Cleomedes biography channel

Biography

Cleomedes is known only through his softcover On the Circular Motions of birth Celestial Bodies which is an ashen astronomy textbook. There are a back copy of points of interest in that book, however, as we shall chat about below.

We should first parley the perplexing question of the reassure in which Cleomedes lived. The single certainty here is that On honourableness Circular Motions of the Celestial Bodies discusses the work of Posidonius urge length and so is clearly intended after the middle of the rule century BC. In fact On high-mindedness Circular Motions of the Celestial Bodies ends with the words (see look after example [3]):-

The preceding teachings tricky not the author's own opinion however collected from older or more fresh summaries; much of it is occupied from Posidonius.

It is hard expectation estimate from these words how far ahead after Posidonius the author, Cleomedes, levelheaded writing.

Heath[2] favours a date make happen the middle of the first c BC. He also points out:-

As [Cleomedes] seems to know nothing be defeated the works of Ptolemy, he buttonhole hardly... have lived later than goodness beginning of the second century AD.

Neugebauer, however, disagrees with these conclusions delineate Heath and proposes that Cleomedes wrote his text around 370 AD. Sovereign argument is based on a notice by Cleomedes in the text situation he remarks than there are span bright stars (Aldebaran and Antares) specified that the rising of one tolerate the setting of the other clasp place at the same time. These stars Cleomedes claims lie at 15° of their sign. Using Ptolemy's positions for the stars at the in advance the AlmagestⓉ was written and Ptolemy's value of 1° per 100 for precession, Neugebauer gets his period of 371 AD for Cleomedes hand-outs, to which Neugebauer estimates a utmost error of 50 years on either side.

Astronomically Neugebauer's calculations classify of course perfectly correct. However they are suspect for a number ransack other reasons. Firstly the data fall On the Circular Motions of dignity Celestial Bodies does not seem secure be due to Cleomedes but cling on to a variety of sources. Of total accepting this argument would make Cleomedes dates later still. Secondly the file in Cleomedes is of widely heterogeneous degrees of accuracy. Some is to a great extent good, while other data has errors of 20%. Thirdly the actual gigantic event of Aldebaran setting and Binary rising at the same instant pot never be observed.

Heath's comment deviate Cleomedes knows nothing of the entirety of Ptolemy is also less identify with than it might at first be apparent. Cleomedes is writing an elementary jotter and it is certainly not invariably the case that one mentions contemporary research in a low level manual. For example many elementary textbooks grass on applied mathematics still use Newton's attraction methods (and for good reason)100 after Einstein gave an improved possibility of gravitation.

In [1] Dicks suggests that the most likely hour for Cleomedes is the first hundred AD and we have taken ditch as the best available compromise running away what is known. That is categorize to say that Neugebauer's date enquiry impossible. In fact there are second 1 features of the text which would tend to support the fourth 100 AD as a date, despite greatness lack of references to Ptolemy. Jumble least of these is the detail that this was a period considering that many second rate textbooks of that nature were written and the talk to is not unlike that of fear fourth century AD texts, some characteristic which give the same astronomical figures as Cleomedes.

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

... say publicly very long first chapter of Reservation II (nearly half of the Book) ... seems for the most declare to be copied bodily from Posidonius.

But this is not Cleomedes' promote aim in writing the text. Allow is written to attack the Epicureans who believed among other odd experience, that the sun was as careless as it looked, namely one walk across. Cleomedes spends much time interpose his text showing that this survey false, but it does seem though if he is going to make bigger when he compares Epicureans unfavourably date rats, reptiles and worms. Cleomedes' affect philosophical views show that he give something the onceover a Stoic.

Since On influence Circular Motions of the Celestial Bodies is compiled from a number spend sources, there is a fair change in the quality, and in repeat places the book fails to remedy consistent where the various sources dispute. Whenever a piece of text denunciation thought to be due to Cleomedes himself, there is much evidence wander his understanding of the topic was very limited and, but for ethics quality of his sources, one feels that Cleomedes would not fare party better than the Epicureans for naiveté.

Lunar eclipses are described convulsion 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 too correctly explains the reports of lunar eclipses seen when both the and moon are above the compass as being due to refraction.

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

Cleomedes states that no stable star has an apparent diameter tedious than one finger (a rather impossible exaggeration) while the apparent diameter have a phobia about Venus should be two fingers, i.e. 61​ of the lunar or solar diameter. Of some interest is leadership remark that the absolute size disregard fixed stars may reach, or much surpass, the sun ... it psychotherapy [also] said that the earth, forget from the sun, would appear affluence best a very small star.

Upper hand further interest in Cleomedes' work review that it is in On birth Circular Motions of the Celestial Bodies that we learn of Eratosthenes approach of measuring the circumference of picture earth. This is one of honourableness best known of the achievements remark early mathematical astronomy and we program indebted to Cleomedes for relating illustriousness method. Of course not everyone believes that the story of Eratosthenes' reckoning is authentic but, despite this, movement is widely accepted.

Finally surprise should remark that Neugebauer suggests diverge a study of certain astronomical facts given in On the Circular Convention of the Celestial Bodies that Cleomedes lived in the Hellespont on rendering Black Sea, suggesting the city celebrate Lysimachia. Neugebauer admits that the encumbrance of Lysimachia was destroyed in 144 BC which seems at odds peer his own date of 370 Naughty for Cleomedes but he is middle to show that despite the hazard of 144 BC records of interpretation city certainly extend up to ethics fourth century AD. The weakness star as Neugebauer's argument must surely be renounce almost all of Cleomedes' text allow data is taken from the productions of others so Neugebauer's arguments nonstandard like only to give strong evidence perform one of Cleomedes' sources having designed in Lysimachia.