Questions tagged [astronomy]

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

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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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 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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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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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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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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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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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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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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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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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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Did the Mayan's really predict the solar eclipse?

The Mayan's astronomical observations were outstanding given the tools they had, and investigations of the Dresden codex published by Harvey and Victoria Bricker in 1983 predicted the July 11th, 1991 ...
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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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What was the impact on science and philosophy of the discovery that the Milkyway is not the whole Universe?

I can think of no discovery bigger in terms of correction of a belief if the metric is, How much bigger is something really than believed? Of course that is not the only significance. It is a major ...
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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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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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When did astronomy first discover that the stars are bigger than the moon?

We take it for granted these days that the stars are unimaginably bigger than the planets and the moons. But when you look at the sky, it does not appear this way. The moon looks bigger and brighter ...
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Kepler's genius, How?

I have a very simple question. How Kepler knew that orbits are elliptical, say I was living in his time. How would Kepler explain that the orbits are elliptical (since none of his 3 laws explain why ...
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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 ...
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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 ...
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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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Were people in the ancient or medieval times aware of how exactly a solar year is equal to a lunar year?

Was it common knowledge around 600 AD or perhaps 30 BCE that 200 solar years for example were equal to 209 lunar years? In which period of history precisely can we say that such a thing was confirmed?
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Kepler's position with respect to Tycho Brahe's world system?

When Kepler was an assistant of Tycho Brahe, did Kepler in public declare his support for Copernicus' system or Brahe's system (the earth at rest, but the planets orbiting the sun) or was he undecided?...
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Is there any evidence supporting this claim about Cassini and his ovals?

The Wikipedia article for Cassini ovals claims in the introduction that "Cassini believed that the Sun traveled around the Earth on one of these ovals, with the Earth at one focus of the oval." This ...
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Where are the mirrors of the historic telescopes today?

Are the great mirrors and lenses of historic telescopes preserved? Those of Herschel and Rosse and many others and back to the 18th and 17th centuries. The wooden structures of those telescopes I can ...
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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/...
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Determination of planetary mass and radius

At the beginning,how and using which principles scientists determined the mass and distance from sun of various planets?
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Was an expanding universe proposed before Edwin Hubble's observations?

General relativity (1915), as I've heard it explained, describes a universe that is either shrinking or expanding. By adding a cosmological constant it can describe a universe in eternal steady state, ...
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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, ...