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For the purposes of first-semester high-school physics, one
can imagine that lifting a book imparts an energy E = m g h
that resides "in" the book. However, even back on Day One of
modern science, Galileo was quite aware that such a simple
approach was valid only for laboratory length-scales, and
could not be applied to planetary length-scales or beyond.
By second-semester high-school physics we discuss Newton's
law of universal gravitation, in which the book and the
planet play symmetrical roles. You could say the energy is "in"
the planet rather than the book, and it would make equally
much sense, i.e. no sense at all.