This is one of a series of questions dealing with the magic explained below:

In my fantasy world, magic is an energy similar to radiation. It alters the DNA of living cells, causing them to mutate or die. There are people in this world capable of controlling the magic. They can control the change, using magic either to kill cells, or change them in a host of beneficial ways. For example, they might give themselves night vision by altering their own eye cells.

This particular question deals with the speed of the magic. How fast could a magic-wielder work change in his victim? Is it instant, a long, slow process, or somewhere in between?

Remember that magic is for all purposes controllable radiation. It works on a cellular basis and can only affect a cell's DNA. Magic should affect DNA at the same speed radiation does. Disregard for the moment any time required for the magic-user to control the magic.

Please let me know if additional details are required.

  • $\begingroup$ How do they control the target organ? I.e. if they are targeting the liver to make it capable of processing poisons, how do they manage to not affect all the layers among the liver and the outer environment? $\endgroup$ – L.Dutch - Reinstate Monica Aug 14 '17 at 6:27
  • 1
    $\begingroup$ Do you want to know how fast the actual changing would be or do you want to know how long it would take until the desired result is obtained? The answer to the first question is somewhat around femtoseconds/attoseconds depending on whom you ask and the last question completely depends on what you want to accomplish. Please also note that DNA isn't some magical molecule, radiation in fact interacts with a lot. Does your magic only alter DNA or is it exactly like radiation but just controllable with your mind? $\endgroup$ – Raditz_35 Aug 14 '17 at 11:03
  • $\begingroup$ @L.Dutch That is something I have not yet determined. For the moment assume they can be exclusive in what they effect. $\endgroup$ – Thomas Reinstate Monica Myron Aug 14 '17 at 14:56
  • $\begingroup$ @Raditz_35 I'm looking for how long until the result is obtained. If the answer depends on what I'm trying to accomplish, perhaps you could give me some different examples so I can get an idea? I'm not a radiation expert, but I understand that it occasionally mutates cells instead of killing them. To my knowledge it does this by messing with the DNA. That's what I want my magic to do. What else does radiation do besides mess with DNA? $\endgroup$ – Thomas Reinstate Monica Myron Aug 14 '17 at 14:58
  • $\begingroup$ Ionizing radiation ionizes as it pleases. It destroys basically everything in your body, so let's say it damages your tissue, kills your cells. It can also randomly destroy your DNA which might result in tumors. There are different kinds, slow and fast growing ones - this is my example you asked for. It cannot simply introduce a gene for night vision, but if it would introduce new stuff, I suspect the time for new stuff that helps you see at night is somewhat related to tumor growth and what stuff looks like, e.g. volume. Btw, this is what a virus does - it alters the genetic code. $\endgroup$ – Raditz_35 Aug 14 '17 at 15:36

Radiation changes DNA instantly; for all practical purposes. The killing of cells takes minutes or hours, when they can no longer produce energy and waste builds up and smothers their ability to work.

That said, even if a change to DNA can give you night vision, there is going to be a growth process for those cells to reproduce and replace other cells in the eyes. Or anything similar, if the user wishes to change their appearance, or grow taller, or change gender or natural hair color.

For such growth processes, you should expect them to work no faster than any other biological growth, radiation will not speed that up in the slightest.

So on some simple changes (night vision, skin color) consider it like the time from cut to fully healed scar; which is generating new cells and clearing away dead cells. Bigger changes (growing taller by two inches) would take months to year. Changing gender could take several years (based on an approximately six year biological process for a pre-pubescent human female to change into a fully adult woman that is no longer changing due to puberty; I presume reversing that process (woman->man) would take at least as long).


If all you want magic to do is kill cells, it should work as fast (and in the same way) as radiation therapy. On a scale of hours.

But if you want to cause an effect by changing the DNA of a cell, the time scale will be much longer -- months or years or generations. Here are some examples in order of time scale:

1) Make the subject high. Up-regulate production of dopamine in neurons in the medulla and the adrenal glands. If your magic can affect all of them at once, then the subject should start feeling giddy within hours. If you can only change one gene in one cell at a time, then this spell is useless to you.

2) Make the subject able to digest wood. Splice genes for lignin-modifying enzymes into some of subject's gut bacteria. Feed them sawdust. It might take a week or two for the wood-eating bacteria to out-compete unmodified bacteria.

3) Make the subject glow. Splice luciferin genes into some of the subject's skin cells. Wait for those cells to multiply and somehow make sure the glowing cells have an advantage over unmodified cells. Over the course of the next month or two, glowing patches on the subject's skin will grow together until the whole epidermis glows.

4) Horns. You'd have to do the same sort of thing as in (3) but with the subject's ostoblasts. Their turnover time is high (here's a nice list of the turnover rates of different types of cells) but they still have to grow the bone. It'll probably take six months to a year to get decent horns. Other growth modifications like bony armor or changes to general body shape will take longer. Some will be impossible to work on adults, but will work on pre-puescent children or infants.

5) Wings. You'd probably need to modify an egg or sperm cell or a blastocyst and wait for the baby to grow.

  • 1
    $\begingroup$ So would I be correct in assuming that no change worked by this magic will have instant results? Or even results within minutes? $\endgroup$ – Thomas Reinstate Monica Myron Aug 14 '17 at 15:17
  • 1
    $\begingroup$ I guess you could just zap someone dead with it, although that might take a lot of energy. But otherwise no, you're changing DNA and then waiting for the cells to do whatever it is you want them to. $\endgroup$ – Daniel Bensen Aug 14 '17 at 19:47

Since the magic is intended to work like radiation, it would be logical for speed to work like irradiation: depending on the dose received and the exposure duration.

For example, a high dose of magic can make an important change quickly, while a small exposure deals little change and is more of a long and slow process.

Moreover, speed varies depending on the organ exposed - an internal organ needs more exposure.

  • 1
    $\begingroup$ Be warned that exposition may be lethal to your readers/viewers, while exposure may be lethal to your characters. $\endgroup$ – Frostfyre Aug 14 '17 at 12:35


Radiations are the most flexible part of your magic. You can tune their intensity, wavelength according to the proficiency of the mage. From weak radio waves to a powerfull laser.
Therefore, when it comes to destroying cells or altering DNA, it all depends on how you manage magical energy. There could be some property changes depending on wavelength, like color change for standard radiations...
As for travel time - it's lightspeed.


DNA is only used during the formation of the cell, during/after duplication. Therefore, for your magic's effect to start producing mutated cells you'd have to wait for at least one duplication. But duplication rate varies a lot depending on what kind of of cell it is. The body can produce about 2 millions blood cells per second while some cells of the eye won't duplicate even once in a lifetime.
That means that it would be faster to grow new eyes, or replace the existing ones than waiting for the originals to mutate.
Those limitations can bring interesting elements, like blood magic used to kickstart a mutation on another body part (actually, blood cells are produced by other organs, bone marrow and potentially liver, so technically this example wouldn't work) or accelerating duplication which would be consuming more of the user's energy and increasing the chance of random, dangerous mutation (some kind of magic instability)...

  • $\begingroup$ So say someone used magic to thicken the blood and clog arteries... how fast until a heart attack? $\endgroup$ – Thomas Reinstate Monica Myron Aug 14 '17 at 16:19
  • $\begingroup$ With 2 millions blood cells per seconds and a good clogging process it could take about a minute. A clot might just form inside the brain or the heart and the enemy would die even faster (coma, then death). Also, you could make the new blood cell able to duplicate too so that the spreading of clogging cells becomes exponential. $\endgroup$ – Velraen Aug 14 '17 at 22:33
  • 1
    $\begingroup$ I've calculated that it'd take 10min to produce 1 cubic mm of blood cells, more than enough to make a clot in the brain.. but to stop the heart I think it'll take longer. Well, that's without taking into account that the other blood cells will probably aggregate around these and accelerate the process. $\endgroup$ – Velraen Aug 14 '17 at 23:25

Given that your magic is essentially radiation, the effects take place on two time scales:

Individual magical interactions would take place at the speed of light. Individually these won't have a noticeable effect, which is why the speed of change will depend almost entirely on the magic output of the wielder and the number of interactions necessary to effect the change.*

The faster the magical radiation is delivered, the more interactions will take place and so the faster the change. Likewise the more interactions required, the slower the change.

We can express this relationship via the formula:

Time = Output / Interactions

*Plus the time required to control the magic, which (as per the question), we're ignoring.

  • $\begingroup$ The radiation is moving at the speed of light, the DNA doesn't move. The particle interaction would be practically instantaneous. Different changes would require a different number of cells to have their DNA changed, which would therefore require a different number of interactions. See here for a link explaining how ionizing radiation affects DNA as an example. $\endgroup$ – walrus Aug 14 '17 at 11:31
  • $\begingroup$ The phrase 'the faster the magical radiation is delivered, the more interactions will take place' should read 'the faster the magical radiation is delivered, the more interactions will take place in a given amount of time' $\endgroup$ – walrus Aug 14 '17 at 11:32
  • $\begingroup$ I'm not sure what you mean by 'move' here: when ionizing radiation breaks apart the base pairs of DNA, does it move? This damage seems like it would take place with a speed of light delay (which is probably a better way of phrasing that) and I would imagine that the changes induced by the magic would be just as quickly. You need to change multiple cells because that's specified in the OP's question: kill cells, or change them in a host of beneficial ways. For example, they might give themselves night vision by altering their own eye cells. $\endgroup$ – walrus Aug 14 '17 at 15:04
  • $\begingroup$ I'm not a biologist, and I can't say I understand the processes by which DNA changes happen; I just wanted to make the point that the changes induced by the magic would start with only a speed of light delay, even though they would take longer to complete in most cases. $\endgroup$ – walrus Aug 14 '17 at 15:06
  • $\begingroup$ For the record, I understood this answer fine. $\endgroup$ – Thomas Reinstate Monica Myron Aug 14 '17 at 15:15

The energy transferred to a substance through electromagnetic radiation depends on two factors:

1. The energy of the individual photons

Energy is directly linked to wavelength (the "colour" of the light). Microwaves will transfer more energy at the same intensity than radio waves. Visible light will be higher than both, and getting up to X rays or gamma rays will allow to magic to impart energy at a higher rate.

2. The intensity of the radiation

This is the number of photons emitted per second (the "brightness" of the light). Higher intensity means a higher energy transfer rate.

Balancing these two

An object has a colour because it absorbs some wavelengths of light, and reflects the other wavelengths that result in its colour. This means that magic users may have to use the correct wavelength to be absorbed by their target. As a general rule, the shorter the wavelength the more likely it is to be absorbed. (Most things reflect radio waves, but gamma waves are pretty much lethal to everything.) This means that a higher level magic user may be able to use higher frequency radiation, which lets them use magic on more difficult targets.

Some frequencies can pass through certain objects, such as a window which is transparent, but reflects a small proportion of the light that hits it. This could be taken into account by your magic users.

The intensity of light will change the rate of energy transfer (and the speed of spells). Perhaps higher level magic users can use higher intensities?


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.