Questions tagged [astronomy]

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

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3
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2answers
80 views

How was longitude determined in the 1700s?

I'm going through the journals of Alexander Mackenzie (ca 1790) and I came across this passage: I gather that he's determining his latitude and longitude but I'm not clear on what units he's using, ...
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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 was it realized that the giant planets do not have solid surfaces?

When was it realized that the gas giant planets Jupiter and Saturn, and the ice giant planets Uranus and Neptune, do not have solid surfaces? When was that idea first proposed and when was it accepted ...
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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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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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Can "Laplace limit" phenomenon be considered the first example of non-convergent Fourier series?

Traditionally, the first example of a non-convergent Fourier series of a function is considered to be the example constructed in 1870 by the mathematician Paul David Gustav du Bois-Reymond. His ...
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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 many stars dimmer than Polaris. So what was Polaris called, in any language, before it became ...
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Why do we call Tycho Brahe by his first name?

Why do we use the fist name in Tychonic system or Tycho's comet of 1577, instead of using the last name of Tycho Brahe? For comparison, we have the Ptolemaic system and the Copernican system. I am ...
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What pre-GR alternatives to Vulcan were advanced to explain Mercury's perihelion precession?

Any account of the precession can be characterized by perturbations due to bodies other than the Sun and a modification of the Binet equation's right-hand side, which is constant for an inverse-...
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Did Ibn Al-Haytham believe that the Moon reflects sunlight or that it is self-luminous?

There are at least two articles about Ibn Al-Haytham in Encyclopedia First and Second Both these articles have one major difference that is according to the First article: The Light of the Stars (III ...
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How accurate was the measurement of the period of Earth's orbit in the 19th Century?

There was a section on my textbook on history of theories of sun's energy source. It talks about how the Meteorite Theory was dismissed, as it would decrease the period of Earth's orbit by 2 seconds ...
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In Newton's cannon image, where do the shapes drawn into the sphere come from?

I find quite interesting the choice for the shapes drawn into the sphere that resembles continents. Was this choice arbitrary or do we know if there is some justification behind it?
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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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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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Tycho Brahe and the distance to the fixed stars

How far away did Tycho Brahe estimate that the fixed stars were? In multiples of our sun I imagine!
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What did Copernicus and Tycho Brahe actually contend about stellar parallax? [duplicate]

It's often stated that Tycho Brahe objected to Copernicus' heliocentric model on the basis that, if Earth were revolving around the Sun, stellar parallax would be observable, due to the changing ...
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1answer
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The Rejection of Solid Orbs by Geo-Heliocentric (Tychonic) model of the solar system

Some sources (modern sources, and Kepler himself) claim that in his Geo-Heliocentric (Tychonic) model, Tycho Brahe saw that the orbs of the Sun and Mars intersect, and this was one of the reasons ...
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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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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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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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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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Lunar distance measurement reference

While preparing trigonometric exercises for my students, I learned that, in 1771, French astronomers determined the distance of the Moon from the Earth by measuring the appropriate angles from both ...
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To what extent was astronomical knowledge in ancient Greece common knowledge?

I have a question about ancient Greek astronomy. We know certainly that the likes of Pythagoras, Aristotle, Anaximander, et al had much to say about the motions of the stars, planets, comets, etc, ...
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Did Bacon analogize planets to holes in the head to explain why their number was (believed to be) seven?

I'm looking for a source (of which I've only ever read a quote) discussing the then seven known planets. In particular, I'm looking for the part where the author explains why that number seven makes ...
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1answer
101 views

When did contemporary practices for indicating ecliptic longitude supplant those containing zodiacal signs?

Ecliptic longitude may be expressed in degrees; my understanding is that prior to the 19th century, expressions of ecliptic longitude contained zodiacal signs. What contemporaneous accounts describe ...
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Where did Wm. Herschel plan to put their head? Peer over the edge of the famous 40-foot telescope or try to get less off-axis; closer to the center?

From here: click for larger Herschel's 40 foot telescope had a diameter of 48 inches (122 cm) and was f/10. It was not a good mirror (cast in metal) and apparently not used that much. But my ...
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What is the origin of the parsec?

In astronomy the parsec is a unit of length: A parsec (abbreviated pc) is a unit of distance used by astronomers, cosmologists, and astrophysicists. 1 parsec is equal to $3.08567758\times10^{16}$ ...
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Is it true that there were "wooden guiding structures" proposed, by the ancient Greek, to account for the motions of the planets?

I can remember after attending a philosophy of science class, I put forward the thought ancient Greek had about the motion of the planets. I had read about them thinking there are wooden circular ...
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Earliest numeric value for helium D3 line

In late 1868, Norman Lockyer discovered the existence of the D3 emission line of helium in the solar spectrum. What was the earliest published example of a numeric value for the wavelength of this ...
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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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How does Copernicus explain the discrepancy from "On the Revolutions of the Heavenly Spheres" Book 5. chapter 16

In "On the Revolutions of the Heavenly Spheres" Book 5. chapter 16, Copernicus appears to acknowledge a discrepancy between the old Ptolemy observation and the model. Here is a Google ...
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When was the surface temperature of the Sun first measured?

William Herschel thought that the Sun was inhabited as did others at that time. Presumably there was no knowledge of its surface temperature, so when was it first realised that the surface was far ...
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Why did it take so long to discover the shape of the Milky Way?

It was not before the early fifties of the last century that the shape of the Milky Way was figured out. Uptill then only other galaxies were known to have certain shapes It's always easier to find ...
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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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1answer
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Who else measured the circumference of the Earth in the Antiquity?

The first famous measurement of the Earth's circumference was made by Eratosthenes. But he wasn't the only one to carry out this measurement. For instance Posidonius provided the estimate of the ...
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How was the first parabolic telescope mirror made, and how was it used, and for what kind of telescope was this work done?

This answer to When was the first true Gregorian telescope built? explains: Newtonian uses one concave and one flat mirror (or just one concave). Gregorian uses two concave mirrors, and Cassegrain ...
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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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Were Kepler's Laws of Planetary Motion the first formal definition of an ellipse?

It seems to me that Kepler's Laws necessitate some definition of an ellipse in terms of a coordinate system. I am wondering whether Kepler's Laws mathematically defined what an ellipse is, or if he ...
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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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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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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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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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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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335 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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217 views

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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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 ...