Listening to the Feynman lectures on CD (the one on electromagentism is quite a challenge on CD :-) we got to gravity, and I was rather struck by a historical note he made, concerning the shift from geocentrism to heliocentrism - essentially, the process of working out how the planets really moved, and why.
The first I've heard elsewhere: that once you have some idea of momentum, then you realise that the invisible angels you need to push your planets around suddenly change direction: instead of pushing from behind the planets to make them go round in circles, suddenly they are pushing the planets towards the sun. So all of a sudden the idea that the sun might be the source of the invisible angels becomes rather more likely.
And the second was that the person he selects as making the outstanding initial contribution is Tycho Brahe. Feynman phrases it something like this: "and then someone had a great idea... instead of just arguing from first principles about the planets motions, why not measure them carefully to see what they actually did". This is interesting, because in the versions of the story I know, Brahe is a somewhat minor character: a rich but rather uninspired figure, mechanically making careful observations that he didn't know what to do with; the big boys of that story are then Copernicus and Kepler, and then Newton. I think Feynman's view isn't really historically accurate; but it is a new way to look at the story.
Well Feynman was a theorist. In spite of the famous Einstein quote, all the physicists I know understand it is the data that matter - after it has been reproduced.
"though quite how it could have been thought atmospheric when it rotated wrt the surface of the earth I don't know"
Becoming as bright as Venus and visible in the daytime, which could put it within the atmosphere, perhaps it wasn't regarded as a celestial body, similar to some comets?
Correction above in my second sentence. It was inverted. It should read: "After Brahe's sudden death Kepler manipulated the findings for the purpose of trying to show heliocentrism.
Most people do not realize that science in general is a very corrupt practice driven by those with an ideological agenda. The supposed truth of so much we have been told all our lives is simply not the impartial objectively arrived reality that the high priests of secular society, our scientists, would have us believe. It is extremely difficult for most people due to a life time of conditioning to think outside the box in opening their minds to a examination of geocentrism. Let me put it to you this way. If you were Planck size (Google it) and you were at the center of a bowling ball (which would obviously look very different to you!) proportionately that bowling ball would be much larger to you than the entire known observable universe is to us with a breadth of 93 billion light years. That ladies and gentlemen is a fact and yet if you were that Planck size character it would be easy to see how you would find it extremely difficult to fathom how that bowling ball could rotate around you once every twenty four hours. Many people think that space is more or less empty. Wrong! Google "dark matter." It constitutes most of the mass of the universe and it need to be understood.
According to writings of historians of science I read, astronomy and philosophical thoughts about the structure of universe (maybe called cosmology) were different disciplines. Astronomy was a technology to predict the positions of planets etc. based on observations and some theory (which must be useful but not necessarily true) to support navigation and astrology (which was believed useful then). Copernicus's contemporaries thought that he made some advance in this technological discipline, but did not think he revolutionized another philosophical discipline. It seems to be Kepler that transcended the boundary and used (Tycho's) astronomical observations to discuss (Copernicus's and his own) hypotheses in cosmology.
Fantastic post I hope see more, thanks.
Depends on whether you are an experimentalist or a theoretician, I suppose. Theories come and go, but a good data set is forever. Or so I have heard.
Not sure about the historical accuracy either, but I remember that Brahe first did some major observational and then theoretical work (especially with Tycho's Nova) to refute the idea of celestial spheres. It was only well after this that he got funding for his big lab at Uraniborg.
[I was looking at that yesterday. The work was showing that the nova had no parallax, and therefore could not be atmospheric (though quite how it could have been thought atmospheric when it rotated wrt the surface of the earth I don't know; the only answer I can see is that people were so desperate not to have the nova amongst the "unchanging" stars that they would pluck out answers without really thinking). although that is sort-of theoretic, it doesn't begin to compare with the tedious calculations needed to compute planetary orbits -W]
I think Feynman's view isn't really historically accurate;
Maybe you should watch episode 3 of Sagan's Cosmos: The Harmony of the Worlds.
Sagan basically says Copernicus, as brilliant as he was, would've been nowhere without Brahe.
Depends somewhat on age. Brahe was much more revered 50 years ago, if for no other reason that there was less physics and astronomy.
There is a reason a prominent crater on the moon is named Tycho. Without Tycho's careful observations, Kepler wouldn't have had the data from which to derive his laws of planetary motion. Kitty Ferguson's Tycho and Kepler is a decent introduction to the history.
Sagan basically says Copernicus, as brilliant as he was, would've been nowhere without Brahe.
Sorry, meant to say Kepler, not Copernicus.
[That makes more sense. yes, Brahe made more accurate and more continuous observations, and I doubt the discrepancies with the epiclycles would be nearly as clear without that -W]
Kepler was into the occult big time. His mother Katherina was as well and this may have led to her being tried as a witch. (The woman relative who raised Katherina was executed for practicing witchcraft.)
Kepler was employed by Brahe, a geocentrist and Brahe intended to use his 40 years of painstaking labors to demonstrate geocentrism. After Brahe's sudden death Kepler manipulated the findings for the purpose of trying to show heliocentrism.
[Note: I've corrected an inversion of K and B in the sentence above, which the commenter also noted in an unpublished follow-up -W]
Recent forensic findings done after the exhumation of Brahe's body show lethal levels of mercury poisoning just hours before his death. There is very strong circumstantial evidence to show that Kepler actually murdered Brahe. (See, for example, the well documented book Heavenly Intrigue by Joshua Gilder and Anne-Lee Gilder.)
Those interested in examining what appears to be the most comprehensive and detailed scientific treatise on the issue of heliocentric vs. geocentric cosmology ever compiled would do well to see the stunning new 2 volume work Galileo Was Wrong: The Church Was Right at www.galileowaswrong.com. The accompanying blog site which readily examines with the most up to date science the various objections to geocentrism can be found at www.galileowasrong.blogsite.com. It is to be noted that contrary to popular belief heliocentrism has never actually been proven nor has geocentrism ever actually been disproven!
[Oh dear. As we all know, the Church was wrong about the science. More fundamentally, the very idea of having the church decide the science was wrong, too. We also know that Galileo was wrong as well, since he espoused Copernicalism (possibly without fully understanding it) which was also fundamentally wrong, although not as wrong as the geocentric stuff (unless you take a strictly GR perspective, of course). Arguably the church wasn't as wrong as it is usually presented: if the issue had been presented more tactfully, the church probably wouldn't have painted itself into a corner quite so badly -W]
WOW! an honest to goodness geocentrist, out in public.
/me gently escorts James P back to his display case in the museum.
[Aiee, I meant to repress that one. I even sent him an email saying I'd done so. Please folk don't fill up the comments section with too much bozo-baiting, or I'll have to repress it properly -W]
Not directly to the point, but a recent biography of Robert Hooke strongly suggests that Hooke had the right concepts before Newton. He wrote about those ideas in a letter to Newton; Newton knew the analysis which Hooke did not and wrote his famous books. Robert Hooke never forgave Sir Issac for failing to give Hooke the credit due him (at least in Hooke's opinion).
According to writings of historians of science I read, astronomy and philosophical thoughts about the structure of universe (maybe called cosmology) were different disciplines. Astronomy was a technology to predict the positions of planets etc. based on observations and some theory (which must be useful but not necessarily true) to support navigation and astrology (which were believed useful then). Copernicus's contemporaries thought that he made some advance in this technological discipline, but did not think he revolutionized another philosophical discipline. It seems to be Kepler that transcended the boundary and used (Tycho's) astronomical observations to discuss (Copernicus's and his own) hypotheses in cosmology.
[I think that is correct, or at least there was that distinction. I also think this was a little-appreciated problem with overturning the existing theory: it did no good to come along and have a brilliant heliocentric model, because people would immeadiately say "ok, if your theory is so good, lets see you predict the positions of the planets". Which is to say, there was an immense barrier to entry into the system: for example, you actually needed access to all the obs, and a vast calculational effort. I have seen it written that Copernicus's model didn't actually predict the planets much better (which isn't too surprising, since it was just another set of epicycles) -W]
Arthur Koestler's history of astronomy "The Sleepwalkers" is an early work that gives prominence to Tycho Brahe.
[I've read that, and would recommend it -W]
Actually, Kuhn's Copernican Revolution (pre-SSR) is my favorite: Koestler makes it all look too inevitable. As to #10, Kepler's original work, as I remember (reading of) it,wasn't much of an improvement either until it was more thoroughly developed over the decades. And C's early version, while it did contain epicycles, managed to pare out some of them. It therefore possessed a certain elegance the prevailing theory did not have.
By the way, this is also a good argument against crude Deductivism (early Popper). A brand new theory will almost certainly be easier to falsify than an older, more established one. It has been argued against Popper that if scientists really acted according to his precepts that no new theories would ever overturn old ones.
W: (though quite how it could have been thought atmospheric when it rotated wrt the surface of the earth I don't know; the only answer I can see is that people were so desperate not to have the nova amongst the "unchanging" stars that they would pluck out answers without really thinking)
But remember in those days there was no real notion of dynamics of celestial bodies yet, or any clear physical notion of the Earth's atmosphere; there was no reason to use lack of diurnal motion as the measure of being "sub-lunar".
[The atmosphere was supposed to rotate with the earth, as indeed it largely does. Anything atmospheric would be expected to rotate in the same way. You could I suppose imagine something sub-lunar but above the atmosphere that happened not to move - that happened to behave in exactly the same way as the fixed stars - but you'd only do that if you were desperate -W]
The main source of my previous comment (#10) is the following book.
Hanne ANDERSEN, Peter BARKER & Xiang CHEN, 2006: The Cognitive Structure of Scientific Revolutions. New York: Cambridge Univ. Press.
The book also says that, in Copernicus's system (as well as in Ptolemaios's), each planet accompanied a spherical (3-dimensional) "orb". Kepler arrived at a conceptually different system where each planet has an "orbit" which is a closed (1-dimensional) line on a (2-dimensional) plane.
The modern view of the solar system was not established by a single person. But if we choose one person who revolutionized the most, it seems to be Kepler. And the observational works by Tycho Brahe, conducted within the older discipline, were essential ingredients to the revolution.
Coincidentally, I came across this whilst re-reading Norman Feather's 'Mass, Length and Time' (Penguin Edition 1961, first published in 1959 by Edinburgh University Press). Two of his observations on Brahe:
"For a short time Kepler was assistant to Brahe, and without his master's observations his own attempts at systematisation would have been of no avail."
" ... as a result of his [Brahe's] patient observations he corrected the value of almost every accepted astronomical datum, leaving this vast material in perfect order for his successors. That is sufficient title to enduring fame."
Elegantly making the same point as Feynman and Sagan, I think.
> but you'd only do that if you were desperate
Hmm William, I don't know... does it also require, or demonstrate, desperation to believe that heavier objects fall faster than light ones? Very different times, back then...
[It is an observable fact that a lead ball falls faster than a feather :-)
There is an interesting twist to that, BTW, that you might not know: Galileo's first experiments with wood and lead found that the wood, initially, fell faster; later on the lead caught up. The true explanation turns out to be that you have an unconscious bias towards dropping the lighter object first (and that lead does indeed fall a bit faster than wood due to air resistance, of course). But the interesting point is that Galileo managed to rationalise this observation away: he was still thinking in terms which now seem to unnatural that the details fall out of my mind; but it seemed natural that the wood could acquire this more quickly, being lighter -W]
Further to comments 10 and 14 by Kooiti Masuda...
Permit me to quote:
Essays on Galileo and the history and philosophy of science, Volume 3- By Stillman Drake, Noel M. Swerdlow, Trevor Harvey Levere
From the very beginnings of universities, mainly in the twelve and thirteenth centuries, Aristotelian natural philosophy dominated all education in science. Astronomy was usually taught by mathematicians, rather than by natural philosophers, probably because Aristotle's book on the heavens, 'De caelo', dealt not with astronomy, but only cosmology. Whether astronomy was a science under Aristotle's definition is questionable, for about 150 BC the Greek astronomer Hipparchus showed that the Earth cannot be at the exact center of the Sun's apparent motion, as required by all cosmologists, Aristotleans and Platonists alike. A compromise, attributed to Geminus, was soon reached by which astronomers would refrain from considering causes of celestial motions, contenting themselves with framing mathematical hypotheses in accord with the measurements a leaving causal explanations to philosophers. The compromise went unchallenged until the Copernican revolotion.
It was Kepler who (working virtually alone) destroyed this "compromise". His mentor, Michlael Maestlin (another early adherent to heliocentrism) actually warned Kepler against publishing his causal hypotheses, as they were not then considered relevant to astronomical inquiry.
Kepler, in his 'Astronomia Nova', took the causal idea of a 'motive force' - supposed to be emanating from the Sun, and diminishing with distance - and applied to it the constraints that Tycho's measured data imposed. The result was the first two "laws" that bear Kepler's name.
To those interested in the finer details, I would recommend
"The Birth of History and Philosophy of Science:
Kepler's A Defence of Tycho Against Ursus with Essays on Its Provenance and Significance"
by Nicholas Jardine.
#1: isn't that "good data set is forever" quote from one of the Leakeys? I think I've seen it mentioned here in blog comments before.
#12: I'd expect the new theory to be aimed specifically at explaining something that the old theory had trouble with. Maybe the new theory could be "falsified" elsewhere, but a reasonable application of Popperism would give them the chance to work the kinks out.
#17: very helpful. I had thought Copernicus was somewhat betrayed by his friend who published his work posthumously with the publisher introduction describing it as merely a thought experiment. Sounds like it was just fitting into the tradition of the time.
William, yes that's interesting...
What may be the reason for Galileo not being taken in by these effects is that he experimented extensively on inclined planes, which 'dilute' the effect of gravity into slow motion, so you can see better what is really happening. True free fall is a limiting case (remarkably modern physical thinking BTW). In other words, he had trained his physical intuition.
BTW another finding of Galileo that you hear less about was, that the acceleration of free fall also doesn't depend on the already existing state of motion. That's how path travelled is proportional to the square of time elapsed since rest, and cannonball paths curve into parabolas, etc. That was quite something, without having calculus.
#18: I believe that's from Mary Leakey.
Also, your second point: that's how the later Popper accounts for the problem. The theory is allowed to germinate for a time. The problem is that Popper's deductivism depends on the application of a logical law--modus tollens. So a "reasonable" application suspends logical reasoning for a certain period of time. Which,if you are trying to construct a "logic of scientific discovery", is kind of embarrassing.
O/T, but on the notion of precedence, I came across a wonderful little monograph on Eunice Foote, who apparently demonstrated the CO2 greenhouse effect 3 years before Tyndall's famous paper.
I've confirmed the source and emailed the author. It's the real deal.
"Prof. Henry then read a paper by Mrs. Eunice Foote, prefacing it with a few words, to the effect that science was of no country and of no sex. The sphere of woman embraces not only the beautiful and the useful, but the true. Mrs. Foote had determined, first, that the action of the rays increases with the density of the air. She has taken two glass cylinders of the same size, containing thermometers. Into one the air was condensed, and from the other air was exhausted. When they were of the same temperature the cylinders were placed side by side in the sun, and the thermometers in the condensed air rose more than twenty degrees higher than those in the rarified air. This effect of rarefaction must contribute to produce the feebleness of heating power in the sun's rays on the summits of lofty mountains. Secondly, the effect of the sun's rays is greater in moist than in dry air. In one cylinder the air was saturated with moisture, in the other dried with chloride of lime; both were placed in the sun, and a difference of about twelve degrees was observed. This high temperature of sunshine in moist air is frequently noticed; for instance, in the intervals between summer showers. The isothermal lines on the earth's surface are doubtless affected by the moisture of the air giving power to the sun, as well as by the temperature of the ocean yielding the moisture. Thirdly, a high effect of the sun's rays is produced in carbonic acid gas. One receiver being filled with carbonic acid, the other with common air, the temperature of the gas in the sun was raised twenty degrees above that of the air. The receiver containing the gas became very sensibly hotter than the other, and was much longer in cooling. An atmosphere of that gas would give to our earth a much higher temperature; and if there once was, as some suppose, a larger proportion of that gas in the air, an increased temperature must have accompanied it, both from the nature of the gas and the increased density of the atmosphere. Mrs. Foote had also tried the heating effect of the sun's rays on hydrogen and oxygen, and found the former to be less, the latter more, susceptible to the heating action of sunlight" (Wells, 1857, p. 159-160).
Scan of the original volume:
[I've seen this before and commented on it, but can't recall where. Its wrong, no? Observing higher T in an evacuated as against a airfull jar has nothing to do with CO2 absoption -W]
Are you sure you read the extract in full?
"Thirdly, a high effect of the sun's rays is produced in carbonic acid gas. One receiver being filled with carbonic acid, the other with common air, the temperature of the gas in the sun was raised twenty degrees above that of the air...."
There follows supposition about an increased amount of CO2 in the real atmosphere.
Do you still see anything wrong with the experiment re CO2?
[I'm very dubious, that such a large temperature rise is plausible. I don't know what the absobivity is over such a short part length but I doubt it is large. My suspicion is that the experimental conditions were not adequate -W]
Well, the source is verified. The experiments are simplistic, but demonstrate the effect sufficiently enough that the correct conclusions are drawn regarding CO2 in the real atmosphere. The temp measurements are in Farenheit, and we don't know the size of the vessels or the environment in which they were situated. But the general result is correct and shown 3 years before Tyndall. I can't see why this footnote in history should be troubling.
[That is what I'm trying to say: I don't think the result is correct. Or at least, I'm very doubtful -W]
I'm kind of thrilled that in an era when women were much less of a force in science, Eunice Foote may very well have been the first person in the world to demonstrate the greenhouse effect with CO2. No need to rewrite the history books, but this is certainly worth acknowledging, to my mind. Spencer Weart said as much when I sent him a copy of the monograph.
[You need to send it to someone competent in the physics. Eli, perhaps. I'll tell him -W]
For reading on Galileo/Brahe/Kepler/the Church, I find thonyc's blog, http://thonyc.wordpress.com/, quite interesting. I particularly recommend http://thonyc.wordpress.com/2011/06/22/but-it-doesn%E2%80%99t-move/.
Thanks. I posted it to the latest thread at Eli's.