One of the obstacles to realistic - yet interesting - space battles is that of effective computation. If all trajectories and whatnot can be computed much faster than a human could follow, it leaves the human characters in the story with nothing to do. All combat would be over the horizon, in a way, because there's no reason to ever get close.

My idea is minor variations in universal constants. Microchips are small enough that quantum effects are relevant (or could plausibly be, if they're not yet in the real world). So if the Planck constant varied with location, maybe computation wouldn't work after travelling large distances (or rather, you could build a computer there but it would be slightly different from the computer you'd build here).

My question is twofold: which constants would this be plausible with (Planck, speed of light, gravitation, etc), and would it be plausible without affecting the ability of humans to survive?

  • $\begingroup$ As is clear from the answer below, changing universal constant is disruptive and may lead to catastrophic consequences. If you want to limit your computation, have you considered dissipative effects of the computational devices or other mechanism that reduces efficiency over time? $\endgroup$ Commented Apr 11 at 6:15
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    $\begingroup$ Another issue: if the universal constants aren't invariant, then you've produced a preferred frame of reference for the Universe (en.wikipedia.org/wiki/Preferred_frame) and irreparably screwed up relativity. $\endgroup$ Commented Apr 11 at 12:48
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    $\begingroup$ Computing is a lot less sensitive to universal constants than biology. $\endgroup$ Commented Apr 11 at 21:05
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    $\begingroup$ You would better introducing impossible tech (say, Dune-like forcefields) than fiddling with what we already know that works. Good sci-fi is additive ("our universe, but there are elf-like aliens", or "our universe, but realistic robots exist") instead of subtractive. Try to add new things that could work instead of taking away things that we already know how they work. $\endgroup$
    – Mermaker
    Commented Apr 11 at 23:24
  • $\begingroup$ My answer on another issue might help you: worldbuilding.stackexchange.com/a/168228/3245 $\endgroup$
    – Mermaker
    Commented Apr 11 at 23:26

3 Answers 3


The problem is that too much else depends on those constants. If you change them, lots of things besides microchips will break. Like star formation, or the exceedingly delicate and complex organic chemistries life depends on. There probably wouldn't be any people around to be made redundant by computers in such a scenario.

  • $\begingroup$ There's an amount of variation which wouldn't prevent stuff like star formation but could affect other things. That page notes that a 2% change in the coupling constant could be significant, but what about 0.2%? Could that affect computing enough to make my computer not work without ruining biology? 0.02%? $\endgroup$ Commented Apr 11 at 4:49
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    $\begingroup$ A lot of biology (for example, neurons) depend on voltage differences across cell membranes, which involves the same principles that electronics use to function. Anything disruptive enough to prevent the function of electronic microchips will probably mean no neurons, either. (Note I'm not actually a physicist or biologist, so perhaps take with a grain of salt.) $\endgroup$
    – Ton Day
    Commented Apr 11 at 4:52

No, you can't do that

If you changed basically anything about the physical constants, you're screwed. There's something called the anthropic principle which aims to describe why they are what they are; the idea is that if they were at all different, humanity never would have existed for one reason or another: neurons wouldn't be able to properly interact, our planet wouldn't've held together, or our Sun would've never formed. Or, hell, the Universe wouldn't have undergone the Big Bang. But since humanity does, in fact, exist [citation needed], we know that the physical constants have to be in a combination that allows for humanity to exist. Hence, $h=6.62607015\cdot10^{-34}$, $c=299792458$, etc.

All evidence points to quantum physics being a valid, invariant theory - that is, constants and equations don't change place to place or time to time. This is an important property of our theories and in the Liu Cixin novel The Three Body Problem (recently turned into a Netflix show for its popularity) invariance is thought to not hold true, and it ultimately leads to science being "broken" and a bunch of scientists quitting (either science or life entirely). So that's off the table. The Planck constant, the speed of light, and the gravitational constant are all absolutely not going to change without wrecking something important about the Universe.

Here's another option, though. Say that your space battles are happening in a fairly complex environment - there are moons about, the planet's under you, and asteroids are nearby. This makes finding a firing solution difficult. Of course, not difficult by the standards of someone with a computer: a computer can take in real-time data and calculate such a solution in a matter of milliseconds. But it's difficult enough that running that computer takes power. A lot of power.

So what do we do?

Suppose that you're running a standard desktop in the back of your ship's bridge to handle all its firing solutions (modern tech is more than capable). You're drawing about a kilowatt of power to run it, and the thing is that ultimately the vast majority of that kilowatt of power gets converted into heat. As it turns out, conduction and convection aren't a thing in space, so you're going to need to run a lot of radiators to dissipate that constant 1 kW of heat energy pouring into your ship. If the situation is more complex, the power required to run your computers only gets bigger, and you need ever-more radiators and an ever-larger power source to keep from passing out from heat stroke.

There's your solution: computers are too hot. This means that on huge capital ships that are like cities unto themselves, they're more than equipped to have computers onboard to make them even more dangerous to fight against, but on small corvettes that only house a few different people or on standard cruisers, dealing with the heat output of firing computers is just too expensive, so instead you have the heat-efficient humans do the job.

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    $\begingroup$ Computers are much more heat-efficient than humans when it comes to doing brute calculations. They say your typical cell phone has more power than NASA needed to reach the moon- it also puts out several times less heat than a human. $\endgroup$
    – Edward
    Commented Apr 11 at 17:10
  • $\begingroup$ Actually reaching the moon is a very easy task - plotting a course, timing burns, etc. takes a computer maybe a few operations at the very start, plus course correction. Managing PDCs in a dogfight is another question. $\endgroup$ Commented Apr 11 at 17:34
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    $\begingroup$ @controlgroup: humans generate at least 100 Watts of heat, more if they're excited or physically active. You can absolutely build capable computers that use less than that: a kilowatt is a very high figure for a modern desktop. $\endgroup$ Commented Apr 11 at 21:02

Your starting premise is mistaken...

One of the obstacles to realistic - yet interesting - space battles is that of effective computation. If all trajectories and whatnot can be computed much faster than a human could follow, it leaves the human characters in the story with nothing to do. All combat would be over the horizon, in a way, because there's no reason to ever get close.

If you can compute trajectories from long range in less time then it takes the objects to reach you, then defence becomes easy and over the horizon attacks less effective - forcing space battles to take place at close quarters with no change to the rules of the universe.

  • $\begingroup$ A very good callout. When you can hit their powerful missile with a much weaker one that's just strong enough to blow it up, or their kinetic shot with something moving fast enough to deflect it slightly, you're really safe from long range attacks (until you run out of defensive ammo). And lasers can be dodged just by random velocity changes, since the light speed lag would have them aiming where you would have been. $\endgroup$
    – Bobson
    Commented Apr 15 at 10:15

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