by Ella Alderson – source: medium

A look into the popular sci-fi method of travel

Imagine you want to get from point A to point B. Point A in this case is Earth, and point B is our nearest exoplanet, Alpha Centauri Bb at 4.24 light years away. Because the laws of physics prevent anything from traveling faster than the speed of light, that means the minimum number of years it’ll take to reach point B is a little over 4 years. However, for now — and for many more years to come — we don’t have the means to travel anywhere near the speed of light. What we can do with our current technology is travel at around 20,000 miles per hour or 0.003% the speed of light. At this rate it will take us 142,000 years to reach Alpha Centauri Bb.
To send anyone to the exoplanet would take either incredible advancements in human preservation or sending generations of people to live onboard a spaceship, somehow overcoming the problems of reproduction in space, as well as the physical and psychological strain it would put on the families. Then there’s also ship design. What material will hold up for hundreds of thousands of years? How will that many resources — food, water, fuel — fit onto the craft? How will communication work across such a vast distance?
So there is no way to get from point A to point B. Not unless there was some kind of shortcut that would drastically reduce the time and distance needed to reach the other planet.

That’s where the wormhole comes in. They’re bridges in hyperspace (higher dimensions) from one place to another, whether it be 4 light years away or 100,000 light years away. You take the fabric of spacetime, fold it in on itself, and create a hole from the origin to the place you want to go, bypassing the vast area you would have originally had to travel. This shortcut could cut your travel time significantly; in some cases you’d arrive at your destination immediately after entering the wormhole.

When they were first proposed as a solution to the equations of general relativity, they were called Einstein-Rosen bridges after Einstein and Nathan Rosen who collaborated on the solution. General relativity says that gravity works by bending spacetime. If spacetime can be bent by mass, then surely it can be twisted and manipulated in other ways. The math does check out — wormholes do not in anyway violate the laws of physics. But the same laws that say wormholes are possible also tell us they wouldn’t be useful.
Inside the wormhole, the walls of the tunnel would be completely unstable. Each side would be attracted to the other so that it would collapse and kill any passenger during travel. Not only that but destabilizing a wormhole would create a supernova explosion, wreaking havoc on any nearby solar system.
To keep it open would require something that repels gravitationally — that is, it has to have negative energy. Negative energy is essentially taking energy from a vacuum. Exotic matter could have the antigravity properties we need if we could just find it. Curiously enough, dark energy has been causing an increase in the expansion of the universe, overcoming gravity just like the particle we’d need to act as a gravitational repellent. But even if this turns out to be the key to keeping the tunnels open, there would need to be too much of it for it to occur naturally and only a civilization much more advanced than ours could hope to gather enough of it to introduce the two artificially.

Not that we’d survive the journey even then.
According to quantum mechanics, the inside of the tunnel would be full of strange new particles and an immense amount of radiation that would severely burn anything attempting to go through. Assuming you can fit. And assuming the wormhole does end up being a shortcut and not, in fact, a longer path than the original.
Stephen Hawking theorizes that wormholes already exist, only they’re on a scale so small that we can’t see them. Just like zooming in on any seemingly flat surface will reveal its gaps and roughness and holes, so too does zooming in on time reveal that it’s not completely smooth. Wormholes are constantly appearing, disappearing, and reappearing at the quantum level. It’s possible in this theory to somehow enlarge a primordial wormhole and make it big enough for a person or a spaceship to go through. One might also enlarge naturally as the universe continues to expand. Smaller ones could be used to send information.
Whether on a huge scale or a subatomic one, to date we haven’t detected any wormholes in our universe. According to some researchers, this might be because they’re hiding behind black holes. This would be in line with general relativity which says that wormholes could have black holes at each end. It would also be more consistent with quantum mechanics, where black holes are still mysterious anomalies that would make more sense if they ended up concealing a wormhole.
Like wormholes, white holes are predicted to exist by general relativity but have never been detected. It’s possible that there is a black hole on one end concealing a wormhole, and a white hole on the other where a traveler can exit. Some wormholes even allow for multiple exit points, like a subway train. There’s intra-universe wormholes that stay within one universe and then there’s inter-universe wormholes that connect multiple universes. There’s one way wormholes, two way wormholes, wormholes that are traversable and non-traversable. Really the design for these elusive tunnels is always changing.

“Since we do not yet have a theory that reliably unifies general relativity with quantum mechanics, we do not know of the entire zoo of possible spacetime structures that could accommodate wormholes.”
– Avi Loeb, Harvard-Smithsonian Center for Astrophysics

So much depends on facts we still don’t have and physics we’ve yet to understand. Before being able to say confidently whether wormholes do or don’t exist, we must first better understand the history and geometry of our universe. It’s true that they most likely don’t exist in nature, but there’s also not much proof — if any — that a wormhole will collapse each time it’s traversed. A lot of the evidence points to these bridges as being nothing more than science fiction but at the same time we don’t have enough math to disprove them altogether. Some scientists still propose looking for them by checking how their gravity might distort the light behind them. Others say wormholes provide an answer to the fascinating black hole paradox. For now, we just don’t know. They must continue to live only inside the realm of science fiction.