Mmm, Donut-shaped Universes

What is the shape of space? Does the universe extend indefinitely, like an endless plain, or does it have limits?

A new theory of space proposes that if you travel in any direction for a sufficient time you'll end up back where you started. It's like the behavior of the pieces in the classic video game Pac Man; whenever a blob disappears from the left it reappears on the right and vice-versa. Mathematically, such an interconnected space is called a "toroid" or donut-shape.

You can trace two different kinds of circles around a donut (with icing perhaps) showing the ways it is connected: a big ring around the outer edge and smaller circles that pass through the hole. Three-dimensional space, if it is indeed toroidal, would have three perpendicular ways of traveling around it. Light would take many billions of years, however, to complete such circles, if it could do so at all.

Scientists are currently examining the fine details of the cosmic microwave background--the relic radiation leftover from the Big Bang--to figure out if and how the universe connects up with itself. Could we living in a colossal donut or something more like flatbread?

Curiously, in the Simpsons television series, Homer proposed his own donut-shaped universe theory. It was on an episode where Cambridge physicist Stephen Hawking guest-starred. Hawking humorously remarked, "Your idea of a donut-shaped universe intrigues me Homer; I may have to steal it."

Indeed, the long-running animated series has numerous references to astronomy, physics, math and other fields. Many of the show's writers have scientific backgrounds and try to mix in science with the humor.

Explore donut-shaped universes, androids, aliens, time-travel, invisibility devices, teleportation and other amazing science on the Simpsons in my new book:

What's Science Ever Done For Us? What the Simpsons Can Teach Us About Robots, Life, and the Universe