Star Trek and Star Wars offer visions of the future that have become so familiar that it’s all too easy to over-credit the plausibility of the technologies they present. But how much of what they depict is plausible science fiction and how much is implausible science fantasy?

Modern physics is incomplete, but not in the sense that it’s going to casually overturn core constraints like the light‑speed limit, energy conservation, or causality. Any future theory will still be bounded by those hard limits where we’ve already measured them to absurd precision. So betting that some future “breakthrough” will make Star Trek‑style tech real is not cautious skepticism; it’s wishful thinking.

First and most fundamentally, let’s start with the Vulcans visiting Earth. As much as we like to fantasize about technologically advanced aliens visiting us now or ever, to help us or to destroy us, this is implausible. As I discuss in my book (see here) and in this blog article (see here), aliens certainly exist, but they can never visit us. There is only an extremely remote chance that we could ever even detect signs that they existed somewhere, at some time, in the distant past.

Yes, you can always wave your hands and say “maybe some unknown physics will let them come here,” but that’s not reasoning, it’s magical thinking. Given what we already know about distances, speeds, energy, radiation, and biology, the probability that flesh‑and‑blood aliens will ever cross interstellar gulfs and happen to visit us is effectively zero. Not small, not unlikely, but zero.

I wanted to communicate that most strongly as it is so critical to understand. And of course since no alien could possibly ever visit us, it is equally implausible that we could ever visit them. The only remote possibility could be sentient machines who could survive inhumanly long and dangerous journeys. In this sense, the Transformers franchise (those in which organic makers are canon) could be the most plausible science fiction. I also depict such a plausible “space travel” science fiction in my short story The Dandelion Project (see here).

So while virtually everything that follows in Star Trek cannot happen, let’s set aside the basic implausibility of interstellar space travel and look at some of the other fictions that writers concoct to make it all seem plausible once we grant the possibility of space travel.

First, there is warp drive which overcomes the inconvenient reality of time and space. This is science flavored magic. While the physics of faster than light travel may have some plausibility at the mathematical level, it has zero plausibility at practical scale. Faster‑than‑light travel isn’t just “very hard.” It clashes directly with the way spacetime is structured. To get around the speed limit you have to either break causality (allow time travel paradoxes) or rely on enormous quantities of exotic matter that may not exist in any usable form. When a “solution” demands both magic materials and broken causality, that’s not serious speculation, that’s fantasy dressed in equations.

This is similarly true of the magical energy sources that the science fantasy writers concoct to make the fantastic power requirements seem plausible. They construct anti-matter reactors stabilized in a dilithium matrix. Again, even where anti-matter technologies are theoretically plausible they are effectively hopeless in any practical sense. Antimatter is real and ridiculously energy‑dense, but producing and storing it in useful quantities is so far beyond plausible engineering that it may as well be sorcery. Talking about “antimatter reactors” powering star cruisers is like proposing a jet engine that runs on bottled lightning captured in jars. You can write that into a script and make it sound theoretically plausible but you simply cannot build it in this universe.

The implausible power requirements involved in fantasy space travel also apply to weaponry. Hand phasers and similar variations are simply implausible. Directed energy starship weaponry is somewhat plausible, but certainly nowhere remotely near the hull-slicing power depicted in the shows.

And speaking of weaponry, even if hand phasers were plausible, they would at best fire invisible millisecond bursts. Phaser gun fights would never happen. Advanced weaponry would have computer targeting and essentially never miss. One could certainly never “duck” out of the way of an energy beam. A hand‑held weapon that fires at or near light speed, with computerized targeting, does not produce Western‑style shootouts. Once the weapon can lock onto you, your chances of side‑stepping a beam that crosses the distance in microseconds are exactly zero. The only real “dodging” is not being targeted in the first place—and that’s a software and sensor game, not a reflex test.

The same logic destroys the idea of starship dogfights. If you ever had vehicles throwing serious energy around at interplanetary ranges, the fight would be decided by who detected whom first and whose fire control software shot first. It would last seconds, or less, and the human crew would learn the battle was over when the computer informed them that their enemy had been destroyed.

We don’t need to imagine futuristic AI to see the problem. Even today, guidance computers outclass human pilots in reaction speed, precision, and ability to juggle massive sensor inputs. Scale that up to space combat and the idea that a flesh‑and‑blood pilot is “flying” a starship in combat is as quaint as imagining a locomotive engineer sprinting ahead to lay track by hand.

In that vein, there would be no possibility of human (or any organic) navigators or tactical crew members. Computers would certainly handle all the piloting and targeting. There would be no time for a real-time Captain to shout even one order as he’s flung around the bridge. Han Solo would not be able to pilot the Kessel Run safely in even a fraction of the time it would take a computer-controlled ship, if at all. Operating any function of a star ship would not be a job for humans.

As to other technologies, transporters, replicators, “subspace” radios, and hard‑light holograms all have the same problem: each one quietly assumes away a core rule of the universe. They don’t just extrapolate technology; they ask you to believe that information, energy, and matter can be shuffled around with a casual disregard for limits that we’ve already measured in laboratories. That makes for great science fantasy, but it is not remotely plausible science fiction.

But there are a few places where I suspect they get the possibilities more right than wrong, even if only for practical production and storytelling limitations.

There is the plausibility that many alien planets would be so familiar to us. Given that life can only evolve in a very limited set of conditions, and that the rules of physics, chemistry, and evolution are the same throughout the universe, I don’t find it implausible that many environments, and even many alien species, would be quite familiar or at least quickly understandable to us (see here). Life that can build radio telescopes is probably confined to a very narrow zone of temperatures, chemistry, and environmental stability. Under those shared constraints, evolution is pushed toward a limited set of workable body plans—eyes, limbs, mouths, sensory clusters. So yes, there are good reasons to think that intelligence elsewhere might wear a shape that is surprisingly close to our own. That doesn’t mean “humans with bumps on the nose,” but it does mean that “unrecognizable swirling gas minds” are probably rarer than TV’s familiar human-like bipeds.

Also, one thing that Star Wars got right was recognizing that in the future all medical diagnoses and procedures would be performed exclusively by medical droids. I can understand that it would take all the fun out of the fiction if they also admitted that Han piloting the Millennium Falcon or Luke manning the gun turrets would be just as obsolete, even with The Force assisting him!

There is a fashionable kind of optimism that treats science as an unbounded well that can eventually make anything possible if we just “don’t close our minds.” That’s not how science works. Science narrows possibilities by discovering hard limits. We don’t say “maybe one day we’ll find a way around conservation of energy” or “maybe light will decide to go faster.” We already know that won’t happen. The technologies I’m calling fantasy aren’t just impractical; they lean on the hope that the universe will overturn its own rules to realize our fantasies.

Just to say, I love these science fantasy shows. If they depicted a more plausible future with computers basically running everything they would be a whole lot less inspiring and engaging. But just as with a good horror or superhero movie, we can love the fantasy while still fully appreciating that it is mostly fantasy.

Often the distinction between science fiction and science fantasy becomes much muddier in a world where science seems capable of such magical and limitless achievements, but it is still critical that we recognize one from the other.