Nearly a century ago, Edwin Hubble’s discovery of red-shifting of light from galaxies in all directions from our own suggested that space itself was getting bigger. Combined with insights from a handful of proposed non-Euclidean geometries, Hubble’s discovery implied that the cosmos exists in more than the three dimensions we’re familiar with in everyday life.
That’s because parts of the cosmos were moving further apart, yet with no physical center, no origin point in three-dimensional space. Just think of an inflating balloon seen only from the perspective of its growing two-dimensional surface, and extrapolate to four-dimensional inflation perceived in the three-dimensional space that we can see. That perspective suggests that three-dimensional space could be curved, folded, or warped into a 4thdimension the way that the two dimensional surface of a balloon is warped into a 3rd dimension.
We don’t see or feel more dimensions; nevertheless, theoretical physics predicts that they should exist. Interesting, but are there any practical implications? Can they become part of applied physics?
1. Warp Drive
Teaching about the 4th dimension, physicists have used analogies, like drawings of something called a hypercube, and even the 19th century novella Flatland by Edwin Abbott Abbott. The book imagines two-dimensional beings living on a planar world that has only length and width. Unable to perceive a third dimension, the Flatlanders see only one plane of three-dimensional visitors, kind of like how computed tomography or magnetic resonance imaging shows the body in slices. Two slices through a leg, one a few millimeters up from the other, look almost the same, but a slice through the waist or chest gives a very different picture. We can relate to this analogy, imagining our three-dimensional environment as just one of an infinite number of slices of a four-dimensional environment.
But moving beyond four dimensions, it gets even weirder, and very hard to visualize. The main theory here is called M theory, which is a theory in physics that unites various types of what’s called superstring theory. In M theory there are a bunch of dimensions, either 10 or 11, depending on who explains it to you. In addition to the three we’re familiar with there are compact dimensions. It’s all related to phenomena called branes that vibrate like strings, but what’s most relevant to this discussion is that the extra or compact dimensions don’t necessarily have to remain compact. Like a jack-in-the box, it might be possible to unpack the extra dimensions, says Richard Obousy, director of Icarus Interstellar, a non-profit organization promoting starship research.
“If an advanced civilization learns how to manipulate higher dimensions, they might use them for technology, including warp drive,” Obousy noted to me, the idea being that some kind of controlled decompacting of extra dimensions could have the effect of squeezing or expanding one of the three big dimensions that we know.
But don’t start packing for your Alpha Centauri vacation just yet, because there’s one tiny little complication, which Obousy is the first to admit. So far, we don’t have a shred of evidence that the hypothesized extra dimensions even exist. Someday, soon, we might get some evidence from the Large Hadron Collider, but even then it’s anyone’s guess whether that would lead to a warp drive technology.