I have read conflicting guidelines for when the proper noun the EARTH, meaning our planet, used with the article the, should be capitalized. I understand that earth, as in soil, is not capitalized, and that idioms have their own guidelines, so I am just asking about when the EARTH, used as a proper noun, should be capitalized.
Here is the conflicting information I have found:
1) YES! The word the Earth should be capitalized if it refers to our planet. If Earth is used as a proper noun, then it is capitalized. If used as a common noun, then the word Earth is lowercased. According to English capitalization rules, proper nouns are always capitalized. Therefore, when referring to the Earth as a planet or celestial body, it should be capitalized such as in the following sentence: The Earth takes about 365 days to orbit the Sun.
2) NO! Don't capitalize the earth, when it uses the article the. When the noun earth refers to our planet, it is capitalized only when it’s a proper noun (meaning it acts like a name and is not preceded by the—for example, everything on Earth). The word is not capitalized when it is a common noun (meaning it does not act like a name and is preceded by the—e.g., everything on the earth). https://grammarist.com/style/earth/
3) MAYBE? It's a choice to write the Earth or the earth. It is acceptable to leave earth lowercase and use the with earth if you are talking about it as the planet we live on: The earth rotates on its axis. https://www.dictionary.com/e/earth/
What do you think I should tell my students?