48 votes
Accepted

Why do we call Tycho Brahe by his first name?

The short answer is that this is how he referred to himself. He was born Tyge Otteson Brahe but at the age of 15 (1561) changed 'Tyge' to Latinized 'Tycho', see Redd's biography of Tycho and Thoren's ...
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  • 66.2k
26 votes

Did Galileo Galilei believe in astrology?

Galileo not only believed but taught and actively practiced astrology, like Ptolemy and Kepler before him. His primary source might have been Porphyry’s commentary on Ptolemy's Tetrabiblos. In ...
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23 votes
Accepted

Who first measured the distance to the Moon? How was it done?

It happened long before Newton. In the second century BC Hipparchus used lunar parallax to calculate a value for the minimum and maximum distance of the earth and moon. His results are very close to ...
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  • 3,325
23 votes

When was it realized that the giant planets do not have solid surfaces?

Prehistory goes back to the second half of 19th century after Fraunhofer introduced astronomical spectroscopy, and then Kirchhoff identified some spectral lines in the Sun's spectrum in 1860s. ...
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  • 66.2k
18 votes
Accepted

Why did 18th century writers think that Mars had 2 satellites?

It is a funny story, a comedy of errors, that started with Kepler and Galileo, and was likely picked up by Swift as a target of satire. It is assumed that Voltaire followed Swift, but it paid off for ...
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  • 66.2k
17 votes
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How did Babylonians figure out that the evening star is the morning star?

I doubt that many Babylonians or Greeks or any others who cared about such things ever thought Hesperus and Phosphorus were different objects any more than we think the Morning Star and Evening Star ...
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16 votes
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When did it become possible to predict the time and place of solar eclipses?

The principle was known long ago, to the Babylonians and Hellenistic Greeks but the accuracy of prediction depends on the detail of the Lunar motion (the motion of the Sun is relatively simple). ...
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16 votes
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When & how was it known that our Sun is the same thing as the night time stars?

As quoted from this article: Many people's work was needed to prove that the Sun is a star. The first person we know of to suggest that the Sun is a star up close (or, conversely, that stars are ...
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  • 1,516
16 votes

What is the historical basis for the length of a year?

First of all, whether the earth is rotating or everything else is rotating around it, is completely irrelevant for the question. This is just the matter of point of view. As seen from the earth, the ...
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15 votes

How did Kepler "guess" his third law from data?

You can read Kepler's Harmonia Mundi (there is an abbreviated English translation, but it includes that part.) Kepler was looking for all kinds of numerical relations for many years (most of his life)....
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15 votes

Who was the first to postulate that space was a vacuum?

The idea of vacuum, or void as it was called in antiquity, did not originally come from considerations about air and Earth's atmosphere, but rather from natural philosophic speculations about the ...
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  • 66.2k
14 votes

When did humans realize that there is no air on the Moon?

There is no sharp difference between "no air" and "very little air". That it is "very little" is seen when we observe the Moon with a telescope. An atmosphere creates a visible haze, especially on the ...
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13 votes

How did Kepler "guess" his third law from data?

I agree that it is amazing and a credit to Kepler's insight into numerical patterns, which is reminiscent of Euler's. It took Kepler extra 12 years to discover the third law after discovering the ...
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  • 66.2k
13 votes
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What attracted Einstein to the anomalous precession of Mercury?

Who or what attracted Einstein's attention to Mercury, and when? What alerted him to the idea that Mercury's case was different from all those other cases, when a mundane explanation was involved? ...
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13 votes

Has science fiction ever caused scientists to do real research?

Science fiction author Arthur C. Clarke is often credited with the idea of communication satellites. link That was in 1945, long before any artificial satellite had been launched in reality.
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  • 8,407
13 votes
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Did Bacon analogize planets to holes in the head to explain why their number was (believed to be) seven?

This probably refers to the "argument" of the Florentine astronomer Francesco Sizzi against the validity of Galileo's discovery of the moons of Jupiter. His "argument" was ...
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12 votes
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Is there an astronomical reason behind the order for the names of days of the week?

One theory says, `If you order the "planets" according to either their presumed distance from Earth (assuming the Earth to be the center of the universe) or their period of revolution around the ...
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  • 1,468
12 votes
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What data did Kepler work out his laws from?

Today, sky coordinates are measured as "Right Ascension" (RA) and declination. These are similar to the angular coordinates we use for the Earth's surface but are measured on the celestial sphere ...
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  • 2,048
12 votes
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Why didn't Aristarchus' theory of Heliocentrism stick?

I agree with the answer of David, but I would like to add few points to it: It is a common misconception that Aristarchus found (or attempted to find) the sizes of Sun and Moon or distances to them. ...
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12 votes

Did the ancient Chinese know the earth is a sphere?

There appear to be conflicting accounts of when the Chinese came to view the earth as spherical. Chinese sources might suggest the 11th century, while western sources suggest the 17th century. ...
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  • 6,004
11 votes

Who first measured the distance to the Moon? How was it done?

This is an ill defined question. It can be interpreted as "Who was the first to TRY to measure the distance to the Moon", or "Who was the first to give a correct number", and what ...
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10 votes

What data did Kepler work out his laws from?

At the time of Brahe and Kepler they did not use the right ascention and declination to record the movement of planets. These coordinates are related to the Earth, and it is known since the times of ...
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10 votes

Why should February have 28 days?

The reason is simple. Baiscaly 365 (approximate number of days in a year) is not divisible on 12 (desirable number of months=the number of Zodiac signs). Then it was proposed to have 6 months of 30 ...
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10 votes

Why didn't Aristarchus' theory of Heliocentrism stick?

Firstly, since the theory was sound and the results reproducible, why didn't it catch on? Aristarchus' heliocentric model was not sound and the results were not reproducible. Not only was there an ...
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  • 1,687
10 votes

How did ancient Greeks explain moon phases without reflection of sunlight?

Yes. According to this, we don't know who it was to explain the phases using a spherical model, though it was before 600 B.C: The first person to correctly explain the phases of the Moon is lost ...
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  • 8,092
10 votes

Hidden agenda of the Galileo trial?

The Assayer & Redondi's "G3" Michele Camerota's 2008 Complete Dictionary of Scientific Biography entry on Galileo describes this theory in a section entitled "Atomism and the ...
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  • 5,041
10 votes

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

We do not know. First, Syene and Alexandria are not on the same meridian, Alexandria is about 3° to the West, and second, Syene is not on the tropic (where the Sun is straight up on the summer ...
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  • 66.2k
9 votes

Nowadays I see a distinct "line" dividing people working in Mathematics and the Physical Sciences. Why?

You do not say what field of mathematics you are working in, and perhaps there are signs of separation there. Overall however, lively interaction between mathematics and physics is alive and well. ...
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9 votes

Did Galileo Galilei believe in astrology?

The Galileo's astrology activities are well summarized in Conifold's answer. But, in relevance to the question at hand (did he believe it worked) I'd like to make a couple of points: The fact that ...
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8 votes
Accepted

Who first distinguished planets from the stars?

We can try to find the necessary informations browsing some History of Astronomy books, like : Anton Pannekoek, A History of Astronomy (1961, original ed : 1961) Christopher Linton, From Eudoxus to ...
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