What is Spacetime?

  • By Arlo Perez
  • Posted 05.30.18
  • NOVA

A mysterious concept changed the way we understand reality.

Running Time: 02:06


What is Spacetime?

Published May 30, 2018

Narrator: He needs mathematics that describes how objects move in space and time and soon realizes that the best tool for the job is a strange but powerful concept called “space-time.”

Janna Levin: If I think of space, I know that I can find anything, if I know where it is North-South, East-West and up-down, three points. But that doesn’t mean I can find it, because I also have to know where it is in time. And so, if we start to think, to know everything about an event in the universe, I have to know, not just its spatial coordinates, but also its time coordinate. I can begin to think about where it is in space-time.

Narrator: Imagine a camera filming an action, capturing each moment in time as a single frame.

Robert Dijkgraaf: Einstein basically tells us, think of a movie reel: we have all these little pictures. Now, cut them apart, one by one, and stack them on top of each other. You get this pile. And if you go up in the pile, you go up in time. And now, kind of glue them all together into one big block, and that block has both space and time, and that’s the space-time continuum.

It’s almost looking at a movie, not frame by frame, but seeing the whole movie at once. There would now be kind of, two strands going up in space and time, and they would be, kind of, spaghetti strands. In fact, we all are spaghetti strands moving in this space-time.



Digital Producer
Arlo Perez
Editorial Review
Julia Cort, Ari Daniel
© WGBH Educational Foundation 2018



Related Links

  • Inside Einstein's Mind

    Retrace the thought experiments that inspired his theory on the nature of reality.

  • Einstein on Newton

    In 1927, 200 years after Newton's death, Albert Einstein wrote a glowing appreciation.

  • Gravity and Spacetime

    Learn how gravity can be described by the curving of spacetime, in this video from NOVA: Black Hole Apocalypse.