We have adjectives relating to various celestial bodies: 'Solar', 'Lunar', 'Martian', 'Venusian' etc. What would be the counterpart to Earth? 'Earthian' sounds very awkward to me... is it valid?

For example, the situation where Earth is eclipsed by a celestial body on the visual path between the observer and Earth, what would be the counterpart to 'Solar eclipse' and 'Lunar eclipse'?

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    According to Merriam-Webster's Eleventh Collegiate Dictionary (2003), the first meaning of terrestrial is "of or relating to the earth or its inhabitants." Does that fit the meaning you have in mind? – Sven Yargs Jun 14 at 8:13
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    Terrestrial eclipse. google.it/… – user070221 Jun 14 at 8:20
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    From Dominic Ford, The Observer's Guide to Planetary Motion (2014): "Likewise, what we call a solar eclipse on Earth might reasonably be called a terrestrial eclipse on the Moon." Ford is by no means alone in taking this view, as a search for "terrestrial eclipse" in Google Books (also suggested by user110518) will confirm. – Sven Yargs Jun 14 at 8:22
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    @SF. - sorry, what is your question exactly? is it about eclipses? quora.com/Can-we-see-terrestrial-eclipse-from-the-Moon – user070221 Jun 14 at 8:28
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    I suggest you make your question clear. If you are specifically looking for the more appropriate adjective in the specific case of an eclipse, you should mention that or probably ask on the astronomy site. – user070221 Jun 14 at 9:03
up vote 138 down vote accepted

Terrestrial:

  • relating to the earth

(Cambridge Dictionary)

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    Might be nitpicking here, but I interpret that as meaning, relating to conditions on the surface of the planet, not relating to the planet itself. For instance, one might say: "Terran species can only survive in terrestrial environments", meaning [from-earth] species ... [like-earth] environments. – Benubird Jun 14 at 13:33
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    @Benubird I don't think so, otherwise the antonym extraterrestrial wouldn't mean also "from outer planets". – Lorenzo Donati Jun 14 at 13:55
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    @LorenzoDonati It doesn't. It means not from earth. extra = from-somewhere-other-than, terrestrial = the-environment-of-earth. Try comparing it to a term for another planet: extramartian does not make sense, the same way extraterran doesn't make sense. If terrestrial/martian matched earth/mars, then extraterrestrial/extramartian would also fit, but they don't. – Benubird Jun 14 at 14:25
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    @Benubird: It certainly can mean what you say; but it can also mean what the question asks for. In some contexts it can mean other things still: e.g. in zoology you can distinguish terrestrial animals (ground-dwelling) from arboreal (tree-dwelling), aquatic, etc. It’s not at all unusual for a word to have several related but slightly different meanings! – PLL Jun 14 at 19:52
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    @Benubird Well, sorry but I don't agree in general. The meaning of a word may be context-dependant. Try going to a Sci-Fi convention and ask everybody what do they mean by "extraterrestrial". Moreover "extramartian" is sometimes used to mean "not from the planet Mars", as you can see in this Wikipedia article: Mission highlights include the initial 90 sol mission, finding extramartian meteorites such as Heat Shield Rock... – Lorenzo Donati Jun 15 at 12:22

Earth is "Terra". The corresponding adjective would be "Terran".

https://en.wikipedia.org/wiki/Terra

I see user110518 has added in Terrestrial, which I think is a better answer.

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    "Terran" refers to creatures, plants, and so forth native to the planet Earth. "Terrestrial" refers to things more directly of the planet Earth. "Terrestrial eclipse" versus "Terran insects". – Ben Barden Jun 14 at 13:28
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    Terran isn't even listed in Collins, and Merriam-Webster defines it as "earthman". Oxford online defines it as "(in science fiction) an inhabitant of the earth". And yet, it seems to me "terran" is used in this context (more than just people) in science fiction, so eventually it may enter the lexicon. – T.J. Crowder Jun 14 at 15:49
  • The Oxford English Dictionary gives 2 senses for terran, the first of which is indeed "(Science Fiction.) adj. Of or pertaining to the planet Earth or its inhabitants.", attested as early as 1881 (under the variant spelling Terrane), no less. – Ty Hayes Jun 15 at 10:24
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    Yeah, Eureka should remove their self-flagellating note and just clarify. The answer to the original question is 'Terran', particularly in SF discussions of comparative lifeforms, and 'terrestrial' is what you'd use for the eclipse in the second question. – lly Jun 15 at 14:45
  • If you wish to include terms common in science fiction then consider Tellus/Tellurian as well. However, terrestrial seems the obvious choice here. – Alchymist Jun 15 at 15:25

As user110518's answer states, terrestrial is the required adjective. However, attacking the "eclipse" angle...

A Solar eclipse is when we cannot see the Sun (because the Moon is in the way):

      /     \            ____                                  /
     /       \          /    \                                |
    |  Earth  | ==>    | Moon |                               |   Sun
     \       /          \____/                                |
      \     /                                                  \

A Lunar eclipse is when we cannot "see" the Moon (because the earth [mostly] blocks the Sun's light from reaching it):

      ____            /     \                                  /
     /    \          /       \                                |
    | Moon |    <== |  Earth  |                               |   Sun
     \____/          \       /                                |
                      \     /                                  \

From these, we can take it that an X eclipse is when we cannot (fully) see "X" because something (unspecified) is in the way.

Thus, someone on the Moon as the Earth passes between it and the Sun (the arrangement we call a lunar eclipse) would experience a Solar eclipse (because the Sun is blocked):

      ____            /     \                                  /
     /    \          /       \                                |
    | Moon | ==>    |  Earth  |                               |   Sun
     \____/          \       /                                |
                      \     /                                  \

The reference that Sven Yargs pointed out in a comment, The Observer's Guide to Planetary Motion, 2014 by Dominic Ford confirms this [emphasis mine]:

As seen from the Moon, the Earth's disk appears to pass in front of the Sun at a lunar eclipse. [...] It is rather curious to think that what we on Earth call a lunar eclipse might reasonably be called a solar eclipse by an inhabitant of the Moon.

He (Dominic Ford) then goes on to introduce the term terrestrial eclipse, but I think he does so incorrectly [emphasis again mine]:

Likewise, what we call a solar eclipse on Earth might reasonably be called a terrestrial eclipse on the Moon. If our hypothetical lunar inhabitant were to see a partial solar eclipse—the Earth's disk partially covering the Sun—then the part of the Moon's surface beneath his feat would lie within the Earth's penumbra. However, if he were to see a total solar eclipse—the Earth entirely covering the Sun's disk—then he would be standing within the Earth's umbra.

The problem is that although he starts talking about a solar eclipse from the Earth's perspective (where the Moon is in the middle; 1st diagram), the remainder of the paragraph describes a solar eclipse from the Moon's perspective (when the Earth is in the middle; 3rd diagram). This arrangement, we have already agreed, is a solar eclipse because the view of the Sun (from the Moon) is blocked.

One plausible definition of a terrestrial eclipse would use the same arrangement that we (on Earth) call a solar eclipse:

      /     \            ____                                  /
     /       \          /    \                                |
    |  Earth  |    <== | Moon |                               |   Sun
     \       /          \____/                                |
      \     /                                                  \

In the same way as a lunar eclipse is where light falling on the Moon is (partially) blocked by the Earth we're standing on; here, a terrestrial eclipse would be where someone on the Moon, looking at the Earth, sees [a small] part of it obscured by the Moon they are standing on.

However, just as a full solar eclipse (where the Moon completely blocks the Sun) can only be seen from a small area of the Earth; here, only a small area of the earth would be dimmed by the Moon: it is, perhaps, only technically an eclipse.

The other definition of a terrestrial eclipse – and one only very recently available – would be where the observer's view of the Earth is blocked by something else. This would never have been visible from the Moon (there's nothing large-enough between the Moon and the Earth to get in the way): it is only recently1 that space-probes have offered us such a view (although this is still only a partial terrestrial eclipse:

      /     \            ____                                 +--------+
     /       \          /    \                                |DSCOVR  |
    |  Earth  |        | Moon |                           <== |L1 point|
     \       /          \____/                                +--------+
      \     /                                                  

1 The most recent, and (presumably) best images of this are available on NASA's From a Million Miles Away, Moon Crossing Face of Earth page. There, it also notes that NASA's Deep Impact spacecraft captured a similar view in 2008, but only from a distance of 31 million miles.

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    +10! A great explanation! And the ASCII diagrams are a nice touch too. :-) – Greenonline Jun 14 at 23:46
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    Excellent answer. There is a nice diagram of various eclipses from various viewpoints in G.F. Schilling & R.C. Moore, "Eclipse Observation," in Proceedings of the First Lunar International Laboratory (LIL) Symposium (1966). The authors write,"Note that someone on the Moon would be observing a solar eclipse when we on Earth would be observing a lunar eclipse. Similarly ... – Sven Yargs Jun 15 at 6:14
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    ...a terrestrial eclipse —really a lunar shadow transit—is seen from the Moon when a solar eclipse is observed on earth." So, according to Schilling & Moore, a more accurate descriptive term for terrestrial eclipse, if you are talking about the view from the Moon, is lunar-shadow transit. (And as I mentioned earlier, the illustrations on page 88 of the paper are quite clear and well labeled.) – Sven Yargs Jun 15 at 6:15
  • Your drawings are really great! – Pavel Jun 15 at 7:15
  • Why you keep repeating "the Earth"? Nobody says "the Mars". If you are to capitalize Earth as a proper noun, then it is simply Earth, and alternatively, "the earth" which applies to the "ground made of dirt", i.e soil, which can be found on planets other than Earth. – dtech Jun 18 at 8:36

It's always 'terrestrial' with reference to an eclipse. For what it's worth, 'earthian' isn't the adjectival form of 'earth', though. The actual words are

Earthly

(attest. from OE) Of or relating to earth or Earth, variously

  • Restricted to Earth; hence non-spiritual, material; hence worldly, base, coarse.

  • On Earth; hence (obs.) on or in the ground or (in quest. & neg., esp. before 'no' or 'any') in any possible way.

  • (arch.) Made of earth.

  • Like earth; hence (arch.) ready for a tomb, pale and lifeless.

  • (chiefly SF) From Earth or resembling sth from Earth.

  • (n., in plural) Earthly things or people.

  • (n., UK colloq.) An earthly chance.

Earthling

(attest. from OE) A being of the earth, variously

  • (obs.) A farmer.

  • (obs.) Some kind of bird, now uncertain.

  • (Xian.) A person dwelling upon the earth.

  • (now chiefly SF) A person from Earth.

  • (arch.) A materialistic person.

Earthy

(attest. a. 1400) Of or relating to earth, Earth, or (chem.) the earths, variously

  • Like earth; hence (minerol.) lusterless, friable, rough, &/or uneven or (elec.) similar in potential to the ground or (now chiefly pseudosci.) heavy, material; hence (esp. of humor) unrefined, crude; hence unpretentious, down-to-earth.

  • Made of earth; hence (now chiefly pseudosci.) restricted by its earthy composition, gross.

  • Covered with, full of, or containing earth; hence dirty.

  • On Earth; hence on or (esp.) in the ground.

  • (uncommon) Terrestrial.

  • Restricted to Earth; hence non-spiritual, material; hence worldly

Earthish

(attest. c. 1533; now chiefly SF) Earthly, of earth.

Earthite

(attest. 1814; now chiefly SF) A person from Earth.

Also earth-bred and -born; their latinate equivalents terrigenous and terrigenal; and, only dealing with things made of, like, or restricted to earth, earthen.

Little used these days, but another name for the planet is Tellus, and its adjective form is Tellurian. For what it is worth.

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    Even though the name ends in -us, usually associated with masculine-gendeer nouns in Latin, Tellus was a Roman earth-goddess, the counterpart of the Greek earth-goddess Gaia. – tautophile Jun 14 at 16:22
  • "Tellurian" was used in this sense by E E "Doc" Smith in the very early days of genre science fiction, before a literary convention had developed around the use of "Terran". – Mike Scott Jun 18 at 12:24
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    @tautophile tellūs, tellūris (long u) is a 3rd-declension noun, which means the gender is less predictable from the ending. As it happens, the common noun tellūs is feminine, and means earth, ground, land, as well as being used as a name for the goddess. – LarsH Jun 18 at 16:02

"terrestrial" literally means "having to do with the Earth", but can also be used in a more metaphorical sense of contrasting with ethereal, spiritual, etc. "terran" in another option.

However, if we're talking about eclipses, the naming conventions are highly dependent on point of view. When the Earth's shadow falls on the moon, we call that a "lunar" eclipse. When the moon's shadow falls on Earth, we call that a "solar" eclipse. So in the first case, the eclipse is named according to what body the shadow is on, and in the second case, it's named according to what body the shadow is from. The naming is highly Earth-centric: when we see a change in the moon's appearance, we call that a "lunar" eclipse, and when we see a change in the sun's appearance from Earth's point of view, we call that a "solar" eclipse. If you were on the moon, a "solar" eclipse would look like a terrestrial eclipse, and a "lunar" eclipse would look like a solar eclipse.

  • "but can also be used in a more metaphorical sense of contrasting with ethereal, spiritual, etc. "terran" in another option." A better word for that is 'mundane'. – Cubic Jun 14 at 15:35

tellurian perhaps from tellus which is a Latin word for Earth, gaian from Gaia another word for earth ?

tellurian
tɛˈljʊərɪən formal literary

adjective
1. of or inhabiting the earth.

noun
1. an inhabitant of the earth.

Tellurian is used in E.E. "Doc" Smith's science fiction novels

When either Mercury or Venus is seen to cross the disk of the Sun, that is called a "transit" of the planet. The disk of the planet is very small compared to the disk of the sun, so it doesn't qualify as an "eclipse" Arthur C Clarke wrote a story called "Transit of Earth" [1971], where the Earth (and the Moon, I think) crossed the disk of the Sun as seen from Mars...and the transit of Earth in the story will really occur on the date the story was set (2084). The most recent transit of Earth as seen from Mars took place in 1984, but nobody was there to see it. When the Moon or a planet passes in front of a star or other celestial body as seen from Earth, that is an "occultation". There are photos taken from satellites of the Moon's shadow moving across the Earth during a solar eclipse. I suppose if you were on the Moon, and the Earth was between you and the Sun, you might call it a "Terran eclipse", but people on Earth would call it a lunar eclipse.

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    This is interesting comment about eclipses. But can you emphasize the part where you give the 'Earth' version of lunar and solar? – Mitch Jun 14 at 16:32
  • Not quite sure what you're asking, Mitch, but a solar eclipse (as seen from the Earth) is one where the Moon's shadow is cast on the Earth. A lunar eclipse (as seen from the Earth) is one where the Earth's shadow is cast on the Moon. In a total solar eclipse, the sun is completely blotted out for observers on Earth for a short time. This enables us to see the solar corona, which is otherwise blotted out by the sun's glare. In a total lunar eclipse, the Earth's atmosphere refracts enough sunlight to the Moon that the Moon never quite disappears from sight to observers on the Earth. – tautophile Jun 17 at 18:51
  • Tautophile, the OP is about the word for the earth that is analogous to lunar and solar. You've done a lot of explanation of astronomy which is very interesting but mostly irrelevant. In the end you suggest 'terran' as the word. All I'm saying is that you should somehow emphasize that suggestion rather than emphasize all the astronomy. – Mitch Jun 17 at 20:17
  • You've got a point there, Mitch. It occurs to me that, if you're on the Moon and the Earth comes between you and the Sun, that's a solar eclipse from your point of view, but a lunar eclipse from the point of view of your colleague back on Earth. If you're on the Moon and the Moon comes between the Sun and the Earth, you might call what you see a "terran" (or terrestrial or tellurian or maybe even simply an Earth) eclipse, but to your earthbound colleague, it would be a solar eclipse. "It's all how you look at it." – tautophile Jun 17 at 20:34

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