In most of the numerical simulations that depicted the motions of the solar system's planets in the future, everything proceeded as expected. But in one percent of those simulations, things when literally sideways — thanks to Mercury's orbit flattening, causing chaos to other planet's orbits. Perhaps the solar system was not as stable as people once thought. For centuries, ever since Isaac Newton formulated his laws of motion and gravity, mathematicians and astronomers have grappled with this issue. Now, in three research papers, a trio of scientists have proved for the first time that instability inevitably arises in a model of planets orbiting a sun. Rafael de la Llave, a professor in the School of Mathematics whose speciality is dynamical systems, didn't work on the research papers but is quoted in the article.