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[6] [7] [8] Quizlet's blog, written mostly by Andrew in the earlier days of the company, claims it had reached 50,000 registered users in 252 days online. [9] In the following two years, Quizlet reached its 1,000,000th registered user. [10] Until 2011, Quizlet shared staff and financial resources with the Collectors Weekly website. [11]
The works of Ptolemy (astronomy) and Galen (medicine) were found not always to match everyday observations. Work by Vesalius on human cadavers found problems with the Galenic view of anatomy. [187] The discovery of Cristallo contributed to the advancement of science in the period as well with its appearance out of Venice around 1450.
Ptolemy I and other early rulers of the dynasty were not married to their relatives, the childless marriage of siblings Ptolemy II and Arsinoe II [22] being an exception. The first child-producing incestuous marriage in the Ptolemaic dynasty was that of Ptolemy IV and Arsinoe III , who were succeeded as co-pharaohs by their son Ptolemy V , born ...
The Planisphaerium is a work by Ptolemy. The title can be translated as "celestial plane" or "star chart". In this work Ptolemy explored the mathematics of mapping figures inscribed in the celestial sphere onto a plane by what is now known as stereographic projection. This method of projection preserves the properties of circles.
Three important textbooks, written shortly before Ptolemy's time, were written by Cleomedes, Geminus, and Theon of Smyrna. Books by Roman authors like Pliny the Elder and Vitruvius contain some information on Greek astronomy. The most important primary source is the Almagest, since Ptolemy refers to the work of many of his predecessors. [3]
Work continued for most of the Ptolemaic dynasty; the main temple was finished in the reign of Ptolemy IV in 231 BC, and the full complex was only completed in 142 BC, during the reign of Ptolemy VIII, while the reliefs on the great pylon were finished in the reign of Ptolemy XII. Other construction work took place at a range of sites ...
The geocentric system was still held for many years afterwards, as at the time the Copernican system did not offer better predictions than the geocentric system, and it posed problems for both natural philosophy and scripture. The Copernican system was no more accurate than Ptolemy's system, because it still used circular orbits.
Ptolemy did not predict the relative sizes of the planetary deferents in the Almagest. All of his calculations were done with respect to a normalized deferent, considering a single case at a time. This is not to say that he believed the planets were all equidistant, but he had no basis on which to measure distances, except for the Moon.