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
124 views

What are some modern policies that can be applied to or improve 17th-century European society? [on hold]

Supposedly, a relatively smart + educated young woman from modern society is transmigrated into a body of a woman living in a country that is similar to 17th-century Europe. Monarchy and nobility ...
2
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5answers
320 views

How could one become rich when suddenly be transferred back in time by 100 years? [closed]

I assume he is unprepared for such an event and therefore does not have specific detailed knowlede of the stockmarket, ground prices or similar assets. Also without initial capital buying some ...
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8answers
842 views

What minimalistic message from the future would make you most successful? [closed]

I'm a tinkerer, working in my garage on a time machine. I had some success. Saying "I built the time machine" would be too much. I built the receiver. It can provide exactly one bit of information, 0 ...
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1answer
134 views

What would religious debates look like in a religion designed by a time-traveler to help mankind? [closed]

A time traveler, Roy, is marooned in the ancient era. Time and place are negotiable: ancient Greece, Roman Judea, ancient China, etc. There's no hope of getting back, but he's an intelligent fellow ...
38
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13answers
7k views

Keeping supplies for 1000 years

My main protagonist is going to fast-forward himself in time by 1000 years. He will simply reappear in the same place (marked by a small beacon), the process being instant for him (no hibernation etc)....
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2answers
151 views

The North Star in the ancient world sky

Question: Would a modern-day teen, trained in using the north star for directions when camping/hiking, notice a difference in how the "north star" (Polaris) works when transported suddenly to 1350 BCE?...
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5answers
196 views

Advance human society by time-transporting a book. Which to choose? [closed]

Humanity has done it - the first time-machine was built! However, the machine's capabilities are very limited as it is very costly and fragile, which means we only have one shot. Building another one ...
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22answers
5k views

How could an engineer advance human civilization by time traveling to the past? [closed]

Earth in the near future (in 2081) is invaded by aliens who are just "a bit" more technologically advanced than humans. The war is not a one sided extermination of humans, but humans are about to lose ...
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8answers
6k views

What does it actually mean to have two time dimensions?

The trivial answer is that it just means "you have two dimensions with inverted sign in your spacetime metric". But the perceptual result of that kind of choice doesn't actually look qualitatively ...
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11answers
6k views

Which modern firearm should a time traveler bring to be easily reproducible for a historic civilization?

Eureka! Our hero just discovered the secret of time travel, but what to do with it? "I know!", he says. "I will travel back in time as far as I can and hand them a modern firearm. They will learn how ...
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2answers
317 views

Intragalactic velocity past the central black hole

In my story people are traveling from somewhere beyond the opposite side of the galaxy to Earth. The distance traveled is approximately 66 million light-years. I would like the travelers to ...
52
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46answers
18k views

Plausible reason why my time machine can only go back a certain amount of time?

So, I have built a Time-Traveling machine. It’s a prototype, and I’ve noticed a few kinks in the machine. If the control pad gets jammed in home mode, the universe will repeat the same day for all ...
145
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40answers
47k views

If time travel is possible in the future, no matter how distant, why haven't they come back to tell us?

In a world where time travel is possible, but has not been invented yet, would travelers from the future come back to prove it exists? Surely, they would bring that technology back in time to let the ...
31
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10answers
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 ...
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6answers
3k views

Bootstrap paradox with a time machine in iron

I wonder if a time machine can be the cause of a bootstrap paradox? Background: Let's say one day I found in my room a portable time machine. I use this machine to travel to the future, where I ...
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1answer
163 views

Which languages would be most useful for time travelers to learn? [closed]

Title pretty much says it all. Which languages would be most useful to a time traveler?
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1answer
231 views

The World is ending, but we have a time-machine [closed]

Let's say an event is occuring that within a short timeframe makes at least the entire solarsystem uninhabitable. However, in a global effort, scientists and engineers have developed a backwards time ...
11
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5answers
2k views

If you had a giant cutting disc 60 miles diameter and rotated it 1000 rps, would the edge be traveling faster than light? [closed]

As if there was a giant angle-grinder in space that slowly increased its speed. The question assumes that material exists to make this super-disk that doesn't rip apart. What happens as the edges ...
3
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1answer
230 views

What would happen if we sent a modern computer into the past? [closed]

According to Moore's law, the number of transistors in an integrated circuit doubles about every two years. Therefore, a modern household computer has the computational capabilities of a supercomputer ...
29
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6answers
3k views

At what point in European history could a government build a printing press given a basic description?

Say a time traveler ends up back in time and has earned the good graces of one of the nations' kings by sharing some of his future knowledge. Knowing that the printing press was an important ...
10
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3answers
822 views

Command and control structures in a war where time-travel is possible

Firstly: I'd like to note that this post ( and the world it's based in) is partly inspired by the time travel mechanics of the game Achron. If you're confused by my question go watch some videos of ...
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1answer
1k views

How long can language drift before it becomes indecipherable, and how to minimize drift?

A general question here, relevant to many world-building scenarios. Language drifts, to the point that I likely could never understand old English, but I'm not sure how much. I want to know how long ...
9
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4answers
3k views

Would a US marine teleported in the Cretaceous be able to survive a T-rex attack [closed]

A US marine fighting in the Middle East inadvertently falls in a hole that happens to be a time portal and is teleported in the Cretaceous era, 70 million years in the past. Our Marine is equipped ...
3
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3answers
236 views

Solar cells in the Renaissance

An engineer goes back in time to attempt to rewrite history: since global warming has wiped out all but a few living species at his home timeline, he wants to prevent it without preventing an ...
9
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4answers
974 views

What would happen if I showed the Vikings advanced technology? [closed]

Today, I answered a question in an essay which related to time travel and what I would do if I could go back to a historical period. This got me thinking, and I came up with a hypothetical scenario in ...
4
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7answers
840 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 ...
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0answers
112 views

Can you mine bitcoins or other data a time loop? [closed]

You have your own time loop. For one day only: at midnight, if you choose, you can transport your mind back 24 hours and relive the day, but with all the memories you have gained. Nobody else will be ...
40
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12answers
6k views

Where could a person from the 14th century appear such that they would not notice modern technology for a week?

In this case, a person from a world similar to ours, at a time and technology roughly equivalent to our 14th century, but with magic. Through some odd spell, this person was teleported far away from ...
2
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3answers
212 views

Passing a message back in time

I have built a machine that I have connected to an ordinary desktop computer, which is in turn connected to the internet. When turned on, the machine isolates a pair of quantum-entangled particles; ...
7
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4answers
551 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
102 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 ...
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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 ...
11
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13answers
418 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
396 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
7k 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
343 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 ...
40
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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
200 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
159 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 ...
14
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6answers
443 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
443 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
241 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
219 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 ...
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7answers
324 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 ...
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6answers
647 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
248 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
63 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 ...