How do Einstein's and Newton's ideas about gravity differ?

• A. Einstein explained what gravity is while Newton explained how gravity works
• B. Einstein explained how gravity works while Newton explained what gravity is
• C. Both explained both aspects equally well
• D. Newton explained the curvature of spacetime

Answer: (A)

Gravity is described in two complementary ways. Newton treated gravity as a force: a pull between masses that acts at a distance and can be quantified by the inverse-square law. He’s explaining how gravity behaves and affects motion. Einstein, by contrast, redefines gravity as the effect of mass-energy on the shape of spacetime itself; objects move along the straightest possible paths in this curved spacetime. In that sense, Einstein explains what gravity is—the curvature of spacetime—while Newton explains how gravity works—the force that causes acceleration between masses. That’s why this answer fits best: Einstein describes what gravity is, Newton describes how gravity operates. The other statements either misattribute curvature to Newton or mix up who explains what.