I mean can time be controlled within an area or even a small portion of space?

I would like to mention time-bombs, which either reverse time in a radius of explosion or take time forward. Also nanobots which can control time within tiny areas.

Time span can be controlled.

Is this theoretically possible from what we know about time or is it only fiction?

I have an interesting theory that time can really be controlled locally. There of course is a blended edge at which locally controlled time is blended with current time. However, locally controlled time works differently for objects that were or will be there before or after the current time for the span set and objects that weren't there in the past or won't be there in the future throughout the time span set.

I mean if you reverse time for a zone or take it forward, the slip-through objects were there or will be there for only a certain amount of time (they simply slip-through this area on their way) and thus can't exist there for more or less than that very time. However objects which were there all the time can be reversed to a point back in time, but objects which are taken forward much depend on what could happen in the future to this object, thus it can either stay in that area and we'll see its future in the current time, or it will disappear in the time zone. But since local time is ahead and global time is behind, we won't have this object anywhere anymore, because in our time outside the time zone it doesn't yet exist, but within the time zone at that future time it doesn't already exist.

The human idea is the same.

Imaging you (you-1) are walking with a reversing time bomb in your hand and stop suddenly because you see yourself (you-2) appearing out of nowhere. You-2 starts talking to you and you-1 answer, this goes on for some time until you find yourself (you-1) walking forward while you-2 starts slowly disappearing and then you come to the spot where you-2 was, turn around and throw the reversing time bomb at the spot you were several minutes before. At this moment you become you-2, but in fact you are you-1, whereas you holding a time bomb appears in the local time becomes you-1, while in fact he is you-2. Current you-1 cannot intersect with you-2 outside of what had been done before, you-1 do exactly the same movements the previous you-2 did and say the same words.

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    $\begingroup$ I vote to move this question to physics.se $\endgroup$ – Asqiir Jul 12 '18 at 9:53
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    $\begingroup$ @Asqiir It's fine here, no need to move it just because it might be on topic elsewhere $\endgroup$ – Tim B Jul 12 '18 at 11:52
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    $\begingroup$ can a really good kiss count as a time slow? $\endgroup$ – Reed Jul 12 '18 at 13:06
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    $\begingroup$ @Asqiir btw if you close the name of the site in square brackets, ie [physics.se] it creates a magic link: Physics $\endgroup$ – bendl Jul 12 '18 at 18:15
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    $\begingroup$ Does the time need to be "translated" for matter, or is simply affecting the perception of those present enough? $\endgroup$ – user10328 Jul 12 '18 at 20:13

In modern physics, the only thing which is capable of altering the flow of time with respect to two points in space is gravity. In general relativity, the passage of time and gravity are inherently entwined, so "time travels slower" near massive objects. If you have a very massive object (as in black-hole massive), you can noticeably distort time. Of course, given that you've got enough mass/gravity to distort time, you also make a mess of things in space as well. If you've got enough mass to slow things down meaningfully, you most likely also have enough mass to simply rip matter into teeny-weenie bits, which probably makes a bigger impact than the time slowing.

Other than that, time manipulation effects are 100% science fiction. Even stuff that's quite far from what I would call "nanobots controlling time" like wormholes back in time are still considered to be science fiction as they require that our current theories work perfectly in extreme situations and call for exotic forms of matter that we literally don't even see whispers of.

At the very least, if you are inventing such a science fiction device, pay attention to whether or not it could be used to create a perpetual motion machine or infinite energy. It's really really easy to accidentally make a pseudo-physics which permits time manipulation that also lets you do cheap tricks (like gathering the energy from a nuclear bomb, then using time travel magic to rewind time for that bomb and set it off again). You either want to come up with a rationale why your approach cannot create infinite energy, or create a world where your physics won't break down in the presence of such infinite energies.

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    $\begingroup$ @DarthDonut That, of course, assumes there is almost no energy cost associated with the time travel compared to the energy event being harnessed. It is extremely doubtful any form of time travel will be energy cheap. Also, time machines can be expected to break before they can generate infinite energy. $\endgroup$ – a4android Jul 12 '18 at 7:38
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    $\begingroup$ "time travels slower" near massive objects... from the perspective of a different observer. Time passes normally for you and the observer, regardless of acceleration or the gravity that's experienced, but they'd disagree on what the other would have been through. That's assuming you're not making a blackhole, in which case nobody would know anything about anyone. $\endgroup$ – isanae Jul 12 '18 at 8:09
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    $\begingroup$ +1 for the issue of infinite energy and other shenanigans. This is not specific to time travel, as it applies to any scientific discovery or magical ability, but it can completely wreak the suspension of disbelief of the readers when one realizes that there's a way to create infinite energy/matter... $\endgroup$ – Matthieu M. Jul 12 '18 at 8:14
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    $\begingroup$ @MatthieuM. : True, even just a simple portal system can do it, by placing two portal upon each other horizontally, letting a magnetic object to fall infinitely, and putting coils around it. $\endgroup$ – vsz Jul 12 '18 at 8:22
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    $\begingroup$ @BladeWraith Paradoxes like that only tell you the physical model is wrong. Physicists have a mantra" "Infinities mean there's new physics ahead." Any time travel where you use the same fuel earlier will prevent the first time travel from happening. I've published enough articles on time travel not to believe in infinite loops. $\endgroup$ – a4android Jul 12 '18 at 9:11

Under currently understood physics, time cannot be sped up or reversed in any way. However, time can be slowed down with the use of gravitational wells or extreme speed (which essentially equate to the same thing at some point). This leads to the possibility of using small black holes to slow down time in specific areas to mimic some of the effects you were listing. Theoretically, these black holes could be controlled through electromagnetic fields if they were highly charged enough (see: https://physics.stackexchange.com/questions/64379/do-black-holes-have-charges).

However, in no case could this reverse time. Additionally, I think nanobots would be impractical given that they would have to carry around black holes at insane speeds. However, speeding up time could be mimicked by slowing down time for everything around whatever you want to speed up. This could lead to some interesting scenarios if you could weaponize a black hole that's made entirely out of electrons or something.

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  • $\begingroup$ There is one way to speed up time: just be in a reference frame in which time is slowed down from the other guy's perspective. $\endgroup$ – Ray Jul 13 '18 at 5:28

Any way I try to handwave this, it goes wrong or very wrong. From less to more nasty (or from more fiction to less fiction):

  • It works, it causes the particles inside to evolve backwards in time. Pretty much nothing special happens, as most phenomena has time symetry. Perhaps a few dedicated experiments can figure out something is going on.
  • We just say it works like a tape recorder. We throw an object, and the detonate the time bomb in the path of the obejct. The object is on the other side, beyond the radius of the bomb... but time inside is reverted... will a second object sudently appear? This can create time duplicates. We could get free energy.
  • There is idea in science that antiparticles are particles traveling back in time. If this is true, and the bomb reverses time... Everything inside is antimater for the outside, and everything outside is antimater for the inside. Anihilation ensues, huge nuclear explosion.
  • Let's say we break the principle of universality to allow different laws of physics to work on different places of the universe: Everyway the arrow of time goes one way, but in a bubble it goes the other. Now you have an edge, that will split apart atoms and whatnot, we have runaway fission, a nuclear fire ball.
  • Let us say, we change it smoothly. Time goes normally outside, but in the inside time goes backwards, this means that there must be an event horizon at which time is stoped. We have created a gravitational well, so strong that it can stop time, for all uses and purposes we created a black hole.
  • Let us say, we use wormholes instead. We need to bring the past to the future. However, traversable wormholes works both ways. If we want a single way wormhole, we are talking about a whitehole-blackhole pair... with a blackhole in the past and whitehole in the future. Even if things couls survive the fall in the blackhole, the whitehole would push them out in all directions (they explode).

And all that without saying that we need infinite energy to make it work.

I must conclude that for this to work in your world, you will have to consider a universe different from ours.

I only have a couple of solutions:

  • This is a universe where there is real and imaginary time, and there is some phenomenon that allows to rotate time, allowing to change the flow of real time (making some or all of it imaginary, or even reverting real time) without the need of gravity.
  • The universe is a simulation, and it has been programmed to allow such thing.
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  • $\begingroup$ You have a very interesting thought there. I was thinking about it a lot. Earned myself a headache the previous night in fact. If we throw an object and then blow up a time bomb in an area the object earlier passed then as time goes in reverse in that area, the real object must start disappearing and the very same object should start appearing first at the edge of the time-reversed zone and then start moving backwards in the direction it was thrown from, when it exits the time zone it simply disappears withing the time zone and starts reappearing later in time after it had been thrown before, $\endgroup$ – SovereignSun Jul 13 '18 at 4:34
  • $\begingroup$ The real time for this object shouldn't change if it initially was outside the time-reversed zone. The object wasn't there at the time time went in reverse so we only allow time to show us the object in the past, itself and its state, movement, etc. $\endgroup$ – SovereignSun Jul 13 '18 at 4:37
  • $\begingroup$ However, if we time-reverse an object which was in the time zone all of the time from now to years in reverse then we do reverse the object, because the object is already there at the time reversed from current time. $\endgroup$ – SovereignSun Jul 13 '18 at 4:38
  • $\begingroup$ The same goes for taking time forward. $\endgroup$ – SovereignSun Jul 13 '18 at 4:39
  • $\begingroup$ @SovereignSun If bomb reverts time of all the particles that passed the area, given that they were there but no longer, it would look as if the bomb attracts them, which is why I started thinking of it in terms of gravity. If the bomb does not affect objects outside its radius, then we could get time duplicates, that if you can extract, will allow for free energy, as I mention in the answer... Are they the past of another object, and we have paradox? - on that thought, see the no-cloning theorem, the duplicates would diverge at quantum level. $\endgroup$ – Theraot Jul 13 '18 at 6:08

if we accept that time is global to the universe, with local distortions in deep gravity wells, then no, you cannot have local effects.

IF you also postulate alternate universes and that they can be created, manipulated, and destroyed on the fly then you could:

  1. wrap a part of our universe in a pocket universe
  2. change the rate of time flow in the pocket
  3. open the pocket to restore the part removed

that would have the effect of localized time alterations .. with a whole lot of hand waving at the physicists that are writhing in pain as they read this hokum. Enjoy.

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