I have a middle-aged character who is stupidly messing around with some very dangerous quantumly-entangled unobtanium. He accidently creates a localised time reversal field. After the field collapses a few minutes later, a dust-covered traumatised young boy emerges from the rubble of the destroyed lab.

This is not the fountain of eternal youth that he discovered but rather a way to reverse time in a localised field. This means that any normal person wouldn’t be able to remember their lifetime’s worth of memories, only the ones from when they were that age at the end of the transition. SIDENOTE This character of mine, let’s call him Bob, has an artefact made of applied phlebotonum that can, purely by coincidence (largely by design), provide him with his ‘lost’ memories.

Once Bob gets over the initial shock of what felt like to him an instantaneous (and painful) transition, he discovers, with further experimentation with the Unobtanium, that he has found a way to manipulate time. Bob can't explain how exactly, just that it does! (although he would never admit to not knowing how it worked!) He can reverse, slow and speed up time within a localised field. He cannot travel back in time. He cannot travel forward in time. He would just grow younger/older in the time-field and when he emerged it would only be a short time later in real-time!

He has also found a way, to reverse and speed up time at different rates. So he can use the field to research something for a long time and come out and it’s only a few minutes later in real-time (and if necessary use a fast time reversal field to get his younger body back). Naturally Bob doesn’t have much use for the slow age reversal time field.

I’m assuming that the energy from the Unobtainum temporal ‘explosion’ would provide his body with the energy it required to survive a rapid transition from old/young man to young/old man. I can require Bob to eat a lot after such an event to make up for any lost nutrients etc. But what happens in the slower time fields…

Question. If Bob can survive an almost instantaneous time transition from a middle-aged man to a young toddler without any food or water, would he require such for a ‘slower’ speeded up rate of time? I.e. if he experiences several days/weeks/months/years inside the time field would food and water be needed?

Would it be that the almost instantaneous age reversal/progression could have slightly different biological requirements than the 'slower' time field speeds; what would explain this?

I need to figure out if I need to stockpile large amounts of food and water before Bob initiates the ‘slower’ time fields. Urgh, suddenly had an image of what happens after all that food and drink is um, eaten and drunk. If there is a way to limit the amount of literal S%*t that would pile up - That would be great!

Handwave away the energy requirements for all this. The Unobtanium provides all. I've used the science-based tag purely to limit scenarios to real-life possibilities and not rely on magic or pseudoscience, after all none of this is possible anyway. I'm working on the premise that oxygen can still make it through this temporal field. Light can too but it will be diminished. There are lots of related questions to the characteristics of speeded up/slowed down time, so for the time being I'm not too worried about all of that very important background stuff.

Bonus points for anyone who can answer whether any of Bob’s scars would be removed while in the reversal field? (I figure that any scars he had when he was a young boy would remain but any from his adventurous youth would be gone – but I could be wrong)


2 Answers 2


I'm fairly wary of the mass difference. Your initial transformation, of adult to child, might use up the extra mass for energy while transforming, or it might discard the extra as dust, or both. It is possible to make something smaller from something bigger, that is, discard mass. However, to build it up again without raw materials seems really unlikely. I would say that the body could only grow (physically get bigger) only a little bit before the mass requirement hit Bob, and he would need to eat - possibly altering his growth pattern since he would be following a feast-and-famine metabolic pattern, not regular small meals pattern. Creating matter from no-where is really problematic, and his body would have to process the food to rebuild his body, as well. There might be a little bit of hand-waving involved, so that anything he has eaten can be used directly in a quick transformation as raw materials, or that the speed at which this metabolism and growth happened triggered the body to very efficiently use everything it could in the food and drink, and produce minimal waste - there would still be some, though. His growth would be very strictly limited by his ability to replace the lost mass, or else he would face consequences for overgrowing his bodily resources.

For temporal transformations where the mass difference is little, though, it might be possible to be more flexible, or give Bob a higher tolerance. Quickly going from age twenty to thirty probably will be more about almost cosmetic changes (subtle differences in wear-and-tear, and physical biological properties) - though it will likely still stress the body a great deal, and will probably use energy sources (like food, or stored fat) to offset some of the strain. It probably won't take the same amount of energy as aging the normal way, since some expenditures of energy (like keeping the body warm or moving over years living vs. minutes while transforming), will not be reproduced. Covering the same range of changes more slowly would take more energy, since the body has to "live through" the changes, and cover the intermediate stages, and spend energy moving around. I suspect it will probably also be a lesser shock on the body to more slowly age up or down, and take some of the energy as food, rather than trying to induce a instantaneous transformation.

I would expect that if you want a more "magical" transformation, where mass differences and state-of-being at different ages (details of appearance like haircuts, weight, or scars - and maybeso even clothing) are easily and faithfully reproduced, you will actually have to deal with the eventual ability to travel forward and backward in time. I can't see any other way that can be done.

The other possibility, if you're altering the state of your person and not actually sending them through time, would be to have the temporal field interact with something like body-memories to "rejuvenate" or de-age them, superimposing whatever information there can be had about the body's prior state over the person's current state, and providing energy (and some transformational mechanism) for the cells to re-write themselves to what they think they're supposed to be. Since that includes the physical state of the brain, the memories stored will also be reset.

Its kind of like rolling back changes made on a computer, to undo problems - with enough extra energy to also "roll back" physical changes. More like physically tricking the system into thinking it is younger and letting it fix the discrepancies, rather than moving it around in time. Healing will actually reverse cosmetic wear-and-tear (aka aging) with only a little encouragement, so minor changes are very realistic, but bigger changes will still be tricky to explain when there's no mechanism for it.

Aging forward is much less tricky, it only need to speed up the metabolism and let everything else (perception and actions) speed up with them, which will accelerate the wear and tear, and also the perceived time. If they're doing and experiencing more because they're faster, and wearing down their bodies more in any given unit of time, they will be essentially aging much more quickly than normal, but experiencing more in that time frame as well. Your field pretty much encourages superspeed within its boundaries to "age forward".

With this setup, where it's more about physically tricking the body rather than superimposing the body of different times on the present, there would be some limitations in play. One limitation would be about the state of the body, things that were physically altered over time. A scar, for example, would persist because the injury happened, and without actual access to the time stream it can't unhappen. The flip side of the question is this - will the wounds re-appear out of nowhere as the person is aged forward (and changed if, for example, the wound isn't stitched the second time around)? Probably not, since the body is resetting, not accessing the original times. The transformations and 'resets' could minimize and eventually heal the scar into invisibility, as the area was healed and aged, and the scar tissue replaced by skin cells (which happens to minor scars over time, so just speeding up the process).

I would expect that other changes which require physical intervention, like haircuts, would also not be faithfully preserved. And, for things like muscle mass, or weight gain - I expect over time, the body will tend to equalize towards the genetic blueprint, for how the body is supposed to work. If someone gained a lot of muscle mass by working hard, or gained weight through poor diet, the process might originally remember some of it (those body-memories I mentioned) but would over time "forget" the original circumstances and modifications, and just work off the stable blueprint that is DNA.

  • $\begingroup$ I had thought of maybe tricking the cells into thinking they were younger/older but I couldn't figure out how to explain the 'slower' speed up time fields...and I was aware of the conservation of mass which is why I thought he would need food inside the field. He wouldn't really be using the fast forward time field to grow lots older...who purposely wants to age 60years in a few minutes?! So any ageing would be in small steps. Bob, used other test subjects to figure all this out... He's one of my characters who has so many chances to do good, but doesn't! $\endgroup$ Aug 1, 2016 at 7:46
  • $\begingroup$ @EveryBitHelps - I was having a harder time figuring out the quicker transformations, since the slower time fields are just playing with metabolism and using DNA to predict the difference, and modify the body to match. I ended up thinking that a big transformation would skip the middle steps, just superimpose the end state over the beginning (as determined by "body memories" or DNA). Maybe the machine pulls more power when the image is very "different", and uses the extra to forcefully transform the body, but when there's less "difference" it just supports the body in altering what it can? $\endgroup$
    – Megha
    Aug 1, 2016 at 8:55

Your fields are allready so far away from hard science, that you might as well handwave the food away as well.


Mark the position of a single atom in your body and write down the datetime. Now wait five seconds. Now mark the position of the atom again and write down the datetime. Now wait five seconds. Mark the position of the atom again and write down the datetime.

Connect the marked spots with arrows.

These arrows together with the noted times signify the passing of time.

Now try to split the arrows in such a way, that you get one arrow denoting how you moved between two measurements, and one that only shows the movements that caused your body-cells to age. You get no further information, than what you have written down so far.

This is, what your time-fields can apparently do absolutely effortlessly, otherwise your protagonist would have just exited the time-explosion at the point where he had entered it's radius previously. [Not to mention that his backside would start moving forwards again, before the frontside had finished moving backwards; messy.]

Without knowing how your machine does that, there can't really be a "science based" answer for your question. Or to put it differently: If you allready ignore causality, and destroy space-time, it's a little bit late to worry about basic chemistry.

  • $\begingroup$ Yeah. I think a lot of world building takes an 'impossible' scenario and trys to find away to make it sound plausible. Eg FTL. I kinda had thought about half the body changing while the rest stayed the same (it had been mentioned in precious questions) but my Bob is completely covered by the field when it starts and ends. This means that his entire body is going through an 'equal' amount of change. He cannot move through the field. He'd be torn to pieces if he tried that! $\endgroup$ Aug 1, 2016 at 12:26
  • $\begingroup$ @EveryBitHelps What I meant to say with this was, that it probably would be best to abandon the "time" aspect in favor of something that would give you the same results. I'll try to edit to reflect this. $\endgroup$ Aug 1, 2016 at 13:28

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