Skyscript Astrology Forum

I am not sure if this discussion has already taken place, if so then possibly if someone could give a link to it, that would be great.

In some light research on Hipparchus, Wikipedia article states that Ptolemy work was copied from Hipparchus. The below quote states: THE mentioned researchers have shown conclusively that Ptolemy did indeed copy Hipparchus.

In the St. Andrews University of Mathematics bio on Ptolemy, it states Tyco Brahe, was the first to make accusations against Ptolemy for fraud, then many others after.

Also in James Holden's Book: History of Horoscopic Astrology, Holdens opinion of Ptolemy falls just short of plagarism, and does not speak too highly at first of Ptolemy, or the Tetribiblos.

My question is: What are the opinions of Skyscript members?

The references on the bottom to the article are impressive.

The link to the below is: http://en.wikipedia.org/wiki/Hipparchus

Delambre, in 1817, cast doubt on Ptolemy's work. It was disputed whether the star catalog in the Almagest is due to Hipparchus, but 1976?2002 statistical and spatial analyses (by R. R. Newton, Dennis Rawlins, Gerd Grasshoff,[26] Keith Pickering[27] and Dennis Duke[28]) have shown conclusively that the Almagest star catalog is almost entirely Hipparchan. Ptolemy has even (since Brahe, 1598) been accused by astronomers of fraud for stating (Syntaxis, book 7, chapter 4) that he observed all 1025 stars: for almost every star he used Hipparchus' data and precessed it to his own epoch 2? centuries later by adding 2?40' to the longitude, using an erroneously small precession constant of 1? per century.

Another source, references the same accusations: Scotland?s University of St. Andrews, Mathematics Dept. Toward the end of the article.

Ptolemy Link Print Version:
http://www-history.mcs.st-and.ac.uk/his ... olemy.html

I find Ptolemy many times does not mention his sources, and just says "the ancients", as if he is in a hurry in writing, or compiling the Tetribiblos, he doesn't give alot of credit to his sources much anywhere, so in that sense, I do agree with James Holden, in his book, History of Horoscopic Astrology, regarding that point.

So if he copied Hipparchus, then how much of the rest is plagarised, and even that he leaves out a volume of information that was available at the time in Greek Astrology. Again a point I agree with James Holden.

What are your thoughts?
Take Care,
Morning Sun

First off, Ptolemy is famous for two books. There is the Syntaxis, commonly called the Almagest, in which astronomy is discussed. Then there is Tetrabiblos (or 'the four books', confusingly) in which astrology is discussed. The Hipparchus issue is concerned with the Almagest and not Tetrabiblos.

As for whether Ptolemy did "plagarise" Hipparchus, it is worth noting that the citations in the piece you quoted are from notable mavericks in the history of astronomy discipline. The Dennis Duke citation, for example, was for an article in his own journal, so there is a question mark over the peer review process. You might want to look at http://en.wikipedia.org/wiki/Dennis_Rawlins for a more balanced view of his reputation?

I will conclude by noting that Ptolemy states that he examined Babylonian astronomical records going back to around 700 BC and as that would appear to be the start of any systematic Babylonian records, that would seem about right. Ptolemy did not just sit back and use Hipparchus' data exclusively. Too, both Almagest and Tetrabiblos are towering achievements; Almagest because it formed the basis of, and was the standard text for astronomy for the next 1500 years, and Tetrabiblos because it crystallised an objective scientific philosophy of astrology which today, two thousand years later, is still the lens through which we view astrology.

Geoffrey

Hello Geoffrey,

Yes, I believe most people here are familiar with Ptolemys books. If you read both links, and the full bio, not only of these links, but any university links, Sanford, Princeton, encyclopedia Brittanica on Hipparchus, Ptolemys use of Hipparchus' observations and calculations, are stated almost everywhere, as if it is common knowledge. As stated in the first link, Tyco Brahe was the first among several, to accuse Ptolemy of using Hipparchus' observations and calculations.

Research sites in mathematics, astronomy and philosophers, will bring up the same info. Of course, as the articles/bio's say he still made major contributions to astronomy and mathematics in his own right, and more so in geography and map making. However, it seems this long standing debate of copying Hipparchus has been settled that he did, in light of the most current info.

Even in the Tetribiblos, there is something quite not right, As I mentioned in my first post and that I agree with James Holden's assessment in his book, The History of Horoscopic Astrology.

Always appreciate your point of view, as it's late I will have to read the link you posted as well as some of the other reference links tomorrow.
Take Care,
Morning Sun

varuna2 wrote: Some (e.g. Weber and Burgess ) have said this alternative verse is attributing the text to the Greeks and specifically to Ptolemy - but there is one discrepancy here: the surya siddhanta gives the rate of precession (at the time of the compilation) as 54", whereas Ptolemy and Hipparchus gave the rate of precession as 36". The current value being somewhere around 50.26". If they copied Ptolemy and Ptolemy's predecessor, then how did they not also copy their error?

Hello Varuna,

Enjoyed your post!

The bio from St. Andrews Math Dept. states that Hipparchus's value was 46" and Ptolemy's 300 years later was 36", compared to the modern value of 50.26. So it was a huge contribution to Science and no small feat to discover the precession and Ptolemy does give Hipparchus the credit for that.

However the real jist of the fraud accusation against Ptolemy as I understand it, is that he stated that the observations he made were HIS observations for this star catalogue, when in actuality his observations could not have amounted to more than half the catalogue. Apparently, he used the same numbers Hipparchus did, which the researchers say, was from Hipparchus' LOCATION and adjusted for the precession, rather than from Ptolemy's own observations. In addition he used the precise value that Hipparchus did, which produced errors in the rest of his work, which apparently gave rise to the grounds of the accusations, he would have had to have an error of 28 hours in his observation of the equinoxz to produce that error, which as stated in the (St Andrews bio on Ptolemy), was unbelievable that he could have made an error of this magnitude.

Hipparchus also introduced the division of a circle into 360 INTO Greece. Tracing back further, Thales of Miletus (Turkey) is unanimously ascribed to bringing the introduction of mathematical and astronomical sciences into Greece. (620-546 BC). And it is interesting that all of the Greek mathematicians and astronomers, traveled to Egypt, including Pythagoras, Heracitus, Eudoxus, Empedocles, and brought back the information to Greece.

I agree with you Varuna and Geoffrey, that the knowledge was built upon the Sumarians, Babylonians ( zodiac constellations were already named by the Babylonians, and the Math from the Egyptians, and improved upon throughout the ages.

It is also interesting to note that in the "History of Horoscopic Astrology" by James Holden, states that Ptolemy's Tetrabiblos was not mentioned by any astrologers until Porphyry, over 100 yrs later. Many other points he makes about the Tetrabiblos which I agree with, such as most astrologers of the day used the Egyptian terms, I believe Zoller still uses those also, as well as not mentioning his sources, only to describe them as ?the ancients?. My feeling is that Ptolemy was in a hurry and took shortcuts, due to time constraints.

All food for thought! Interesting.
Take Care,
Morning Sun

Pankajdubey,

Thanks so much for the Link!!

varuna2 wrote:Thanks PD.

I had read that thread and what Deb wrote and forgot about it, perhaps last summer.

Now I also know why they were so obsessed with Hipparchus.

According to them, Mesopotamia was the 'cradle of civilization' in their arrogant conceit, and Hipparchus was using Mesopotamian data.

If Indians' only defence against Alexander was to scare him to not go beyond Punjab because it full of strange people ,then you cannot blame the Greeks for thinking Mesopotamia was the cradle

There is a nice paraphrasing of the issues in an article, "The Great Ptolemy-Hipparchus Dispute", by Bradley E. Schaefer in "Sky and Telescope" magazine, February 2002.

Schaefer shows that the answer would appear not to be clear cut. Ptolemy would appear to have used several data sources to compile his star catalogue, but the data were mixed and matched in complex ways which - after two thousand years - is now probably impossible in untangle.

That did not stop Schaefer having another stab at solving this dispute and the results of this attempt are described in a paper, "Atmospheric extinction in early star catalogues" in the Journal for the History of Astronomy (February issue this year). Schaefer's idea was a clever one and based on the fact that Ptolemy's catalogue not only gives the positions of the stars, but also their magnitude - how bright they appear to be.

Now, the light from stars that are near the horizon is dimmed because it has come to the observer obliquely through the atmosphere and so is absorbed. When stars get very close to the horizon, the light from them is absorbed so much by the atmosphere that we are no longer able to see them. How close the star can be to the horizon before we lose sight of it depends on how bright it is, and a rule of thumb is that the "extinction angle" in degrees above the horizon is equal to the magnitude of the star - so a forth magnitude star will not be observable if is it less than four degrees above the horizon.

The Southern most stars in Ptolemy's catalogue would never have crawled far above the horizon, so Ptolemy's observed magnitudes for those stars should be less than for stars which he would have observed higher in the sky, and which we know from modern measurements have the same magnitude. So, by seeing by how much Ptolemy's magnitudes of those Southern most stars are reduced, it is possible to determine at what latitude the observations were done. Was it Rhodes at 37 degrees? or Alexandria at 31 degrees? Ptolemy's magnitudes were actually good enough that we should be able to get at the latitude of the observatory within half a degree, and so determine if it was Ptolemy at Alexandria who made the observations, or Hipparchus at Rhodes.

But - Schaefer found a most surprising result. The magnitudes for Ptolemy's catalogue were corrected for the dimming due to the atmosphere! Since it is not until the 18th century that anybody came up with any sort of formulation for the dimming of starlight by atmospheric absorption, and it is only in the last few decades that the complex formula was finally arrived at, it is extraordinary that Ptolemy's catalogue shows that his magnitudes were extinction corrected. Unfortunately, it also means that we cannot tell at which latitude the observations were taken for the catalogue, so we are still no nearer a definite resolution to the problem.

Geoffrey

http://arxiv.org/pdf/1303.1833.pdf

I did not understand the very technical bits but what is interesting is that when Tyco Brahe got confused about the magnitude of discrepant stars he agreed(or copied) 42% of them from Ptolemy !!

Hopefully, there were not many more Ptolemy's after our Ptolemy who kept on modifying Almagest.This was not uncommon in olden times.If you are big enough to take the title ,you are considered clever enough to modify the work of the predecessor.

Varahamihira mentions a Surya Siddhanta which takes a very different shape and the verses removed by the time it is compiled in its current form.So, the siddhantas could be modified as well.

Thanks for that PD. In particular, thanks for the electronic version of Schaefer's paper. There is a lot more information than in the JHA hard copy version of the paper. Schaefer referred there to detail that was in the electronic paper, but did not give a URL web address where to find it.

It is interesting that not only Ptolemy's star 2nd century catalogue was extinction corrected, but also that of Al Sufi (10th century) and that of Tycho Brahe (16th century). None of them say a word about how they corrected their magnitudes for atmospheric absorption.

Lest PD's comments give the impression that Tycho simply lifted Ptolemy's star magnitudes, let me quote from Schaefer's paper "I evaluate the fraction of magnitudes in Tycho's catalogue that were copied or influenced from the Almagest. This fraction is found to be small, perhaps 10% or perhaps even zero."

Geoffrey

No he wasn't a "fraud." The standards of scholarship were utterly different in the past. Plagiarism without attribution, or attributing one's material to sources who couldn't possibly have written them, were normal. Ptolemy was writing a textbook. He was a real polymath, widely published in different fields. Of course, he got a bunch of stuff wrong. But such is the nature of scientific progress.

I am so sorry for diverting the talking topic , but Could anyone help me which version of Almagest is better? Or you have another recommendation? Thank you in advance.

http://www.amazon.com/Ptolemys-Almagest ... 0691002606
http://www.amazon.com/Almagest-Introduc ... 1888009438
http://www.amazon.com/Ptolemys-catalogu ... 1178325091
http://www.amazon.com/Ptolemys-Catalogu ... 149374240X