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Questions tagged [time-travel]

For questions relating to travel in time. Such travel often involves FTL travel; consider also using the [tag:faster-than-light] tag.

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1answer
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Speed of light, Motionlessness, and Time Travel

i want to ask something I quote from some web and got this : 'According to Einstein’s Special Relativity Theory, time is affected by speed. It’s already been proven in the lab that subatomic ...
4
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3answers
286 views

Non-causality-violating FTL travel. / Can omnipotence beat causality?

While building my sifi world I dug into ftl-travel and encountered these mean bullies, causality and relativity. They told me I can't have faster than light travel, because effect can't precede cause ...
9
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13answers
5k views

What historical events would have to change in order to make 19th century “steampunk” technology possible?

I know this is similar to this question but I'm not interested in suppressing 20th century tech to create 21st century steampunk, but in creating late 19th century steampunk with fantastic, Jules ...
39
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12answers
15k views

What steps are necessary to read a Modern SSD in Medieval Europe?

So the main team of characters is traveling back in time from "modern day" to medieval Europe, arriving around the 1300s. Assumptions: They Know they are going, they have space and time to prepare, ...
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3answers
136 views

Preventing the Big Bang

I travel back in time to the Big Bang in my time machine. I am equipped with all the present day equipment I need. I locate the infinitesimal 'point' where the Universe would come into existence and ...
4
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5answers
179 views

Why would an omniscient immortal needs to record history?

There is a powerful entity, omniscient, omnipotent and omnipresent that came into existence since Big Bang. The entity do not interfere with the order of the nature but to observe it unwinds in the ...
11
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13answers
387 views

Forememory: What could prevent reiteration from working?

I use forememory instead of foresight, due to how the ability works. A cunning and creative person can remember five minutes into the future, and are smart enough to exploit it in any way possible. ...
13
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6answers
1k views

Time travel from stationary position?

This is my first question on this site, which I recently found and can’t get enough of. In many time travel scenarios, the machine is static in space. My question is how to explain this. For ...
13
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6answers
407 views

Could just a brilliant idea advance science by decades, or even centuries?

Inspired by this story, I started thinking. Let's say we have a person, from the modern day, who miraculously gets a superpower: He can rewind time, but retain his own memories. He can rewind all the ...
2
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9answers
393 views

If I travel back in time and do nothing, just being an observer, would that change the past?

This is how time travel in my question works: You go back to a certain point in time, physically, regardless of means. Be it a spaceship or a time machine. So you've reached to the past. You know ...
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4answers
223 views

I have two cellphones that are exactly the same, SIM card and all, and I make a call on one of them. What happens?

Say I had a cellphone, let's call it cellphone A, and made a perfect copy of it - SIM card and all - and let's call this one cellphone B. If I were to call someone on cellphone A, what exactly would ...
6
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2answers
201 views

How would a legal system deal with random groundhog day events? [closed]

I have seen similar questions about groundhog day but they were about either a single unique groundhog day or a permanent one. In this case, each day may or may not repeat. There are no limits so ...
1
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1answer
59 views

Superluminal signal to past (alien technology) [closed]

With our current understanding of physics it is not possible to send anything into the past (although GR mathematically allows it). Could an intelligent alien species with a 100,000+ year head start ...
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7answers
307 views

A Theory for Science-Fiction Time-Travel

From H.G. Wells onward, there have been many stories concerning the phenomenon of time-travel. Few of them provide a plausible mechanism. For my story I would like to put forward such a theory. We ...
0
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1answer
157 views

What will it cost me to travel through Time? (Part 1: Travelling forwards in Time - Time Dilation)

There are many questions on Worldbuilding about what item(s) a time traveller should take back in time in order to alter past events or even simply to survive. There has never as far as I know been ...
43
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27answers
14k views

How could a time traveler have prevented climate change [closed]

Let's say a Moon colonist in the future has discovered an alien time machine. A small remnant of humanity still exists on colony worlds in the solar system, but due to runaway climate change, they are ...
10
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1answer
232 views

Could the equator of a world be a closed-time like loop?

Most works of fiction have quite imaginative views of time travel. Mighty machines that teleport in time instead of space. Gaping portals in space that take you to another time. Mystical beings with a ...
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2answers
105 views

Maintaining assets during time jumps

I started to ask this question in the Writing SE, but realized that I want both a method and a mechanism, so decided that for the latter, I'd come over here. I'm building a novel where the MCs are ...
7
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4answers
234 views

How can a species of natural time-travelers have a meaningful society?

Consider a fantasy species of "natural" time travelers. To define some specifics: Relevant Rules While it is not effortless, this species can move against the "arrow of time" much as a human can ...
0
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3answers
179 views

Backpack contents for a modern person stranded in the stone-age [closed]

A time-travel experiment sends a volunteer back to the stone age. The Stone Age begins with the first production of stone implements and ends with the first use of bronze. Since the chronological ...
3
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3answers
265 views

How to use and maintain assault rifles brought to the past

A group of time-traveling soldiers ends up in 15th century Europe. They have an arsenal of either AR's or SMG's and need to use them until their resources (ammo) run out. How can they maintain the ...
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22answers
8k views

A solution for the time-travel paradox - What could go wrong?

Time travel has been invented and it goes like this. You travel backwards in time at the same speed you normally travel forward. Everything is identical - you do all the actions the same but in ...
21
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10answers
3k views

First innovation for time traveler to low-tech society [closed]

A time traveler goes back in time (one-way trip, and he does not get to choose the exact destination) to a low-tech society, similar to medieval Europe. His objective is to kickstart an industrial ...
0
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1answer
120 views

Sending Messages Back in Time [closed]

It's hundreds of years in the future, and it sucks. I want to send a message to the past using our advanced technology and warn them what to do and what not to do, so the future is better (or, ...
11
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3answers
376 views

What goes in, must come out - limitations of temporal displacement

I am plotting out a sci-fi setting, and trying to figure out the consequences of a non-conventional form of time travel. In the story, time travel has been achieved by means of temporal displacement....
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6answers
737 views

Reactions to a Young Time Traveller

My question is simple. What would people in England in 1700 think of a modern, history loving, 12-14 year old girl? This particular girl was a case of time travel gone wrong. A school trip meant to be ...
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2answers
173 views

Plausible reason why a time machine would be built in a 1990s era sports car? [closed]

So let's say we have a hero and a heroine. The hero doesn't own a time machine, but the heroine does and she built her time machine from a modified 1990s era Japanese sports car. Time travel requires ...
0
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8answers
355 views

What can a bunch of American kids teach ancient Egyptians? [closed]

18 children (ages 2-14) travel from a small American town in 1995 to the year 1312 BCE in ancient Egypt. They stay with Jewish slaves in their village (the structure is more serfs than slaves) for 9 ...
2
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6answers
180 views

Apparel for a time traveler [closed]

Some context: You are traveling to somewhere temperate (55-85 Fahrenheit )in the past, at some random time, post 1000 BC, pre 1800 AD.You do not know where, save that it is in Europe, or a similar ...
2
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2answers
114 views

Earth Time Periods: Choosing for a hidden lair in time [closed]

You are a former nuclear scientist who has researched in the field of fusion, who is in possession of a device that once activated will create a two-way portal into any time period on Earth. The time-...
7
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6answers
799 views

Time Travellers And The Roman Empire, Part 1: Transport and Control

I am a time traveller from the not so distant future. I have gone into the past to the Roman Empire (specifically the Nerva-Antonine period) and via -handwaving magical mumbo-technobabble- have become ...
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4answers
216 views

Could guy with offline wikipedia (and solar charger) that was transported into middle ages conquer the world? [duplicate]

Exactly what is on the tin. Would offline wikipedia (such as phone with kiwix or wikireader) with means to charge it (portable solar charger) be enough for young person to conquer country and ...
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1answer
108 views

Time traveller tasked with finding traces of past alien visits to Earth [closed]

My time traveler is tasked with finding information on previous visits to Earth of a potentially hostile alien civ. What sort of traces might aliens leave that could identify them? I'm thinking some ...
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3answers
169 views

Immediate differences between 1898-2018 [closed]

I have a story where two characters from 1898 apear in the Texas hillcounrty, on a disused ranch. Neither are familiar with ranches, and they come from vastly different socioeconomic backgrounds. What ...
5
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3answers
175 views

How to broadcast Earth's position to someone in the future?

Using current technology, what could I do to optimize the odds of being located by time-traveling humans a thousand years from now? The accuracy must be such that they could "transport" me out of a ...
21
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18answers
4k views

What's the ideal era for harvesting resources by an advanced society?

It's 2100-ish and we're experimenting on our new time travel device, or let's say time travel bunker. What we gathered of information so far are: We can't really go back in time, literally. Every ...
210
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13answers
30k views

Is there a single historic event which could be changed to cause the USA to use SI units?

I am time traveller with aim to make world better. Last time I went to the past, all I heard was: "Kill Hitler!" So I went to the past and I must tell you, April 1945 was pretty loud in Berlin! ...
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1answer
51 views

Moving someone along their timeline [closed]

If one would use something like the Time Stone from the MCU to move someone along their own timeline, would they have all of the memories that they would have made if they had lived out their lives ...
8
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4answers
811 views

Victorian astronomer detecting artificial satellites

To make it short, time-space shenanigans transported everything in a 60 kilometers circumference around an old space-based particle collider to the year 1855. The particle collider was in ...
1
vote
1answer
210 views

If you could travel back in time by transfering your state of mind/memories to your former self, would you transfer your tiredness to him? [closed]

Let's suppose you can travel back in time by passing your state of mind/memories to your former self. You go back to your former self who has slept some hours ago, a day passes without sleeping and ...
1
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2answers
99 views

Plausible way to time travel 10,000 years into a future where there is zero technology [closed]

Ideally the subject(s) would be stashed deep in a cave, and the process would be timed to wake him(them) up after 10,000 years have passed. Because of the low-tech nature of the future and the absence ...
3
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5answers
1k views

Logical explanations for the corpse of a time traveler

Tim managed to create a time machine in secret. Foolishly, he used it on himself, like all good (movie) scientists do and traveled back in time. He thought he configured the machine to five minutes, ...
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0answers
132 views

Would germs brought back in time by a time traveler threaten to kill the population of the past? [duplicate]

This question is in direct response to the early comments on my last question: Time traveler has identified a unknown epidemic is likely spread by mosquitos. How much can he help combat it? The ...
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4answers
4k views

Time traveler has identified a unknown epidemic is likely spread by mosquitos. How much can he help combat it?

In the world I'm envisioning, an individual has been accidently sent to a sort of alternate history version of the world, one that is at roughly feudal level of tech/culture, but with the nations ...
5
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2answers
374 views

How can I make this religion believing in “creating time traveling gods through science” believable?

I want to popularize the following or a similar belief. In many thousand years people will travel back in time to give us an afterlife, if we make it possible, by going the steps, that will lead to ...
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2answers
122 views

If one traveled along a Closed Time-like Curve to arrive in a parallel universe/world-line, would the previous universe cease to exist?

This question makes several assumptions: 1) The "Many Worlds" Interpretation will have been proven through future observation 2) CTC's exist within the rotating event horizon of a Kerr black hole 3)...
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11answers
3k views

How to identify or authorize members of a time travel organisation?

Many organizations today have identity cards, and use passwords and multi-factor authentication to authenticate and authorize people. If there's trouble, things can be done: Identity cards can be ...
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5answers
4k views

How could the Mafia retain its power in New York into the new century?

A mutant who sees multiple futures has predicted that the world will be invaded by aliens. Every future ends disastrously for the human race with us being wiped out. The only one in which we survive ...
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10answers
846 views

How would a time traveller conquer the ancient world?

I have found myself approximately 2000 years in the past, I didn't bring anything with me. But since I am here, I want to conquer the world with my knowledge from the future. Or as much as is possible ...
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2answers
106 views

Maximum span of Time Travel without being detected [closed]

Our protagonist is a completely normal 25-year old who just went on a walk through the city. What he doesn't know: The morally dubious scientists of Evil, Inc. have decided that he is the perfect ...