Questions tagged [astronomy]
The study of celestial objects and phenomena outside of the Earth's atmosphere.
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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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69 views
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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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
81 views
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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1answer
92 views
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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1answer
98 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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102 views
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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143 views
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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114 views
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 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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180 views
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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1answer
104 views
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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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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96 views
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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31 views
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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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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46 views
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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159 views
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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91 views
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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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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381 views
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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158 views
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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105 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
245 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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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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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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228 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
91 views
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
126 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 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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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'...
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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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1answer
125 views
Laplace's Treatise of celestial mechanics
I am interested in nineteenth-century astronomy and Laplace's Treatise of celestial mechanics is often mentioned as one of the most significant contributions to science in this period. The more than ...
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1answer
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Were epicycloids from astronomy acceptable curves in Greek geometry?
My simplified historical understanding is as follows. Euclidean geometry accepted a limited number of geometrical objects (straight-edge and compass constructions, conics). Descartes' Géométrie ...
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1answer
363 views
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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71 views
Historical accounts of a oft-cited quip by astronomer Walter Baade
I am looking for any documented, historical reference to an oft-cited humorous reply by German astronomer Walter Baade (1893 – 1960).
After having asked if other astronomers were familliar with the ...
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278 views
What made Newton realize that the law of gravitation was 'universal'? [duplicate]
Newton's law of gravitation operative near the earth is the same law causes the earth and the other planets to go around the sun and other heavenly phenomena. Was it a giant leap of faith by Newton or ...
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Did pre-Galilean astronomy inspire Mach's principle?
Was Mach, in his formulation of "Mach's principle," influenced by pre-Galilean astronomy, such as that of Aristotle in On the Heavens, where heavenly bodies influence terrestrial ones?
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115 views
What is the historical basis for the length of a sidereal year?
It is understandable that the length of a solar year can be found out using the time of solstices. But how did they find the length of a year with respect to the stars?
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Was the width of the Atlantic first determined in 1584?
In Eclipse: Journeys to the Dark Side of the Moon by Frank Close, it is stated that the 1584 lunar eclipse was used to determine the width of the Atlantic, by measuring the times in London and in ...
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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 ...