Here's why the 'arrow of time' points only toward the future, probably

Time is mysterious, and it only appears to move forward
(Image credit: The Economist/YouTube)

"Why does time pass?" asks The Economist, acknowledging that the question is "so profound that few people would even think to ask it." Many physicists do, however, and the magazine spoke with a handful to understand how time works and why it appears to go only in one direction: forward. That theory is known as "the arrow of time," and according to Albert Einstein's General Theory of Relativity, it needn't point only to the future. But it seems to in practice.

"Our best guess is that you just can't travel backward in time," says Sean Carroll, a physicist at the California Institute of Technology, casually breaking the hearts of science fiction fans everywhere. But Einstein's theory does allow for traveling forward in time, and doesn't obviously forbid wormholes through the space-time continuum — theoretically if not practically. If you're interested in the mysteries of time, the 10-minute video below does a fine job of explaining difficult theoretical physics in a way that's mostly accessible to non-scientists. If the video blows your mind, you can always mellow out and listen to some Pink Floyd or Steve Miller Band. But first, watch below. Peter Weber

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Peter Weber, The Week US

Peter has worked as a news and culture writer and editor at The Week since the site's launch in 2008. He covers politics, world affairs, religion and cultural currents. His journalism career began as a copy editor at a financial newswire and has included editorial positions at The New York Times Magazine, Facts on File, and Oregon State University.