Articles on Spacetime

Displaying all articles

In space, there are four dimensions: length, width, height and time. scaliger/iStock/NASA via Getty Images Plus

Where is the center of the universe?

As the universe expands, it feels like it must be spreading out from some initial point. But a physicist explains why that’s not how it works. Hint: space-time is involved.
Gravity feels like it’s pulling everything toward Earth, but why? AdventurePhoto/E+ via WikimediaCommons

Why does gravity pull us down and not up?

Gravity is something every person on Earth intuitively understands: It is what keeps you on the ground. But how come gravity pulls down, rather than pushes up? Einstein came up with the answer.

Top contributors

More