Wormholes might allow journey throughout the universe so long as your spaceship is microscopic

In my last post, I talked about the idea of ​​the warp drive and whether it might one day be possible. Today I’m going to talk about another trick that’s faster than light: wormholes.

Wormholes are an old idea in general relativity. It is based on the work of Albert Einstein and Nathan Rosen, who tried to find out how elementary particles could behave in a curved space-time. Their idea treated particle-antiparticle pairs as two ends of a space-time tube. This Einstein-Rosen bridge would look like a black hole on one end and an anti-black hole or white hole on the other end.

A passable wormhole would be a shortcut through space. Photo credit: ESO / L. Calçada

The idea of ​​particle physics was never implemented, but the work inspired other researchers to study ER bridges as a possible shortcut through space. If wormholes could be traversed, you could dig your way through spacetime like a worm digging a hole through an apple. It didn’t take long for theorists to find out that this wasn’t going to work. While wormholes are valid solutions to Einstein’s equations, they break down so quickly that you never have time to go through them. In the general theory of relativity, wormholes are not passable.

Of course, impossibility never stops a persistent theorist, and they soon discovered that one can traverse a wormhole by lining it with some sort of negative energy. The same kind of negative energy that could be used for warp propulsion. But as I mentioned last time, matter of negative mass / energy doesn’t seem to exist.

On a small scale, gravity must have a quantum nature. Photo credit: The Wolfram Physics Project

But all is not lost. We know that Einstein’s theory has to break down on a quantum scale because it is a classical theory. Presumably there is a quantum theory of gravity that replaces general relativity. We don’t have a complete quantum gravity model yet, but we have several approximate models that point us in the right direction.

One of these models is known as the Einstein-Dirac-Maxwell theory. It is so named because it incorporates aspects of Einstein’s theory of gravity, Maxwell’s theory of electromagnetism, and Dirac’s theory of quantum particles. Recently, a team found a wormhole solution to the Einstein-Dirac-Maxwell equations.

The team found that the wormhole solution was fully traversable. In addition, the solution does not require negative energy states. In principle, this would allow you to travel through the wormhole without needing negative mass. The only catch is that you’d have to be in a quantum state. Microscopic lumps of atoms could wander through this wormhole, but not humans.

While this is interesting work, it’s just a toy model. There are many solutions to Einstein’s equations that cannot exist for reasons beyond gravity. The team plans to investigate their idea further to see if their solution is another impossible idea or if there is a way to create this type of quantum wormhole. And when that idea works, getting through the eye of the needle is still easier than getting into the distant sky.

Reference: Blázquez-Salcedo, Jose Luis, Christian Knoll and Eugen Radu. “Traversable wormholes in the Einstein-Dirac-Maxwell theory.” Physical Review Letters 126.10 (2021): 101102.

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