Observations made with the European Southern Observatory’s Very Large Telescope in Chile have revealed for the first time that a star orbiting the supermassive black hole at the center of the Milky Way moves just as predicted by Einstein’s theory of general relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton’s theory of gravity. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole. This artist’s impression illustrates the precession of the star’s orbit, with the effect exaggerated for easier visualization. (Image: © ESO/L. Calçada)
Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of “How to Die in Space.” He contributed this article to Space.com’s Expert Voices: Op-Ed & Insights.
Perhaps the most powerful aspect of physics — and indeed perhaps the most amazing thing about the cosmos as a whole — is the universality of physical laws and theories.
A few scant equations — small enough to fit on your favorite T-shirt — can explain a variety of phenomena from one edge of the universe to the other, and from the earliest moments of the Big Bang to the unfathomable future. Let’s get a taste for just how powerful modern physics can be.
Games of gravity
Albert Einstein’s general theory of relativity is our modern theory of how gravity works: matter and energy bend space-time, and in turn the bending of space-time tells matter how to move. The math is a bit complex: it takes a suite of 10 interrelated equations to describe all this bending and warping and moving. But those equations contain enormous power.
For example, in the limit of weak gravity, Einstein’s equations reduce to the more familiar expressions of Newtonian gravity, which is used to explain everything from the trajectories of thrown baseballs to hydroelectric dams. Beyond the surface of the Earth, Einstein takes more control, where the equations of relativity are used to provide accurate positioning with the GPS system and precisely predict the orbits of all the planets.
Those very same equations, without a single modification, go on to greater feats, revealing the existence of black holes and their workings, the growth of the biggest structures in the universe, the presence of dark matter inside galaxies and the Big Bang itself.