explain xkcd - User contributions [en]

2898: Orbital Argument

2024-02-26T15:47:53Z

172.70.110.30: /* Explanation */ Removed incorrect and irrelevant explanation of tides.

{{comic
| number = 2898
| date = February 23, 2024
| title = Orbital Argument
| image = orbital_argument_2x.png
| imagesize = 448x323px
| noexpand = true
| titletext = "Some people say light is waves, and some say it's particles, so I bet light is some in-between thing that's both wave and particle depending on how you look at it. Am I right?" "YES, BUT YOU SHOULDN'T BE!"
}}

==Explanation==
{{incomplete|Created by an ARGUMENTATIVE ORBITAL ELEMENT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
In this comic, [[White Hat]] is using the {{w|Argument to moderation|middle ground fallacy}} to try to make a compromise between the positions of [[Cueball]] and [[Megan]].

Cueball appears to be asserting a {{w|geocentric}} viewpoint, whilst Megan adheres to a {{w|heliocentric}} one, both of which are flawed descriptions of the way things are, but the latter is much closer to reality. White Hat, however, considers it {{wiktionary|politic#Adjective|politic}} to 'split the difference' and declares his intention to compromise with a 'middle' option, to try to uncritically please both parties. (Though it's probable that he may instead just equally annoy them both!)

On a naive reading, which imagines a point of common orbit midway between the bodies, his thesis is simply wrong. However, by one way of looking at it, it happens that he is also correct. Because two bodies exert equal but opposite gravitational forces on each other, each orbits around the average location of the other, and therefore they both orbit a common center. This {{w|Barycenter (astronomy)|barycenter}} is located somewhere between the centers of the two bodies; the distance of each body's center of mass from the barycenter is proportional to the other body's mass. This is most apparent in systems where the two bodies have similar masses, but it is present to an extent in all orbital pairs, even when one body is far more massive than the other. For this reason, Earth does not orbit the center of the stationary Sun as described by the heliocentric model. However, the Earth-Sun barycenter is only slightly different from the Sun's own true center, still well within the Sun. It is around this which the Sun wobbles, in contrast to the way the Earth orbits around this unequally proportioned midpoint.

The Earth-Moon barycenter is located approximately ¾ of the way from Earth's center of mass to its surface, towards the Moon's center of mass.

The equivalent Jupiter-Sun barycenter, meanwhile, is located just ''above'' the 'surface' of the Sun due to the masses involved being not as different (but still significantly so), and the much greater distance between them. As each of the planets and the Sun are simultaneously orbiting/'being orbited' (and every planet also measurably pulls on every other, etc, even discounting every smaller and/or more distant body in the universe), the combined solar-system's barycenter is a less simply-defined point (that being more likely to be within the Sun, at any given point of time), which can often be considered to more simply average out to "<each planet> orbits the Sun" for most purposes, and Cueball is therefore ''least'' correct, and it would be a false solution to give his worldview an equivalence of validity.

That White Hat has worded his compromise solution in a way that (arguably) encompasses the deeper truth of the barycentric viewpoint is not treated as justifying his mediating approach. It is clearly understood (by someone who seems to understand the complexities, e.g. a {{w|Randall Munroe#NASA|NASA physicist}}) that White Hat's 'successful' conclusion is just accidental. Which is vexatious. This seems to be a case of a {{w|Gettier problem}}: White Hat reaches a true statement via unjustified logic.

The title text extends the principle of the comic's astronomical viewpoint down to the correspondingly opposing 'quantum world'. For various well-studied reasons, light is often described ''either'' as particles ''or'' as waves. White Hat's approach would be to give both viewpoints equal credit and suggest a compromising middle-ground explanation. In this case, also, he would have the {{w|Wave–particle duality|correct answer}} but, in the continuing view of an increasingly exasperated witness to his chronic {{w|False balance|"half-and-half"ism}}, not through actually correct reasoning.

Another example of the middle ground fallacy was used in [[690: Semicontrolled Demolition]], although in that case the person offering the compromise solution was not portrayed as getting the right answer by accident.

Orbits of celestial bodies are quantified using a set of parameters called orbital elements. Some of these parameters are commonly known as arguments, such as the {{w|Argument of periapsis}}. However, these kind of arguments tend to lead to consensus rather than disagreements. Independent measurements of the arguments might indeed be combined by taking the mean (to discover the middle ground).

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[From left to right, Cueball, White Hat and Megan standing. Cueball and Megan are arguing. Cueball is raising a finger while Megan's arms are outstretched. White Hat stands between them, both hands out in an equivocal gesture.]
:Cueball: The sun orbits the earth!
:Megan: The earth orbits the sun!
:White Hat: When two people disagree, the truth is always somewhere in the middle. Maybe the earth and the sun orbit a common center!

:[Caption below the panel:]
:It's annoying when people are right by accident.
{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Megan]]
[[Category:Astronomy]]
[[Category:Physics]]
[[Category:Logic]]
[[Category:Compromise]]

Talk:2898: Orbital Argument

2024-02-26T15:46:45Z

172.70.110.30:

May not be (probably isn't!) the inspiration for this comic, but just yesterday there was news of the latest successes in cooling down {{w|Positronium}} (an 'atom' in which nothing is at the nucleus, the charges 'orbit each other' (or the quantum equivalent)). A co-inky-dink, surely, but just thought I'd mention it in passing... [[Special:Contributions/141.101.98.78|141.101.98.78]] 03:13, 24 February 2024 (UTC)

In editing, I'm accutely aware that even the "relatively small" force by the Earth on the Sun is a bad way of putting it. Looked at properly, ''exactly the same'' force is exerted against the Sun by the Earth (heavy item drawn pulled down to light item) as is exerted against the Earth by the Sun (lighter item being pulled down by heavier item). ((Fairly easily proven, these days: e.g. If it were not so, something like a bowling-ball and ping-pong ball could be kept separate by a stick, but released in space where they'd then work as a 'gravity drive' that propelled them one way (or perhaps the other!) without any need for power/propellant.)) Of course, the force should be considered equal (bidirectionally singular) with the inertial framing being the factor that makes the freefalling apple the more obvious thing to fall than the Earth upon which any budding Newton is stood/sat in rapt observation. But the Earth's contribution to the (currently) indivisible joint attraction that drives both sides of any 2-body problem is far more than any given apple and far less than any given star. As and when we can perhaps split this (either directionally 'diode' the flow of gravitational effects, or even independently manipulate inertial and gravitational masses) then perhaps we will need to be more discriminating in calculating/describing about such things. Assuming we don't just go with "gravity is a lie, it's all just mass-curved spacetime", instead. ;) But just thought I'd expound a few different relevent worldviews, of greater or lesser usefulness... [[Special:Contributions/141.101.99.33|141.101.99.33]] 04:35, 24 February 2024 (UTC)

Atomic & subatomic "particles" as discrete units, are a test condition artifact. Everything is waves.
[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 13:56, 24 February 2024 (UTC)
:Or (admitedly 'wavy') strings. Or resonant fields. Or some other esoterically theorised GUT-fodder... ;) [[Special:Contributions/172.71.178.156|172.71.178.156]] 15:49, 24 February 2024 (UTC)
::Submolecular strings are just (helical) waves viewed through a threshold-conditional gate.
::[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 21:34, 24 February 2024 (UTC)

I think comic 690: Semicontrolled Demolition is relevant to this one and should appear somewhere in the explanation of this one, as it touches on the same base idea. {{unsigned ip|15:45, 24 February 2024|172.71.175.75}}

Isn't there something about knowledge being true information arrived at by logically sound reasoning? This meets the first criteria but not the second. [[User:RegularSizedGuy|RegularSizedGuy]] ([[User talk:RegularSizedGuy|talk]]) 17:31, 25 February 2024 (UTC)

I feel there is an additional explanation that White Hat did not intend. The Sun and Earth, the entire Solar system for that matter, orbits the center of the Milky Way Galaxy. Which may also orbit the center of the known Universe? I am not an astrophysicist or knowledgeable enough to attempt a proper explanation. [[User:Vampire|Vampire]] ([[User talk:Vampire|talk]]) 15:31, 26 February 2024 (UTC)

"The Earth-Moon barycenter is located approximately ¾ of the way from Earth's center of mass to its surface, towards the Moon's center of mass. Our tidal bulges (oceanic and otherwise) occur along that line. One bulge is towards the Moon because of the gravitational attraction, and the other is in the opposite direction, by centrifugal force from the Earth's rotation around the barycenter." This is wrong for a couple of reasons. First, both bulges are the result of the same effect, and they would be there even if the Moon and Earth weren't producing centrifugal force by rotating about each other. In the usual explanation of the opposite bulges, you look at the acceleration of a particle on the near side of the Earth towards the Moon by more, the acceleration of the center of the Earth by a medium amount, and the acceleration of a particle on the far side of the Earth by less. Then, to look at things in the frame of reference of the center of the Earth, you subtract the center's acceleration, and find that the near side accelerates toward the Moon by a little, and the far side accelerates away from the Moon by a little. But even that explanation is wrong, or at least, very incomplete - the main driver of the tides is due to the vastly larger volume of water *away* from the line through the Earth's and Moon's centers; when you do that same vector subtraction of the local acceleration from the Moon minus the acceleration of the center of the Earth, you find that you get a tangential component of acceleration, and since water can flow, it does, until it reaches a surface of constant potential (it's not a lot of distance, but it's a lot of volume moving, so the tidal bulge is a significant volume of water). See https://web.archive.org/web/20220115060446/https://www.lockhaven.edu/~dsimanek/scenario/tides.htm [[Special:Contributions/172.70.110.30|172.70.110.30]] 15:46, 26 February 2024 (UTC)