments, sans y ajouter une réfutation concluante, à la suite de quoi j’ai été reconnu par ce Saint Tribunal extrêmement suspect d’hérésie, comme si je soutenais et croyais que le soleil est le centre du monde immobile, et que la Terre n’est pas le centre et se meut. Désirant chasser de l’esprit de Vos Saintetés, comme de l’esprit de tout fidèle chrétien, ce grave soupçon légitimement éveillé contre moi, d’un coeur pur et d’une foi sincère j’abjure, je maudis, je déclare détestables les erreurs et hérésies que je viens de mentionner et généralement toutes les erreurs, hérésies et doctrines hostiles à la Sainte Eglise.
On May 24, 1543, Nicolaus Copernicus, on the bed in which he as going to die that same day, received the first copy of his book, On the Revolution of the Heavenly Spheres, in which he enunciated his famous idea that the earth, like other planets, rotated around the sun, and not the other way around. The idea was not new, but had been forgotten during the Middle Ages; some Greeks, including Aristaschus of Samos, had already proposed this hypothesis. In any case, modern scientific investigation of the motion of planets, including the earth, around the sun as initiated by Johannes Kepler, who, motivated by the theory of Copernicus, analyzed the vast observational data obtained by his teacher Ticho Brahe, and proposed three laws of the planetary motion. The problem of planetary motion around the sun is, therefore, called the Kepler problem.
Kepler, in his book Astronomia Nova (New Aeteological Astronomy or Celestial Physics together with Commentaries on the Planet Mars), printed in 1609, published his discoveries that:
1. Each planet moves in an ellipse, with the sun at one of his foci.
2. The radius vectoe drawn from the sun to a planet covers equal areas in equal times.
Ten years later, in another book, The Harmonies of the Spheres, he added that
3. The squares of the periods of the different planets are proportional to the cubes of their respective major semi-axes.
1. Each planet moves in an ellipse, with the sun at one of his foci.
2. The radius vectoe drawn from the sun to a planet covers equal areas in equal times.
Ten years later, in another book, The Harmonies of the Spheres, he added that
3. The squares of the periods of the different planets are proportional to the cubes of their respective major semi-axes.
In the same year I began to think of gravity extending to ye orb of the Moon and (having found out how to estimate the force with which the globe revolving within a sphere presses the surface of a sphere) from Kepler’s rule of the periodical times of the Planets being in sesquialternate proportion to their distances from the centres of their Orbs, I deduced that the forces wch keep the Planets in their Orbs must reciprocally as the squares of their distances from the centres about wch they revolve: and thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the Earth, and found them answer pretty nearly. All this was in the two plague years of 1665-1666…
I can live with doubt and uncertainty and not knowing. I think it’s much more interesting to live not knowing than to have answers which might be wrong. I have approximate answers and possible beliefs and different degrees of certainty about different things, but I’m not absolutely sure of anything and there are many things I don’t know anything about.
It is our responsibility as scientists, knowing the great progress which comes from a satisfactory philosophy of ignorance, the great progress which is the fruit of freedom of thought, to proclaim the value of this freedom, to teach how doubt is not to be feared but welcomed and discussed, and to demand this freedom as our duty to all coming generations.
What will happen ultimately ? We are going along guessing the laws; how many laws are we going to have to guess ? I do not know. Some of my colleagues say that this fundamental aspect of our science will go on; but I think there will certainly not be perpetual novelty, say for a thousand years. This thing cannot keep on going so that we are always going to discover more and more new laws. If we do, it will become boring that there are so many levels one underneath the other. It seems to me that what can happen in the future is either that all the laws become known – that is, if you had enough laws you could compute consequences and they would always agree with experiment, which would be the end of the line -or it may happen that the experiments get harder and harder to make, more and more expensive, so you get 99-9 per cent of the phenomena, but there is always some phenomenon which has just been discovered, which is very hard to measure, and which disagrees; and as soon as you have the explanation of that one there is always another one, and it gets slower and slower and more and more uninteresting. That is another way it may end. But I think it has to end in one way or another.
We are very lucky to live in an age in which we are still making discoveries. It is like the discovery of America -you only discover it once. The age in which we live is the age in which we are discovering the fundamental laws of nature, and that day will never come again. It is very exciting, it is marvellous, but this excitement will have to go. Of course in the future there will be other interests. There will be the interest of the connection of one level of phenomena to another – phenomena in biology and so on, or, if you are talking about exploration, exploring other planets, but there will not still be the same things that we are doing now.
Another thing that will happen is that ultimately, if it turns out that all is known, or it gets very dull, the vigorous philosophy and the careful attention to all these things that I have been talking about will gradually disappear. The philosophers who are always on the outside making stupid remarks will be able to close in, because we cannot push them away by saying, ‘If you were right we would be able to guess all the rest of the laws’, because when the laws are all there they will have an explanation for them. For instance, there are always explanations about why the world is three-dimensional. Well, there is only one world, and it is hard to tell if that explanation is right or not, so that if everything were known there would be some explanation about why those were the right laws. But that explanation would be in a frame that we cannot criticize by arguing that that type of reasoning will not permit us to go further. There will be a degeneration of ideas.
In this age people are experiencing a delight, the tremendous delight that you get when you guess how nature will work in a new situation never seen before. From experiments and information in a certain range you can guess what is going to happen in a region where no one has ever explored before. It is a little different from regular exploration in that there are enough clues on the land discovered to guess what the land that has not been discovered is going to look like. These guesses, incidentally, are often very different from what you have already seen – they take a lot of thought.
What is it about nature that lets this happen, that it is possible to guess from one part what the rest is going to do ? That is an unscientific question: I do not know how to answer it.
— The character of physical law.
We are very lucky to live in an age in which we are still making discoveries. It is like the discovery of America -you only discover it once. The age in which we live is the age in which we are discovering the fundamental laws of nature, and that day will never come again. It is very exciting, it is marvellous, but this excitement will have to go. Of course in the future there will be other interests. There will be the interest of the connection of one level of phenomena to another – phenomena in biology and so on, or, if you are talking about exploration, exploring other planets, but there will not still be the same things that we are doing now.
Another thing that will happen is that ultimately, if it turns out that all is known, or it gets very dull, the vigorous philosophy and the careful attention to all these things that I have been talking about will gradually disappear. The philosophers who are always on the outside making stupid remarks will be able to close in, because we cannot push them away by saying, ‘If you were right we would be able to guess all the rest of the laws’, because when the laws are all there they will have an explanation for them. For instance, there are always explanations about why the world is three-dimensional. Well, there is only one world, and it is hard to tell if that explanation is right or not, so that if everything were known there would be some explanation about why those were the right laws. But that explanation would be in a frame that we cannot criticize by arguing that that type of reasoning will not permit us to go further. There will be a degeneration of ideas.
In this age people are experiencing a delight, the tremendous delight that you get when you guess how nature will work in a new situation never seen before. From experiments and information in a certain range you can guess what is going to happen in a region where no one has ever explored before. It is a little different from regular exploration in that there are enough clues on the land discovered to guess what the land that has not been discovered is going to look like. These guesses, incidentally, are often very different from what you have already seen – they take a lot of thought.
What is it about nature that lets this happen, that it is possible to guess from one part what the rest is going to do ? That is an unscientific question: I do not know how to answer it.
— The character of physical law.
So I have just one wish for you – the good luck to be somewhere where you are free to maintain the kind of integrity I have described, and where you do not feel forced by a need to maintain your position in the organization, or financial support, or so on, to lose your integrity. May you have that freedom. 8quo 1leu 2wis
— Richard P. Feynman (1918-1988)
— Richard P. Feynman (1918-1988)
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