Talk:Johannes Kepler

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)

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)

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 last one is/M.T.K Al -Tamimi/ Natural Science 2 (2010) 786-792>."

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: http://www.scirp.org/journal/PaperInformation.aspx?paperID=2313 .

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.