There are plenty of technologies in science fiction that make for great stories, but if these highly advanced gadgets and gizmos were actually real, they’d be something you’d want to stay far away from.

The transporters inStar Trekwere invented as a plot device because they were less expensive than building a shuttlecraft and then filming sequences of the crew traveling down to planetary surfaces.

Recreation of a scene from the 1960s television science fiction show Star Trek, where Captain Kirk Doctor McCoy & Mr. Spock beam down to the planet surface.

It’s a core part ofTrek technology, and I would not want it any other way, but like so many actual Trek characters, I too would refuse to step into one.

Transporters work by breaking you down into an energy pattern and reconstructing you at the other end of your destination. Convenient, but this is like a fax machine that shreds and burns the original documents after sending them.

Agent J holding a neuralizer.

The person who stepped into the transporter is dead. The person who steps out of itthinksthey are the original person. This argument has been raised in various shows, and transporter accidents like the photocopy of Commander Riker and (shudder) the creation of Tuvix (read more about him onMemory Alpha) are often part of an episode’s plot.

Even better, the various sentient creatures in Star Trek laugh at the few transporter-phobic characters as backwards and irrational, as if whether the original person dies when they walk into a transporter is just a philosophical question.

A young woman dressed like the character Trinity from ‘The Matrix’ surrounded by green hues.

2The Neuralyzer

InMen In Black,the secret organization that protects Earth from extraterrestrials needs to keep their existence secret from the public. To make this jobwayeasier, MIB agents have a handy gadget known as the neuralizer. Just look into the little lens, and after a flash of light your recent memories are erased, ready to be replaced with whatever story the agent wants to make up.

It’s funny in action on screen, and makes sense in the story, but if a memory erasure device like this actually existed, it would lead to some pretty dystopian outcomes—especially since we see the neuralizer capable of erasing decades of memories with the right settings. Imagine what governments could do with technology like this! It’s not pretty.

A scene from Total Recall where Quaid is forced into the memory implant machine against his will.

3Full-Dive VR

Virtual reality is a normal part of life these days, and there have been millions of headsets sold, letting people have all sorts of embodied virtual adventures. In fiction, there’s an advanced version of VR that’s often referred to as “full-dive” VR. Think of 1999’sThe Matrix(a sci-fi movie inspired by real science) or the animeSword Art Onlinefor a clear example of this. In full-dive VR, signals are sent directly into your brain, cutting you off from your own body, making you feel as if you truly exist in the virtual world.

While this sounds awesome as an experience, there are likely to be numerous ethical, safety, and societal issues if such a VR system actually existed. Of all the technologies on this list, full-dive VR might actually have the biggest chance of becoming real, since it’s pretty plausible, and we’re entering the era of BCIs (Brain Computer Interfaces) developed by companies likeBrainGateandNeuralink.

Iron Man model.

4Fake Memory Implants

InTotal Recall(based on Philip K. Dick’sWe Can Remember It for You Wholesale),a company offers to implant any memories you want. Do you want to remember going on a vacation? Maybe you want to remember a summer romance? Even if these things never happened, you can have happy memories that make it feel like they did.

If we had the ability to implant memories like this, it would quickly lead to serious psychological and societal problems. Human memory is already pretty unreliable, and memory manipulation is already a thing (as per theAPA) so being able to drag and drop convincing memories into someone’s brain would muddle things to the nth-degree.

Worst of all, how would you know if you’d gone for a memory implant or not? Even if you didn’t, someone else could still claim you did, and you’d have no way to prove otherwise.

5An Iron Man Suit

Just like millions of nerds, I love the idea of an Iron Man suit. Powered armor that turns a regular person into a superhuman being, almost impervious to harm. Except, even if you did manage to make a real-world Iron Man suit, it would still have a squishy human inside. Thanks to the laws of physics, that squishy human will turn to jello from the impacts that the suit would endure, even if the suit itself could handle it.

It would make way more sense to teleoperate a system like this (which, ironically, Tony Stark later does in the movies), effectively making the suit a robot. Making war machines unmanned seems to be the prevailing trend these days, and that’s probably the right choice. While powered armor (and their bigger cousins, mechs) are undoubtedly cool, it probably wouldn’t end well for whoever actually tries to pilot them in the real world.

Clearly, there are some remarkable technological concepts that are best left on the pages of sci-fi novels, though to look at what modern companies are working on, you wouldn’t think anyone’s going to heed this particular warning!