#celestial mechanics

[stone-cold-groove]

Phases of the Moon - 1956.

[darkenergyslivers]

the sun’s aura - hdr composite photograph of april 8, 2024 total solar eclipse taken at clarksville, texas by portugal-based astrophotographer miguel claro

[robpegoraro]

Darkness at 1:41 p.m.

The photos I took Monday didn't quite capture what it felt like to see a total solar eclipse for the first time, so I had to try to string some words together.

DALLAS I thought I’d seen enough pictures of a total solar eclipse to guess what it might feel like to see one with my own eyes. But then I got out of bed at 5:30 a.m. Monday to fly to DFW and witness that afternoon’s eclipse with a friend who lives northwest of the city—and that revealed how awestruck I could be left watching celestial mechanics play out in a sky like none above me before. The…

[g-h-o-s-t-2000]

There’s nobody on the other end of the phone?

[sbflux-art]

them

[someminorgod]

Well, let me expand on that fact a little bit.

Jupiter's outer layers are indeed made out of hydrogen and some helium, the main elements of a star. The heavy core is made out of heavier elements, metals, with a higher percentage of mass as compared to the sun.

The reason Jupiter has at least a similar composition to the sun is that it is located behind the frost line. During the formation of the sun, some of its material is left behind, remaining in the protoplanetary disc. All planets were formed in this disc, both the earth and jupiter. Of course, it is generally hotter in this disk near the sun. Close to the sun, these molecules remain gaseous. At greater distances from the sun, molecules such as water and ammonia can exist in solid form, as ice. This ice as well as other dust are used as building material in the formation of planets. Due to this, planets behind the frost line grow significantly larger, so large that their gravity can capture and trap the large amount of hydrogen and helium atoms in the protoplanetary disc.

When the nuclear fission inside the star starts, the loose materials in the disk are gradually blown away and the disc disappears, leaving only solid asteroids and planets. Due to Jupiter's large magnetic field and gravity, hydrogen and helium remain in its atmosphere and outer layers to this day.

To create a star, significantly more material than found in the protoplanetary disc is required. The nearest red dwarf is Barnard's Star, which is the second closest star system to the sun. It's too dim to be visible to the naked eye, and can hardly be recognised in good telescopes. As a red dwarf, it is barely considered a star; it has just enough mass and gravity to initiate thermonuclear fusion in its core.

Barnard's Star has about 150 Jupiter masses. That's a lot of Jupiters. So while it's true that Jupiter's just not big enough to start nuclear fusion, it is actually very, very far from it.

I haven’t posted space so I want to share the most recent photo of Jupiter

Someone had a great theory/fact about this. They said:

“Jupiter is basically a dwarf star and made of the same ingredients that our sun is, just not big enough for the gravitational friction at its core to ignite the nuclear fusion process.”

This makes sent to me and might be true, but I’m not an expert, so if it’s true or have any more explanations about it.

Jupiter is one of the most beautiful planet in the cosmos. If anyone has some cool facts and theories, feel free to share!

Space & Astronomy

[tenth-sentence]

The Earth's center marks out a similar set of waves but considerably shallower.

"The Stars in their Courses" - Isaac Asimov

[nicolae]

Newton's thought on celestial mechanics and its diffusion

Let us indicate, in its essential features, the change of mind produced by the prodigious success and by the diffusion of Newton’s celestial mechanics: at the beginning of the 18th century, a sort of Cartesian orthodoxy reigned almost everywhere in the world; Rohault’s physics was widespread everywhere. In the space of thirty years, she had disappeared everywhere; England abandoned it first; in…

[quranindex]

Discover Quran Verses about #Celestial mechanics @ https://quranindex.info/search/celestial-mechanics [10:5] #Quran #Islam

[stone-cold-groove]

Sun and Planets. Goode’s World Atlas - 1953.

[slapstikcomedyentertainment]

Hilarious Histories - July 5

Newton especially struggled with the problem of counterfeit currency...

On July 5, 1687, a man slightly more brilliant than myself, Sir Isaac Newton, published the “Principia Mathematica.” Two hundred fifty years later to the day, Spam was introduced to a grateful world. Coincidence? I think not. The eminent scientist unveiled several wonders for humanity, which in deference to him share his name. These include Newton’s laws of motion, Newton’s law of universal…

[teachersource]

Johann Gottfried Galle was born on June 9, 1812. A German astronomer from Radis, Germany, at the Berlin Observatory who, on September 23, 1846, with the assistance of student Heinrich Louis d'Arrest, was the first person to view the planet Neptune and know what he was looking at. The discovery of Neptune is widely regarded as a dramatic validation of celestial mechanics, and is one of the most remarkable moments of 19th-century science.

[firesidoni]

okay, so starting out with a disclaimer: i just woke up and my brain’s not in gear, so i may be missing obvious problems with this. it’s also been like a decade since my college astrophysics course, so. i also don’t know jack shit about asoiaf except what i’ve picked up by osmosis and reading comments on this thread; i heard them described as “a song of rape and murder” years ago and decided i wasn’t touching that.

now, @birdylion did a great breakdown of the situation above; i just had a couple thoughts to possibly expand on it, for how you might get seasons defined as lasting multiple years

one small clarification on the above: seasons are determined firstly by which hemisphere is closest vs furthest from the sun, but when the planet is closest vs furthest from the sun in its orbit is also a contributor, at least to the intensity of the seasons.

(note that i’m going to be using “perigee” and “apogee” technically incorrectly here - properly speaking, perigee is the closest point an object comes in an orbit around earth specifically, and apogee is similarly the furthest point in the orbit around earth specifically. i’m pretty sure there’s a generic term for the closest and furthest points in a generic orbit, but i can’t think of it right now, so perigee and apogee it is.)

so for the earth’s orbit around the sun, northern hemisphere summer is when the northern hemisphere is pointed in the direction of the sun, but it actually occurs at the apogee of the solar orbit, so it’s at the furthest point away. similarly, northern hemisphere winter is when the northern hemisphere points away from the sun, but it’s at the perigee of the solar orbit, when the earth is closest to the sun. in both cases, this means that southern hemisphere winter occurs at apogee, when the earth is furthest from the sun, and southern hemisphere summer is at perigee, closest to the sun.

the result of this is that southern hemisphere summers and winters are more severe than northern hemisphere summers and winters - it’s not a huge difference, but it is noticeable. this isn’t directly playing into my idea as such, but it’s a relevant point, so we’ll put a pin in it and come back to it.

now, there’s a few ways you might get the “normal” (sub)cycle of seasons, but the one that’s jumping out at me is binary systems, either a very large moon or a binary planet - basically take a moon and scale it up so that the center of the earth-(moon/co-planet) orbit isn’t under the earth’s surface, but is somewhere between the two bodies. make the cycle of their orbit around each other slow enough that it one full cycle is actually comparable to what we think of as a year. this is how we’re going to define what they think of as a year. (probably the plane of this orbit is tilted relative to the orbit around the sun, so the co-planets aren’t blocking the sun from each other for extended periods of time.) say the variation in distance from the sun is enough to produce a small seasonal variation. it’d probably be a fairly mild seasonal variation, but it’s enough to count for our purposes.

so the combined orbit of planet and (moon/binary planet) around their mutual center produces a significant enough variation that it causes the “normal” four-season cycle that i gather happens. i’m working purely on the assumption that there’s enough factors that there’s actually two cycles of seasons going on here: one from planet/planet or moon/planet cycles, one full cycle of which is used to define a year, which variation continues throughout the Long Winter/Long Summer variation. (i guess we’re using seasons for the planetary seasons and Seasons for the solar seasons.) on top of this, you have the Seasons, which are defined by a solar year.

so basically what i’m thinking is that the seasons and Seasons are operating on two different definitions of a year, and you end up getting seasonal variation that looks something like this:

ignore the numbers, they’re not important. the important part is what they call a year is defined by the small wiggles/“binary planet” year, while the big wiggle is the actual solar year, how long it takes to go around the star. seasons are the small wiggles, Seasons are the big wiggle, and yes apparently “wiggle”. meh, it works.

(mind, how would the actual orbital mechanics of this play out? no clue, because that gets into the three-body problem, and outside of a few specific three-body-problem scenarios we have elegant solutions for (which this ain’t one), the only way to get answers to a three(-or-more)-body problem is to work with specific numbers and run a numerical simulation, which. nah.)

Someone over on Discord asked, "I'm morbidly curious: How BAD is A Song of Ice and Fire in terms of the authenticity George claims it to be?"

My reply was straightforward:

The long and the short of it is that ASOIAF is basically a vehicle for GRRM to present both his rape fetish and his Hobbesian view on human nature and has less historical accuracy than Frozen or most other Disney movies.

That's actually a good way to think of it, now that I've said it--he's Family Unfriendly, they're Family Friendly, but both have the same relationship with History: just Pure Aesthetic with no consideration for how the worldbuilding would work.

[tenth-sentence]

Its orbit was changed as a result of gravitational attraction strictly according to astronomical laws of celestial mechanics.

"The Stars in their Courses" - Isaac Asimov

[befuddled-calico-whump]

Goretober 3: Celestial

prompt list here

[a-dream-seeking-light]

haha what a treat to have this culminate on my birthday!

2023 September 23

Afternoon Analemma Image Credit & Copyright: Ian Griffin (Otago Museum)

Explanation: An analemma is that figure-8 curve you get when you mark the position of the Sun at the same time each day for one year. To make this one, a 4x5 pinhole camera was set up looking north in southern New Zealand skies. The shutter was briefly opened each clear day in the afternoon at 4pm local time exposing the same photosensitized glass plate for the year spanning September 23, 2022 to September 19, 2023. On two days, the winter and summer solstices, the shutter was opened again 15 minutes after the main exposure and remained open until sunset to create the sun trails at the bottom and top of the curve. The equinox dates correspond to positions in the middle of the curve, not the crossover point. Of course, the curve itself is inverted compared to an analemma traced from the northern hemisphere. And while fall begins today at the Autumnal Equinox for the northern hemisphere, it’s the Spring Equinox in the south.

∞ Source: apod.nasa.gov/apod/ap230923.html