Astronomers have announced the discovery of the two biggest black holes ever seen, each one around 300m light years from Earth and with a combined mass equivalent to more than 30bn Suns.
These cosmological objects are some of the strangest in our known universe, where the laws of physics seem to break down and space gets very strange. One thing we know, however, is that getting close to one is a bad idea.
Black holes begin as giant stars (at least six times the mass of our Sun) and, after billions of years they collapse in on themselves into a point smaller than the full-stop at the end of this sentence. Nothing nearby can escape the pull of the resulting gravity.
Even at some distance outside the edge, it would take all the effort in the universe to resist getting pulled into orbit around the hole. Closer still, because of the sharp rate of increase of the forces, if your head was nearer the hole than your feet, the atoms in your hair would feel a stronger force than those in your toes. This difference would quickly tear you apart, turning you into a spaghetti-like line of atoms.
But a black hole would not need to suck the Earth in to cause us trouble. If one wandered within a billion miles of our solar system, its gravity could knock the Earth into a dangerous elliptical path around the Sun, where winters would drop to -50C and summers would reach hundreds of degrees Celsius. Or, if one knocked us out of the solar system, our planet would wander through deep space. Without our Sun, life on Earth would freeze to death within months.
