Questions tagged [astronomy]

The study of celestial objects and phenomena outside of the Earth's atmosphere.

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

It is amazing that Kepler determined his three laws by looking at data, without a calculator and using only pen and paper. It is conceivable how he proved his laws described the data after he had ...
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23 votes
2 answers
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When did it become possible to predict the time and place of solar eclipses?

That is, when did astronomy figure out how to predict when and where a solar eclipse will be visible? It seems people noticed fairly early on that the Sun, Moon and Earth return to the same ...
Semaphore's user avatar
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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
21 votes
3 answers
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Who first measured the distance to the Moon? How was it done?

Who first measured the distance to the Moon? How was it done? I think it had to happen after Newton, but I am not sure.
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Why was China slow to recognise the sphericity of Earth?

Wikipedia notes that, while knowledge Earth is approximately spherical was obtained in ancient Greece, and became standard among educated people in Europe and the Middle East long before 1300 AD, ...
J.G.'s user avatar
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10 votes
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What is the historical basis for the length of a year?

It is currently accepted that a year is equal to the time it takes for the earth to revolve around the sun. However around Roman times, Ptolemy's geocentric model was the widely accepted view of ...
cspirou's user avatar
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27 votes
2 answers
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What attracted Einstein to the anomalous precession of Mercury?

The story is usually told starting with Einstein's 1915 paper Explanation of the Perihelion Motion of Mercury from General Relativity Theory, or at least its drafts from 1913-14. It was the first ...
Conifold's user avatar
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19 votes
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What data did Kepler work out his laws from?

It's well known that Kepler worked out his laws by fitting curves to Tycho Brahe's data on the trajectories of planets through the sky. What was this data? How does one record the trajectory of a ...
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How did Ptolemy know that days were unequal lengths?

Apparently Ptolemy was aware of the fact that the duration of time from noon to noon varied by many seconds throughout the course of a year. In modern times this fluctuation in length of day leads to ...
Jagerber48's user avatar
18 votes
1 answer
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Did Archimedes use epicycles in his planetarium?

Archimedes constructed a planetarium where as described by Cicero "he had thought out a way to represent accurately by a single device for turning the globe those various and divergent movements with ...
Conifold's user avatar
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16 votes
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Hidden agenda of the Galileo trial?

Redondi argued that Galileo's trial on heliocentrism was merely a show trial concealing the real objection against Galileo among the catholic establishment, which was his atomism thought to be at ...
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Did the ancient Chinese know the earth is a sphere?

The ancient Greeks knew this fact. How about the chinese? If not, when did they realize that the earth is a sphere? By themselves or from other people?
S. Kohn's user avatar
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3 answers
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Who first distinguished planets from the stars?

This is a pretty straightforward question, when the first observations of the night sky were being made, who was the first person to suggest that a planet, say Mars, was not a star, in the sense that ...
L.R.'s user avatar
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11 votes
3 answers
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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
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1 answer
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Calculation of Gauss leading to 18:7 resonance between orbits of Jupiter and Pallas

After Gauss helped relocate Ceres, he studied the orbit of the asteroid Pallas and discovered (1812) that Jupiter and Pallas have an orbital resonance that is nearly equal to 18:7. For instance, using ...
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Did Kepler arrive at his planetary laws based on Mars's orbit alone?

Kepler apparently arrived at his first two laws based on the Tycho's data for Mars. But Mars has the largest eccentricity except for Mercury, so it is easier to tell the difference between a circle ...
wdlang's user avatar
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Who was the first person to use physics to suggest that both the Sun and the Earth move?

I imagine it to be Isaac Newton, who brought the discussion of "force" rather than "center" into the modeling of orbits. I imagine that prior to Newton's forces, one had to be either a geocentrist or ...
Jonathan Dunn's user avatar
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1 answer
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When was the first true Gregorian telescope built?

I know that James Gregory came up with the idea of using a parabolic mirror to eliminate spherical aberration in 1663. The theory behind it had actually been around since classical antiquity I think....
Luke's user avatar
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1 answer
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How was the first parabolic telescope mirror made, and how was it used, and for what kind of telescope was this work done?

This answer to When was the first true Gregorian telescope built? explains: Newtonian uses one concave and one flat mirror (or just one concave). Gregorian uses two concave mirrors, and Cassegrain ...
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4 votes
4 answers
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Historical knowledge of Distance of Earth from Sun

I asked the following question on the Physics stackexchange, only to be notified that it was more suitable for this forum. The link to original post can be found at: https://physics.stackexchange.com/...
anurag anshu's user avatar
3 votes
2 answers
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How was stellar parallax tested by Tycho Brahe?

Explanations of stellar parallax that I have found involve examining the apparent motion of a nearer star relative to a background of more distant stars, as the Earth moves around the sun or as the ...
Mars's user avatar
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17 votes
3 answers
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Who was the first to postulate that space was a vacuum?

The fact that space is a vacuum and that the Earth's atmosphere only extends a short way above the surface is accepted as obvious. However, there is nothing a priori obvious about it: you first have ...
Emilio Pisanty's user avatar
17 votes
1 answer
3k views

How did Babylonians figure out that the evening star is the morning star?

Hesperus (Roman Vesper) is the name ancient Greeks gave to the evening star that appears in the sky for an hour after the Sun sets. Phosphorus (Roman Lucifer, sic!), was the name of the morning star ...
Conifold's user avatar
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15 votes
1 answer
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Why did 18th century writers think that Mars had 2 satellites?

At least two 18th century writers wrote that Mars has two satellites: Swift in Gulliver's travels (1726) and Voltaire in Micromégas (1752). How did they guess this? Was Voltaire repeating Swift's ...
Alexandre Eremenko's user avatar
14 votes
6 answers
701 views

Has science fiction ever caused scientists to do real research?

Has science fiction ever caused scientists to do real research? Science fiction here means fiction that tries to explain things in the world rather than speculate about the future or unexplorable ...
rus9384's user avatar
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12 votes
3 answers
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Why didn't Aristarchus' theory of Heliocentrism stick?

This might be more a question for historians, but it's a question I've given some thought to. By using what was essentially Euclidean geometry, Aristarchus was able to calculate, with some measure ...
userLTK's user avatar
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12 votes
1 answer
495 views

Division of the circle and compass constructions

It is well known that every construction that can be performed by a compass and a ruler can be also performed by a compass only. This is a good (and difficult) exercise in elementary geometry. My ...
Alexandre Eremenko's user avatar
10 votes
1 answer
4k views

Did Indian astronomers realize the sphericity of the earth independently of the Greeks?

Reading Wikipedia's articles on the flat earth, spherical earth, and history of geodesy makes it clear that virtually every society recognizing the spheroidal shape of the earth today owes the ...
Mr. Bultitude's user avatar
10 votes
3 answers
2k views

Why should February have 28 days?

According to the Gregorian calendar the second month i.e. February have 28 days and in a leap year 29 days. I am not sure what calculations(science) it takes to decide the total number of days in ...
Amit Tyagi's user avatar
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6 votes
2 answers
774 views

Where did Ptolemy compare the Earth to the distance of fixed stars?

I read the following in C. S. Lewis, Miracles (page 77-8) The immensity of the universe is not a recent discovery. More than seventeen hundred years ago Ptolemy taught that in relation to the ...
Frank Hubeny's user avatar
4 votes
1 answer
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Who determined the temperature of the Sun first?

It is commonplace that it is about 6000 Kelvin. But who came to this value first? And with what method? Based on the black body radiation theory?
John's user avatar
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4 votes
1 answer
322 views

How accurate are Mayan astronomical "ephemerides"?

Because of recent hype surrounding the "end" of the Mayan calendar it is nearly impossible to find an objective quantitative assessment of the accuracy and sophistication of Mayan astronomy. ...
orome's user avatar
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3 votes
0 answers
114 views

Did a boat full of Louis XIV's Jesuits and some Siamese dignitaries plan on seeing a solar eclipse on May 17, 1687

The interesting Cosmic Elk article Eclipses in Siam (now Thailand) History and Legends says: While the Siamese ambassadors and their entourage were visiting ship yards and armouries and making ...
uhoh's user avatar
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3 votes
2 answers
641 views

Was "Kepler's third law" deduced from the Galilean moons, or from planetary motion?

I have read that Galileo was able to start observing the four large satellites of Jupiter in 1610. Did he ever attempt to estimate the relative sizes of the four orbits, and their periods? I made a ...
uhoh's user avatar
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3 votes
2 answers
542 views

Was Newton's successful calculation of precession of equinoxes a fluke?

I have looked at several sources, and Newton was right about the fact that the Earth is not a perfect sphere, but an ellipsoid caused the precession of equinoxes, as the Moon's gravitational ...
Youngsub Yoon's user avatar
2 votes
1 answer
63 views

What laser technology/ies were first used to bounce off of the Apollo 11 retroreflectors to accurately measure distance to the Moon?

Wikipedia's Lunar Laser Ranging Experiments; History mentions the first lasers ever bounced off the whole Moon were in 1962, and probably both the US and Soviet groups used Q-switched ruby lasers. In ...
uhoh's user avatar
  • 2,163
2 votes
1 answer
80 views

How did the earliest measurements of lasers bounced off of Apollo 11 retroreflectors deal with the light from the Moon and pick out single photons?

Wikipedia's Lunar Laser Ranging Experiments; History mentions the first lasers ever bounced off the whole Moon were in 1962, and probably both the US and Soviet groups used Q-switched ruby lasers. In ...
uhoh's user avatar
  • 2,163
2 votes
2 answers
2k views

How did Ptolemy calculate the distance to the Moon?

I've read somewhere that Hipparchus measured the distance to the Moon using the lunar and solar eclipse and obtained a value of around 67.3 Earth radii. It also says that soon after Ptolemy gave a ...
cal's user avatar
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2 votes
3 answers
234 views

Why was in 1584 the eclipse of the moon used to calculate the width of the Atlantic ocean rather than just using the Sun itself?

In this video is explained that in November 1584 the width of the Atlantic ocean was discovered by comparing the hour when the eclipse of the moon started in England with the hour when the eclipse ...
Marijn 's user avatar
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1 vote
1 answer
216 views

How and when did the Titius-Bode rule first become known as a "law"?

The Titius-Bode rule's fit to the solar system was a bit clunky at best, and it was not really testable in its day. It could not have been used to predict something else, and then that prediction ...
uhoh's user avatar
  • 2,163
1 vote
1 answer
171 views

Did knowledge of astronomy spread among Indo-European civilizations in antiquity?

Early civilizations of india, Greece, Babylon, China and Egypt have progressed in astronomy. Is there any shared knowledge among them and if any how can we find out?
Partha Shakkottai's user avatar
1 vote
1 answer
298 views

What is the origin of Zodiac (Kaalachakra) signs?

I think that The Zodiacal signs are of Vedic origin. Hindus, Greeks and Sumerians all have Zodiacal signs. Which is the most likely origin? The middle ring is the zodiac in the same between India and ...
Partha Shakkottai's user avatar
1 vote
1 answer
139 views

On the Ptolemaic theory of the planet's latitude

The Ptolemaic theory of the latitude of the planets is dealt on in Book 13 of the Almagest. This theory (which I was struggling to find info about online) is considered quite complicated, but luckily ...
d_e's user avatar
  • 261
0 votes
2 answers
1k views

When did Europe start accurately predicting solar and lunar eclipses? [duplicate]

I would like to know when Europe obtained the ability to predict lunar and solar eclipses. I remember reading about some story, where Columbus or someone like that used an eclipse chart to convince ...
DrZ214's user avatar
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