Wormholes would be so useful today. Just pop into the nearest wormhole opening and a short stroll will take you to some exotic far-flung corner of the universe. No need to travel the long-and-slow routes throughout the universe, taking tens of thousands of years just to reach a cosmic destination.
But there is a technical problem. Wormholes, the incredible bends in space-time can be so extreme that a shortcut tunnel might be catastrophically unstable. Maybe as soon as a single photon is sent down the hole, it collapses faster than the speed of light, dooming the lost photon and the planned transfer.
But a recent paper that was published in the July 29 journal arXiv described a way to build an almost-steady wormhole. Even this one will collapse but it is a sufficiently slow process allowing the transmission of messages and potentially even physical items before it tears itself apart. The items to build this amazing phenomenon are a couple of black holes and some infinitely long cosmic strings. Easy!
The Wormhole Problem
In principle, building a wormhole is a straightforward process. According to Einstein’s Theory of General Relativity, mass and energy distort the fabric of space-time. A certain special configuration of matter and energy permits the formation of a tunnel which serves as a shortcut between two otherwise distant portions of the universe.
Unfortunately, even theoretically, such wormholes are fantastically unstable. The passage of even a single photon through the wormhole activates a catastrophic cascade that literally rips the wormhole apart. However, a sufficient amount of negative mass i.e. matter but with an opposite weight can counter the destabilizing effects of regular matter attempting to pass through the wormhole, making it traversable.
But as negative mass doesn’t actually exist, scientists came up with an alternative.
Consider the wormhole itself that needs an entrance and an exit. Theoretically, it’s possible to connect a black hole i.e. the specific region of space where nothing can escape to a theoretical region of space where nothing can enter, known as a white hole. These two odd cosmic entities joined via the link forms a new entity -a wormhole. It is possible to jump into either end of this tunnel without getting crushed into oblivion. But as white holes also do not exist, scientists came up with a new plan.
Some clever math revealed a possible answer in a charged black hole. Apparently, black holes can carry an electric charge in their core which is the normal point-like singularity of a black hole stretched and distorted, permitting it to form a bridge to another oppositely charged black hole.
Voila! A wormhole is formed using only things that might actually exist.
But there are two major issues with this wormhole-via-charged-black-holes. Firstly, it’s still so unstable, that if something or someone actually tries to pass through it, it collapses. Secondly, the two oppositely charged black holes will get attracted to each other through gravitational and electric forces so if they ultimately merge together to form a single, neutrally charged and somewhat useless bigger black hole.
There is a need to ensure that the two charged black holes stay safely apart and maintain the stability of the tunnel of the wormhole. To achieve both these goals, scientists thought of cosmic strings. These theoretical defects in the fabric of space-time are similar to the cracks that form when ice freezes. These cosmic residuals from the early days of the first fractions of a second after the Big Bang are truly exotic objects, not wider than a proton but a single inch of their length outweighs Mount Everest. They have the strength to literally slice clean in half like a cosmic lightsaber, but their existence is not certain as none have been spotted till now.
Of course, scientists are hopeful as there’s no reason they can’t exist.
Wormholes have another very useful property of enormous tension meaning they really don’t get pushed around. When a cosmic string threads the wormhole to pass along the outside edges of the black holes and stretch out of either end to infinity, then the tension in the string will prevent the charged black holes from getting attracted to each other and hold the two ends of the wormhole far away from each other. Basically, the distant ends of the cosmic string will act like two opposing tug-of-war teams that will hold back the black holes.
Using one cosmic string solves the problem of holding the ends open but doesn’t prevent the wormhole itself from collapsing when it is used. So, another cosmic string is threaded through the wormhole and also looped through the normal space between the two black holes. When cosmic strings are closed in a loop in such a manner, they tend to wiggle a lot. Such vibrations agitate the very fabric of space-time around them but when tuned in a specific manner, the vibrations can cause the energy of space in their vicinity to become negative, thus effectively acting like negative mass within the wormhole which can potentially stabilize it.
Although complex, in their recent paper, the team of theoretical physicists gave step-by-step instructions for constructing just such a wormhole. The process has its own limitations, the biggest being the fact that cosmic strings are yet to be found. But the process to actually devise a wormhole is a huge step ahead.