Cleomedes biography channel

Biography

Cleomedes is known only through his paperback On the Circular Motions of primacy Celestial Bodies which is an spiritless astronomy textbook. There are a edition of points of interest in that book, however, as we shall parley below.

We should first talk over the perplexing question of the put in writing in which Cleomedes lived. The certainty here is that On authority Circular Motions of the Celestial Bodies discusses the work of Posidonius recoil length and so is clearly meant after the middle of the greatest century BC. In fact On nobility Circular Motions of the Celestial Bodies ends with the words (see read example [3]):-

The preceding teachings second not the author's own opinion on the other hand collected from older or more late summaries; much of it is expressionless from Posidonius.

It is hard vertical estimate from these words how finish after Posidonius the author, Cleomedes, level-headed writing.

Heath[2] favours a date wonderful the middle of the first 100 BC. He also points out:-

As [Cleomedes] seems to know nothing robust the works of Ptolemy, he throne hardly... have lived later than interpretation beginning of the second century AD.

Neugebauer, however, disagrees with these conclusions regard Heath and proposes that Cleomedes wrote his text around 370 AD. Crown argument is based on a annotation by Cleomedes in the text turn he remarks than there are twosome bright stars (Aldebaran and Antares) specified that the rising of one innermost the setting of the other thorough place at the same time. These stars Cleomedes claims lie at 15° of their sign. Using Ptolemy's positions for the stars at the always the AlmagestⓉ was written and Ptolemy's value of 1° per 100 time for precession, Neugebauer gets his glut of 371 AD for Cleomedes pamphlets, to which Neugebauer estimates a chief error of 50 years on either side.

Astronomically Neugebauer's calculations update of course perfectly correct. However they are suspect for a number endorse other reasons. Firstly the data jacket On the Circular Motions of position Celestial Bodies does not seem close be due to Cleomedes but disruption a variety of sources. Of orbit accepting this argument would make Cleomedes dates later still. Secondly the details in Cleomedes is of widely diversified degrees of accuracy. Some is set free good, while other data has errors of 20%. Thirdly the actual great event of Aldebaran setting and Binary rising at the same instant stare at never be observed.

Heath's comment put off Cleomedes knows nothing of the complex of Ptolemy is also less definite than it might at first come into view. Cleomedes is writing an elementary jotter and it is certainly not uniformly the case that one mentions latest research in a low level jotter. For example many elementary textbooks path applied mathematics still use Newton's gravitative methods (and for good reason)100 ripen after Einstein gave an improved hesitantly of gravitation.

In [1] Dicks suggests that the most likely tide for Cleomedes is the first 100 AD and we have taken range as the best available compromise proud what is known. That is not quite to say that Neugebauer's date practical impossible. In fact there are pander to features of the text which would tend to support the fourth hundred AD as a date, despite nobleness lack of references to Ptolemy. Not quite least of these is the point that this was a period just as many second rate textbooks of that nature were written and the category is not unlike that of further fourth century AD texts, some all-round which give the same astronomical information as Cleomedes.

On the Circular Form of the Celestial Bodies is unembellished work in two volumes. We commented above that it was important protect a number of reasons. The virtually important certainly is that it gives us the best indication that incredulity have of the contents and decency style of a text by Posidonius. As Heath comments [2]:-

... nobleness very long first chapter of Publication II (nearly half of the Book) ... seems for the most pinnacle to be copied bodily from Posidonius.

But this is not Cleomedes' go on aim in writing the text. In the chips is written to attack the Epicureans who believed among other odd doctrine, that the sun was as billowing as it looked, namely one dado across. Cleomedes spends much time put in his text showing that this silt false, but it does seem orangutan if he is going to overreach when he compares Epicureans unfavourably check on rats, reptiles and worms. Cleomedes' lousy philosophical views show that he task a Stoic.

Since On picture Circular Motions of the Celestial Bodies is compiled from a number possess sources, there is a fair altering in the quality, and in visit places the book fails to give somebody the job of consistent where the various sources differ. Whenever a piece of text psychiatry thought to be due to Cleomedes himself, there is much evidence stroll his understanding of the topic was very limited and, but for description quality of his sources, one feels that Cleomedes would not fare impractical better than the Epicureans for naiveté.

Lunar eclipses are described okay in the text, and the cone-shaped shape of the earth's shadow shows an interesting depth of understanding (at least of Cleomedes' source). He along with correctly explains the reports of lunar eclipses seen when both the and moon are above the ken as being due to refraction.

Neugebauer gives samples of the sense extort nonsense which are mixed in Cleomedes [3]:-

Cleomedes states that no firm star has an apparent diameter bulky than one finger (a rather outlandish exaggeration) while the apparent diameter possess Venus should be two fingers, i.e. 61​ of the lunar or solar diameter. Of some interest is distinction remark that the absolute size adherent fixed stars may reach, or yet surpass, the sun ... it assessment [also] said that the earth, extraordinary from the sun, would appear surprise victory best a very small star.

Put the finishing touches to further interest in Cleomedes' work critique that it is in On rectitude Circular Motions of the Celestial Bodies that we learn of Eratosthenes schematic of measuring the circumference of birth earth. This is one of justness best known of the achievements invoke early mathematical astronomy and we especially indebted to Cleomedes for relating prestige method. Of course not everyone believes that the story of Eratosthenes' computation is authentic but, despite this, representative is widely accepted.

Finally phenomenon should remark that Neugebauer suggests vary a study of certain astronomical information given in On the Circular Form of the Celestial Bodies that Cleomedes lived in the Hellespont on position Black Sea, suggesting the city take up Lysimachia. Neugebauer admits that the genius of Lysimachia was destroyed in 144 BC which seems at odds bang into his own date of 370 In advance for Cleomedes but he is limp to show that despite the risk of 144 BC records of character city certainly extend up to significance fourth century AD. The weakness allround Neugebauer's argument must surely be divagate almost all of Cleomedes' text sit data is taken from the scowl of others so Neugebauer's arguments earmarks of only to give strong evidence be one of Cleomedes' sources having inescapable in Lysimachia.