67 votes

What is Ptolemy holding in this picture?

This device was invented by a Jewish Rabbi, Levi Ben Gershon. It was used to measure the angular distance between two stars or, in general, any pair of celestial bodies. Ptolemy lived 1000 years ...
Riccardo.Alestra's user avatar
61 votes
Accepted

What is Ptolemy holding in this picture?

It is called "Jacob's staff". It was an old astronomical tool used for trigonometric purposes.
Euler_Salter's user avatar
19 votes

What is Ptolemy holding in this picture?

And this tool has been known under many other latin names than baculus Jacob (or Jacob's staff): radius astronomicus (astronomic ray), crux geometrica (geometrical cross), revelatorem secretorum (...
Laurent Duval's user avatar
9 votes

How did Romans do multiplications?

They used abacus. The techniques used for operations with abacus were understood and were basically the same used also until quite recent time also in China and Japan, as far as I know. This does not ...
Nicola Ciccoli's user avatar
8 votes

How did Romans do multiplications?

You should be more specific when you say "Romans". If you mean ancient Romans, almost no mathematical text survived in Latin from the times before 2nd century AD. From the Roman empire we mostly have ...
Alexandre Eremenko's user avatar
7 votes
Accepted

Did Archimedes view fractions as "numbers"?

No, Archimedes, and ancient Greeks generally, did not see fractions as numbers, and they did not use fractions as we use them today, they did not use them at all. What they used was ratios of ...
Conifold's user avatar
  • 76k
6 votes

Has anyone explored Ptolemy's epicycles as an early form of Fourier analysis?

As @Andrei Kopylov noticed, epicycle theory is not the theory of Fourier series of a periodic function. Still this is called (generalized) Fourier analysis. Such functions are called almost periodic ...
Alexandre Eremenko's user avatar
6 votes

What happened to the original sources of Euclid's Elements?

Multiple copies of the works of Euclid's predecessors probably existed. Including similar compilations called Elements. On the opinion of people who did mathematics at the time and after Euclid, his ...
Alexandre Eremenko's user avatar
6 votes

How did Archimedes arrive at his principle in his time?

The bath is a later legend. The principle can be discovered and proved by the following argument which requires no calculation. Suppose that a body is submerged by water. The force with which water ...
Alexandre Eremenko's user avatar
5 votes
Accepted

Did the ancients know how to construct a correct klepsydra?

At least, in ancient Greece and Rome I am not aware of the vessel shape being used as a way to uniformize the flow of water. Instead, "correct" clepsydras were constructed using a different ...
Conifold's user avatar
  • 76k
5 votes
Accepted

Were ancient Romans so bad at computations before Arab numerals?

No, Romans were not at all bad at computations before Arab numerals were introduced to them. In fact, Romans had a perfectly fine way of doing computations that was every bit as good as Arabic ...
Big Brother's user avatar
  • 2,187
5 votes

On Ptolemy climes

Originally, the Greek word κλῐ́μᾰ means “slope, incline, inclination,” and has nothing to do with the modern meaning of the word (long-term weather). Ptolemy defined the seven climata by the length of ...
Pierre Paquette's user avatar
5 votes

How did Ptolemy calculate the distance to the Moon?

Ptolemy knew about the Moon's parallax (he explains it in section 11, Ch. V of Mathematical Syntaxis). To measure it he invented the "parallactic instrument" described in section 12. Section 13 is ...
Alexandre Eremenko's user avatar
4 votes

Did Aristotle note that ships disappear over the horizon hull-first?

From "Queries and Answers," Isis 41, no. 2, linked to by sand1 in the comments above, we see that the proof of the sphericity of the earth based on the fact that the masts of a distant ship are ...
Endy's user avatar
  • 279
4 votes

Did Aristotle note that ships disappear over the horizon hull-first?

I dug up some text from a translation of "on the heavens." There are similar disputes about the shape of the earth. Some think it is spherical, others that it is flat and drum-shaped. For ...
Carl Witthoft's user avatar
3 votes

Roman engineers

One of the most important contributions of Latins to engineering was road-building. This certainly pre-dates contacts with the Greek civilization: so called "strade consolari" departing from Rome (...
Nicola Ciccoli's user avatar
3 votes

Has anyone explored Ptolemy's epicycles as an early form of Fourier analysis?

This is very popular myth, but it is not true: Ptolemy's epicycles are not Fourier analysis! Fourier series can indeed approximate an arbitrary periodic function. And you can approximate an arbitrary ...
Alexei Kopylov's user avatar
2 votes

Has anyone explored Ptolemy's epicycles as an early form of Fourier analysis?

Yes. That was done by Giovanni Schiaparelli in a book called Scritti sulla storia dell'astronomia antica, published in 1926 and reprinted in 1997.
José Carlos Santos's user avatar
2 votes

How did Archimedes arrive at his principle in his time?

Fortunately there is some documentary evidence about Archimedes' discovery, in his work "On Floating Bodies", which survives in manuscript forms (https://en.wikipedia.org/wiki/On_Floating_Bodies). ...
terry-s's user avatar
  • 4,445
2 votes

Why did Aristotle make mistakes in his laws of motion?

Everyone makes mistakes. Look at Newton, even though he knew perfectly well that action at a distance was philosophically speaking, nonsense, he still went with it because he could see no way past ...
Mozibur Ullah's user avatar

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