Will time expand in a wormhole

Cosmology: Dark sector could stabilize wormholes

With wormholes you can put the universe with its ridiculously large distances on the cross, so to speak: You simply use a shortcut through the space-time structure - and you can cover gigantic distances in no time. This is made possible by two black holes, the singularities of which impress space-time so strongly that a tunnel is formed between them.

Probably the whole thing is only a science fiction story, because the well-known laws of physics put big obstacles in the way of the idea. For example, wormholes that can be traveled through require negative energy inside, as they would otherwise violate a premise of Einstein's general theory of relativity (the so-called zero energy condition). So far, this problem could only be avoided for microscopic wormholes.

Juan Maldacena from the Institute of Advanced Study and Alexey Milekhin from Princeton University now want to have figured out a way that also makes larger wormholes conceivable. To do this, however, one has to make complicated assumptions about the “dark sector” of the universe, in which experts locate puzzling phenomena such as dark energy and dark matter. If this invisible shadow realm consisted partly of energy fields that penetrate a hypothetical fourth spatial dimension, this could stabilize the fragile space-time tunnels, write the two theorists in a specialist article that has not yet been reviewed by experts.

A corresponding extension for the rules of particle physics and cosmology has been under discussion for decades, but it has not yet been proven experimentally. Maldacena and Milekhin now claim that this Randall-Sundrum model enables larger wormholes. Even more: the tidal forces when falling into the tunnel entrance - a black hole with a few hundred solar masses - would be barely controllable for a person. Within a second he or she could cross large parts of our galaxy and would be spat out again at another black hole.

The trip would have a price, however: in the rest of the universe, time would pass much faster. What would seem like a second to the wormhole traveler would be tens of thousands of years to all observers outside. Therefore, all other people would have died long ago if the traveler left the wormhole again, the researchers point out. Also, no other particles should fly around in the tunnel of the wormhole, as they would otherwise accelerate extremely and make the passage dangerous to life for people.

In any case, according to their own statements, the two physicists cannot quite imagine how matter in two places in space-time could be brought into exactly the right constitution and alignment for such a journey. The creation of the wormholes you sketched could therefore be physically impossible. As a result, the researchers are less concerned with concrete clues for astrophysics than with expanding the space of mathematical possibilities a little, as they clearly emphasize in their technical article.