A star orbiting our galaxy's supermassive black hole tests the limits of relativity

Although general relativity (GR) is an elegant theory of gravity, we don't often need to use it.

For most gravitational interactions, Newton's theory of universal gravitation works just fine.

Newton's model is good enough to navigate spacecraft through the solar system and for most stars orbiting Sag A*, the supermassive black hole at the center of the Milky Way. ...