What if there was a faster way to get from place to place in space?

That's the central concept of wormhole theory, which presents the possibility that we could travel super fast through the universe by cutting space-time corners. It's no mean feat: First, we'd need to find an actual wormhole, analyze its structure, send a spacecraft through it and create a way to communicate with the craft once it was on the other side.

In short, it's a long shot — but the science isn't entirely far-fetched. In fact, general relativity supports the idea of these space-time connections. Here's a quick wormhole warm-up.

On the Road Again

The nearest star to our sun is Proxima Centauri. At 4.25 light years, the trip doesn't sound too bad — until you start doing the math.

Consider the Parker Solar Probe, which in 2018 earned the designation of the fastest-ever human-made spacecraft at 247,000 kilometers per hour. By 2024, NASA predicts that the probe will reach speeds up to 692,000 kilometers per hour. The problem? Proxima Centauri is around 40 trillion kilometers from our solar system, meaning even the speedy Parker probe would need 10,000 years for a one-way trip.

Faster craft could help to lower this travel time, but special relativity suggests that light-speed solutions aren't physically possible, meaning we need a workaround. Theories such as warp drive that circumvent this rule are one option but may require more power than exists in the universe to operate. Wormholes might offer a naturally occurring operational alternative.

Someone Call Captain Sisko

The first post-Gene Rodenberry series in Star Trek cannon, Deep Space Nine pushed the episodic storytelling envelope. Its central premise? A "stable" wormhole connecting two quadrants of the galaxy. Travelers passing through the wormhole would always enter and exit at the same fixed locations — and with no damage their ship or crew. It made for great TV, but is it possible in practice?

To answer that question, we'll need to start with the most familiar face in physics: Albert Einstein. As Space.com notes, wormhole theory got its start with Austrian physicist Ludwig Flamm in 1916. While reviewing an analysis of Einstein's general relativity by another researcher, Flamm came up with idea of "white holes" — theoretical, gravitational and temporal opposites to black holes. Almost two decades later, Einstein and contemporary Nathan Rosen crunched the numbers and found that general relativity does, in fact, support the existence of these connective conduits (first called Einstein-Rosen bridges) that connect white or black holes in space and time.

On the surface, the structure of a wormhole is relatively simple. It has two mouths, one at each end, and a "throat" in the middle that serves as a path between the two. This throat might be a simple, straight line, or it could be something more convoluted. In either case, it would significantly shorten both travel time and distance.

In practice, the idea is more complicated. These speedy paths take shortcuts through the curvature of space-time to account for their improved ETA, but there's no way to know exactly what that looks like — or if there's any way humans could ever use wormholes. It's also possible that wormholes may connect two points in time and space depending on the curvature of their connections, meaning crews could potentially end up both somewhere and sometime else after wormhole travel.

Hole-o? Can You Hear Me?

Before we can talk about evaluating wormhole safety or drafting rules of the Einstein-Rosen road, we need to track down a wormhole.

So far? No luck. But it's not all bad news. As APS Physics notes, 10 years of solid scientific work hasn't disproven wormhole theory. While this may not sound terribly encouraging, it's actually a good sign. Why? Because scientists excel at breaking things by finding and exploiting their weak points. As a result, the lack of any glaring faults or impossibilities in wormhole theory puts a positive spin on the concept.

There are caveats, of course. Some experts argue that, while wormholes may exist, they only do so for a fraction of second and are so small they could never be used by humans. Others suggest an inherent instability that would preclude the potential for predictable arrival and departure options. Work is underway to seek out the impact of black hole and wormhole collisions using the recently confirmed concept of gravitational waves, but don't expect speedy results. For this approach to bear fruit, wormholes need to actually exist, a collision has to have occurred at least once, and it needs to be something we can detect.

In short, not great odds — but like some of the best discoveries in science, not impossible.

The Heart of the Matter

It matters. Matter, that is.

Specifically speaking, we're talking about exotic matter — the kind of stuff that isn't found in our universe at large. This very particular product has been predicted in specific vacuum states of quantum field theory and has both negative energy density and negative pressure.

This sets it apart from other matter manifestations, such as the anti- and dark varieties, making it difficult to predict how this exotic alternative will interact with the regular matter of spaceships or the people inside them. In theory, wormholes with enough naturally occurring or artificially added exotic matter could be made more stable and potentially offer a reliable bridge between two points in space-time. But physicist Kip Thorne isn't convinced that what would result would be usable.

"There are very strong indications that wormholes that a human could travel through are forbidden by the laws of physics," he told Space.com.

Do the Worm

Simply put, space — and space-time — are weird.

Still, general relativity continues to hold up when it comes to predictions around black holes, gravitational waves and time distortions at increasing speed. That suggests it's a relatively safe bet that wormholes are also out there, somewhere — but the jury's still out on their ability to safely curtail interstellar commutes.

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general relativity

Wormhole Theory: Solving the Conundrum of Space-Time Commutes?

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