Questions tagged [astronomy]

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

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How long did it take to prove that the Earth revolves around the Sun?

I get that Galileo Galilei was a major contributor in proving the helio-centric theory, and same goes to Sir Isaac Newton. The battle for the theory to become law took centuries to prove. People ...
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On Trigonometric Methods Available to Aristarchus

Approximately 2300 years ago, Aristarchus proposed a method for determining the relative distances of the sun and the moon in relation to the earth. Specifically, he asserted that when the moon is in ...
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Is it known where Eratosthenes first heard of the “well of Syene”?

The American Physical Society's This Month in Physics History; June, ca. 240 B.C. Eratosthenes Measures the Earth says: Eratosthenes had heard from travelers about a well in Syene (now Aswan, Egypt)...
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Is there an astronomical reason behind the order for the names of days of the week?

The seven days of the week seems to be commonly named after celestial bodies. What I find curious is that all seven days apparently share the same names in both West and East. Sunday is, of course, ...
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Does Heliocentrism predate Copernicus?

I have seen this mentioned on the interwebs a few times. people have mentioned that some Greek thinkers and Islamic astronomers came up with heliocentrism before Copernicus and that Copernicus copied ...
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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 ...
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Several questions about Gauss's contributions to observational astronomy

I just want to check if anyone has additional information about a private astronomical research begun by Gauss in 1819, which dealt with the "movements of the solar system" in the galaxy (motion of ...
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How has the estimate of the number of stars in the universe changed over time?

Current estimates for the number of stars in the universe are about 10^22. However, that number has changed several times as new observations have come forth. How has the estimate of the number of ...
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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 ...
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Who were the other European astronomers who identified new stars around the time of Tycho Brahe?

Wikipedia notes: Early European astronomers such as Tycho Brahe identified new stars in the night sky (later termed novae), suggesting that the heavens were not immutable. Who were the other ...
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Notable theories on the far side of the moon pre 1959

On October 7th 1959, the soviet Luna 3 probe took the first picture of the far side of the moon. It has been known since ancient times that the moon was a sphere. It would have doubtless been ...
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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?
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How did Cassini measure the “Cassini state” of the Moon? What measurements were made; what did the data look like?

The Phys.org article Physicists provide first model of moon's rotational dynamics, accounting for the solid inner core describes the September 2018 paper by Christopher Stys and Mathieu Dumberry The ...
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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 ...
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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 ...
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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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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 ...
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Apparent contradiction in Copernicus' Commentariolus

There seems to be a contradiction in the assumptions that Copernicus makes when attempting to explain the motion of the planets: http://dbanach.com/copernicus-commentarilous.htm Assumptions 1 and 3 ...
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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 ...
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Where to find some early discussions of the Equinox(es)?

Said quickly, solstices are rather perceptible while the equinox is a mental construction. Archeoastronomical evidence shows that neolithic people already had knowledge about the solsticial points on ...
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What calculation did Halley or anyone else do to estimate the effects of Jupiter and Saturn on Halley's comet's return in 1758/9?

This answer to the question First observation that the movement of a planet or asteroid in its orbit was affected by another planet says: In 1705, with the mathematical assistance of Issac Newton, ...
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What's the relationship between Aristotle's theory of elements and motion and geometry?

I'm having a hard time gathering my thoughts about this. I'm trying to find a connection or some sort of relation between the first 3 axioms (postulates) of Euclidean geometry (though around Aristotle'...
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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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When did the research field of Astrophysics begin?

I have this vague idea that Astrophysics morphed out of Astronomy as a field of study and research. I am curious if this is true and when did Astrophysics become separate from Astronomy as a field of ...
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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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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 ...
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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 ...
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Who correctly first explained the reason why you can see certain constellations only in certain seasons?

Of course, only heliocentric model can explain this. But, was this Copernicus himself or Galilei?
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Precision of Ancient/Medieval Astronomy (wrt Eclipses)

Today we can predict lunar/solar eclipses down to the precision of seconds.[1] But what was the precision like in medieval times? I imagine it must have improved over centuries. To keep the question ...
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Sphericity of Earth from lunar eclipses - is Aristotle's argument valid?

Aristotle is often credited with proving the sphericity of Earth from the fact that the shadow of the Earth on the moon during lunar eclipses is always an arc of a round circle (as opposed to arcs of ...
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Who first solved the two-body problem in 3D?

Who first solved the two-body problem in 3-dimensions? Was it Laplace?
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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, ...
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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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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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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.
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Who was the first to understand the concept of outer-space?

Who first understood that celestial bodies (stars, planets, and moons) are moving in a 3D space and not points of light moving on Earth's dome? Also, when and how did they realize that celestial ...
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Was Captain Cook’s voyage to observe the transit of Venus going to enable better ship navigation at the time?

On a recent visit to the Royal Observatory at Greenwich I was struck by its proximity to the Naval Academy next door. The theme of the history of clocks and development of astronomy was driven by the ...
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Do astronomers still use decimal time?

Wikipedia states that decimal time - where the time of the day is expressed as a decimal part of the day - "have been used by astronomers ever since [Laplace introduced them]". An example by Herschel ...
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When did mechanical tower clocks start being used?

On a tour of the Royal Observatory at Greenwich I saw the following display on the history of mechanical clocks: The suggest that mechanical clocks and astronomy weren’t really combined in England ...
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When did spring-driven clocks start being used?

On a tour of the Royal Observatory at Greenwich I saw the following display on the history of mechanical clocks: They suggest that mechanical clocks and astronomy weren’t really combined in England ...
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Historical development of role of astrology in medicine?

The OED defines "iatromathematics" as Practising medicine in conjunction with astrology. Pre-17th century, it seems most scientists (physicians included) believed in the influence of the stars on ...
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How scientifically valid were Galileo's heliocentric arguments?

As far as I know, while Galileo's hypothesis about the tides was wrong, his discovery of the phases of Venus while passing the sun should have been sufficient to leave the geocentric crystal spheres ...
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Did Galileo really see Galilean Moons?

I want the answer to incorporate apparent magnitudes of those moons, power of his telescope, light pollution of that time, successful recreation of the scenario of watching Galilean moons using that ...
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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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Who coined the term “degenerate star”?

I'm trying to find a good source for the definition of degenerate matter to differentiate it from Fermi gases. For my research a good section on history would be nice. This question is more ...
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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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What astronomical reason led to the creation of the trigonometric sine and cosine?

Sines and cosines are commonly introduced as ratios of sides of a triangle with its hypotenuse and attributed to ancient Indian scholars. However, I've never actually thought of the reason for ...
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Why is an inch (in the English Imperial system of measure) as long as it is?

My question is about the length of the inch which is a subunit of the Imperial foot. Is there any connection whatsoever between the Imperial system for units of measure and the dimensions of the ...
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How did Ptolemy calculate the distance to the moon

I've read that Hipparchus measured the distance to the Moon using the lunar and solar eclipse and obtained a value around 67.3 Earth radii. It also says that soon after Ptolemy gave a more accurate ...
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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.