And what would be needed to expand this effect, scaling up to the size of a city, or maybe a country?

I've seen this question, and it seems that while one could do it with gravity, the effectiveness and side-effects would be rather undesirable. Please note that while I'm looking for a "plausible" mean to achieve this, I'd like to discard unfeasibility due to the lack of energy or material resources.

So, let's just assume we have an infinite stash of all materials, and an infinite amount of energy. But we still need to get humans inside and they must be able to live exactly as we do: same gravity, same pace and all: it would just be faster from the view of outsiders.

In short terms, the goal is to create a room, or even a city, where time flows faster, at the rate of at least 1 year per second. So, outside this place, I could see what would happen in hundreds or thousands of years.

Another restriction would be that this room cannot be too far from the outside world. I'm talking about maybe some kilometers at most.

Are there any "plausible" ways for this to happen? Please forgive me if this question threads on the lines of nuisance, I'm no physicist.

Also, if there aren't any known ways to distort time like this, are there any unproven theories I could use?

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    $\begingroup$ keeping it close to the planet would be hard. The two known ways for achieving time dilation are either gravity wells (which as you saw in your prior post, isn't useful) or moving at relativistic speeds. Anything else would have to be handwaved a bit, or employ applied phlebotinum of some sort. $\endgroup$ Commented Mar 16, 2015 at 18:48
  • $\begingroup$ Does "all materials" include negative-mass or other exotic materials? $\endgroup$ Commented Mar 16, 2015 at 19:04
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    $\begingroup$ Oops, I missed this part: "it would just be faster from the view of outsiders.", and that's a definite NO. The only known ways to control the flow of time only make it slower. Nothing can make it faster, unless you can make your room have more mass/energy than the entire rest of the universe. $\endgroup$ Commented Mar 16, 2015 at 19:36
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    $\begingroup$ The same way it is done already: make it a custom of your society for males to take females out on "Dates" and invent chick-flicks. $\endgroup$
    – Alec Teal
    Commented Mar 16, 2015 at 22:10
  • 2
    $\begingroup$ You would have a constant stream of old or almost dead people from the fast world to the slow world, "buying more time", for their fast world to find a cure to make them live longer. The slow world would look to the fast world as a way to go into cryostasis. $\endgroup$
    – Pieter B
    Commented Mar 17, 2015 at 15:28

12 Answers 12


You need 3 things:

  1. A Materializing/Dematerializing Cascade. This is a small region of space, no more than a few meters across, separating SpeedTown from the Boring World Out There. It is periodically swept by invisible, but incredibly fine-tuned and hyper-complex energy fields, precisely controlled by an impossibly powerful friendly AI genie. Every 10 seconds, external material objects that have entered the Cascade are destructively scanned and uploaded to a simulation, 'inside' the room. Every 10 seconds, information patterns that have been selected to be 'output' from SpeedTown are materialized, and pushed outside the cascade.

  2. SpeedTown: A powerful simulated city. Your destructively scanned citizens live their lives here. Because of the power of the computronium substrate, the simulated humans therein are perfect simulations down to a subatomic scale (quarks, gluons, electrons and photons in a simulated quantum foam). Not only that, but the substrate is sped up by a factor of about 30,000,000, so that it almost becomes true that every day is an eternity. The 'inner' walls of SpeedTown are rendered to depict the slow, glacial-speed world outside, where birds appear frozen mid-air, raindrops float and people appear to move with the speed of geological processes. The 'outer' walls of SpeedTown, visible from the outside, depict an incredible blur, where new buildings pop in and out of existence in seconds, and individual humans within are just blurs of speed, whereby the whole city seems to be a fast-moving gas of some sort.

  3. A friendly AI, to handle the impossibly complex transitions in and out of SpeedTown, as well as prevent any world-annihilating device completed within to be transferred outside, as well as repopulating from a (troublemaker-corrected) backup in the case the people within manage to blow their entire simulated universe up somehow.

What would happen?

Well, assuming this is built today, somehow, in about 3 minutes, or say 200 seconds, the SpeedTowners will have had two more centuries of technological progress to build on the industrial revolution we so recently started.

In about a day, people within will have been conscious and civilized for as long as Homo Sapiens Sapiens has existed as a species. They will be as far from us as we are from the invention of language.

In about 2 years, they will be as far away from the outsiders, subjectively, as we are from the dinosaur era.

In about 500 years, they will have experienced a span of time equal to the interval reckoned to have passed since the Big Bang.

What does that mean?

  • Sending someone inside, for a minute, will have them returned aged by 60 years, or perhaps dead.
  • Sending someone outside, for two minutes, means that all of your friends inside will be dead, assuming no cure for aging is invented while you were away. Either way, you'll be a distant forgotten memory at best.
  • The people inside will, if SpeedTown is sufficiently large to accommodate a full industrial infrastructure (or if the AI Genie is particularly accommodating), likely progress technologically beyond our wildest dreams, within the limits of the simulation.
  • There will be virtually no trade, since the outside goods will take centuries or millenia to be delivered.
  • The culture and civilization of SpeedTown will diverge exponentially from that of the Boring World Out There.
  • The people inside will likely destroy their world on a regular basis, unless you expect mankind's wisdom to somehow increase with time.
  • Anything coming out of the materializing cascade should be treated as a potentially lethal alien artefact.

But is this even physically possible?

Depends. We currently know of no way of creating a de/re-materializing cascade, but there is nothing that technically forbids it, down to the Heisenberg limit itself. Given that as far as we know, most (all?) consciousness-related processes happen at a molecular level, the level of recording precision should be sufficient for a physically correct capture.

Now the more interesting question is whether a 3e7 speedup is feasible or not. A lot of it comes down to the level of precision we can shave off and the density of the computronium substrate. If a neutron-star level density can be achieved ($5.9×10^{17} kg/m^3$), a one cubic meter substrate would have a computational mass more than sufficient for the purposes of simulating an entire city at the specified speedup with ease.

If we have a denser-than-platinum but less dense than degenerate matter computational substrate, we can probably achieve 1:1 space mapping and still achieve the speedup.

  • 1
    $\begingroup$ I wonder whether there's some entropy constraint that prevents us performing an accelerated simulation to the level of quantum foam using an equal volume of space. But simulation is the first thing I thought of too. $\endgroup$ Commented Mar 17, 2015 at 1:27
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    $\begingroup$ @SteveJessop, it is nowhere written that it must be a perfectly accurate simulation (for instance, there could be a conspicuous absence of pi mesons, or of deep geological processes), or that it takes a 1:1 relationship. Perhaps it's the size of the Sahara, and goes down 10 km deep to simulate a city the size of Singapore. Perhaps the reality is only simulated enough to be believable to those inside it... $\endgroup$ Commented Mar 17, 2015 at 1:32
  • $\begingroup$ @SerbanTanasa Yea it doesn't need to be a perfectly accurate simulation. I really like your answer, I haven't thought of a simulation-based solution before. But is it "feasible"? When you say the substrate is sped up by a factor of about 30,000,000, what really is happening? How is it being sped up? Think we could fit @celtschk's answer into this? $\endgroup$ Commented Mar 17, 2015 at 13:44
  • $\begingroup$ @ConradClark, see edit $\endgroup$ Commented Mar 17, 2015 at 21:07
  • $\begingroup$ This is great, although technically you haven't managed to "get humans inside"! $\endgroup$ Commented Mar 18, 2015 at 12:35

It's not possible.

Time dilation works the other way. You can theoretically accelerate to near light speed or sit in a massive gravity well and time will appear to pass more slowly. To speed up time for a small section of the universe, you would need to do those things to everything except a small section, which can't be done.

Even if you mean to slow down time in the small section, with the restrictions (identical gravity, in a fixed place, and science based) this can't be done. Even allowing for infinite energy or materials. There simply is not a way, known to physics (or any theories I know of), to get time to flow that differently between two places that are near each other, with identical gravity, and based in science.

Think about walking over the boundary to such a place. Your nose could experience a year before the back of your head made it through. Your nose would promptly die and rot off in the six months before the heart was back in sync with it. When switching to fantasy to complete this idea, do thoroughly consider the boundary effects of having such disparate time flows.

EDIT: Thanks to RBarryYoung for pointing out the OP wanted to speed up time in a small area, not slow it down.

  • $\begingroup$ It is physically possible, but no human being could survive it. Orbiting close to a small black hole could do it. Tidal forces alone would shred anything and anyone pretty fast though. +1 for the temporal gradient problems though. $\endgroup$ Commented Mar 16, 2015 at 19:30
  • $\begingroup$ @RBarryYoung I'm not saying one year per second is impossible, I'm saying it's impossible to achieve such an effect in the situation described. $\endgroup$
    – Samuel
    Commented Mar 16, 2015 at 19:34
  • $\begingroup$ Regarding the boundary, if it was a gradient over two kilometers (some kilometers at most is acceptable) then the gradient is only 4.4 hours per second per meter. Assuming a human, presented front first, was traveling through this, they would experience 2.19 hours per second gradient from front to back if they were 50 cm thick front to back. This would make their front about 8 thousand times faster than their back. Still too much for a human travelling slowly, but if you increase their speed, using a rocket sled or similar, I expect you can get them though the gradient quickly enough. $\endgroup$
    – Adam Davis
    Commented Mar 17, 2015 at 11:00
  • $\begingroup$ Given a rocket sled, though, I expect that the OP might allow a 10km distance or more. And the experience would be entirely unpleasant. Getting people in and out still poses a problem similar to trade - if you send people in once per second, the interior would only see one person per year, and if you could only receive one person per second they could only send one person per year. The first people in the bubble would be very lonely unless you can manage mass transportation or teleportation. $\endgroup$
    – Adam Davis
    Commented Mar 17, 2015 at 11:02
  • $\begingroup$ Thanks for the answer, and also +1 for the temporal gradient issues. I haven't thought of this before. $\endgroup$ Commented Mar 17, 2015 at 14:02

Here's one method that doesn't rely on either gravitational time dilation or simulation:

If you look at the basic equations of quantum mechanics, you notice that if you scale all masses by a common factor, you'll get essentially the same physics, just at different length and time scales. In particular, when all masses are multiplied by a factor $\lambda$, all lengths get scaled by a factor $1/\lambda$ and all processes go faster by a factor $\lambda$, The latter being exactly what you want. (Caveat: I don't know enough about nuclear physics/QCD to say for sure that this is the case there, too, but I suspect it is; indeed I seem to remember having read somewhere that the mass scaling is a requirement for the standard renormalization procedures — the way how infinities are avoided in quantum field theories — to work.)

Now the question is of course how you could scale all masses. Well, according to Higgs theory, the fundamental particles get their rest masses from interaction with the Higgs field (all other mass contributions are ultimately just kinetic/potential energies which automatically scale the right way). So one might think that if you find a way to manipulate the Higgs field, you should be able to scale masses that way.

How to apply it to your specific requirements

A speed-up to one second per year would be a factor of about $3\cdot 10^8$, that is, you'd have to scale masses up by that amount. This would also scale down sizes by the same amount, so a human would shrink to about half a dozen nanometers. That is, you could easily put a complete city into a matchbox.

However there's a caveat: Your human would now weight about $10^{10}\,\rm kg$. I guess that would locally give quite strong gravitational fields (gravitation does not follow the scaling law; correspondingly quantizing it the standard way does not work). So quite possibly you'd not be able to achieve that large acceleration without adverse gravitational effects, unless you're also able to locally manipulate the gravitational constant so that also the gravitation plays nice with it. Note also that a strong gravitational field would add a slowdown counteracting your speedup; this is another reason to decrease it.

So in summary: You'd need to be able to manipulate the Higgs field to get the speedup (combined with a shrinking), and additionally to locally manipulate the gravitational constant (to avoid the gravitational effects of the increased masses). But if you can do both, you'll get a sped-up city in a matchbox.

Further caveats to the speed-up

The speed-up inevitably means that any radiation coming from outside will be seen as very low frequency in your town. That means you'll have to ensure sufficient thermal insulation in order to prevent your town from freezing. Similarly, any radiation coming from your town will be shifted up in energy; with one second per year, even visible light will turn into gamma radiation. So to protect yourself, you better surround that city with appropriate radiation shielding.

If you settle with less extreme speed-ups (say, just one day per second), you'll reduce the problems with the radiation from the city; however it will still be very hot when viewed from outside; better make that matchbox out of fireproof material.

  • $\begingroup$ Really interesting answer! Pointing out scale issues and all. Thank you. To be honest, this being my first question at WorldBuilding SE, I'm lost on what question should I accept. There are a lot of answers with a lot of effort, which I upvoted, but I can't decide on which one gets the mark. $\endgroup$ Commented Mar 17, 2015 at 13:59

To expand on part of Samuel's answer, if we set aside the issue of how to achieve it, the result would be largely useless for a few reasons.

  1. The interface between the fast-time and normal-time areas would have a temporal gradient so severe that any solid substance in contact with it would be destroyed, not just for the age problem but for pure structural reasons.
    If your fast-time is running at 1000x normal (16m40 per second) and something is moving at 1m/s inside (relative to the inner frame of reference) it would appear to move at 1km/s observed from the outer frame. If that thing were straddling the border between the two frames the outcome would be "unfortunate".

  2. The vast bulk of energy for an ecosystem is solar, but if you're accelerating a bubble you're going to be depriving them of that energy. If we assume 1000W/m2 of power then our 1000x speed bubble would be getting 1W/m2. Without that solar energy everything goes wonky: food supply, carbon and nitrogen cycles and solar heating are the first ones to jump to mind.

  3. The other energy problem, assuming you have something in there using power, is how does whatever is inside the bubble source it's power? Fossil fuels are likely out, even nuclear is going to be a bit questionable for a period of hundreds of thousands of year.

Other aspects of the question cause more technical questions, but those 3 by themselves make the result of little practical use. You could maybe bypass problems 2 and 3 if you're somehow able to cram a lot of supplies inside that bubble, but problem 1 is going to need some kind of shielding bubble to make the gradient mostly vacuum. You're also probably going to have to insulate the thing from any EM coming in or out.

Quick summaries of some of the other issues:

  1. Being able to view the other frame is a problem in both mechanical and relativistic terms because of the speed of light at the very least.
  2. It would be questionable as to whether your inhabitants would have a sense of gravity since all the orbital forces are equally attenuated.
  3. The inhabitants would have no apparent motion of sun, moon or stars so their own sense of time would be an artificially created one. Realistically they'd have to fake a day/night cycle in much the same way as The Truman Show.
  4. After hundreds of thousands of years, the chances of the ex-humans inside the bubble being even remotely recognisable, on a cultural level if not biological level, is minimal.
  5. After hundreds of thousands of years, any viral or microbial life inside the bubble will have mutated to the point that the poor people outside the bubble will likely have no immunity to it.
  6. Your requested 1 year per second maths out to ~86,400 years per Earth day, one would imagine the energy needed to achieve this would have some rather unpleasant thermodynamic side effects... could actually throw in some ionising radiation as well in the form of gamma rays... you know, just for fun.

As noted, speeding up time in a local area doesn't agree with relativity.

From a layman point of view, think of a car travelling along a road. The car covers a constant 60 miles of road every hour, but if it's travelling up a 50% gradient the horizontal speed is only 30 miles an hour. The steeper the gradient the slower the car travels horizontally.
Reversing that, though, the car can't be made to cover more distance than it can on a perfectly flat road.

A relativistic time slow can be thought of being much the same. Increasing the amount of gravity will slow time down, but you can't reduce the effect of gravity below 0.

(If anyone knows the principles of relativity better than me and thinks that needs correcting, please do so :))

If you really wanted to do this anyway, even with all the problems, the only practical way of speeding up time in a chunk of the universe would be to remove it from the universe. You'd need to discover some method by which your chunk of reality could be wrapped up in a bubble of spacetime that was completely disconnected from our own, while still being manipulatable, and then cause the rate of time within that bubble to move faster than our own.
Imagine the multiverse equivalent of a hamster wheel with the inside spinning away at super speed while the outer context remains synced with the world around it.

That won't get you everything you asked for, as you need a 100% isolation between the pocket spacetime and the real one, so no observation would be possible.

The only thing that you need to hand wave is being able to manipulate the fabric of space time in such a way. It's not that much worse than some space travel techs, though if you're after hard science it might be too much of a stretch.

  • $\begingroup$ Thanks very much for the really detailed answer. I was still working around the energetic question, though I'm seriously considering shortening the gap to be 1 hour per second, instead of 1 year per second, since things are likely to get out of hand. $\endgroup$ Commented Mar 17, 2015 at 16:19
  • $\begingroup$ You CAN have an imaginary gradient to increase the distance to travel. This should work to speed up time.. $\endgroup$ Commented Aug 13, 2017 at 3:15
  • $\begingroup$ @Mathmagician it's a little outside by area of knowledge, but I don't think an imaginary gradient would work, definitely not by increasing distance to travel. There's a theory of imaginary time, adding a dimension to time to allow you to move at the same speed through time but perpendicular to normal. It doesn't work of space though, any gradient applied to the fabric of space serves to decrease the effective passage of time. Think of how the curvature around a black hole impacts things falling in to the event horizon. $\endgroup$
    – Kaithar
    Commented Aug 13, 2017 at 19:54

I just realized how you could do it. Given infinite materials, you could construct a 100% perfect and accurate computer simulation. Sure, it would take the processing power of a galaxy to model something as small as a city, but you have that - and more. With a computer of near-infinite power, you could have a simulation that was as accurate as reality.

  • $\begingroup$ "But we still need to get humans inside". How are you planning to make your humans enter the simulation? Matrix style? $\endgroup$
    – Mast
    Commented Mar 17, 2015 at 10:49
  • $\begingroup$ I think his answer goes off of the assumption that humanity might already reside within this simulation. $\endgroup$
    – Jax
    Commented Mar 17, 2015 at 14:43
  • 3
    $\begingroup$ void Populate(int startingPopulation){ for(int x=0; x< startingPopulation; x++) humanCollection.Add(new Human()); } $\endgroup$
    – David Rice
    Commented Mar 17, 2015 at 15:05
  • $\begingroup$ @DavidRice I sure hope you wouldn't actually program something like this in Java :-). $\endgroup$
    – k_g
    Commented Mar 17, 2015 at 21:35
  • 1
    $\begingroup$ eh, I'd probably just hack it together in perl (xkcd.com/224) $\endgroup$
    – David Rice
    Commented Mar 17, 2015 at 22:00

I think your best bet would be to open a portal to a dimension that time flows at a different rate. 'Creating' such an place would be fairly dramatic, but finding a place that 'exists' might be much more feasible.

The big thing is in either case, you'd have to be able to get all your 'people' there en mass, so that the first person doesn't age 10 years before his wife and children show up.

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    $\begingroup$ This doesn't really conform to the [science-based] tag on the question, which indicates a hard-science answered is requested. $\endgroup$ Commented Mar 16, 2015 at 19:31
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    $\begingroup$ @RBarryYoung I tend to agree with that assessment, but since I can't imagine 'creating' a room or a planet that time flows so much differently in a livable environment in this universe, I thought this might be a more 'realistic' story mechanic. $\endgroup$
    – bowlturner
    Commented Mar 16, 2015 at 19:46
  • $\begingroup$ @bowlturner I thought this might be a more 'realistic' story mechanic - I tried to be as close to reality as I could when I was faced with this "time" issue, and I came to WB as a last resort because I was almost sure it was impossible. I'm already preparing my applied phlebotinum and leaving reality out of this scenario. $\endgroup$ Commented Mar 16, 2015 at 20:09
  • $\begingroup$ @ConradClark as I said, I was giving an answer that I thought would work a little better, the alternate dimension could even be as small as an island if you want, with the ability to manipulate it in different ways, time being one. $\endgroup$
    – bowlturner
    Commented Mar 16, 2015 at 20:14
  • $\begingroup$ I agree with @bowlturner. Another dimension/reality/universe with it's own day and night cycle might make more sense. I can't imagine having to endure 42,300 years of sunlight then another 42,300 years of night. $\endgroup$
    – tls
    Commented Mar 17, 2015 at 13:33

So time dilation isn't the way to go, because that just makes time slow down, not speed up.

I think the only way you're going to be able to do this is by getting into String Theory (M Theory?) a little bit. Which is tricky, but I believe that it does allow for pocket dimensions where time doesn't flow the same way that it does in our perception of reality.

Maybe check with the people over in Physics?

At this point you're getting out beyond anything we can test, so you may have to go to the sci-fi equivalent of magic...


To expand further on Samuel and Kaithar's answers, it's instructive to examine the consequences of energy flow the other way.

So you've got some poor guy living in "the bubble" for a year subjective. A good rough number for metabolic processes in a human is 100 watts. During his year in fast time, he produces 3 gJ of thermal energy, and this must be radiated out into slow time (if it isn't, the guy roasts). This causes the bubble to radiate at 3 GW for one second, which is unlikely to be good for the surrounding area. At a distance of 10 feet, the power flux is about 28 MW/square meter, or 28,000 times the power of the sun. Larry Niven wrote a story which used the effect, and a sped-up researcher burned off the face of an associate with a flashlight.


The simulation idea is pretty fun. If not simulated -

From previous posts, it looks like the issues would be

  • a harsh time-dilation gradient
  • distance from normal world
  • high-energy radiation leaking to normal world and only low-energy radiation reaching fast world.

for something approaching real science, I think you would need to combine some of the ideas to overcome the gradient (eg shrinking over a long period of time and distance)

or just use greater distance, keeping in mind that at super high speeds, that distance can be covered quickly. your "room" could be on a figure-eight orbit between two hypermassive objects and your "normal" space could be a planet or solar system at the point of equidistance between those objects and far enough from both objects that the internal gravitational forces of the solar system are not overpowered by the distant hypermassives (so, the system is not being pulled apart). you need the countering forces of orbit to expose the room to an extremely forceful gravity well without turning the room into hyper-dense slush. and you need distance from normal world for extreme relative velocity.

your room is going to experience some extreme red-shift variations as it accelerates toward each super massive and decelerates away from each. So, there will be burns on the "front" side of the room and anything ahead of it in the trajectory, if it is emitting radiation.

at the point of least relative velocity (intersecting with the gravity neutral point between the hyper massives) the room could use a large energy burn (since the OP is giving us all the e we could need) to decelerate into the normal world. The normal world would have to exists as one of a perfectly balanced set of planets orbiting a binary star system (at minimum) with perfect radial symmetry and the timing or trajectory of the orbits would have to keep the gravity-neutral equidistant point (and all points of room's trajectory within the system) clear - otherwise, our room would have been colliding with or diverted by objects in the target system / normal world. That would take care of the gradient issue and distance, but leaving and entering the room while at velocity would not be an option - so, no walking in and out during time differential.

To throw another wrinkle in and solve the internal energy problem for the room (without resorting to storing high - energy radiation from the "front" side of the room), the room could itself be orbiting a high-mass, high density object and be counterbalanced by a larger, less-dense object for radiation shielding (this would require a double pendulum approach to orbits in order to have the shielding object on the front side of the high density object along its orbit while approaching the hyper-massives). The high density object (like black hole or dark matter) on the figure-8 orbit could be used as an energy source either in the emission of infrared radiation or . . . It could also be a star.


Slowing down time is simple. Speeding it up is tricky. The faster you go, the slower you experience time (relative to an outside observer) but as far as I know there's no way to cause your time to speed up relative to an outside observer. In theory though, you could create a small planet that's (relatively) stationary, and then orbit it at relativistic speeds, thus slowing down the observer's timeframe.


Put rockets on the room/city/country and aim it so that it loses velocity relative to the space everyone else is hurtling through...anti-orbit is an option, closer to center of Earth is another.

Time won't pass that much faster in the room though...kind of a lot of effort for not a lot of payoff.

Think blue clock:


  • $\begingroup$ Thanks for the feedback. My solution without the link will accomplish slowing time for the room, though not to the requested scale (which is indicated). The link merely gives a visual in-case the author wishes to understand the mechanism. I might update this answer again later with a sentence about relativity (the mechanism). $\endgroup$ Commented Mar 18, 2015 at 1:49
  • $\begingroup$ *Oops...meant to say it accomplishes speeding up time for the room. $\endgroup$ Commented Mar 18, 2015 at 2:02

Assuming that you are using a fast-moving planet to do this, one big problem would be what the planet would look like from the perspective of an outside observer, from the outside, the bubble would look slowed down. On the other hand, from the perspective of a person inside the bubble, the outside would look slowed down. So from the perspective of an outside observer, the effect would seem reversed, but from the perspective of an observer on the inside, it would seem as if everything else was slowed down.


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