General relativity

In the mid-19th century, Bernhard Riemann conceived of a new way to think about mathematical spaces, providing the foundation for modern geometry and physics.

The theoretical physicist and best-selling author finds inspiration in politics and philosophy for rethinking space and time.

According to Einstein’s theory of gravity, black holes have only a small handful of distinguishing characteristics. Quantum theory implies they may have more. Now an experimental search finds that any of this extra ‘hair’ has to be pretty short.

A team of mathematicians based in Vienna is developing tools to extend the scope of general relativity.

Physicists hope that understanding the churning region near singularities might help them reconcile gravity and quantum mechanics.

A black hole formula worked out in the 1970s remains the most concrete clue physicists have about the threads of the space-time fabric.

The philosopher Karen Crowther digs into how the space-time fabric could possibly emerge from something non-spatiotemporal.

These three imagined scenarios lead many physicists to doubt that space-time is fundamental.

Until his dying days, the giant of 20th-century physics obsessed over the underpinnings of space and time, and how we can all share the same version of them.