"In what solar system is planet earth?" grammatical? I see "What solar system is planet earth in?", but I don't see "In what solar system is planet earth?" I think both are ok, but I am wondering if you need to add something like a verb after earth to make it grammatical. A verb like situated. I doubt there's a specific rule for that, but just making sure.

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    The question doesn't make sense, because there's only one "solar system" in the universe (ours, with The Sun = Sol at the centre). The nearest equivalent for other locations is that we've recently discovered multiple planetary systems elsewhere in the galaxy. Jul 7, 2022 at 12:00

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The first question is certainly grammatical, and the second probably is grammatical although unnecessarily obscure. I find both to be a bit awkward because of the use of the verb "is" and of the currently fashionable locution "planet Earth." Earth is a planet. Talking about "the planet Earth" is similar to talking about "the city New York City." The redundancy makes the listener or reader wonder whether there is some complex meaning in using two nouns. This is a minor issue compared to the placement of "in."

A question in English is indicated by inversion. Based on usage, I guess we have to say that detaching "in," the preposition leading into the prepositional phrase "in which solar system," from that phrase when inverting to form a question is grammatical. You certainly hear it in speech or see it in informal writing. It violates, however, the general rule that a preposition precedes a prepositional phrase. Violating general rules frequently makes a sentence or question difficult to understand.

The verb "is" is also slightly odd, at least to my ear, but is certainly not wrong.

In which solar system is the earth found?

strikes me as more natural than a bare "is" (assuming we lived in a state where we are routinely talking about multiple planets in multiple solar systems).

But the main issue is that breaking a preposition away from its normally subsequent phrase often interferes with comprehension.

  • In what solar system is Planet Earth? is a more formal way of asking the question, avoiding the sometimes contentious practice of ending a sentence with a preposition. (I agree with Jeff that the Earth would be more correct.) Jul 7, 2022 at 9:09
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    Given the etymology of 'solar', I would say that there is only one 'solar system' in the universe, but plenty of star systems. 'The planet Earth' or just 'planet Earth' are reasonably common, maybe when you need to disambiguate between the planet and soil. Aged 12 in 1964 I inherited my uncle's very extensive (hundreds!) collection of science fiction paperback novels and magazines. I was struck at how many 1950s authors and earlier assumed future people would talk about 'Terra', Sol', 'Luna', etc. Jul 7, 2022 at 9:58
  • 'For here Am I sitting in a tin can Far above the world Planet Earth is blue And there's nothing I can do' - David Bowie Space Oddity (1969) Jul 7, 2022 at 12:34

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