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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19
votes
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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11answers
566 views

How to let people know you are stranded in time?

You've traveled back in time 65 million years, with no way to return. What evidence can you leave to ensure future humans will know of your existence?
60
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14answers
13k views

How to find out a year I'm in?

Let's assume I can travel in a space-time on Earth. Every time I jump I get to almost the same place, but in different past time relative to the first jump: it solves the problem of planet rotation, ...
-2
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1answer
293 views

How to destroy a parallel timeline? [closed]

In a world similar to ours, mankind has invented time traveling technology since hundreds of years ago. Initially, it was very costly and only conducted for scientific purposes but nowadays it's ...
4
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3answers
213 views

Build a vactrain time-machine

Context According to relativity law, it is possible to travel into the future approaching the speed of light. For the 2nd Newton's Law of motion, in absence of friction (or opposite force), we can ...
8
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6answers
2k views

Airliner takes off from JFK in 1966, gets stuck in time warp and lands in London in 2016 [closed]

If an airliner disappeared in 1966 and landed in London 50 years later, without anybody on board being aware that they had been 'lost', what difficulties would they face? I'm thinking that when the ...
16
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8answers
4k views

In a world with time travel, could one change the present by changing the future?

The question I have is about the details of cause and effect occurring out of standard temporal order. Distilling it down to a single scenario: Consider two people, Alice and Bob, in a closed room. ...
5
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7answers
3k views

If time travel was to be invented somewhere in the future, wouldn't all history be filled with time travellers? [closed]

Say that at some point of history in the far future, time travel becomes possible. That means that from then on anybody could travel in time. If that is possible, doesn't this mean that our present, ...
0
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0answers
80 views

Time Travel vs Conservation of matter and energy [duplicate]

If you were to go back in time, how would you account for the extra matter and energy in the Universe you have created? (the laws of Matter and Energy Conservation). Would not every atom in your body, ...
1
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3answers
188 views

time travel paradox [closed]

If you were to go back in time, how would you account for the extra mater in the Universe? Would not every atom in your body, the oxygen in your lungs and all that you brought with you, already exist ...
5
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3answers
265 views

How to design puzzles for an ancient period in Earth history?

I'm writing a Earth history time travel story, and the main character needs to solve puzzles from each time period he visits. I'm going very far back in history and I'm concerned about being able to ...
7
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2answers
720 views

Intellectual Property infringement

My name is George. I am the true creator of peanut butter. Since my discovery, I fell into a time vortex that landed me in 2014 where I have found that my old rival has taken credit for my idea. I'...
-6
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1answer
192 views

How to “milk” a Rex? [closed]

Continue from https://worldbuilding.stackexchange.com/questions/59315/how-to-defend-a-phone-booth-against-horde-of-zombified-carnivorous-dinosaurs. (This question concludes the time traveling phone ...
-2
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1answer
65 views

How to search and rescue missing person in the late Cretaceous? [closed]

Continue from How to tour Cretaceous Period on economic class?. Say one of my VVIP client got trapped alone in the late Cretaceous Period, and his family wish to recover him alive in one piece. I ...
2
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1answer
142 views

How to tour Cretaceous Period on economic class?

Supposedly I found a phone booth that can transport user 65 millions years into the past (location fixed at Chixulub just 30 minutes before the announcement of the arrival of the impactor. Points to ...
1
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1answer
394 views

Would a time-travelling blockchain destroy a cryptocurrency?

The story So Bob, the multi-billionaire, is a wealthy person today but in a not so far away future he will lose quite a chunk of his wealth and become just an ordinary millionaire. Future Bob is no ...
5
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3answers
569 views

A modern-day scientist travels back in time to Nazi Germany [closed]

What can he do with his knowledge of 21st century science and engineering to shift the tides of war in Germany's favor? Saying "help them build a nuke" isn't allowed (because it's way too obvious).
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12answers
6k views

A power source that would last a REALLY long time

OK, so let's say Jim and Bob have a time machine. It's a large construct: Server rooms with quite a bit of human knowledge in them power generators some areas to grow food a voice activated terminal ...
49
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8answers
6k views

Stopping time, by speeding it up inside a bubble

Imagine I have a device that can stop time for the person who holds it (similar to Bernard's Watch). This device works in a very specific way - it creates a bubble around the user (just large enough ...
2
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2answers
601 views

How would I NOT get rich by going back in time and telling myself about Google? [closed]

Suppose someone gets a time machine, somehow, and decides to make some extra cash the usual way. S/he goes back in time to 1997 and tells his/her Past Self about Google. Under the following ...
8
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5answers
580 views

As a time traveler, how would I see quantum randomness change history?

Suppose I have a time-traveling DeLorean (of all things), and I've used it to travel back to 1955. But then I ran out of juice. Fortunately, I just happen to know that a certain clock tower will be ...
-1
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1answer
141 views

About time travelling, multiply yourself

About time travelling, if I go back one year, find my past self, wait until a little before I first went back in time (11 months and 29 days) and both of us go back, we keep repeating this until we ...
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 ...
43
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21answers
12k views

How much could a time traveler earn from selling 2016 tech having traveled back to 2000?

Joe, the average Worldbuilder accidentally slips through time sixteen years back. From September 11, 2016 to September 11, 2000. He gave saving the World Trade Center a thought, but then he decided to ...
6
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4answers
588 views

How to prove you're not from the future?

Imagine this situation: One warm night of 1890, you go home from a pub. You pass a creepy house. In the half-open door, you see the outline of a machine. You go in, and open the lights. You see a big ...
2
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5answers
474 views

Travel (how far?) into the future using a black hole and light-speed space craft?

A person is traveling in a space craft that was designed and built by sufficiently advanced aliens. This space craft left from Earth and is capable of traveling infinitely close to the speed of light. ...
20
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17answers
8k views

Avoiding preventing your own birth in a time travel paradox?

Assume a world with no multiverse theory, just a single unbroken timeline. If you were to go back in time to the town your parents lived in on day of your conception, the air displacement due to your ...
27
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14answers
6k views

Can a single time travelling person prevent the World Trade Center attacks? [closed]

You are a fellow Worldbuilder and while travelling by train, you fall asleep. Next time you wake up you realize you woke up at Grand Central train station. You quickly realize that you traveled not ...
2
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4answers
367 views

If I travelled to 1979 how easy would it be to become the Worlds richest person? [closed]

Lets say I was teleported back in time as an healthy average intelligence but street smart 21 year old reconstituted in NYC naked in Central Park at 23.59 hours on December 31st 1979. How easy would ...
13
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7answers
2k views

How could a time-traveler change a medieval society if he can prepare and bring something from our time?

I have been daydreaming about this scenario a lot. There are many similar questions here about time travellers being thrown to the middle ages, but they usually can't prepare and can't bring anything ...
1
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4answers
214 views

How to keep a machine running for thousands of years

How would I future-proof a complex machine or set of machines so that they will still be running 2000-3000 years from now? Is this possible with our current level of engineering and we just don't do ...
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)....
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 ...
3
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4answers
1k views

How to jerry-rig a power cable for laptop when time traveling back in time

Say I have a 2016 era laptop, and I travel back in time something like 20-70 years, but forgot to bring my power cable. How can I jerry-rig a power plug? Sure, including adapter / surge protection is ...
5
votes
8answers
197 views

Best way to bring information back in time

When traveling back in time, if you want to bring as much information as possible with you, there are 2 competing things you need to balance. On the "future" / giving end, you want to gather ...
7
votes
6answers
373 views

Concealing your accidental backwards time travel, finding other backwards travelers

Say you are 30 years old, and something happens and you wake up and find that you've been transported backwards in time to when you were a teenager [you were inadvertently sent back, you do not have ...
1
vote
5answers
387 views

How do 21st century time travelers tour prehistory safely?

Suppose in this modern era we have the technology and means to time travel a couple millions of years into the past with a return trip less baggage of course! The science community owns the tech and ...
0
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2answers
165 views

If Time travel exists [closed]

Time travel hasn't been invented yet. Which sucks:< Who wouldn't want to change their past mistakes. What if it has been invented in the future and people do travel back. However, every time they ...
7
votes
2answers
461 views

Is our memory capable of repeating exactly a full day of memorized actions?

Major William die in a combat versus aliens. Now he have the capacity to wake up on the same point of time every time he dies. (Movie: Edge of tomorrow) He uses this power to win the war, but he has ...
4
votes
3answers
247 views

Sending some people into the far future

And I mean faaaaar future. Like, twenty thousand years minimum. 13 million years at maximum. Let's say the Earth is doomed and to avoid the impending extinction of the human race, we throw most of ...
2
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2answers
1k views

Time travel: theories about how it could really work with all these incoherences [closed]

Time travel is in many movies, books and video games. But there are differences on how it works and its consequences. A thing I always think is: OK, they go back to the past to change the future, but ...
0
votes
1answer
139 views

Making an internally consistent, logical set of rules for time travel (based off of this video)

https://youtube.com/watch?v=XayNKY944lY Something similar to this. Okay, so the basic plot structure I want is that there are two parallel timelines, both of them potential futures for our world. ...
7
votes
2answers
295 views

What psychological problems can result from experiencing death on several occasions?

I am a clockmaker: I work with time and can control it on a small scale. One of my powers allow me to return some minutes back in time after having experienced my death, but I remember everything ...
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 ...
29
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10answers
10k views

How far back in time would Maths be understandable to a modern mathematician?

Shamelessly inspired by this question (sorry), but I got this question after Michael gave a answer - my mathematician would essentially have to relearn maths, as mathematics in Ancient Greece is ...
9
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4answers
1k views

How would a mathematician compare to a scholar in Ancient Greece?

Somewhat based on this question, let's say a normal person from our world for some reason goes back into time - to the Hellenic Greece around 490 BC and somehow manages to become a philosopher. My ...
48
votes
10answers
15k views

How could we time travel backwards without killing everyone with germs from the future?

Consider a world in which time travel has been made viable possibility. Initially, many are ecstatic at the new technology and the knowledge it will unlock. However, biologists and other scientists ...
109
votes
8answers
31k views

How far back in time would English be understandable to a modern speaker?

As we all know, language in England has changed massively over the centuries. How far back would someone be able to travel in time and still have a basic understanding of what most people are saying?...
17
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24answers
3k views

Time travel, assassination, and stunting technological growth [closed]

You are an evil person, and you have a Paradox Free 9000 Time Travel Ray Gun(tm). Sadly it came with only one shot left. You can pick one person in the last 2000 years to shoot and kill at any point ...
1
vote
7answers
442 views

Safely inventing in the past?

Some questions focus on what the most important discovery will be (in the past), while others wonder if we can survive in certain time-periods. However, my question is - is it even possible to be able ...