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29 votes
2 answers

How did Eratosthenes know the Sun was very far away?

Eratosthenes calculated the radius of the Earth from the difference of the lengths of shadows between Aswan and Alexandria were different (see also here). But this could also happen if the Earth were ...
Rohit Pandey's user avatar
11 votes
3 answers

How did Eratosthenes determine that Alexandria and Syene were on the same meridian?

As discussed over here, Eratosthenes measured the earth’s circumference by comparing shadows cast at apparent noon at two locations separated by a known distance. Although accounts of the event (like ...
Chaim's user avatar
  • 309
10 votes
3 answers

How did Eratosthenes know the distance between Aswan and Alexandria?

In his well-known measurement of the Earth, and according to Cleomedes, Eratosthenes estimated in 5000 stades the distance between Aswan and Alexandria. Modern accounts state that he calculated the ...
xxavier's user avatar
  • 694
9 votes
1 answer

When was it discovered that the Earth wasn't round?

We know the Earth isn't a sphere: that is, the equatorial circumference isn't equal to the polar circumference. When (and how) was this discovered? I can put a lower bound of around the 3rd century ...
Mark's user avatar
  • 495
8 votes
2 answers

Why did Columbus think the Earth was much smaller than it is?

Columbus set off on his westward journey to Asia, believing the Earth was much smaller than it is. There was some apparent disagreement about the size, and Columbus was staking his life on it. Why ...
MWB's user avatar
  • 181
7 votes
2 answers

When was the issue of time zones at different longitudes first described?

What are the earliest recorded acknowledgements of the concept that motivates time zones - that the sun and other celestial objects appear in different parts of the sky to people at different ...
Isaac Moses's user avatar
6 votes
1 answer

How did cartographers of past centuries determine latitude and longitude?

When were the concepts of latitude and longitude first introduced? How did cartographers determine them?
Leandro Caniglia's user avatar
5 votes
2 answers

Did the coordinate system used by Eratosthenes influence the development of the Cartesian coordinate system?

The first coordinate system was used by Eratosthenes to locate things using 2 points. Did this influence the development of the Cartesian coordinate system in any way?
user avatar
5 votes
1 answer

Early geographically accurate drawings of Earth

The first, known to me, drawing of a simulated view of Earth from outside—roughly passable* by modern standards—is this pic from 1834 attributed to Henry De la Beche (source: Was ...
Incnis Mrsi's user avatar
5 votes
1 answer

How many people knew that Earth is spherical in different ages?

For the umpteenth time, I'm reading in some book (no intention to pillory the authors here) that, say, 500 years ago people believed in a flat Earth, since, in the author's opinion, there is no ...
DaG's user avatar
  • 223
4 votes
2 answers

How did Scott and Amundsen detect the South Pole?

How did Scott and Amundsen detect the direction to the South Pole during their expedition? How did they determine the exact South Pole on reaching there? Comparison of the Amundsen and Scott ...
Ritesh Singh's user avatar
4 votes
1 answer

What is the origin of the four cardinal directions (North, East, South, and West)?

Why are there four? I would guess it was fixed after the egocentric/"relative" directions (left, right, front, back). Or was it because human used to consider the ground as flat and 2-dimensional? How ...
Poland Spring's user avatar
4 votes
1 answer

Circular reasoning in Eratosthenes's measurement of the Earth's circumference

I remember that I read, some time ago, that Erathostenes calculated the circumfernce of the Earth using the distance between Syene and Alexandria, calculated in turn by others starting from the ...
Lucio Tanzini's user avatar
4 votes
0 answers

Why couldn't Robert Peary use his theodolite at the North pole

Robert Peary writes in his book The North Pole: The instruments used in taking observations for latitude may be either a sextant and an artificial horizon, or a small theodolite. Both these ...
Frigo's user avatar
  • 191
3 votes
2 answers

Why are there so few Iberian mathematicians in history?

I have been analysing the rise and fall of the various centres of mathematical excellence, and following how, for example, Ancient Greece gave way to the Arab and Persian world, which inherited from ...
Prime Mover's user avatar
  • 1,289
3 votes
1 answer

On Ptolemy climes

Reading Dante's Comedy, I was interested in understand a little bit how medieval geography worked, so I decided to have a look at Edward Luther Stevenson's translation of Ptolemy's Geographia. I've ...
Charo's user avatar
  • 279
2 votes
0 answers

History of triangulation

Snell tends to be quoted as the person to develop triangulation in geodesy. I don't believe, however, that triangulation was invented only then. For example, here Al-Biruni is mentioned to have "...
Paula's user avatar
  • 173
2 votes
0 answers

How widespread was the belief in Europe that the Earth is round until the Renaissance?

Already in antiquity, Greek mathematicians realized that the Earth is round, and the idea was operative in Europe ever since. But how widespread was this belief in the centuries until the Renaissance? ...
Frode Alfson Bjørdal's user avatar
1 vote
4 answers

Why does Eratosthenes method for calculating the circumference of the Earth requires the city of Alexandria and Syene to be in the same meridian?

I'm reading a book where the author claims that in order for the method of angles and proportions used by Eratosthenes to work, the two cities would have to be located in the same meridian, or at ...
zlaaemi's user avatar
  • 113
1 vote
0 answers

Why is so much of modern mathematics rooted in Germany?

Whenever I read some Mathematic theories, I find it they are typically done by some people living in Germany. Eg: Riemann, Gauss, Moses Schoenfinkel etc. I want to know what Germany did to arise so ...
Babu's user avatar
  • 473