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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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4answers
537 views

Traveling Back in Time at the End of the Universe

Suppose humanity lives on for the next trillions upon trillions of years. One day we'll get to a point where no useful work can be done and hence no life can exist: the heat death of the universe. ...
0
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1answer
84 views

Speed of light, Motionlessness, and Time Travel [closed]

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 ...
19
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9answers
4k views

How do you prevent causal loops from happening with the Novikov self-consistency principle?

The Novikov self-consistency principle states that all changes that occur due to time travel into the past were always part of history, and so the course of events is not changed. While this is useful ...
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 ...
5
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7answers
678 views

How far in the past could unprepared humans survive?

A small late medieval county, consisting of a very small town, a small castle, and a couple of surrounding small villages suddenly and inexplicably gets transported into the past. It's not a spherical ...
11
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13answers
389 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. ...
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....
33
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7answers
6k views

Could a modern times time traveler produce an antibiotic in medieval times?

Joe Everybody, a modern day man with average knowledge (high school and Wikipedia) in biology, medicine and chemistry, wakes up in an medieval city. He sees a lot of sick people and remembers about ...
4
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3answers
288 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 ...
39
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12answers
16k 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, ...
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 ...
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3answers
137 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 ...
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
413 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
396 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 ...
30
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8answers
9k views

How far back in time can I go before people stop accepting my money from the future?

Lets say I go back in time with a wallet full of, say, 150 dollars worth of bills. How far can I be sent back before I reach a point where I'm unlikely to be able to use my money because it looks too ...
6
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2answers
202 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 ...
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 ...
-3
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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 ...
1
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6answers
640 views

What would the economic impact of FTL time travel be? [closed]

Okay, so we found exotic matter and can power our Alcubierre drive. It turns out though, such devices allow travel to the past. The Novikov self-consistency principle holds. My question is, in this ...
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 ...
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 ...
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 ...
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15answers
3k views

Why would time travel affect the body in any major way, especially damaging? [closed]

Obviously, I'm talking about sci-fi time-travel and not just being as time moves by, slowly but surely. Is there a reason one would actually bleed from any orifice? For any pain to occur? Dizziness? ...
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vote
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
votes
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 ...
57
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14answers
15k views

What would be the impact of a modern programmer and laptop being dropped into World War II, possibly breaking Enigma?

I've always found the idea of intelligent every-man sent back in time using his knowledge of the future tech to realistically impact the past. The first time something like this came to my mind was ...
7
votes
11answers
555 views

How could a well-educated person hurled back 2000 years and able to communicate with the locals most influence progress?

If a well-educated man or woman (master's degree level of education) with 20 years of experience in a field of your choosing was hurled back in time 2000 or so years, how could they most influence the ...
19
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6answers
2k views

Would a person from the past be able to survive for a week in New York?

A person from the 15th century Europe, by way of an Assiti Shard, gets thrown forward in time to 21st century New York City. They are aware they're going someplace weird, because the shard manifests ...
3
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3answers
266 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 ...
26
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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 ...
0
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3answers
181 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 ...
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
121 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, ...
5
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6answers
747 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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17answers
3k views

Lost in the multiverse: how to find home?

You have an individual who can travel backwards and forwards in time. They normally maintain an observer status but occasionally a butterfly is stepped on. Because, home is where the heart is, how ...
18
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8answers
5k views

What services could a time traveller offer a medieval king? [closed]

A brilliant modern scientist/engineer has been sent back in time to medieval Europe (somewhere between 800 and 1100 CE). It would be very advantageous for him to have many friends among the various ...
10
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4answers
892 views

Santa is a time traveller. How does he not violate causality?

People wonder how Santa can deliver all his presents in one night. It's, simple: he's a master time traveller. (This post will form the base of a long series of questions). Here's how Santa's usual ...
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! ...
14
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3answers
2k views

Bringing potatoes to the middle ages

A time traveller wants to save medieval Europe from famines by introducing the potato. The plan is, on first sight, simple: Just bring potatoes back with a time machine, and convince people to ...
41
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28answers
10k views

Why buy tech from the future?

The Demonstration You're a rich, successful CEO/capitalist working in the electronics business. Your R&D division is exceptional and routinely fabs state of the art processors at bleeding edge ...
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29answers
7k views

How can I explain that a time travelling apparatus moves itself through time but appears in the same location?

For the purposes of this question, let's ignore the causality issues of time travel itself. Suppose our hero, or an accomplice of our hero, has invented a time travelling apparatus. It works like ...
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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
357 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 ...
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1answer
148 views

Time travel only possible when we go behond light's speed [closed]

Friends here are my views on Time Travel: I think with every past second the light rays of that particular second travel in a different dimension & therefore the light rays of next second travels ...
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6answers
181 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 ...
73
votes
12answers
22k views

How would people in 17th century Salem react to modern day clothing

So I and two others are working on a time machine, and I accidentally press a wrong button and whoosh, all my friends and I are in 17th century Salem, Massachusetts. Nobody sees us appearing out of ...
2
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2answers
116 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
votes
6answers
805 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 ...