Talk:Johannes Kepler/Archive 2

Political and religious difficulties in Graz
"Political and religious difficulties in Graz dashed his [Kepler's] hopes of returning immediately to Tycho"

What kind of difficulties were that? I think this should be explained in more detail.

Top.Squark (talk) 19:01, 13 April 2010 (UTC)

Epitome
Kepler's "Epitome" should have a separate article about it. His other books already have. —Preceding unsigned comment added by 93.97.194.200 (talk) 14:19, 29 July 2010 (UTC)

"focus"
In time span 5:18-5:28 of this California Institute of Technology video, http://video.google.com/videoplay?docid=2003674873092336626#, Kepler is said to have been the first to use the Latin word "focus", meaning "fireplace", in reference to the ellipse. He did so because he placed the Sun, the greatest fireplace he knew, at the focus of all elliptical planetary orbits. This is a great story about the origin of the use of the word "focus" in relation to the conic sections. Shouldn't it be mentioned in appropriate Wikipedia articles? (I'm afraid I don't have time to do it.) Sks23cu (talk) 16:16, 25 September 2010 (UTC)

Advisor to Wallenstein
Why Lutheran Kepler became an advisor to the Catholic general Wallenstein during the Thirty Years' War? Wasn't it a betrayal of his own beliefs? Top.Squark (talk) 21:02, 26 April 2010 (UTC)


 * Kepler served the Catholic Emperor Frederick II; Wallenstein also served the Catholic Emperor Frederick II. Kepler needed the support of a strong patron.  That's adequate explanation for me.  --SteveMcCluskey (talk) 19:01, 2 December 2010 (UTC)

Who is this Catholic Emperor Frederick II whom Kepler served? I am only aware of his serving Ferdinand II and having some brief crossover with his brother Matthias when he succeeded the throne. As regards the initial question, Kepler is well known to have been extremely tolerant of other faiths throughout his life (see "Kepler's Witch" chapters 2-3 or "Tycho and Kepler" pp. 225-6). —Preceding unsigned comment added by 192.218.246.2 (talk) 05:50, 20 April 2011 (UTC)

Work for Tycho
It seems appropriate to remove the text at the end of this section. While a colorful piece of information, it not only requires citation but is not really about Kepler at all. It could easily be found by going to the page on Tycho Brahe, which is already linked to at least twice in this article.

The section of text I refer to is the following: "A year after Kepler started working with Brahe, Brahe died of a complication with his bladder. He had gone to a dinner party and drank too much wine. He did not want to be rude and leave the dinner table to go and urinate. So shortly after, he died." —Preceding unsigned comment added by 192.218.246.2 (talk) 06:34, 8 April 2011 (UTC)

No one has stated any objections to having this removed, so may I take it upon myself to do so? —Preceding unsigned comment added by 192.218.246.2 (talk) 05:37, 20 April 2011 (UTC)

Knowledge of gravity
Kepler is not given near as much credit for understanding gravity as well as he did. I believe this is an English language chauvinism. Even Stephen Hawking gets it wrong in the extremely popular "A Brief History of Time". He wrongly states Kepler thought the attraction was magnetism and that Newton first thought of attraction based on mass. To show how well Kepler understood masses of all types attract and that the force is proportional to their respective masses, consider these quotes:

"Every corporeal substance, so far forth as it is corporeal, has a natural fitness for resting in every place where it may be situated." Newton's 1st law, long before Newton.

"Gravity is a mutual affection between cognate bodies towards union or conjunction, so that the earth attracts a stone much rather than the stone seeks the earth." "If two stones were placed in any part of the world near each other, and beyond the sphere of influence of a third cognate body [like the Earth], these stones, like two magnetic needles, would come together in the intermediate point, each approaching the other by a space proportional to the comparative mass of the other." This is derivable from F=ma, but I do not know if he knew F=ma. Nevertheless, he gets the same result, so it seems he knew of F=ma at least by some round-about way. If he had known the density of the moon was less than that of the Earth, he would have been able to compare their "animal force" (centripetal force) to their gravitational force: "If the moon and earth were not retained in their orbits by their animal force or some other equivalent, the earth would mount to the moon by a fifty-fourth part of their distance, and the moon fall towards the earth through the other fifty-three parts, and they would there meet, assuming, however, that the substance of both is of the same density." Again, he gets the same result as newton would have calculated years with from F=ma.

He believed "Newton's" 1st law could counteract the effect of gravity to the point of overcoming the pull of gravity: "But although the attractive virtue of the earth extends upwards, as has been said, so very far, yet if any stone should be at a distance great enough to become sensible compared with the earth's diameter, it is true that on the motion of the earth such a stone would not follow altogether; its own force of resistance would be combined with the attractive force of the earth, and thus it would extricate itself in some degree from the motion of the earth."

Wiki says he believe the force of gravity was 1/r instead of 1/r^2. Kepler was aware of Galileo's experiments, so he had the information needed to connect his planetary laws to gravity and F=ma, but it took Newton's math skills to reconcile Kepler's knowledge into a simpler, coherent picture. Given that Kepler new the 1st law, Galileo's experiments, the motions of the planets, and that larger masses attract with a proportionally stronger force, it leaves me feeling that Newton contributed much less than is normally believed. I would like to see the article give credit where it is due. Newton was not the first to know the 1st Law, nor that masses such as apples and planets attract proportionally to the mass. Ywaz (talk) 16:20, 2 December 2010 (UTC)


 * While this is a potentially interesting revision, it's not the place of wikipedia, which is just an encyclopedia of current understanding, to make such a revision, per WP:OR. Perhaps publishing something on the matter in an appropriate forum could eventually lead to a shift in the scholarly views regarding Kepler, and thereby a change in this article, but this is not the place to start. siafu (talk) 16:57, 2 December 2010 (UTC)


 * I think it is also incorrect WMC 18:26, 2 December 2010 (UTC)


 * That may be true, but we should avoid delving into that here, as wikipedia is not a forum. siafu (talk) 18:33, 2 December 2010 (UTC)


 * There are historical discussions of this passage from Kepler, and the consensus seems to be that his concept of attraction differed from Newton's concept of gravity in two ways:
 * The attraction was between "cognate bodies" (apparently between bodies of the same element) and was not universal as Newton's was.


 * The attraction was limited to a certain "sphere of influence", and did not extend indefinitely as Newton's gravitation did.
 * You might want to look into the historical literature on this issue. --SteveMcCluskey (talk) 18:34, 2 December 2010 (UTC)

Quotes from the source are not original research. The following can be taken as a reference that recognizes its importance: http://www.fullbooks.com/Kepler.html   I do not know on what basis SteveMcCluskey is claiming Kepler's law of gravity was limited in distance. Consider this quote: "If the attractive virtue of the moon extends as far as the earth, it follows with greater reason that the attractive virtue of the earth extends as far as the moon and much farther; and, in short, nothing which consists of earthly substance anyhow constituted although thrown up to any height, can ever escape the powerful operation of this attractive virtue." Newton himself did not believe the effect of gravity extended indefinitely because if it did, a static universe was not possible. His explanation was that gravity cancels itself at great distances due to the universe being infinite and attracting from all sides. A similar belief seems to be the basis of Kepler's comments. Kepler even knew tides were caused by the moon. If this does not show a basic understanding of gravity, I don't know what does. His only error, that I have not been able to confirm, is that he thought it varied with 1/r instead of 1/r^2.Ywaz (talk) 21:23, 2 December 2010 (UTC)


 * Referring to primary sources and interpretting them is indeed original research, or at BEST novel synthesis, which is still contrary to the, admittedly limited, mission of wikipedia. siafu (talk) 21:25, 2 December 2010 (UTC)


 * I do not know where you are claiming I made an interpretation. Getting back to the other "substantive" complaint that Kepler thought it only occurred between similar bodies: it is abundantly clear from his comments that is not the case. I do not see any validity to the complaints so far. Ywaz (talk) 21:35, 2 December 2010 (UTC)


 * To cite an obvious example, inferring that connecting the tides with the moon implies knowledge of gravity is an interpretation, as there are other potentially valid interpretations. My initial complaint, which still stands, is that this is original research: it's certainly not the commonly held view of experts in the field that he had this understanding, and it is wikipedia's job to present what is verifiably known.  You may also wish to review WP:Secondary source, to whit: "Any interpretation of primary source material requires a reliable secondary source for that interpretation. A primary source may only be used on Wikipedia to make straightforward, descriptive statements that any educated person, with access to the source but without specialist knowledge, will be able to verify are supported by the source."  I am specifically not trying to address the actual veracity of your claim that Kepler understood gravity, but trying to point out that the discussion itself is inappropriate for wikipedia.  This theory is more appropriate discussed at an archeoastronomy forum, or published in an archeoastronomy journal.  Once it has been picked over by experts and accepted into the mainstream, then it will be ready for prime-time wikipedia. siafu (talk) 21:46, 2 December 2010 (UTC)


 * I did not provide the quote about the tides, but he said it was due to gravity coming from the moon. That newton is overrated when compared to kepler is not original research.  Consider this reference from 1930:  http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&d=EP19301227.2.54  But I concede that I can't find enough to overcome your objection.  Part of the problem is that many sources mis-represent Kepler.  Claiming he meant magnetism is the most egregious error.  Other errors include not thinking he meant it for planets or, conversely, that he didn't mean it for objects on Earth.  Even his 1/r error could be a false claim.  You see two more errors above. Ywaz (talk) 21:57, 2 December 2010 (UTC)


 * Considering he didn't use the word gravity, he could not have said it "due to gravity coming from the moon". Furthermore, "that Newton is overrated when compared to Kepler" is not something we are in a position to judge, not that a racializing newspaper column from eighty years ago is sufficient to demonstrate anything to us, anyway.siafu (talk) 14:58, 3 December 2010 (UTC)


 * The English translation *did* call the effect gravity. The word was first used in English in 1505, and I believe it was used to refer to the force that pulls objects to the ground. You would have to use some exotic assumptions and twisting of reasoning to come to belief that his use of the word gravity at the beginning of the paragraph was not what he had in mind at the end of the paragraph. Ywaz (talk) 23:52, 3 December 2010 (UTC)

Please allow me, a newcomer to this discussion, to add to it. I think Kepler's suppositions on gravity are perhaps a valuable point to raise in this article. It is a topic of general interest, one that is treated in many books about Kepler, and one on which Kepler himself spent a good deal of research. As such I would like to put forward the following text as a starting point from which to consider a possible addition to the Kepler article on this topic. Even if it cannot be included in the article, I hope it is useful for any future consideration on this matter.

Kepler and Gravity

Numerous passages in Kepler's writings may tempt the modern reader to imbue him with an early understanding of the force of gravity as later explained by Isaac Newton. As early as his first publication, "Mysterium Cosmographicum," Kepler proposes an "animus matrix," a "living force," that resides in the sun and acts more strongly on nearer bodies than on distant ones. (*1) He also makes a great stride in moving beyond the previously held view that falling objects "strive" for the earth. The pre-Copernican view of gravity was largely Aristotelean, assuming that objects fall to the earth because the center of the universe and the center of the earth are one and the same. That objects fall to earth is a happy coincidence of the fact that objects "strive" to the center of the universe. Kepler's idea of gravity replaces this "striving" with a mutually attractive force which he describes in "Astronomia Nova" as well as in his posthumously published book the "Somnium" (*2). In note 66 of the latter, Kepler defines gravity as "a force of mutual attraction." (*3) Much is also made of Kepler's discussion of the moon's effect on the tides of earth's oceans. In note 202 of the "Somnium" Kepler says of this relationship, "the causes of the ocean tides seem to be the bodies of the sun and moon attracting the ocean waters by a certain force similar to magnetism." (*4)

Such early whiffs of an understanding of gravitation should not be taken alone but seen in light of other passages in his writing. In describing the aforementioned motive force residing in the sun, Kepler makes several suppositions that would be peculiar in terms of Newton's later theory of gravitation. In the "Mysterium" he contemplates the relationship of the sun's force and the distance of the planets and in so doing makes, as astronomer J.L.E. Dreyer points out, "the erroneous assumption, from which he never swerved, that the effect of this force is inversely proportional to the distance of the sun." (*5) Furthermore, in a letter from 1600, Kepler describes a concept for the force attracting the moon to the earth. Recognizing the moon's attraction to the earth but unable to give up the sun's position as the "primary origin" of the moving force, Kepler supposes that "a sort of ray of moving force emerges from the sun and continues straight ahead through the body of the earth, where it nests, as it were. Through this continuation a kind of secondary force, as an offshoot of that solar force, is created and persists. It spreads out again spherically from the earth, as its new dwelling-place, in order to make the moon revolve around the earth." (*6) Dreyer, who in his "History of Astronomy" is consistently magnanimous in not judging harshly the notions of astronomers past, describes at length Kepler's thought process on gravity in terms of magnetism. He explains Kepler's concept of planets' axis of rotation as a product of their magnetic field reacting to the sun as well as his concept of planetary orbits varying according to the intensity of magnetism. Dreyer concludes, "The active force is magnetism pure and simple, and Kepler never tired of emphasizing this whenever an opportunity offered," and adds, "Thus the thesis No. 51 of his [Kepler's] little polemical book 'Tertius Interveniens' (1610) states that 'the planets are magnets and are driven round the sun by magnetic force, but the sun alone is alive." (*7)


 * 1 - Mysterium Cosmographicum, chapter 20 (ref. Johannis Kepleri Astronomi Opera Omnia, p 173.)
 * 2 - Rosen, Edward "Kepler's Somnium: the Dream, or Posthumous Work on Lunar Astronomy," Dover Publications, 2003, p. 219
 * 3 - Ibid, pp. 218-220.
 * 4 - Ibid, p. 220
 * 5 - Dreyer, J.L.E., "A History of Astronomy from Thales to Kepler," Dover Publications, 1953, p.379
 * 6 - Rosen, pp. 219-220.
 * 7 - Dreyer, p. 397 —Preceding unsigned comment added by 192.218.246.2 (talk) 06:11, 22 April 2011 (UTC)

MTH314 St. Martin's Uni. WIKI PROJECT
It is interesting that Kepler discovered his first two laws of planetary motion almost in reverse order. He found that first, that the planet’s move out away from some center equal movements at equal times. He then discovered that the oval-like shapes the planets moved were actually ellipses. Kepler had an intense interest in logarithms during his life, which led him to finalize and come to conclusion on his third planetary law. http://www.mathpages.com/rr/s8-01/8-01.htm

The book mentions that Kepler was the first to identify volumes through an idea of curvilinear areas with the sum of an infinite number of infinitesimal elements of the same dimension. Before this revolutionary idea of continuity in today’s sense, the methods of estimation, taxation and in particularly the volume of wine casks were greatly inaccurate. Kepler’s discoveries were before those later discovered in integral calculus, even though the ideas had a very similar flavor. Burton, David. The History of Mathematics: An Introduction. Seventh Edition. New York, NY: McGraw-Hill Publishing, 2011. Print.

This site talks about how Kepler was a bright student during his early years, but as communicated in his writings, did not support the taught astronomical system of the day. Kepler was taught geocentric astronomy at the time, where he pursued learning the Copernican heliocentric system. He supported this system completely and began his observations and studies of the system. Kepler was also very vocal about his opinions, and because of such he was ex-communicated from the Lutheran Church. He did grow higher in social esteem as a scholar, but he never was able to lift the Churches excommunication set on him. http://www-history.mcs.st-andrews.ac.uk/Biographies/Kepler.html

Kepler’s ideas are rooted in largely Pythagorean and Platonic values, but his ideas are scientifically rooted with Copernican rational, having also introduced physics to the solar system. Kepler’s mysticism led to many hypothesis’s about the universe, including the geometric shapes that help determine the distance of planets from each other. http://www.nndb.com/people/342/000086084/ —Preceding unsigned comment added by 76.121.153.100 (talk) 07:19, 4 May 2011 (UTC)

Based off of the first link you posted, I find it very interesting that Kepler had an interest in logarithms before even discovering its relatedness with planetary motion. Although it does make sense, using logarithmic scales to reduce wide-ranging quantities. MTH314ccc (talk) 07:37, 4 May 2011 (UTC)

It is interesting to see that Kepler used 7 planets instead of the six that was used by Copernicus in order to prove Copernicus' Planetary Motions Theory.Slim3658 (talk) 17:27, 4 May 2011 (UTC)

Portrait Caption "Joe Kepler"
I don't see how to edit the caption on the first portrait or I would do it myself. The caption says "Joe Kepler". Joe is short for Joseph. Johannes is John, n'est-ce pas? —Preceding unsigned comment added by 91.150.223.26 (talk) 10:02, 19 May 2011 (UTC)

Misuse of the Panis Qudragesimalis
The Panis Quadragesimalis is not a geocentric representation of the motion of Mars,it represents both the motion of the Earth and the motion of Mars in combination hence no geocentric perspective - "Copernicus, by attributing a single annual motion to the earth,entirely rids the planets of these extremely intricate coils,leading the individual planets into their respective orbits,quite bare and very nearly circular. In the period of time shown in the diagram, Mars traverses one and the same orbit as many times as the 'garlands' you see looped towards the center,with one extra, making nine times, while at the same time the Earth repeats its circle sixteen times " Kepler .It is essential to understand completely how Kepler worked in this respect and the original representation of Kepler is second in importance to the Copernican arrangement of the planets around the central Sun.Gkell1 (talk) 18:18, 12 July 2011 (UTC)
 * I think you're misinterpreting Kepler here, for he explicitly says in the passage you've quoted that the intricate pretzel-like diagram does not represent the motion of Mars in Copernicus's heliocentric model: "Copernicus ... entirely rids the planets of these extremely intricate coils." These complex loops do not appear in Copernicus's (or Kepler's) sun-centered model; the loops of the Panis quadragesimalis (pretzel) are a characteristic property of the motion of the planets in geocentric models. --SteveMcCluskey (talk) 20:48, 14 July 2011 (UTC)

http://en.wikipedia.org/wiki/File:Kepler_Mars_retrograde.jpg Look at both the Panis Quadragesimalis and the description of Kepler explaining the motion of Mars against the stellar background with special emphasis on the retrograde loops which represent the Earth overtaking Mars so that Kepler's representation is fully representative of both the Earth's and Mar's orbital motions http://apod.nasa.gov/apod/ap080511.html .Run your cursor on the image and you see the background constellations which match Kepler's Panis Qudragesimalis with Mars and the Earth passing through the familiar Gemini and Taurus field of stars in our common orbital circuits. http://upload.wikimedia.org/wikipedia/commons/thumb/0/05/Astro_signs.svg/260px-Astro_signs.svg.png. In conclusion, Kepler's expression of the motion of Mars seen from a moving Earth has no geocentric signature which can be inserted into this extremely important astronomical representations of the motion of two planets.For those who match 21st century time lapse footage with the old Panis Qudragesimalis,they will gain an immense satisfaction from the minimal effort it takes to tune into the approach Kepler took to variations in orbital speeds and geometry in a form that modern imaging,such as seen in the APOD sequence, tends to enhance.Gkell1 (talk) 20:03, 21 July 2011 (UTC)

Early years: "Protestant school in Graz (later the University of Graz)"
I believe the passage at the end of the section "Early years" that describes the school where Kepler taught in Graz as later becoming the University of Graz is in error. In fact, of importance in understanding Kepler's experience in Graz at this time is the fact that there were the competing Protestant school (the Schtiftsschule) and the Catholic college. The Catholic college was founded by Archduke Charles II (a.k.a., Archduke Karl II Franz), a Catholic Habsburg, hence the original name of the University of Graz, i.e., Karl-Franzens Universität. Please see Casper's "Kepler" (p. 54) for reference and cross check with the University of Graz website for confirmation. It is important not to conflate these schools and accidentally place Kepler among the faculty of his Stiftsschule's rival Catholic college. Are there any objections to deleting "(later the University of Graz)"?

It's only been a short while, but so far no objections have been raised to the above change. I will now delete the aforementioned parenthetical statement. In case it is necessary to replace the deleted statement, I include here the full sentence as it is now: "Despite his desire to become a minister, near the end of his studies Kepler was recommended for a position as teacher of mathematics and astronomy at the Protestant school in Graz (later the University of Graz)." — Preceding unsigned comment added by 81.57.75.228 (talk) 17:15, 1 August 2011 (UTC)

Bangla translation
This version of the featured article on Kepler has been translated into Bengali. Thanks to all the editors who helped create this nice wiki entry on Kepler. -- Khan Muhammad (talk) 23:16, 21 February 2012 (UTC)

= Emoticons =

There is an emoticon in the third paragraph of http://en.wikipedia.org/wiki/Johannes_Kepler#Dioptrice.2C_Somnium_manuscript_and_other_work — Preceding unsigned comment added by Themystic ca (talk • contribs) 03:55, 1 May 2012 (UTC)

Kepler's astrology
The article section 'Dioptrice, Somnium manuscript and other work' quite badly misrepresents Kepler's attitude towards astrology. Kepler had purist views on astrology and saw it as a very spiritual study. He disliked it being used for predicting what will happen because he believed that souls were responsible for their own choices. The kind of astrology he disliked was that which catered to the crowd or individual curiosity, but he never regarded astrology as "evil-smelling dung" - what he opposed was the abuse of astrology for trivial matters. The article states this:

""While Kepler considered most traditional rules and methods of astrology to be the "evil-smelling dung" in which "an industrious hen" scrapes, there was "also perhaps a good little grain" to be found by the conscientious scientific astrologer.[40]""

This is innacurate, and it is not what the source says. In fact if the relevant pages quoted are read, it is clear that Kepler argued much more strongly in favour of astrology than against it. What he actually said was this:

"It should not be considered unbelievable that one can retrieve useful knowledge and sacred relics from astrological folly and godlessness. From filthy mud one can glean even an occasional escargot, oysters or an eel for one's nutrition; in this enormous heap of worm-castings there are silk-worms to be found; and, finally, out of this foul-smelling dung-heap a diligent hen can scratch up an occasional grain-seed - indeed, even a pearl or a gold nugget."

- (Tertius Interveniens, 1.5, 1610)

He was making an anology to the fact that astrological pearls of wisdom are found even amongst what appears to be the most trivial elements of the subject. This is not the same things as saying that he considered most traditional rules and methods of astrology to be the "evil-smelling dung". In the same text (where he was mediating between extreme views), he made it clear that he held the subject in high regard, not in low regard. We can see his belief in its practical usefulness in comments such as this :

"All the natural qualities of the five planets, as well as of some of the more prominent fixed stars can be grasped by the human understanding, although not perfectly, and can be integrated into a kind of science or body of knowledge, which can be used for prognostication of future events as well and as completely as can be done in medicine with the various and sundry herbs."

- (Tertius Interveniens, 9.6 1610)

And for his view of the worthiness subject note this comment - where he is moaning about the need to produce a detailed astrological prediction for a client: "Am I nevertheless supposed to let myself be used as a comedian, a performer, or some other kind of marketplace entertainer? There are plenty of young astrologers who are so inclined, and have faith in such games. Whoever wants to be fooled with eyes wide open, let him make use of their efforts and entertainment. Philosophy, and therefore genuine astrology, is a testimony of God's works, and is therefore holy. It is by no means a frivolous thing. And I, for my part, do not wish to dishonor it."

- (Revised Delineation of This [Wallenstein's] Horoscope)

The article leaves the impression that Kepler thought astrology was a frivolous thing. He clearly did not, what he thought was frivolous, was the use it was sometimes put to, to satisfy idle curiosity. --  Zac   Δ talk! 00:21, 22 November 2011 (UTC)


 * Thanks for correcting this. Rwflammang (talk) 11:06, 4 July 2012 (UTC)

Odd edit
There is an odd edit in the fourth line of the paragraph entitled "Reception of his Astronomy". — Preceding unsigned comment added by 86.183.203.240 (talk) 10:43, 7 July 2012 (UTC)

Latin Mistranslation?
Keppler's epitaph is given as:


 * Mensus eram coelos, nunc terrae metior umbras
 * Mens coelestis erat, corporis umbra iacet.


 * I measured the skies, now the shadows I measure
 * Skybound was the mind, earthbound the body rests.

My Latin is far from perfect, but I think this is back to front. The English should read:


 * I measured the skies, now I measure the earth
 * Skybound was the mind, the body rests in the shadows.

Perhaps someone with better Latin than me could check this.


 * The Latin is okay. In poetry, a paraphrase is pretty much necessary. The only changes I'd recommend for a literal translation are shown in brackets:


 * I [had] measured the skies, now the shadows [of earth] I measure
 * Skybound was the mind, [the shadow of] the body rests.


 * Rwflammang (talk) 00:17, 29 August 2012 (UTC)

and i love taylor laughtner — Preceding unsigned comment added by 108.56.162.73 (talk) 01:28, 9 November 2012 (UTC)

Kepler's second law not a law according to Kepler
Forgive the typos as it got processed by an OCR. I don't want to add it but people should be aware. Also this book would make a good primary source.

Since, therefore, in addition, the real diurnal arcs which are in proximity are greater still on account of the greater velocity, and the real arcs in the remote aphelion are smaller still on account of the retardation, it results, as l have shown in my Commentaries on Mars, that tbe apparent diurnal arcs of one eccentric are almost exactly inversely proportional to tbe square of tbeir distances from tbe Sun.‘ As, for instance, if a planet in one of its days when it is in aphelion is distant from the Sun 10 units, in any measure whatsoever, and in its opposite day, when it is in perihelion, is distant 9 units of exactly the same kind, it is certain that, as seen from the Sun, its apparent progress in aphelion will be to its apparent progress in perihelion as 81 is to 100. Now this is true with these reservations: ﬁrst, that the arcs of the eccentric be not large, that they may not have different dis- tances varying greatly, that is, that they may not cause a sensible variation in the distances of their ends from the apsides; secondly, that the eccentricity be not very great, for the greater the eccen-

‘ Or “the ratio of the apparent diurnal arcs of one eccentric is almost exactly twice the inverse of the ratio of their distances from the Sun." M X % = twiCe ‘/2. (Note by translator.)

tricity, that is the greater the arc, the greater is the increase of the angle of that appearance in comparison with its own advance toward the Sun, according to Theorem 8 of the “Optics” of Euclid. But there is another reason why I give this warning. The arcs of the eccentric about the middle of the anomalies are observed obliquely from the center of the Sun, and this obliquity diminishes the size of their appearance, while, on the other hand, the arcs around the apsides are presented to the sight, which is supPosed to be on the Sun, from directly in front. When, there- fore, the eccentricity is very great, the relation of the motions is sensibly disarranged if we apply the mean diurnal motion without diminution to the mean distance, as if it appeared from the mean distance as large as it is; and this will appear below in the case of Mercury. All this matter is treated at greater length in “Epitome Astronomiae Copernicae," Book V, but it had to be given here because it concerns the very terms themselves of the celestial harmonies, when considered apart each by itself.

A source book in astronomy, by Harlow Shapley and Helen E. Howarth New York ètc. McGraw-Hill book co. 1929. 1St ed. pages 36-37 (From “Harmonice Mundi," Opera Omnia, Volumen Quintum; Edidit Dr- Ch. Frisch, 1864; translation by Dr. John H. Walden, 1928.) — Preceding unsigned comment added by 207.229.179.97 (talk) 04:51, 19 November 2012 (UTC)

Please remove
Someone who is confirmed might want to remove the :( from the section "Dioptrice, Somnium manuscript and other work". — Preceding unsigned comment added by 128.244.42.5 (talk) 21:00, 14 November 2012 (UTC)
 * Still there months later. 99.245.248.91 (talk) 23:06, 28 February 2013 (UTC)

Deleted reference
I deleted a reference in the "Reception of his astronomy" section of this article. Specifically, the text originally read: "Several astronomers tested Kepler's theory, and its various modifications, against astronomical observations."

The reference mentioned is: Mohammad Tayseer Kayed Al-Tamimi (2010) "Great collapse (kepler's first law)," Natural Science 2 (7) : 786-792. The pdf file containing this article is available on-line here:.

The journal "Natural Science" is an on-line journal that is hosted in the nation of Jordan. The author, Mr. Al-Tamini, is not fluent in English, but his basic argument is that the celestial equator does not coincide with the Earth's equator, and that if it did coincide, there would have been various consequences in Earth's climatic history, which have not been observed.

Since, according to Wikipedia's article on the celestial equator (and other sources), the celestial equator is defined to coincide with Earth's equator, Mr. Al-Tamini must be confused. I therefore deleted this reference.Cwkmail (talk) 19:02, 19 April 2013 (UTC)

After further study of Mr. Al-Tamini's article, he appears to have confused the "plane of the ecliptic" (the plane of the Earth's orbit around the Sun, which he calls the "Celestial's equator") with the "celestial equator" (the plane of the Earth's equator).Cwkmail (talk) 23:32, 19 April 2013 (UTC)


 * I'm unsure also about the reliability of the Connor source. A science historian describes the Casper reference as the standard biography and accuses the Connor reference of plagiarising from it (among other strongly dismissive criticisms). Shouldn't we just stick with the more authoritative source? Cesiumfrog (talk) 04:46, 23 June 2013 (UTC)

Odd sentence
Under "Other research", the odd sentence appears, "When he was an old man...". — Preceding unsigned comment added by 86.179.39.98 (talk) 14:27, 19 December 2013 (UTC)
 * It was probably vandalism. It was there for some months. — Preceding unsigned comment added by 86.179.39.98 (talk) 15:20, 19 December 2013 (UTC)

Why is Tycho Brahe constantly referred to by his first name?
I must have missed it where an entire editing staff became friends with a deceased astronomer, for what reason on earth is formality being excluded and Tycho Brahe constantly being referred to as Tycho instead of his last name Brahe? Since when is informality supposed to be accepted or commonplaces, especially for an article that used to be of such quality?
 * It is standard practice to refer to Tycho Brahe as Tycho (look at Brittanica or any of a number of other sources). As to why this is so, I don't know. Paul August &#9742; 16:55, 6 February 2015 (UTC)

Kepler's Equations - a kinematical deduction
In this e-book, the author presents a new deduction of the famous Kepler's equations using exclusively kinematical concepts. It contains the basic mathematical model to explain the true nature of Gravity and, consequently, of dark matter and dark energy. https://www.clubedeautores.com.br/book/133352--EQUACOES_DE_KEPLER?topic=cienciasexatas#.VSKqaMy5eM8 — Preceding unsigned comment added by 191.180.151.210 (talk) 15:50, 6 April 2015 (UTC)

Did Kepler steal Brahe's data?
In The Mechanical Universe, it is claimed that Kepler stole the data from Brahe's family after he died. Is this well founded?? Michel Djerzinski (talk) 09:13, 29 July 2015 (UTC)

Request
Can someone who has the book verify two things for me? It pertains to this change.


 * "He admitted later on after Susanna became ill…"

Firstly, can someone check Connor's book to see whether it was after Susanna's death or her falling ill that Kepler made this admission?

Secondly, regarding his admission, no luck seeing the pages via Google preview, but Amazon's look inside let me see that, on p.&#8239;228, Kepler is quoted: "I fell for her because of her tall build and athletic body…" This quote, however, is not within the page range (pp.&#8239;251–4) given in the cite for Connor's book. --YeOldeGentleman (talk) 14:46, 30 September 2015 (UTC)

Kepler's polyhedra
The article says "(within the accuracy limits of the available astronomical observations)". I am not sure that this is true. With his selected arrangement of his polyhedra, the errors were still in the region of 10%. This seems to be bigger than the errors in the observations. — Preceding unsigned comment added by 79.183.16.116 (talk) 12:34, 30 April 2015 (UTC)
 * See Johannes Kepler. — Preceding unsigned comment added by 109.158.49.171 (talk) 15:33, 1 October 2015 (UTC)
 * See www-groups.dcs.st-and.ac.uk/~history/Biographies/Kepler.html The biography says "the greatest error being less than 10%". This figure refers to Kepler's selected arrangement of polyhedra. — Preceding unsigned comment added by 90.215.231.115 (talk) 12:43, 3 October 2015 (UTC)

Kepler Fabricated Data In Nova
I made an edit citing a New York Times article (which itself cited a paper published by Harvard) explaining how Kepler lied in Nova in order to promote his elliptical orbit idea. This was undone with the explanation, "No thanks." I feel that feeling ungrateful for my edit does not justify its removal so with all due respect I am going to revert it soon. — Preceding unsigned comment added by 173.202.168.129 (talk) 22:52, 5 October 2015 (UTC)

Veneration
Kepler and Copernicus are said to be honoured by the Episcopal Church of the USA. Kepler was not an Episcopalian or an Anglican. Copernicus was not a Protestant at all. Some of this has already been noted. — Preceding unsigned comment added by 86.136.176.166 (talk) 11:57, 6 September 2016 (UTC)

Kepler portrait
I have painted and uploaded a portrait of Kepler performing optics experiments ('Kepler studying Imago and Pictura'). Could we add this picture to the article? It does not show up in the public version, yet. — Preceding unsigned comment added by Sascha Grusche (talk • contribs) 20:45, 30 September 2016 (UTC)

Discoveries
Kepler discovered many important facts about today's science — Preceding unsigned comment added by Mackenzieziegler (talk • contribs) 02:08, 16 January 2017 (UTC)
 * Indeed, and the article reflects that very well. As a featured article, it is one of Wikipedia's best articles, after all. – Finnusertop (talk ⋅ contribs) 02:20, 16 January 2017 (UTC)

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Date format
Why does a bio for a German uses the American date format? Is that deliberate, or should this be changed to the dmy format that is in common use in Europe?  Schwede 66  20:02, 18 March 2020 (UTC)
 * Well, an IP editor has just swapped it all over to dmy dates (pending changes, of course). So I'll ask again – why does this article use mdy?  Schwede 66  05:13, 20 April 2020 (UTC)
 * I believe dmy dates should be used here. See, for example, Carl Friedrich Gauss. —Bruce1eetalk 06:14, 20 April 2020 (UTC)
 * I've had a look and it was this edit in 2011 that placed the  tag. No other reason than that format already present in the article.  Schwede  66  07:31, 20 April 2020 (UTC)
 * MOS:DATETIES seems to indicate that dmy dates should be used here. —Bruce1eetalk 07:41, 20 April 2020 (UTC)
 * Indeed. Give it another 24 hours and if nobody who is watching this page pipes up, let's just accept those changes. My initial comment has certainly had enough air time.  Schwede 66  08:28, 20 April 2020 (UTC)
 * There may be a case for changing to DMY, but the IP is also changing American English spelling to British, and that violates MOS:RETAIN. Favonian (talk) 08:45, 20 April 2020 (UTC)
 * Sure. I could always run WP:MOSNUMscript; that would overcome that issue.  Schwede 66  08:54, 20 April 2020 (UTC)

Conversion to dmy is done.  Schwede 66  18:04, 21 April 2020 (UTC)
 * Thanks. —Bruce1eetalk 20:25, 21 April 2020 (UTC)

Rudolph or Rudolf?
Anyone have a strong opinion? It looks like olf is correct, but this article mostly uses olph William M. Connolley (talk) 13:14, 16 November 2020 (UTC)

Possible inspiration of Kepler's
See Jofrancus Offusius, who was mentioned by Kepler and who used Platonic solids. He might have inspired Kepler himself. — Preceding unsigned comment added by 186.64.208.32 (talk) 12:53, 11 January 2021 (UTC)
 * Tycho, Kepler and Cardano mentioned Jofrancus's book, of 1570. — Preceding unsigned comment added by 2A00:23C4:7C87:4F00:F0C3:26D6:7EE1:A427 (talk) 10:55, 24 November 2021 (UTC)

WP:URFA/2020
I am reviewing this (old or very old) FA as part of WP:URFA/2020, an effort to determine whether old featured articles still meet the featured article criteria. This article does not meet current FA standards. There is considerable uncited text. The "See also" section needs attention: FAs are supposed to be comprehensive, so most items worthy of mention in See also should be already incorporated into the article. Unless someone can bring the article to standard, it should be submitted to WP:FAR. Sandy Georgia (Talk)  23:31, 21 February 2022 (UTC)


 * I've addressed the specific citation needed tags; one section is still marked as needing improvement overall, but that may actually be more a matter of tone than footnotes (since it's pretty clear that nothing there was named for Bob Kepler of Peoria, Illinois). I've also culled the "See also" back to a more reasonable level. XOR&#39;easter (talk) 19:47, 16 July 2022 (UTC)

Wrong portrait of Kepler
According to arXiv:2108.02213 this picture does not show Johannes Kepler but most likely his teacher Michael Maestlin. I don't see a good replacement but it seems to me that this picture should not stay on the page! Is it possible to use one of the two more believable pictures from the arXiv article?Paepse (talk) 09:25, 6 August 2021 (UTC)
 * @Paepse: File:Portrait of Johannes Kepler.jpg or File:JKepler.jpg. --Thibaut (talk) 13:51, 6 August 2021 (UTC)
 * @Paepse and Thibaut: FYI: In the Dutch version this proposed correction is already applied by ChaokangTai on Aug 9 2021, by replacing said portrait with this one by Hans von Aachen. --C04DF16B (talk) 14:44, 28 January 2022 (UTC)
 * @Paepse and Thibaut and C04DF16B: for information, I have written a new paragraphe in the de-Wikipedia and fr-Wikipédia about Keplers portraiture. My feeling is : if the Kremsmunsters Kepler-portrait is wrong and became iconic after 2006, it is because Wikipedia has diffused it. So Wikipedia has to recognize this fact and to explain why this image has been taken back. If you agree, I propose you to make the seem in the en-article. A good source-document is for example aryabhata '(de)'. Regards. --Jacques Mrtzsn (talk) 14:50, 3 May 2022 (UTC)
 * I don’t see why not. Thibaut (talk) 16:55, 3 May 2022 (UTC)


 * It seems like this decade long misrepresentation of Kepler on Wikipedia itself is worthy to be mentioned in the bio. Tom Ruen (talk) 14:15, 28 December 2022 (UTC)
 * How a fake Kepler portrait became iconic (So how did the fake Kepler portrait spread? Except for Wolf’s and Günther’s mentions, we cannot find any examples of the portrait attributed as being Kepler before 2005. That’s the year the portrait first appeared on Wikipedia, and thereafter it became ubiquitous. For example, it appears in a European Space Agency press release from 2011 (explicitly citing Wikipedia))
 * File:Johannes Kepler 1610.jpg (Often mistaken for Kepler but is a 19th century copy of an unknown original, allegedly from 1610. It is more likely based on the portrait of Michael Maestlin, Kepler's teacher. )
 * I see it is still linked various places, including here:

pls make me a slideshow on the life of kepler it’s for science and you are very smart and nice.
I have a project in science and i need a slideshow in his early life, adulthood, late time and a story from their life 50.237.188.172 (talk) 13:17, 19 January 2023 (UTC)
 * We typically don't do homework for people here. However, if you'd like to look up some free-to-use images for your slideshow, scroll way down to the bottom of the article under the "external links" section, and there is a link there in a box titled "Wikipedia's sister projects" with a link to "Media from Commons". That will be a good place to look. Ivanvector (Talk/Edits) 13:36, 19 January 2023 (UTC)