How a wormhole can become a time machine

General relativity predicts that wormholes could connect two distant parts of the universe in a way that could be traversed almost instantaneously. Given that special relativity had previously demonstrated that traveling faster than light would be equivalent to time travel, this raises the question of whether wormholes could also allow us to time travel. A new exploration of the subject argues that the answer is yes, at least in some circumstances.

Wormholes remain a very theoretical phenomenon. We have never knowingly observed one, although last year one paper concluded that at the angle where we see it, we cannot tell if M87* is a black hole or a wormhole. However, their importance and fascination are such that physicists spend a lot of energy trying to figure out what wormholes would look like if they existed.

The latest effort focuses on a specific type of wormhole called a ring wormhole, which, unlike “standard” wormholes, contains no matter, making the passage much less dangerous. They do, however, have a thin shell of material around one of the mouths. The journal calculates that such a wormhole would produce “closed time curves” in spacetime, which means that objects traversing the curve would end at the same time as they began. “This process inevitably transforms such a traversable annular wormhole into a time machine”, concludes By this they mean that it would be possible to walk through the wormhole one way, come back the other, and emerge at a time before the first entry.

One of the main characteristics of general relativity is that space can be shaped, for example by strong gravitational fields. The idea is usually represented by a two-dimensional stretch material deformed by heavy weight. According to physicists, things could be so distorted that two points in space come close enough to each other in an extra dimension while being very far apart by means of ordinary travel. . This led to the concept of the Einstein-Rosen bridge, popularly known as the wormhole, proposing that the two points could be joined.

After considering whether wormholes can exist, the next most important question is whether it is possible to survive by the way. Traces include whether it is possible to send back messages about what is found (yes according to an articlebut only if you are fast).

If the fabric of the cosmos is the space-time continuum, as relativity proposes, then using a wormhole to traverse between two points can also time travel.

The new paper builds on previous traversable wormhole modeling and considers one in a weak gravitational field, undisturbed by a nearby star or planet. The authors conclude that when such a wormhole first forms, it will not function as a time machine, but will inevitably become one later.

The time it takes for this to happen is approximately equal to RLc/GM where R and M are the radius and mass of the thin shell, L is the distance between the two mouths, and G is the gravitational constant. You can’t do much about G, but if you want your time machine soon, increase the radius of the shell while reducing its mass. Once you have your time machine, the wait won’t be relevant of course, but until then it’s probably as painful as it is for the rest of us.

Maybe there is a space species with a proverb that translates to “a guarded wormhole never turns into a time machine”.

The paper was accepted for Physical examination D and a preprint can be viewed at

[H/T Sciencealert]

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