Science fiction movies often encourage audiences to dream up technologies beyond their wildest dreams, making them seem realistic enough to be plausible, only to be bitterly disappointed by the limitations of real-world science. The most ambitious science fiction movies have presented a wide variety of settings, from the spacefaring fantasy worlds of Star Wars to the grounded realism of films like Arrival. As a result, the cutting-edge inventions presented by these films run the gamut of plausibility, with many being closer to magic than science.
The laws of physics are a definitive roadblock in the path of developing many of the most famous science fiction devices in the real world. Try though they might to explain away reality-defying objects with undiscovered materials, rare elements, or fictional applications of real-world physics, some of the most exciting ideas from the genre are doomed to never make it past the ideation stage, operating on assumptions about the natural world that simply can’t be replicated in reality. No matter the technology level humans are able to one day achieve, some sci-fi gadgets will sadly manifest in the real world.
One of the most iconic movie weapons ever created, lightsabers need little introduction. The mythical weapons of both the legendary Jedi order and the insidious Sith, these blazing hot swords of pure light can slice through nearly anything in the Star Wars universe, barring specialty-made materials like Durasteel. Not only that, but they’re also capable of deflecting bolts from energy-based blaster weapons, making them an impressive source of offense as well as defense. In the lore of the franchise, the lightsabers are powered by the mysterious Kyber crystals.
The lightsabers operate on different laws of physics than those in reality. Creating a powerful enough beam of light to cut through solid metal would result in a much longer, unwieldy weapon, not limited in its projection to a mere three feet. Even ignoring the issues regarding the lightsabers’ power source, which would easily need to be connected to some kind of power-generating backpack with today’s available technology, the ability of the weapons to physically clash with one another disobeys the properties of light. In reality, crossing lightsabers would simply pass through one another.
The only thing better than traveling at speeds surpassing light itself is the ability to near-instantly teleport, and plenty of science fiction films have put their own spin on the concept. Perhaps the most famous is the Transporter technology of the Star Trek series, activated by a remote operator at the behest of the classic phrase, “Beam me up, Scotty!” With its signature sound and colorful special effects, Transporters are some of the most iconic imagery of the legendary science fiction franchise, opening up the imagination to instantaneous planetside travel without the need of landing shuttles or orbital drop pods.
The issue with teleportation technology isn’t so much the scientific possibility, but the philosophical concerns regarding teleporting a thinking human. It’s actually not too outlandish to imagine the disintegration of physical objects into intangible data that can then be received at a different access point and reconstituted. In real life, scientists have succeeded in teleporting single photons. Yet there’s no guarantee that if a human being were to use teleportation, their exact copy would retain any of their previous memories. Even if they did, the technical death and copying of a single person creates an uncomfortable “Ship of Theseus” problem.
Frank Herbert’s Dune novels have been seeing an incredible resurgence in popularity thanks to Denis Villeneuve’s excellent adaptations, introducing hordes of new fans to the far-out technology of the series for the first time. Dune: Part One and Dune: Part Two both feature some pretty unbelievable technology, such as prophetic psychoactive drugs and bullet-deflecting energy shields. However, one charming piece of iconic Fremen equipment, the Thumper, seems like a straightforward mechanical device — Simply plant it in the sand, allow the pulses to travel, and wait for a giant sand worm to show up.
Unfortunately, even the humble Thumper seems to be outside the reach of believable technology, despite seeming like a simple mechanical device. As pointed out by pop-culture physicist Niel DeGrasse Tyson on Twitter following Dune: Part Two‘s release, the idea of soundwaves traveling through sand in order to draw out a subterranean creature is impossible on any planet. Sand is an incredibly effective dampener of sound, meaning that even massive shockwaves sent through a desert wouldn’t have much of an effect. The idea that the Shai-Hulud could hear across such vast distances underground is impossible to begin with.
Another unbelievable invention to spring from the mind of George Lucas, the Hyperdrives of Star Wars fame have less than a passing relationship with the real-world laws of physics. In the universe, Hyperdrives operate by propelling a spacefaring vessel to velocities greater than the speed of light, allowing them to enter the mysterious dimension of Hyperspace. In reality, the speed of light is a limit inherent to the laws of physics, meaning that it would take an infinite amount of energy for material objects to accelerate to the lightspeed, let alone surpass it.
The controversial Holdo Maneuver of Star Wars: The Last Jedi further complicates matters. Assuming that Hyperspace is an immaterial dimension that objects traveling faster than the speed of light quickly enter, they shouldn’t be able to have an effect on the physical world. Otherwise, it makes no sense that the Star Wars series isn’t filled with lightspeed weaponry being haphazardly fired across every naval battle between spaceships. Regardless, the premise of outspeeding light itself is in direct defiance of a proven universal constant.
Holograms are one of the most iconic science fiction creations, being inherent to no single series. Popularized time and time again by Star Wars, Star Trek, and even Tony Stark in the Marvel Cinematic Universes, holograms present a far more futuristic idea for a user interface, interacting with technology with constructs of light that might even respond to human touch. Unfortunately, the real-world behavior of light particles once again rears its ugly head when it comes to the actual practicality of holograms.
Holograms do exist in a sense, infamously used by the musical talents of Hatsune Miku and the late Tupac. However, these projections are quite literally the work of smoke and mirrors, relying on optical illusions, meaning that true holograms are still a distant dream of sci-fi creators. In actuality, it would be impossible to establish a way for light to arbitrarily stop at a predetermined distance, meaning that any attempt at creating a hologram would quickly devolve into a standard projector screen. That’s not even to mention the concept of being able to touch and move holograms around Tony Stark-style.
Shrinking technology has a flirtatious relationship with science fiction movies, showing up in places like the MCU’s Ant-Man trilogy and the upcoming reboot of Honey, I Shrunk The Kids. There’s even a strangely specific trope used in various TV shows regarding a situation in which characters are forced to undergo a fantastic voyage within the body of another character, typically with the aid of a shrinking submarine. It’s fascinating to imagine exploring the world from a more diminutive point of view, allowing scientists to study natural phenomena like insects up close and personal, though the dangers would certainly be palpable.
Sadly, the concept of shrinking a living being down to size remains a distant dream of fantastical science fiction movies. Atoms are the basic building blocks of all matter, and to shrink an object, one would either have to be made out of less atoms or change the actual size of the atoms themselves, both of which present their own problems. In the case of the former, this could work with certain inorganic matter, but no living thing could survive the process. Otherwise, atoms are simply the smallest unit that physical matter can be subdivided into, with no exceptions.
Time travel has long been the subject of fascination for science fiction movies, being a subgenre all of its own. From the Terminator franchise to the Back to the Future trilogy, each movie has its own rules for time travel. While time travel to the future could be theoretically possible, with movies like Interstellar exploring the delicate relationship high-speed travel and time have with one another, moving backwards is a scientific impossibility. Some versions of general relativity suggest that the necessary warping of spacetime time travel would require wouldn’t allow potential voyagers to move backwards in the time stream.
One of the better episodes of Futurama, season 6, episode 7, “The Late Philip J. Fry“, played with this concept. Professor Farnsworth, Fry, and Bender all booking a one-way ticket to the distant future, comically witnessing the birth of a new universe identical to their own, allowing them to return to their own time in a roundabout sense. While it may be possible to step into the future, going backwards a la Marty McFly is a pure fantasy.
Another way to time travel in a sense, the concept of cryogenic stasis has been played with in a great deal of science fiction films. Used most notably in the Alien franchise, the scantily-clad warrant officer Ellen Ripley begins the first film fresh out of a cryogenic stasis pod, allowing herself and the rest of her crew to endure the brutal distances of interstellar travel. In real life, the effects of such technology would extend far beyond one’s legs falling asleep.
Freezing someone to wake them up at a later time is simple enough in concept — After all, some real world frogs and insects use a similar form of hibernation to last through tough winters. Over such dramatic time periods, however, ice crystals would inevitably form between the very cells of the human body, wreaking havoc on the hapless sleeper. Additionally, the levels of glucose that creatures who use cryogenic stasis in real life use as a sort of biological antifreeze would easily kill a human being, making such techniques exist only in the realm of science fiction.