Questions tagged [astronomy]
The study of celestial objects and phenomena outside of the Earth's atmosphere.
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How did the earliest measurements of lasers bounced off of Apollo 11 retroreflectors deal with the light from the Moon and pick out single photons?
Wikipedia's Lunar Laser Ranging Experiments; History mentions the first lasers ever bounced off the whole Moon were in 1962, and probably both the US and Soviet groups used Q-switched ruby lasers.
In ...
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What laser technology/ies were first used to bounce off of the Apollo 11 retroreflectors to accurately measure distance to the Moon?
Wikipedia's Lunar Laser Ranging Experiments; History mentions the first lasers ever bounced off the whole Moon were in 1962, and probably both the US and Soviet groups used Q-switched ruby lasers.
In ...
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How did Scott and Amundsen detect the South Pole?
How did Scott and Amundsen detect the direction to the South Pole during their expedition? How did they determine the exact South Pole on reaching there?
Comparison of the Amundsen and Scott ...
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Did the ancients know about the law of universal gravitation?
Just looking into the dialogue by Plutarch "De facie quae in orbe Lunae apparet" and my impression is, they knew the law of universal gravitation quite well.
For instance, it is argued that
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Kepler's Mysterium Cosmographicum with regular polygons: in which nesting order?
Kepler tried to use regular polygons before using the 3D platonic solids in his Mysterium Cosmographicum.
My question is: which regular polygons did Kepler try to use and in what nesting order?
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Ancient parallax
When ancient Greeks could not observe any parallax, what were the two bodies they were looking at to determine this? I imagine the stars (or a specific star) would have been one of these, but what was ...
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What happened to the data from the survey that discovered the first pulsars?
The first pulsars, starting with B1919+21, were discovered in the late 1960s in data from the Interplanetary Scintillation Array at Cambridge. The data from the telescope was recorded on paper by four ...
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Could ancient astronomers have proven heliocentrism?
Could ancient astronomers have proven heliocentrism and, if so, how could they have done so?
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Did the Ptolemaic system have rotating center of the deferent for Venus?
I've come across this diagram of the Ptolemaic model. Am I understanding correctly that this means that all the planets' deferents rotate around a point which next to Earth, while Venus' deferent ...
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Were ancient astronomers (Babylonians, Egyptians or Greeks) aware of the solar analemma?
Is there any proof or even just indication that they did: I can't find anything online and was hoping for some help.
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Was Aristarchus the first to propose heliocentrism?
It's known that Aristarchus was the first to propose heliocentrism, and Wikipedia also says so, as quoted in this site at Does Heliocentrism predate Copernicus?
But in a different place in Wikipedia ...
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How did the Astronomical model of Sacrobosco differ from Ptolemy's?
According to Wikipedia, Sacrobosco's De Sphaera described the Ptolemaic system, but drew on additional ideas from Islamic Astronomy. How did Sacrobosco's model differ from that of Ptolemy?
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Entry 97 in Gauss's diary and the status of "lunar parallax" in the late 18th century
P.539-542 of volume 10-1 of Gauss's werke include entry 97 in Gauss's diary:
I have found new exact formulas for the parallax of the moon.
as well as the formulas themselves (which were rather found ...
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How did the ancients determine the exact time of equinoxes and solstices?
Hipparchus seems to have known that 94.5 days passed from the winter solstice to vernal equinox. How did he measure this?
Equinoxes and solstices don't happen only at noon when the Sun is highest, but ...
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How did Hipparchus measure the length of the tropical year?
My understanding is that he counted the number of days between every other equinox. The first year he would have counted 365 days, but after 4 years the tally would have reached 1461 days. Dividing ...
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How did Ptolemy know that days were unequal lengths?
Apparently Ptolemy was aware of the fact that the duration of time from noon to noon varied by many seconds throughout the course of a year. In modern times this fluctuation in length of day leads to ...
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Original description of point sources and point spread functions
I already asked this question in the Astronomy community, but there it was recommended to me to also try my luck here.
I would like to know the original description of point sources and point spread ...
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Is Koestler's ‘The Sleepwalkers’ still well regarded? Is there a more recent similar source?
Arthur Koestler's The Sleepwalkers is well-known as both a group biography of Copernicus, Brahe, Kepler and Galileo and an account of the revolutionary turn in astronomy that, in Koestler's phrasing, ...
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How did Copernicus find the nodes of Mars? what were they?
I'm trying to find the location of the nodes of Mars (i.e., the point of intersection between the ecliptic and Mars's plane [rather I should say Mars average plane]) given by Copernicus. According to ...
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Why does Eratosthenes method for calculating the circumference of the Earth requires the city of Alexandria and Syene to be in the same meridian?
I'm reading a book where the author claims that in order for the method of angles and proportions used by Eratosthenes to work, the two cities would have to be located in the same meridian, or at ...
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Why was Principia Proposition 43, Theorem 22 not published?
Why was Proposition 43, Theorem 22, of Newton's Principia not printed?
Weinberg, To Explain the World (2015) describes this proposition:
In an unpublished “Proposition 43” that did not make it into ...
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First to realize that seasons were reversed above and below the equator?
I assume this conclusion was hard to make empirically in the days of slow travel -- one could not as we can today fly from above the equator to below it and observe the difference in weather and even ...
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Was religion not present at all in the Astronomy of the Ancient Greeks?
I attended a lecture on the history of Astronomy and Mathematics, and I was somewhat puzzled by how scientific the early Greeks were. Yes, I am aware that they have many of the greatest mathematicians ...
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Comparison of the accuracy of the Ptolemaic and Copernican models
A Japanese book on mechanics says the following (English translation by me):
As a young boy, Tycho Brahe became interested in astronomy when he was impressed by the fact that the solar eclipse ...
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What was the Ptolemaic system used for?
Ptolemy's model is less accurate than Copernicus', but it is said to have been in use for a long time.
What was the Ptolemaic model be used for?
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Is there any book dealing with the history of both astronomy and geometry?
I am preparing an introductory course on the history of astronomy and geometry for intermediate students. The intention is to teach Copernican heliocentrism, Kepler's laws of planetary motion & ...
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In orbital determination of celestial bodies, why did the case of parabolic or nearly-parabolic orbits require separate development?
In Buhler's biography of Gauss, who made huge contributions to the development of efficient orbital determination methods in his Theoria Motus (1809), the following information is mentioned:
The ...
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When did we have first calculations of moon phases?
I'm interested in knowing more about the history around lunar tables and calculation of moon phases.
When did we have first (reliable) calculations of moon phases and first (reliable) lunar tables? ...
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What data did Copernicus use to construct his heliocentric model?
I think Copernicus and his contemporaries were modeling based on some data.
What data was Copernicus using and who created it?
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On the Ptolemaic theory of the planet's latitude
The Ptolemaic theory of the latitude of the planets is dealt on in Book 13 of the Almagest. This theory (which I was struggling to find info about online) is considered quite complicated, but luckily ...
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When was the discovery of the first pulsar announced?
The first pulsar was discovered on August 6, 1967 by Jocelyn Bell, but it took a while (and the discovery of a second pulsar) to figure out what was being observed. So I'm guessing this discovery wasn'...
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Is it possible to narrow down possible dates for the following eclipse pattern?
I am searching for an year which satisfies the following criteria.
Dates are in Gregorian calendar.
Criteria
Year range 3800 BC to 500 BC
Solar Eclipse of any kind between October 14 and October 22 ...
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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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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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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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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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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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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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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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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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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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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 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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