Questions tagged [astronomy]

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

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What can be inferred about the eyesight of early astronomers from their recorded observations?

The journals kept by the likes of Galileo, Kepler and Herschel provide details about what objects they discovered and what kinds of optical instruments they used to discover them. Taken together, ...
user5502's user avatar
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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 ...
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When William Herschel discovered Uranus, who else at the time had a comparable telescope?

William Herschel built a big telescope and observed Uranus in 1781. I'm trying to figure out who else had a comparable telescope at the time, who could verify these observations? Apparently Johan ...
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English translation of Parisian Alfonsine tables (the 1400s)

I'm interested in an English translation of the Alfonsine tables published in Paris in the 1400s. I know there is an English translation of what survived of earlier Alfonsine tables from Castile, but ...
Gerard Ashton's user avatar
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When was the mechanism behind seasons on Earth discovered

When was the mechanism behind seasons on Earth discovered? I'm talking about the angle between the Earth's rotational axis and its orbital axis. I read on Wikipedia here that Earth's obliquity ...
Antoine's user avatar
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When did the Bayer designation Gamma Sagittarii become Gamma1 & Gamma2 Sagittarii?

Some authors talk about Gamma Sagittarii as a single star, while others use Gamma1 Sgr for W Sgr and Gamma2 Sgr for 10 Sgr (Gamma Sgr being then ambiguous). SIMBAD database uses Gamma1/Gamma2 as of ...
Eynar Oxartum's user avatar
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2 answers
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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?
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How did the Arabs determine the longitudes of cities?

I am reading the book by Berggren, 'Episodes in the mathematics of medieval islam'. An important problem is determing the direction of Mecca with respect to a local city. The book introduced a method ...
S. Kohn's user avatar
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What was Galileo's opinion of Kepler's work?

They were contemporaries. Kepler lived from 1571 to 1630, and Galileo lived from 1564 to 1642. The former's life span was contained in that of the latter. So, did Galileo hear of Kepler's work and ...
S. Kohn's user avatar
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How did Kepler make his discovery?

It is often said that he used Tycho's data. But the apparent motion of a planet is chaotic, right? The reason is simply that we are living on and observing from the earth, but not the sun. So, how ...
John's user avatar
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Did Bruns establish that the 3 body problem has no non-trivial conservation laws?

I'm reading Colin Pask's book Magnificent Principia and in 16.7.2 he states that the difficulty of the 3 body problem is in part tied to the lack of additional conservation laws at our disposal. In ...
L.P.'s user avatar
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When did the estimates of planetary distances made between Ptolemy and Copernicus produce the pattern suggesting heliocentrism?

Two patterns in the structure of the Ptolemaic model make the transformation of coordinates to the Copernican model seem "natural" to modern eyes: the alignment of the radii of the (second) ...
orome's user avatar
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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 ...
Mikhail Katz's user avatar
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At what point did Einstein realise that gravity was curvature of spacetime?

Did he realise this as soon as he thought of light curving due to gravity or was this something that took him a while to realise?
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What are epicycles, deferents, eccentrics, equants, etc.?

What are epicycles, deferents, eccentrics, equants, etc.? Who first introduced them, and when? Why were they introduced? How do they work? Are there visualizations of this? e.g., what is St. Thomas ...
Geremia's user avatar
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What role did meteors and comets play in early astronomy?

Apart from the location, brightness and color of the stars themselves, astronomy obviously originated from an interest in transient phenomena against the fixed but rotating star sky. The rise and set ...
LocalFluff's user avatar
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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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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 ...
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Before the IAU, what was the international governing body for naming astronomical bodies?

Today, the commonly recognized authority on the naming of astronomical bodies is the International Astronomical Union (IAU). It was created in 1919, and quickly rose to a position of prominence within ...
HDE 226868's user avatar
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Determining the temperature of a remote star by using the black body radiation formula

I am new to astrophysics. There is a question about the celebrated Harvard classification. Can people at 1900 determine the temperature of a remote star using the black body radiation formula? I ...
John's user avatar
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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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Nowadays I see a distinct "line" dividing people working in Mathematics and the Physical Sciences. Why?

The direction in which leading research is heading in these subjects (Math, Physics) is very much different and don't seem to be in tandem. Is this something that developed in more recent times? This ...
Wave Metric's user avatar
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Why does the start of the calendar year not correspond to a natural event?

Why is Jan. 1, the start of a new year, several days after the Winter Solstice, instead of coinciding with a solstice or equinox or other natural annual event? Note: The question does not ask why ...
WBT's user avatar
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How did Kepler infer three-dimensional positions from Tycho Brahe's data?

This has bugged me for some time. Tycho Brahe's data on planetary observations, presumably, consisted of the direction in which a planet was observed at a given date and time, but not the distance to ...
Emilio Pisanty's user avatar
4 votes
1 answer
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Why was Charles Hutton's estimate of the density of Mercury so far off?

In the Schiehallion experiment (original paper), Charles Hutton computed the density of the Earth, and from there estimated the densities of the major bodies of the Solar System. His numbers for most ...
Mark's user avatar
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When did we first learn that Jupiter was a gas giant?

The term "gas giant" was invented in the 1950s, but I think the concept has been known longer than that. When did we first learn that Jupiter was a gas giant, not a terrestrial-type planet?
Joe's user avatar
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When and how was water first detected outside of Earth?

When and how was water (in ice or any other state) first observed outside of Earth? What is the high-level chronology of this discovery, and how did the scientific community first reach reasonable ...
Amelio Vazquez-Reina's user avatar
4 votes
1 answer
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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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Why did Greek Olympic games take place every fourth year?

I was wondering why Greeks chose to have Olympic games every four years. Now, since we usually every fourth year is a leap one, it makes sense; but the reform of the calendar which stated this is due ...
mau's user avatar
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Did Archimedes know about Callipus?

Various sources, such as Cicero's Republic state that Archimedes had made a machine consisting of glass spheres that represented the Eudoxian system of the world. Considering that Callipus died over ...
Michal Paszkiewicz's user avatar
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1 answer
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What theoretical basis did Reimers base his mass loss law on?

In his 1975 paper, Circumstellar absorption lines and mass loss from red giants, Reimers gave a relation for mass loss from red giants via stellar winds as $$\dot{M}\propto\frac{L}{gR}$$ where $\dot{M}...
HDE 226868's user avatar
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6 votes
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Why did scientists think the orbit of Mars had the shape of a limaçon in the geocentric model?

While looking up the old Copernican model for orbits, I encountered the following image (courtesy Wikipedia): This seems... weird. Not only would it be an odd thing to come up with or express in ...
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9 votes
1 answer
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When did we learn that our galaxy was merely one amongst many billions?

This Kurzgesagt YouTube video claims that Without [the Hubble Space Telescope], we would never have known that our galaxy is one of billions in an enormous universe. But, the actual human, Mr. ...
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4 votes
5 answers
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Why did the ancients believe celestial matter was of a different type than terrestrial matter?

Why did the ancients believe celestial matter is of a totally different type than terrestrial matter? From a footnote in Christopher A. Decaen's The Thomist 68 (2004): 375-429 article "Aristotle's ...
Geremia's user avatar
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10 votes
3 answers
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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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9 votes
2 answers
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Was science the driving force behind the Apollo program?

Was science really the driving force behind the Apollo program? Or was the "race to the moon" the primary reason and the science objectives were put together as a secondary step?
Cedric H.'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
3 votes
2 answers
440 views

Why does JPL at NASA give two different values in astronomical units for planetary distances?

Why is it that JPL (Jet Propulsion Lab) at NASA gives astronomical unit values for the planets for two different time periods, namely 3000 B.C. to 3000 A.D., and 1850 to 2050?
John Shanahan's user avatar
7 votes
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 ...
KCd'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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3 votes
1 answer
301 views

Planets/stars as more than points of light

Who was/were first one(s) to recognize that what we see in the night sky are not just points of lights but full blown lands(in case of moon and some planets) and so on? I am guessing it would not have ...
AHK's user avatar
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12 votes
2 answers
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How did ancient Greeks explain moon phases without reflection of sunlight?

Did the ancient Greeks understand that the moon shines by reflection of sunlight, and that this was the explanation of its phases? Did this allow them to conclude that the moon was a sphere? From what ...
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7 votes
2 answers
622 views

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
7 votes
1 answer
210 views

Who created the energy conditions?

The earliest text I've been able to find that explain the GR energy conditions is "The large scale structure of space-time" (1973) by Hawking and Ellis. However in Barcelo and Visser's paper "...
Rammus'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
5 votes
1 answer
512 views

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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14 votes
3 answers
7k views

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

What is the easiest evidence that there is no air on the Moon? Frankly speaking, I myself have no idea how to prove it.
wdlang's user avatar
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6 votes
1 answer
370 views

Hevelius-Hooke dispute

Johannes Hevelius of Danzig (1611-1687) was the most famous astronomer of his time, and also the last famous astronomer who did not use telescope. Most books on the history of astronomy (and even the ...
Alexandre Eremenko's user avatar
3 votes
0 answers
74 views

Who found out about galaxies? [closed]

As the world developed new technology, astronomers discovered more celestial bodies, such as asteroids and black holes and such. Galaxies were probably discovered long ago before these modern ...
Anthony Pham's user avatar
12 votes
3 answers
7k views

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 ...
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