Science fiction novels and movies are packed with distant ideas, most often as a springboard to an action-packed adventure rather than a serious attempt to predict future trends in science or technology. Some of the most common tropes, such as accelerating a spacecraft to amazing speeds in seconds without crushing the inhabitants, are simply impossible according to the laws of physics as we understand them. Still, the same laws seem to allow other seemingly distant sci-fi concepts, from wormholes to parallel universes. Here’s an overview of some of the sci-fi ideas that could really be done — at least in theory.
The idea of a wormhole — a shortcut through space that allows for almost instantaneous travel between distant parts of the universe — sounds as if it was created as a fictional story driver. But under its more formal name on an Einstein-Rosen bridge, the concept has existed as a serious theoretical concept long before sci-fi writers got a grip on it. It’s coming out Albert Einstein‘s general theory of relativity, what views gravity as a distortion of space-time caused by massive objects. In collaboration with physicist Nathan Rosen, Einstein theorized in 1935 that points with extremely strong gravity, such as. black holes, could be directly related to each other. And then the idea of wormholes was born.
The forces around a black hole would destroy anyone who came close to it, so the idea of actually traveling through a wormhole was not seriously considered until the 1980s, when astrophysicist Carl Sagan decided to write a sci-fi -novel. According to BBCSagan urged fellow physicist Kip Thorne to quickly come up with a possible way to travel interstellar distances. Thorne duly found a way – possible in theory, but extremely unlikely in practice – that humans could achieve interstellar travel by crossing a wormhole unscathed. The result found its way to Sagan’s novel “Contact“(Simon and Schuster: 1985), which was subsequently adapted into a film starring Jodie Foster.
Although it is very unlikely that wormholes will ever become the simple and convenient means of transportation depicted in movies, scientists have now come to a more viable way to construct a wormhole than Thorne’s original proposal. It is also possible that if wormholes already exist in the universe, they can be located using the new generation of gravity wave detectors.
An essential prerequisite for most space-based adventure stories is the ability to get from A to B much faster than we can today. Wormholes aside, there are several stumbling blocks to achieve this with a conventional spaceship. There is the enormous amount of fuel required, the crushing effects of acceleration and the fact that the universe has a strictly imposed speed limit. This is the speed at which light travels – exactly one light years per year, which in a cosmic context is not very fast at all. Proxima Centauri, the second largest star on Earth, is 4.2 light-years from the Sun, while the center of the galaxy is a full 27,000 light-years away.
Fortunately, there is a gap in the cosmic speed limit: it only dictates the maximum speed we can drive through space. As Einstein explained, space itself can be distorted, so perhaps it is possible to manipulate the space around a ship in such a way that it undermines the speed limit. The spaceship would still travel through the surrounding space at less than the speed of light, but the space itself would move faster than that.
That was what the writers of “Star Trek” had in mind when they came up with the concept of a “warp drive” in the 1960s. But for them, it was just a plausible sounding sentence, not really physics. It was not until 1994 that theorist Miguel Alcubierre found a solution to Einstein’s equations that produced a real chain effect, Live Science’s sister site It informs Space.com, contracts space in front of a spaceship and extends it to the rear. To begin with, Alcubierre’s solution was no less constructed than Thorne’s crossable wormhole, but researchers are trying to refine it in the hope that one day it may be practical.
The concept of a time machine is one of the great sci-fi plot devices that allows characters to go back and change the course of history — for better or worse. But this inevitably raises logical paradoxes. In “Back to the Future”, for example, Doc would have built his time machine if he had not been visited by the future Marty using the same machine? It is because of paradoxes like these that many people assume that time travel must be impossible in the real world – and yet according to the laws of physics it is can really occur.
As with wormholes and space chains, physics, which tells us that it is possible to travel back in time, comes from Einstein’s theory of general relativity. This treats space and time as part of the same “space-time” continuum in which the two are inextricably linked. Just as we are talking about distortion of space with a wormhole or chain drive, time can also be distorted. Sometimes it can become so distorted that it folds back on itself in what researchers refer to as a “closed pre-existing curve“- even though it could just as accurately be called a time machine.
A conceptual design for such a time machine was published in 1974 by physicist Frank Tipler, according to physicist David Lewis Anderson, who describes the research on Anderson Institute, a private research laboratory. Called a Tipler cylinder, it must be large – at least 97 kilometers long according to Humble – and extremely dense with a total mass comparable to that of the sun. To make it work like a time machine, the cylinder must rotate fast enough to distort space-time to the point where time folds back on itself. It may not sound as simple as installing a flux capacitor in a DeLorean, but it has the advantage that it would really work – at least on paper.
The archetypal sci-fi example of teleportation is “Star Trek“ carrier, which, as the name suggests, is simply manufactured as a convenient way of transporting staff from one place to another. But teleportation is quite unlike any other mode of transportation: instead of the traveler moving through space from the starting point to the destination, teleportation results in the creation of an exact duplicate at the destination while the original is destroyed. Seen in these terms – and on a par with subatomic particles rather than humans – teleportation is actually possible, according to IBM.
The real world is called quantum teleportation. This process copies the exact quantum state of one particle, such as a photon, to another, which can be hundreds of miles away. Quantum teleportation destroys the quantum state of the first photon, so it actually looks as if the photon has been magically transported from one place to another. The trick is based on what Einstein referred to as “spooky action at a distance”, but is more formally known as quantum entanglement. If the photon to be “teleported” is brought into contact with one of a pair of entangled photons, and a measurement of the resulting state is sent to the receiving end – where the other entangled photon is – then the latter photon can be switched to the same state as the teleported photos.
It’s a complicated process, even for a single photon, and there’s no way it can be scaled up to the kind of instant transport system seen in “Star Trek.” Yet quantum teleportation has it important applications in the real world, e.g. for hack-proof communication and super-fast quantum computation.
The universe is everything our telescopes reveal to us – all billions of galaxies expanding outward from Big bang. But is that all there is? Theory may not say: There can be a whole multiverse of universes out there. The idea of ”parallel universes” is another familiar sci-fi theme, but when depicted on screen, they typically differ from our own universe only in minor details. But reality can be much stranger than that, as the basic parameters of physics in a parallel universe – such as the force of gravity or nuclear forces – differ from our own. A classic depiction of a truly different universe of this kind and the creatures that live in it is Isaac Asimov’s novel “The Gods themselves“(Doubleday: 1972).
The key to the modern understanding of parallel universes is the concept of “eternal inflation”. This shows the infinite matter in space in a state of eternal, incredibly rapid expansion. Every now and then, a localized place in this space — an independent Big Bang — falls out of the general expansion and begins to grow at a more leisurely pace, making it possible to form material objects like stars and galaxies inside it. According to this theory, our universe is one such region, but there may be innumerable others.
As in Asimov’s history, these parallel universes could have completely different physical parameters than our own. At one time, scientists thought that only universes with roughly the same parameters as ours would be able to support life, but recent studies suggest that the situation may not be as restrictive as this one, Live Science previously reported. So there is hope for Asimov’s foreigners yet – though perhaps not to make contact with them, as happens in the novel. Nevertheless, the traces of other universes can be demonstrated to us in other ways. It has even been suggested that the mysterious “cold place” in the cosmic microwave background is scarred from a collision with a parallel universe, wrote Ivan Baldry, professor of astrophysics at Liverpool John Moore’s University in the UK in The conversation.
Originally published on Live Science.