einstein

A wormhole — a shortcut through spacetime connecting two distant points — would revolutionize physics, transportation, and our place in the universe. But the physics suggests it would also be unstable, possibly lethal, and almost certainly a one-way trip.

If the speed of light were dramatically lower — say, 100 km/h — relativistic effects would dominate everyday life. Cars would gain mass as they accelerated, time would dilate for joggers, and the universe would look profoundly different.

Space and time aren't separate things — they're a single four-dimensional fabric that can bend, stretch, and warp. Massive objects curve spacetime, and that curvature is what we experience as gravity. Here's what Einstein actually discovered.

Time travel forward already happens — astronauts do it, in tiny amounts. Time travel backward is much harder, but Einstein's equations don't strictly forbid it. Here's what physics actually says.

Astronauts return from space slightly younger than they would have been on Earth. The explanation is real physics — Einstein's theory of relativity — and it has measurable consequences for everything from GPS to interstellar travel.

Einstein predicted them in 1916. We detected them for the first time in 2015. Gravitational waves let us "hear" cosmic events that produce no light. Here's how they work and what they reveal.