Einstein believed that black holes didn't really exist. But they do: that much we know. We don't know much else about them.

Let's turn the sun into a telescope. In fact, we don't have to do any work—we just have to be in the right spot.

First, the outer boundary of these cosmic titans is a one-way light-trapping surface called an event horizon ... Einstein's 1915 theory of gravity, called general relativity, scientists can ...

April 21 is a date rich with historical significance, marked by events that have shaped cultures, nations, and the course of ...

Einstein’s general theory of relativity, which is used to describe ... of a black hole are decoupled by a boundary called the event horizon. Because black hole gravity is so strong, anything ...

The basic idea is that you send a beam of light around a pair of black holes spinning around each other prior to a merger, or a single black hole spinning quickly, and use the higher-energy ...

Black holes are objects whose gravity is strong enough to trap light, and the traditional black hole of general relativity is surrounded by an event horizon. Seen from outside the event horizon, such ...

"In classical general relativity ... "For an external observer, when a material body crosses an event horizon all knowledge of its material properties is lost. Only the new values of M [mass ...

Instead they’d be fuzzballs: fuzzy balls of vibrating branes that lack the traditional features of black holes—an event horizon ... Einstein’s general theory of relativity and quantum ...