Did Ptolemy 's theory agree with the quantitative observations known in Ptolemy's time? How were

Did Ptolemy 's theory agree with the quantitative...

Key Concepts

Quantitative Observations in Ancient Astronomy

These are precise measurements of celestial positions and movements made by ancient astronomers using careful recording methods. The quantitative aspect was central in verifying and refining astronomical theories, including assessing the accuracy of the geocentric models in relation to the apparent paths of the planets and stars.

Ptolemaic Theory

This refers to the geocentric system developed by Claudius Ptolemy, in which the Earth is positioned at the center of the universe and all other celestial bodies move in complex paths involving circles and epicycles. It was designed to mathematically reproduce the observed motions of the planets and was the dominant astronomical framework for many centuries.

Astronomical Instruments in Antiquity

Ancient astronomers employed a range of instruments, such as the astrolabe, armillary sphere, and sundial, to measure angles and track the movements of celestial bodies. These tools allowed them to obtain numerical data on the positions and phases of planets and stars, which was critical for the development and validation of models like Ptolemy’s.

Transcript

00:01 Here we're going to address the question about why ptolemy's model lasted so long.

00:08 So just for point of reference, ptolemy created the model about in 150 ad.

00:16 And the bottle and its predictions were included in a large work that you can find translated online called the almagest, which proved to have accurate predictions up until about 1400 ad.

00:39 So the predictions were starting to get off by a couple degrees.

00:46 And what i'm going to specifically point out the predictions of planetary positions in the sky.

01:02 And at that time, in roughly 1400 ad, what you would have is people, still using the model to revise the predictions.

01:13 Like we know the sky does precess, i should say the earth precesses, and it does change the way the sky appears over very long time periods.

01:27 In fact, if you go get a star map that's printed out as opposed to being on the internet where it can be revised and updated regularly, star maps themselves are really.

01:38 Remade every 50 years.

01:42 But anyway, this is pretty good that these predictions of planetary orbits and positions in the sky would have been good for close to 1 ,500 years.

01:54 So not bad.

01:57 The other thing to note is that people really were, how to say, vested in having these positions accurately predicted, simply because astrology was a big deal, bigger deal several thousand years ago than it is now.

02:17 People would have been using astrology to make political moves, for example, moves for war or planning for famines and things like that.

02:30 Anyway, how did the model, how did people compare the model to observations? so you have to have some sort of measurement technique.

02:41 Now, telescopes have not been invented, so we are talking all about naked eye observations, which sounds pretty flaky, not to be trusted, but people did have measuring tools.

03:02 So think about protractors and rulers.

03:14 You can make pretty good measurements with those instruments if you're careful and if you know what you're doing...

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