counterearth

American  

[koun-ter-urth] / ˈkaʊn tərˌɜrθ /

noun

1. (in Pythagorean astronomy) a planet, out of sight from our part of the earth, whose shadow upon the sun and moon, cast by a central fire that is also out of sight, causes the eclipses.

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Etymology

Origin of counterearth

1855–60; counter- + earth, as translation of Greek antíchthōn