Questions tagged [astronomy]

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

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5answers
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Did Galileo Galilei believe in astrology?

The Wikipedia page on Gallileo Galilei mentions, among other things: His multiple interests included the study of astrology, which at the time was a discipline tied to the studies of mathematics and ...
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In which year the notion of star death started?

In which year, does the fact: every star will ultimately die came in to existence?
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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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1answer
110 views

Martian dust as ferric oxide and Rupert Wildt

Samuel Glasstone, in The Book of Mars (NASA, 1968, p. 109), wrote "In 1934, the German-born astronomer Rupert Wildt suggested that the bright areas on Mars were composed 'of strongly oxidized ...
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1answer
760 views

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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How long is the “Great Year” in the Antikythera Mechanism?

Through antiquity it was understood that after a finite time interval the configurations of the planets will repeat and this was called a "Great year" or, eventually a "Platonic year&...
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Could 17th century astronomers in the Netherlands predict solar eclipses a few months in advance?

In the 17th century Netherlands, could the astronomers, or sailors trained in stellar navigation, predict either total or partial (at least 40% obscured) solar eclipses over the the town of Aardenburg ...
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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 ...
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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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454 views

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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1answer
321 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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How critical were Tycho Brahe’s accurate observations?

I am speculating about the value of Tycho Brahe’s - for his time - accurate observations and Kepler’s calculations. Might it have been possible for Kepler to formulate his laws based on Ptolemy’s ...
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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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247 views

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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2answers
347 views

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 ...
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146 views

How did Kepler know that orbits are elliptical?

Suppose I was living in his time. How would Kepler explain that the orbits are elliptical? Since none of his 3 laws explain why orbits are elliptical, I assume he must have had other reasons to ...
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1answer
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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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861 views

Was Kepler aware of the following golden relationship between the planets?

Was Kepler aware that Venus and Mars have a golden section relationship other than that he attributed to them in his 5 perfect solids model of the Solar System? The dodecahedron and the icosahedron, ...
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354 views

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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2answers
462 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 ...
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Who first reported the Crab pulsar's pulsing but was dismissed by an astronomer?

This answer to Has great eyesight been necessary for astronomers? mentions Astronomer Jocelyn Bell Burnell's recounting of a likely first visual observation of a pulsar. This can be found for example ...
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1answer
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Did Ptolemy and other Greek scientists actually measure the distance to the Sun?

According to Subhash C. Kak: Early Theories on the Distance to the Sun: “Pancavimsa Brahmana states that the heavens are 1000 earth diameters, de, away from the earth. The sun was also taken to be ...
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1answer
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How did the initial scientists conclude the new moon phase is not an eclipse?

My apologies if this is too naive a question. I keep wondering what steered people away from assuming the new moon to be an eclipse and hence go on to figure the angular difference in the orbital ...
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How large were the differences in the orbit of Uranus which led to the calculation of the existence of Neptune?

After Uranus was discovered and its orbit calculated, its future orbit was calculated, and its future positions as seen from Earth were calculated. And observers of Uranus began to notice that Uranus ...
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1answer
120 views

What astronomy efforts required multiplication of large numbers around 1600?

I'm reading an article about the history of logarithms and it says: One problem that was plaguing people at the time, especially astronomers, was arithmetic. Astronomical calculations required the ...
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How did the first astronomers define what a planet is?

What is the origin of the term "planet" and how did astronomers first define the term?
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Greek astronomy vs astrology

I wonder if would be right to say that while most ancient astronomical activities, such as building and improvement of observational structures, had a strong astrological component, the Greek ...
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510 views

What were the applications of conic sections before Kepler?

When recently asked for a practical application of parabolas, I responded by talking about objects in free-fall. Afterwards as I was re-thinking this conversation it occurred to me that an object in ...
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Historical proofs of the series expression for the Bessel function of the first kind

Introduction The Bessel function of the first kind $J_n(x)$ ($n \in \mathbb{Z},\ x \in \mathbb{R}$) appeared early among other topics, in Celestial Mechanics, in the series expression of the true ...
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3answers
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Name of Polaris before it became a pole star?

It seems that all stars as bright or brighter than Polaris have names dating to ancient times, including some stars even dimmer than Polaris. So what was Polaris called, in any language, before it ...
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243 views

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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2answers
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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 ...
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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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Has anyone explored Ptolemy's epicycles as an early form of Fourier analysis?

Whilst researching science in the ancient world, I came across an observation, which unfortunately I did not make a note of, and so cannot credit, that Ptolemy's epicycles were an early form of ...
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100 views

How did Hertzsprung-Russell diagrams end up so confusing?

HR diagrams show in which of several sequences individual stars fall, each respecting the rough principle that hotter stars are of higher luminosity. (Sequences other than the main sequence may bend ...
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1answer
106 views

What did the ancient Greeks know about the solar system, and how?

I'm aware that it was known to the ancient Greeks that the planets were somehow different from the stars. But in what depth did they know the solar system? In particular, did they know: that the sun ...
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71 views

Who was the first to state that scientific theories could be used to make predictions?

It seems to me that very few if any scientists/philosophers stated that science could be used for predictions before the early 1900s. In the scientific context I have only encountered the use of the ...
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2answers
174 views

How did Khayyam calculate the year so accurately?

Regarding the Islamic mathematician and astronomer Omar Khayyam, known (among other things) for his accurate calculation of the year, quoted from https://www.famousscientists.org/omar-khayyam/ ...
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1answer
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In which year, people found that sun is not the only star in the universe? [duplicate]

It is a well-known fact now that the sun is one of the multiple stars in the universe. But in which year people at least hypothesized the fact that we are living in a universe with multiple stars?
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History of: Galaxy rotation rate estimates

Out of sheer curiosity: When was the first discovery/estimate of the rotation rate of our Galaxy? (To my understanding: in astronomy the angular velocity of the Solar System with respect to the Milky ...
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1answer
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Was Herschel ever inspired to write music through his astronomy research?

While it is known that William Herschel was both a composer and an astronomer, could it be that he ever wrote music based on astronomy, or how he felt his research was proceeding? Just as Beethoven ...
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1answer
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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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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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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 ...
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1answer
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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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1answer
154 views

Could someone have discovered the moons of Jupiter before Galileo?

As Hans Lipperperhey had made a decent telescope albeit worse telescope before Galileo, source, would he have been able to theoretically view the moons of Jupiter before Galileo if he had looked?
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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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2answers
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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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1answer
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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 ...
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Literature on Mayan mathematics

I asked this question on math.se and they sent me here. It is well known that Mayan people used vigesimal (base 20) numeral system, and had had an advanced calendar system. Except for these facts, I'...