View source for Eithalica (planets)

{{Infobox
|title = Eithalica
|image = https://eithalica.world/assets/img/planet-DCI-2K.jpg
|key1 = Type
|val1 = [[#Celestial Classification|planet system]]
|key2 = Number of bodies
|val2 = 4
|key3 = Total mass
|val3 = 23.05 &times; 10<sup>24</sup> [[Wikipedia:Kilogram|kg]]
|key4 = Component radius<ref>That is, the distance from the center of [[Eith]] to the outermost surface of one of its moons.</ref>
|val4 = 24.97 &times; 10<sup>6</sup> [[Wikipedia:Meter|m]]
|key5 = [[Wikipedia:Sidereal time|Siderial day]]
|val5 = 20,149.0 [[Wikipedia:Second|sec]] (5 [[Wikipedia:Hour|h]] : 35 [[Wikipedia:Minute|m]] : 49 [[Wikipedia:Second|s]])
|key6 = [[Wikipedia:Synodic day|Synodic day]]
|val6 = 20,161.8 [[Wikipedia:Second|sec]] (5 [[Wikipedia:Hour|h]] : 36 [[Wikipedia:Minute|m]] : 02 [[Wikipedia:Second|s]])
|key7 = Direction of rotation
|val7 = [[Wikipedia:Retrograde and prograde motion|prograde]] (same direction as orbit)
|key8 = Orbital period
|val8 = 31,754,824 [[Wikipedia:Second|sec]] (367.53 [[Wikipedia:Earth|Earth]] days)<br><br>1,575 [[mios]]
|key9 = Orbital radius
|val9 = 150.23 &times; 10<sup>9</sup> [[Wikipedia:Meter|m]]
|key10 = Axial tilt
|val10 = 22.9[[Wikipedia:Degree (angle)|&deg;]]
|key11 = Members
|val11 = * [[Eith]]
* [[Chessol]]
* [[Siothum]]
* [[Temalar]]
}}
'''Eithalica''' (pronounced &ldquo;eye-{{smallcaps|thal}}-ik-ah&rdquo; &mdash; [[Wikipedia:International Phonetic Alphabet|{{smallcaps|ipa}}]]: /aiθˈælɪkə/) is a [[#Celestial Classification|planetary system]] of four bodies, or a '''&ldquo;quadruple planet.&rdquo;''' It is home the [[Chetnum (civilization)|Chetnum civilization]] and two known [[Anthropomorphic intelligence|intelligent]] species:
* [[Klevem]], a humanoid species, and
* [[Yalengem]], a flying [[Wikipedia:Tetrachromat|tetrachromat]] with pronounced [[Wikipedia:Bioluminescence|bioluminescence]].

The [[Wikipedia:celestial bodies|celestial bodies]] of Eithalica include:
* [[Eith]], the one in the center and the largest (by a slim margin).
* Three outer bodies or &ldquo;moons&rdquo; (the term &ldquo;moon&rdquo; here is [[#Celestial Classification|used loosely]]):
** [[Chessol]] (the primary moon for the [[Chetnum (civilization)|Chetnum]] civilization)
** [[Siothum]]
** [[Temalar]]

Partly due to the [[Lethean Age]], the people of [[Chetnum (civilization)|Chetnum]] have not yet explored much of Eithalica. They remain ignorant of [[Siothum]], [[Temalar]], and the non-[[chesward]] parts of [[Eith]] to this day.

= Description =

All the bodies in Eithalica have nearly the same physical characteristics, which (when considered per-body) are essentially [[Wikipedia:Earth analog|earth-like]]: mass, mean radius, mean density, surface gravity, general composition, climate, etc. They even have comparable types of global ecosystems and share some [[:Category:Environment|flora and fauna]]. This approximate homogeneity is one of the [[#Paranatural Traits|paranatural traits]] of the system and gives rise to its [[#Celestial Classification|classification trouble]].

On top of these similarities, the orbital configurations of Eithalica are striking in at least four ways:
* All three &ldquo;moons&rdquo; orbit extremely close to Eith (and each other) with very short periods.
* All orbits are [[Wikipedia:Geostationary orbit|geostationary]] to Eith, a condition kept stable by [[Wikipedia:Tidal acceleration|tidal forces]].
* All bodies are [[Wikipedia:Tidal locking|tidally locked]] to each other.
* The system is radially symmetrical, another [[#Paranatural Traits|paranatural trait]].

Due to these characteristics, all the moons have [[Wikipedia:Roche limit|Roche limits]] that are even closer to Eith&rsquo;s surface than the moons are themselves. This means that, although they are so [[Wikipedia:prolate|prolate]] that it's obvious to the naked eye, each moon is still internally stable. In fact, the lack of variability in prolateness means no added stress from [[Wikipedia:Tidal heating|tidal flexing]] (and therefore no extra [[Wikipedia:volcanism|volcanism]]).

As a result of the system-wide tidal locking and geostationary orbits, Eithalica appears almost like one contiguous, rigid mass&mdash;as though its members are all fixed to each other by invisible arms. This, together with the extreme closeness of the moons, made it possible for [[Chetnum (civilization)|Chetnum]] to build a [[#Moon Bridge|bridge from Eith to Chessol]] during the [[Imperial Age]].

The [[#Effective Potential Map|gravitational pattern]] also results in nine different [[Wikipedia:Lagrange point|Lagrange points]] that are also fixed relative to the system.

= Moon Bridge =
''Main article: [[Moon Bridge]]''

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= Effective Potential Map =

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= Celestial Classification =

Eithalica is a unique system that resists conventional classification.

A casual observer might see that Eith sits permanently in the center of all the &ldquo;lunar&rdquo; orbits, and suppose this means Eith is the host for those orbits. But this is a deceptive consequence of [[#Paranatural Traits|the system&rsquo;s overall symmetry]]. In reality, the gravity from Eith plays a smaller role in defining each moon&rsquo;s orbit than does the combined gravity from the other two moons. So the system is truly mutual like a [[Wikipedia:Star system#Higher multiplicities|quadruple star]], but of [[Wikipedia:planet|planets]]. Hence it receives the term '''&ldquo;quadruple planet.&rdquo;'''

In this wiki and other real-life English works, the outer bodies of Eithalica are still called &ldquo;moons&rdquo; in a virtual sense, and for simplicity. However, a [[Wikipedia:moons|moon]] is defined as a naturally occurring [[Wikipedia:satellite (disambiguation)|satellite]], i.e. a body which [[Wikipedia:orbit|orbits]] another. To say that one body orbits the other, and not ''vice versa,'' is to presume a hierarchy between the two which in the case of Eithalica and each of its moons is very tenuous.

Theoretically all bodies in a system exert at least some [[Wikipedia:gravity|gravitational force]] on all other bodies in the system, but for most planet systems the masses involved are defined by a hierarchy so enormous that it&rsquo;s unmistakable and indisputable. Often the influence of the smaller bodies on the larger is negligible.

In real-life astronomy so far, most disputes on this topic concern possible [[Wikipedia:Dwarf planet|dwarf planets]]. Every one of Eithalica&rsquo;s bodies is too large to be remotely considered &ldquo;dwarf-size,&rdquo; yet it still exists at an utmost edge of these definitions&mdash;a new, somewhat different edge.

= Paranatural Traits =

The term &ldquo;paranatural&rdquo; used here should not be confused with the word &ldquo;paranormal.&rdquo;

== Homogeneity ==

== Symmetry ==

= Footnotes =

<references/>