Questions tagged [astronomy]

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

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293 views

Did Isaac Newton make astronomical observations?

What role did astronomy play for Isaac Newton? He was a good friend with Edmond Halley the astronomer. Kepler's laws were obviously the foundation for his physics. And he revolutionized optics too, ...
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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 ...
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How important was the prediction of Neptune in 1846 for the Oxford evolution debate?

The short story is that based on Kepler's and Newton's physics, in 1846 Le Verrier mathematically predicted the existence and current location of Neptune within a single angular degree, and it was ...
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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, ...
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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 (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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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What is Galileo's opinion of Kepler's work?

They are contemporaries. Keper lives from 1571 to 1630, and Galileo lives from 1564 to 1642. The former's life span is contained in that of the latter. So, did Galileo hear of Kepler's work and give ...
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277 views

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 ...
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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 ...
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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) ...
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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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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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412 views

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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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. ...
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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 ...
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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 ...
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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}...
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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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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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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 ...
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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 ...
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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?
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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 ...
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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?
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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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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 ...
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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 ...
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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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When was the issue of time zones 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 ...
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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 "...
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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 ...
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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....