I like toying around with systems of magic, and I recently had the idea of a system of magic where someone could slow down the flow of time (by a factor of, say, 500) for everything except their brain's own processing speed. For example, if a practitioner of this magic were shot at by an archer, they could slow down time to observe its trajectory and figure out how best to dodge once time resumed at normal speed.

This, like most magical abilities, ends up being hard to balance. For exampe, a user could slow down time to think about something and make apparently instant decisions. And since the brain's processing doesn't slow down, one could take all the time they want to to memorize something, even if they only saw it for a fraction of a second. What sorts of limits could I place, and how could I explain them?

(I understand, also, that there are probably scientific consequences of this. Feel free to mention them, but it's not what the question is about.)

  • 2
    $\begingroup$ Does said person age normally throughout the time dilation? As in, if I make 10 seconds last 10 minutes, do I age 10 seconds or 10 minutes? If I only age 10 seconds, what’s stopping me from continues casting this spell to give me the illusion I’m living longer (relative to myself, not the outside world) $\endgroup$ Apr 3, 2023 at 23:43
  • 13
    $\begingroup$ the brains processing does not slow down, then neither does its demand for glucose and oxygen, so you don't have long to think. overdue it and you could very well kill yourself from oxygen debt. $\endgroup$
    – John
    Apr 3, 2023 at 23:55
  • 6
    $\begingroup$ Hi nearsighted! It's generally best practice to not award the green checkmark until several days or a week have passed after you ask a question. This allows other people time to prepare answers --- and who knows if one of those won't be better? Also, awarding the green checkmark sends the message that you got what you came for and they may not even bother to give you that spectacularly better answer. $\endgroup$
    – elemtilas
    Apr 4, 2023 at 0:35
  • 1
    $\begingroup$ @elemtilas thank you ─ if it's not obvious, I'm new to Stack Exchange. $\endgroup$ Apr 4, 2023 at 1:19
  • 3
    $\begingroup$ The abilities you describe don't seem terribly overpowered in the first place - I don't often finding myself making a difficult decision that's difficult only because I don't have enough time to think about, and the memorization aspect gives the user the power of a camera (which pretty much everybody carries already in the form of a cell phone). $\endgroup$ Apr 4, 2023 at 13:22

10 Answers 10


You only get a few seconds

If the brain's processing does not slow down, then neither does its demand for glucose and oxygen, so you don't have long to think. A few seconds of brain time and you're fine, a few minutes of brain time and you're unconscious even if you start time back up. (You'd also better hope being unconscious turns it back off or you're dead.)

Overdo it and you could very well kill yourself from oxygen debt. Your blood only has so much oxygen in it so even if you start time back up you may very well drop unconscious afterwards since your blood can't meet the demand fast enough.

Heat is also an issue,; a working brain generates heat but now nothing is removing that heat. This will limit you to minutes, not seconds and the further you push it the duller your thinking gets from heat.

Also you had better hope you have photographic memory because your visual image gets darker and darker once your power kicks in, since there is little light reaching your eyes. That is, assuming your eyes are considered part of the brain; otherwise it goes dark as soon as you turn on your powers.

  • 4
    $\begingroup$ Good answer - there's also the question of how well a viewer could judge the trajectory of something that they are seeing moving 500 times slower. Studies (with quarterbacks in US football) have shown that there is no correlation between IQ and the ability to judge trajectories - the brain does not do mathematical ballistics computations, rather it works on learned instinct. $\endgroup$ Apr 4, 2023 at 2:20
  • 5
    $\begingroup$ a 500x reduction in light won't be a problem outside of in poorly lit areas. Our eyes have much better dynamic range than cameras. Typical indoor lighting is more than 200x dimmer than a sunny day. 500,000 would be the sun vs the full moon. sunlightinside.com/light-and-health/light-and-the-winter-blues $\endgroup$ Apr 4, 2023 at 15:00
  • $\begingroup$ @KerrAvon2055 that's an interesting point, there was also a study about baseball batters. They say they see the ball trajectory, but scientists say that from the eye's "framerate" and ball speed they cannot capture more than like 2 or 3 images, not enough to make a trajectory. It's the brain that composes the trajectory from the arm movement before the lauch and makes the batter "see" it. I wonder how it would be affected too $\endgroup$
    – Kaddath
    Apr 4, 2023 at 15:58
  • $\begingroup$ @Kaddath Would also be interesting to study the actual framerate of a good ball-player's eyes. Not all people are the same. Some small percentage of people can see the individual frames from a TV set for that matter. $\endgroup$
    – Perkins
    Apr 4, 2023 at 21:19
  • $\begingroup$ So, basically it's the same how such powers are balanced in video games: limited duration, and a cooldown time before it can be used again. $\endgroup$
    – vsz
    Apr 5, 2023 at 17:20

More than most magic, time magic is notoriously difficult to balance out, both for narrative and RPG purposes.

If you want to do so, think of a catch or penalty one must pay to use it. Here are a few options.

Time magic is very rare

This needs no explanation, if only half a dozen creatures in your world are capable of it, that limits the wide-scale consequences considerably.

Time magic takes its toll on the body

All that speeding up and slowing down can't be very healthy for the human body. It could lead to immediate exhaustion (after all, your body consumes 500 times the energy in the same amount of time) or premature aging.

Time magic takes its toll on the mind

Sure, you can think fast while the magic is active but over time your regular thinking might deteriorate as a result, as you get far too used to having all the time in the world to contemplate your next action.

Time magic draws unwanted attention

Altering the fabric of space-time in a world eagerly watched by powerful entities may not be the safest thing to do, especially if those powerful entities are outside the world, looking for a gap or opening to push themselves through...

But at the end of the day, time magic is meant to be powerful: if it exists, it should be front and centre of the narrative and so should any limitations you place on it.

Edit: as for the specific arrow/archery scenario, let's not forget that in a world in which powerful chronomages exist, seeking arrow magic would probably also exist, and good luck trying to dodge them. Especially when a lesser mage could simply raise a hastily conjured force shield.

  • 2
    $\begingroup$ Especially like the taking the toll on the mind idea ... kind of like what parents always say about using screens. $\endgroup$ Apr 4, 2023 at 0:07
  • 1
    $\begingroup$ @nearsighted : username checks out :) $\endgroup$ Apr 4, 2023 at 15:05

You're talking about thought-acceleration, not brain acceleration. Nobody can really say why we experience time at the speed we do. It's kind of a "maximum processing speed" thing, but what part of the processing sets the limits? For this magic to work, you're basically giving the person a co-processor, which might actually work faster than the person's brain.

This is a common trope, like where Peter Parker's spider sense allows him to study the hairs on Flash Thompson's arm as it goes by. "Frozen in time" is often portrayed as a magical effect that lets some villain have a conversation with someone they want to intimidate.

  • Vision is an amalgam of the visual perceptions we've seen over time. Our eyeballs dart around quite a lot patching what we see into a full picture. If you were thinking extremely quickly, your vision would be like a painting that someone was spitting paint at, updating painfully slowly. Attempts to examine an environment would cause extreme muscular strain. Can you imagine how painful a sprained eyeball would be?

  • On the worse end, perceiving sight might deplete your vision, so you'd wind up waiting for the next photon to hit, hoping it filled in the right spot.

  • You perceive light frequencies based on which cones and rods are being stimulated, and the frequency is fixed based on the proteins expressed. Audio, on the other hand, senses the speed of vibration of the hairs in our cochlea. If your mind was moving faster, it might result in sounds coming in at a lower pitch.

  • A small but consistent mental speedup would do you more good in combat than stuttering freezing. You won't be dodging bullets, but your reaction speed and ability to poke at exactly the right spot would make you indomitable.

The biggest self-limitation is that you can think about things, but you can't act on them much faster than you already would. If you can't tune it—sliding up and down the time gradient at will—you'd be stuck at one speed until the spell wore off. Perhaps you can stretch a tenth of a second into an hour, but can only stretch a minute into two minutes. If it's a spell, then maybe casting it requires you to "store up" spare time. Maybe it just takes longer to cast than it gives back.

  • 1
    $\begingroup$ As far as I could gather, the cochlea and hair cells in it don't transduce the mechanical vibrations into neural pulses of the same frequency. It would in fact be impossible, as a neuron can only fire so many (about 500-1000) times a second. Instead the hairs all have different lengths and thus resonate at different frequencies, and (here I'm not entirely sure, but I believe that) the hair cells only signal that a certain frequency is present. and there are so many of them that basically the whole spectrum is covered. So I'd predict that in fact you'd hear normally, but veeeery sloooowly. $\endgroup$ Apr 4, 2023 at 15:24

Firstly, it's not as useful as you might want it in a combat situation.

Let's just say the caster can freeze time to think indefinitely. If you can't move a muscle, that means you can't hear a thing, move your eyes, smell anything. In other words, I imagine it like a freeze frame, and you can't gain new information that isn't on this frame. So if the arrow you're trying to dodge is all blurry or in your peripheral vision, tough luck.

You would still have to react to the arrow in the first place, and then execute on your carefully planned dodge maneuver. Physically dodging isn't going to be trivial by any measure. You'd have to kill your momentum or otherwise change its direction in a snap. Magically dodging will require you to immediately prepare another spell which may already take more time than you have.

For reference, if you get shot at by a slow longbow, you might get 2 seconds of reaction per hundred metre, but a fast crossbow you're looking at half a second. Forget about dodging bullets.

So it's a useful spell, but it's not necessarily super broken. But here are some ways to nerf it anyways.

1. Cast and recovery time

The first easy way to nerf your magic is to say it takes a literal second to cast, and/or that the effect of ending it may include disorientation for a second or two. Effectively, you have a small amount of time before and/or after the spell that can't be used for anything.

In a combat situation, that's downright lethal, and might completely nullify the spell.

In a high stake competitive conversation, the delay might be dangerous, but maybe you'll just look a little slow. In non-time-sensitive conversation, you can achieve the same effect by saying the magic words "hmm, let me think about it for a moment" anyways so who cares.

2. Brainergy

Your brain runs in automatic mode something like 98% of the time. It's crazy the amount of things your brain does without your conscious intervention. And the reason it's like that is because actively using your brain eats a lot of energy. Like, a lot a lot.

So firing your brain on all cylinders to overthink a situation is fine and all, but it's super exhausting. If you stop time to think about arrows once, okay, that might fly. If you do it every twelve seconds over the length of a battle, you'll kill yourself before the end. And in a casual conversation, if you stop to think about the perfect pick up line for an hour, you might just end up falling asleep on the bar.

In practice, that means it's a spell you can use only so much before you need to rest, and not resting isn't an option for very long. It can be useful in a pinch, but you can't abuse it.

3. Madness

It's just you and your thoughts up there. Time freezes around you, but that's not how you perceive it. What you perceive is being trapped in your own body with only your thoughts. Doesn't that sound appealing?

It's also easy to overthink details while overlooking stuff right in front of you. And we've all experienced that, and we've probably all spent even more time thinking about how to do things differently. You know, that perfect and witty rebuttal that came to you only ten seconds too late after you've already said something incredibly lame. But at least we can reassure ourselves knowing we didn't literally have all the time in the world to come up with a flawless plan, we just improvised in the moment.

But I'm sure the wizards will be fine being trapped motionless contemplating their own failures at length.

  • 1
    $\begingroup$ The "a lot a lot" of brain power consumption is definitely worth paying attention to. Kasparov apparently burned about 3000 Calories a day just playing chess and had trouble keeping weight on... $\endgroup$
    – Perkins
    Apr 4, 2023 at 21:23

The Law of Conservation of Duration

Ultimately you have to pay back what you take. You can stretch a second out into a minute, but at some point you'll then have to let a minute pass you by in a second. Using it to dodge an arrow is of little use if you then spend the next several seconds immobile with brain freeze.

This also open up ways to play around with how it's used, as well. A skilled mage might be able to delay payback for an hour or two, until they are out of harm's way, or inversely slowing themselves down before an expected fight to build up a sort of time credit to use during it. Perhaps they could smear out the repayment so they experience the next hour or two going past a few percent faster than normal, behaving slightly delayed to others but still able to function. Possibly there's something to the theories of that up-and-coming wizard Einstein, that time is in fact relative and you could cheat the system if only you could find the right way to twist time and space. But for most people, the same number of seconds has to pass everywhere and they will have to repay the time they borrow.

  • 2
    $\begingroup$ I really like this answer as it allows you to show the character as forward-thinking and tactical. But later in the story you could have them being chased with no time to repay the Conservation. Every second they hold off repayment takes a toll on their body and senses. I could imagine an incredibly tense scene where they are being pursued, building that debt but unable to repay and the tension grows as they lose their faculties. You could even have it leak, so their hearing or balance starts to get delayed while their other senses continue at a normal pace. $\endgroup$
    – Conor
    Apr 6, 2023 at 15:36


Magic does not need to be instant, so the user might need to time it well to truly make use of it.

Hard to balance (heh).

We have programs in our body that help us move. Someone with Parkinson loses this and has to focus on every movement to walk and coordinate their movements. This would also happen with someone who is sped up 500 times (or even someone sped up 1.2 times). Your sped up people would have a lot of trouble balancing their body, meaning that their movements would all need to be deliberate. You can fire a gun with enough focus, you can’t put your weight behind a punch very well.


A few suggestions:

  1. This magic has a time limit and a cool-down time. Meaning it can only activate for a while and then can't use again until some time has past. Maybe it is not a magic originated from the user, but a magical trinket that the user needs to activate in order to use this slo-mo magic. And once the time is up, the effect is gone and you have to fight in normal time like your opponent. And it also means your opponent may also have the same trinket and can use slo-mo magic as well.

  2. This magic only slow down time, not stopping it. So as long as the incoming speed of the attack is faster than the rate of slo-mo, slo-mo guy still can't dodge it because the attack still too fast. Or, your opponent is moving faster than you can see it, then when you slow down time, you only see the attacker's after-image. Then you would plan to dodge his fake move. But in fact, the attacker is already behind you--where you can't see.

  3. It only allow your brain to think, but your body is also frozen in time. So if the attack is board and wide enough (like a beam with 6 km diameter), you still can't dodge it.


You can't slow time for the rest of the universe, the energy cost would be prohibitive. Instead you affect as small a volume as possible to get the job done. In this case that means either slowing time in a small area around you or speeding time up for just yourself. Or, alternatively, just speed up the processing speed of the brain using some other method that doesn't actually mess with time.

How that works is up to you. If you really want to reconcile the magical effect with some semblance of physics then you've got a bit of an uphill climb ahead of you once time manipulation is involved. If you just modify the time for your brain itself at a reasonable ratio, say 5:1, then you have about 30 seconds max (subjective time) before you pass out from lack of oxygen, and your thought processes are only going to be "normal" for the first 10 seconds or so. So you'll have a very short time (2 seconds objective, 10 seconds subjective) to figure out what you're going to do. At higher differentials the numbers change even more.

Taking a leaf from the various comic book speedsters, you could adjust the time ratio over your entire body. This looks like classic Haste spells, where you get to move faster and so on. Without some sort of force compensation (like how the Flash uses the Speed Force) you won't be able to move a lot faster because of friction with the air and all that, but your brain will at least continue to receive the necessary nutrients, cooling and oxygen. You might have some issues over a few minutes or so (subjective) due to the effect of oxygen crossing the temporal interface, so try not to do it too much. Oxygen starvation hits pretty hard and leaves a nasty hangover.

Beyond the scientific you could rule that the brain is just the interface between your consciousness and your body, and all you have to do is speed up your "soul" (or whatever people in your world call the intangible bit that does the actual thinking) and wait for the slow meat to catch up. This isn't necessarily a temporal manipulation, it might just be that your consciousness runs on some limited resource that you can increase.

Of course you could always just ignore the mechanism behind it and just describe the effects. From a storytelling perspective this is pretty common. How does it work? Magic. What is the magic doing? Hell if I know, you prep the spell, pay the mana cost and when you trigger the effect... it just works.

There's even a good in-universe reason for that: almost all mages are technicians working with existing spells rather than experimental scientists trying to understand the inner workings of magic. You might get the odd geeky wizard who spends his whole life trying to study how magic actually works, but mostly it's just spell slingers of varying schools and levels of power. And most of them don't care how it works only that it does work.


I wouldn't go too far in thinking that magic power has to be balanced to the point of being a zero-sum game - it's supposed to offer advantages that people without it don't have.

For exampe, a user could slow down time to think about something and make apparently instant decisions. And since the brain's processing doesn't slow down, one could take all the time they want to to memorize something, even if they only saw it for a fraction of a second.

But that's the reward for the years of study and practice (or just being the seventh son of the seventh son or whatever).

Anyway, because your body is limited to the rest of the world's time-scale you can't exactly dodge bullets or anything - so it's not an immensely powerful ability - you can think fast, that's it. Maybe be able to simulate a photographic memory (which is still limited by your brain-capacity)

Even the ability to speed-read would be limited: your eyes have to move in slowed time too, so focusing and looking at different parts of a page would take a long time. (Try reading a page of text while focused on just one point!)

You should probably just concentrate on finding loopholes where it can be abused and closing them, rather than trying to "balance" the overall power. But I wouldn't consider the examples you provided as abuse, just being the normal use of the power.

An example of abuse might be that the user has it "always on". To counter this: Like all abilities, it's tiring to keep it up, and this would make life unbearably boring. Imagine playing a long computer game with the CPU severely slowed down.


I suggest that the magic user should have to expend magical "energy" for every second that they slow time and also the more they slow the time the more energy it takes. This magical energy could not only slow time but also take care of all the problematic "overhead" effects of brain overheating etc.

Great mages would have a lot of magical energy and could slow time almost to a stop for a short period or could slow time considerably for a much longer span. Lesser mages would not be able to slow time as far or for so long.

One problem if the mage doesn't perceive the arrow he could be dead before he was able to slow time. So he would be vulnerable to being shot in the back or even shot at high speed from close quarters from concealment.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .