The Man Who Sold the Moon by Robert A. Heinlein

More to the point, Jeff is not in love with her but with Holly. Ariel is twice the age of the teenagers, and could never be interested in Jeff. In the hospital afterward, Ariel gently explains some things to Holly. Holly swoops down and saves her life, breaking both arms in the process as she cushions Ariel's fall. However, during her first flight, Ariel loses control at a great height, falling toward the ground. Ariel wants to try flying, and Holly, in order not to appear jealous, offers to teach her. Living in an underground city on the Moon, Holly and Jeff's hobby is flying with strap-on wings in a great cavern, made possible because the gravity field is one sixth the strength of Earth's and the air pressure in the cavern is kept high enough. As Jeff spends more time with Ariel, Holly becomes jealous and begins to doubt his friendship. Holly's best friend Jeff develops a crush on the 'groundhog' visitor, Ariel. She is assigned a young guide named Holly, a 15-year-old girl and aspiring starship designer who is the first-person narrator. The 'menace' of the title is a glamorous woman tourist who visits the Moon colony. The story is set in the near future, when the Moon is colonized with people living in underground cities. Heinlein, first published in the August 1957 issue of The Magazine of Fantasy & Science Fiction.

'The Menace From Earth' is a science fiction short story by American writer Robert A. The Magazine of Fantasy & Science Fiction

The Man Who Sold the Moon by Robert A. Heinlein