27

The Character is Taken Back to a Spot in His/Her History In Edge of Tomorrow the character is set back to the first day of enlistment, several days away from where most of the action is. In Groundhog Day the character is sent back to bed at the beginning of the morning. In either event, the character has to re-win all the little victories between; and can ...


21

Y1900 problem. Time machine software has a bug that prevents it from correctly handling years before 1900. Despite all efforts, people still think it's a hardware issue.


17

This is a bit strange, but maybe time starts in the year 1900. For some reason, the universe began in the year 1900, and everything that appeared to happen before that actually didn't. Since you can't time travel to where there was no time, you hit a barrier at the year 1900.


14

Possible limitations for the resetting-ability: Destination limited to special points The protagonist can't use his ability to jump back to any point in time, there are some restrictions. For example it has to be any midnight. Startingpoint limited to special points The protagonist can't use his ability to jump back from any point in time, there are some ...


13

It uses a nickel-iron signature as a lock-on to stabilize Time machines don't really exist, handwavium all around to justify them. The real question here is just how to justify picking any given year and using it as a backstop for the time machine. So I did some digging, and the nickel-iron battery was invented in 1899 by Waldemar Jugner, later improved by ...


9

Time divergence and human error. Lets say you get into a fight and someone cuts your arm off because you are a worse fighter than your opponent. So the next time you know what your opponent will do! Unfortunately your opponent will not know what you will do, so your opponent will simply react to what you are doing. You wont return to the exact same spot at ...


9

Time Machines are Electrical in Nature, and timelines can't be breached by technology exotic to the time. It IS possible for a time machine to go back in time, but there is a catch; the time machine cannot carry materials or devices that could not have existed in that time. So, for example, your time travellers can't wear polyester clothing if they want to ...


9

How can it be set up? By the governments agreeing to it, as you mentioned. Should it be more efficient for the computer to synchronize and the internet to all run in the same time zone (same clock, same time, same number)? Not really. For the computer it's just a matter of keeping the UTC time and then adding/substracting the local offset before showing ...


8

In classical fairy stories, people who entered a hill of the fae for a single night of partying would return and find that many years had passed in the real world, without themselves having grown any older. Usually, their spouses have died and their children have grown up. Ursula Le Guin has a science fiction version of this in her 1964 short story "The ...


7

They don't know In theory they should be able to but anyone who tries fails to return. Automated testing time machines also fail to return. There is no sign of them ever arriving. The scientific community is stumped. The first time machine went back to the year 1900AD Since then, no machine has been able to go back earlier. Scientists suspect the ...


6

It's not a reset, it's a recall. Instead of their power letting them say "I will now send my consciousness back in time by 3 hours", it instead lets them say "In 3 hours, my consciousness will be sent back to now". They can't cancel it, and they can't set a new reset point until their memories have been sent back, in either timeline. ...


5

Alright, so first off go lookup the plot of Avengers Endgame and SOMA. I’ll wait here.... Alright, here we go. So in Endgame, the characters are able to travel through time quite freely, (as long as they have fuel to do so) BUT, any changes they make to the past will create a new timeline instead of changing the one they are in. This is because when you ...


5

Nuclear class explosions cause ripples\markings in space time that the time machine uses for targeting. The Tunguska event is the oldest explosion we know enough about to target.


5

The TV-Show "Rick and Morty" did something similar recently in "The Vat of Acid Episode". It seemed to be a reset device as you suggest, but since the main protagonist considers himself to be above needing time travel, it wasn't really a reset divice. Instead the device transports the users consciousness into one of the many parallel ...


5

Two Suggestions drawing inspiration from Re: Zero - Starting Life in Another World and Steins Gate (both great stories involving very similar premises) Re: Zero - Starting Life in Another World Re: Zero - Starting Life in Another World is a Light Novel/Anime you could take inspiration from. The protagonist has a similar power with extremely large drawbacks. ...


5

Your protagonist's biology doesn't reset. This means that if they wipe out on a motorcycle because of loose gravel on the road and break their arm, going back in time 2 minutes before the crash will lead them to "spawn" on their motorcycle with a broken arm. It keeps them from using it as an injury-avoidance technique. It also means they keep aging!...


5

We can do this on timescales on the order of 1 minute at the moment, if you'll allow me to stretch the boundaries of the question a bit. There are essentially two ways to do this: Slow light, where the refractive index of a medium is drastically increased, in the process slowing down the pulse velocity of a beam of light. Stored light, where the quantum ...


5

How can it be set up? Governments pass laws (probably on a national or regional basis) to mandate clocks be set a different way, and when the time to change rolls around, people update things. Not too difficult to set up legally, but probably hard to enforce — see, for example, people in western China, who sometimes run their own clocks differently from ...


4

You cannot trivially overclock a human brain. You are limited by various important things, including the speed at which signals propagate along axons, and the maximum signal pulse rate, limited by the refractory period of nerve cells. You'll need to increase both, and you'll need to increase them proportionally and throughout the brain so that the brain ...


4

Light wavelengths double as they enter my eyes. Visible light becomes infrared, UVA becomes red, UVC becomes blue. What does the world look like to me? You won't be seeing that much. The transmission spectrum of our atmosphere has several hills and valleys. Our window of 380-740 nm will become for your eyes 190-370 nm. As you can see from the ...


4

Time scars. The first time, you reset, it's easy. The second gets harder. The third, harder yet. No, this doesn't involve the trust issue, unless perhaps the character has to learn to trust the people who figure out the problem.


4

The protagonist does not reset, they get reset To prevent the protagonist from resetting at will you could make it so that instead of resetting time themself they can allow someone else to reset time (and only the other person keeps their memories). You could further restrict the number of uses by only allowing the protagonist to give someone the ability to ...


4

Limitation 1: This is not a get out of death free card! Using this power takes concentration and time. If they get shot they will not have that time. Limitation 2: There is a time limit. They can only go (say) one hour back. They can't go around this by multiple jumps. If they have seen some version of ten o'clock, they will never be able to go back ...


4

Aging and nutrition Everyone requires daily nutrition to stay healthy [citation needed]. If someone walks into a time burst, they start to age rapidly, including their metabolism. Unable to get out because of time shenanigans[citation needed], they would die of thirst. With 50 to 100 years of sunlight directly on them inside the time burst, they quickly dry ...


3

Just some ideas : An entity that guards the flow of time / fate, like if someone can alter fate, depending on how huge the effect, it might be ignored, once or twice, but repeated use, the user might feel something or get some kind of warning, until they meet with the entity itself the rest is up to your imagination. The protagonist think the only one ...


3

There are three main approaches that I know of. Fixed Time There's no difference in time between alternate worlds. Time passes at the same constant rate for both places, so a year in World A is the a year in World B. Useful if you're doing a lot of world jumping between locations, like Planar Travel in a D&D inspired-setting, or something of that ...


3

There are a lot of options, depending on your world Depending on the rules of your portal world and the specific method in which you enter it, almost all aging scenarios are possible and many have been done before. Rather than list all the examples, I'm going to look at one scenario, and calculate the aging options in it. We are going to look at the ...


3

Using too much power could damage the machine With the current V1 Delorian time machine, the further back in time you go, the more power/fuel is required. 1.21 gigawatts will take you back 350 years or so (which right now is around 1900). Using more power than that could risk burning out the flux capacitor, making it a one way trip if you go back any ...


3

The time machine was invented in 1900 The time machine can only transport a person to the past of the machine itself. Much like how a train can only get you as far as the tracks go, some iteration of the machine was first constructed in the year of your epoch date. It would have been an early version, probably not functional at all, but the core remains ...


3

Carrington Event If you are a little flexible about the year you could make a connection to the massive solar flare known as the Carrington Event which happened in 1859. https://en.wikipedia.org/wiki/Solar_storm_of_1859 Perhaps in the story, that event wasn't really a solar flare, but an electromagnetic time disruption caused by an early botched attempt ...


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