&Bullet; physics 14, p28
New theories about wormholes – postulated tunnels through space-time – are investigating whether they could be traversed by humans.
A wormhole is a hypothetical abbreviation that could connect one side of a galaxy to another. Although wormholes populate many science fiction plots, they have been difficult to justify in theory. Now two separate groups are presenting models that make wormholes appear less exotic and a little more believable for human use [1, 2] .
The idea of a wormhole is almost as old as that of a black hole. However, the existence of wormholes remains an open question. Even if a wormhole could form, the gravitational pull of matter inside would likely cause his throat (the narrowest part of the tunnel) to close, preventing side-to-side movement. Theorists have suggested ways of keeping a wormhole open, usually by adding exotic matter whose properties will resist gravitational collapse. Now, Jose Blázquez-Salcedo of the Complutense University of Madrid and his colleagues have found a traversable wormhole solution that does not require exotic materials  .
The team modeled their wormhole using a semiclassical framework in which matter is treated as a set of generic fermions (spin 1/2 particles such as electrons and positrons) that are described by quantum wave functions. Matter interacts through classical electromagnetic fields, which simplifies the equations.
By varying parameters, including the charge and mass of the fermions, Blázquez-Salcedo and colleagues found that traversable wormholes could exist if the ratio of total charge to total mass inside the wormhole exceeds a theoretical limit that applies to black holes. The researchers speculate that this solution should remain valid in a more complete model in which the fields corresponding to the matter interactions are quantized.
But the wormholes that Blázquez-Salcedo and his colleagues imagine are microscopic – too small to squeeze through a person. Juan Maldacena of the Institute for Advanced Study, New Jersey, and Alexey Milekhin of Princeton University have explored wormholes that would allow intrepid travelers to travel safely  . Your model assumes that wormholes form in a five-dimensional space-time, as suggested in some string theory cosmologies (see Focus: An Invisible Dimension). The researchers show that a human-friendly wormhole – with accelerations of less than 20 g – could enable a journey through the galaxy in less than a second. This short duration would only apply to the person in the wormhole, as an outside observer would measure the journey as thousands of years.
Michael Schirber is the corresponding editor for physics based in Lyon, France.
- JL Blázquez-Salcedo et al., “Traversable wormholes in the Einstein-Dirac-Maxwell theory”, Phys. Rev. Lett.126, 101102 (2021).
- J. Maldacena and A. Milekhin, “Wormholes that can be crossed by humans”, Phys. Rev. D103, 066007 (2021).