Questions tagged [time-travel]

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

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5answers
154 views

Effectiveness of a modern-built Q-ship in the Napoleonic Wars

Let us suppose that at the beginning of the Napoleonic Wars, we have a 5th-rate ship similar in appearance to the 38-gun HMS Lively with a displacement of approximately 820 tons, and a top speed under ...
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2answers
166 views

Hacking the simulation to do time travel (with quantum computers?)

I am trying to come up with a plausible speculative physics explanation for a story I am writing where the conceit is that phsyicists discover the universe is a simulation. The idea is that the ...
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5answers
958 views

"Busted" from the past

Imagine someone claimed she was from Mesopotamia, one of the earliest civilization and had time travelled 5000 years into the future which is now our current modern day, she was completely naked so ...
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6answers
310 views

If a time traveler from the near future went back in time to kill Hitler and failed, could the nazis reverse engineer modern tech with 1940's tech?

Suppose someone went back in time to kill Hitler and fails and some modern tech falls into nazi hands. What modern technology could they realistically reverse engineer with 1940's tech? I'm leaving ...
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2answers
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What is the earliest that a time-traveling electric vehicle of current era could be recharged?

Taking modern gas engines into the past is hard because the fuel isn’t refined enough and damages the engines. But electricity has been the same since time began, limited by human capacity to produce ...
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5answers
109 views

What tests might someone do to assess possible brain damage from time travel? [closed]

I have a character who travels in time, but after making major jumps (like 100 years forward), she begins experiencing side effects—first nose bleeds, but the symptoms begin to increase to things like ...
2
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2answers
108 views

Interstellar Space Travel via Time Travel

Building upon the questions from @States Time travel from stationary position? and @Travis Time travel from stationary position?, would it be possible to travel to other star systems within our galaxy ...
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18answers
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What would be the most effective role to place 150-300 modern soldiers in during the Civil War?

So, let’s say 300-ish modern American Soldiers/Marines are sent back to the civil war. They lack any heavy weaponry, but overall this is what their armament consists of: 250 of them have basic M4 ...
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4answers
191 views

How could a time paradox caused by a manufactured deity fail to produce a full retcon of history?

The Leviathan https://villains.fandom.com/wiki/Scarlet_King is an entity formed as the manifestation of the tension between the modern world and the pre-modern world and the rage it creates. ...
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7answers
368 views

How can controlling the flow of time prevent you from altering history?

The Leviathan is an ancient deity that exists outside the mortal plane. It seeks to enter the human world, which is separated from him by an all-enclosing barrier protecting it. However, the ...
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12answers
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What's needed for a solar powered past?

The person in the story falls through a plot hole into the early 1800 years. Like, steam engines are still new and ineffective, but industrialization is nothing foreign anymore. Light bulb, car & ...
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13answers
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How long will it take for a medieval human to adapt to our current world?

Meet Henry, he is a sharp and quick-witted rich young adult from the High Medieval Ages(1000-1347). He can be described as someone with decent adaptability skills, though not much He found a time-...
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8answers
331 views

What would really happen if an adult's mind was dumped into his five year old self's brain?

We’ve all read those Isekai mangas... or at least I have... but how realistic would they really be put into practice? Say a normal average dude suddenly gets caught in some weird temporal event that ...
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3answers
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Can we use shrink rays to go back in time? [closed]

I researched muons, the Higgs boson, and quarks, and at least one of them can be used for a shrink ray. I'm not asking if we could build a shrink ray, I know it is possible to build one. I'm asking if ...
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7answers
359 views

Is this time travel scheme internally consistent?

I know there are similar questions, but not similar enough, and in fact, I don't remember seeing this kind of time travel in fiction. Before I start, it doesn't matter how the time machine works in ...
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1answer
219 views

"cloaked" stars and gates viable to stop causality paradoxes

So I was lying in bed this moring(summer break, yaaaay) when it suddenly occurred to me that most causality paradoxes are caused by the exchange of information, so if when moving FTL no information ...
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0answers
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Will we ever be able to understand history with 100% accuracy [closed]

Asked the same question on History SE and was directed here. Link with the context is here And this is the question: First of all, I am not a historian or anything of the like, but this question was ...
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2answers
188 views

Proving to the past that I am from the future [closed]

Let's say I've been able to travel in time and I am back in the past (just by a few years or even centuries). I do not have any modern gadgets or even modern clothes, just me and my 21st century mind. ...
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6answers
204 views

Create a machine to detect a signal sent from the future [closed]

Suppose the inhabitants of my world wish to build a time machine capable of receiving information sent from the future. It is only necessary to build the receiver; building the transmitter can be ...
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4answers
281 views

Implications of post-cognition on societies

There are fictions where we can travel to the past, but it often raises causality paradoxes. There are others where we can see into the future, and it has also some implication on free will. But what ...
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2answers
143 views

What kind of building structures could a group of eleven people make whilst stranded on a tropical island?

I'm just curious to know what kind of structures a group of people would make on a tropical rainforest island. Context After an incident in the beginning the story these eleven young people (young ...
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9answers
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What disease could my time traveler find a definitive 'cure' for, without recognizing the specific disease

I've been toying with a story of person sent to a alternate reality that mirrors medieval Europe, but not necessarily with identical history/countries. The time traveler would earn the trust/support ...
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5answers
589 views

How can I implement time travel on a somewhat realistic way?

Requirements for answer: -hypothetically can work (I don’t care if it’s hard or energy expansive) Made by Mankind Can be used at any time preferably works for going to the past it’s enough if I ...
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19answers
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How can I hide my island in the 1600s?

I have time traveled to the past on an oriental country in southeast Asia. I want to hide my island from European colonists using some technology available in both the future and the past. Would ...
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2answers
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Reconcile time travel paradox using entanglement

Imagine a crazy nut with exceptional intelligence managed to sent radiowave signals across multiple timelines, 10 years into the past and the future. That messages contained a blueprint of a time ...
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2answers
129 views

Would this time-travel scenario work? [closed]

In a novel I am writing one of the antagonists travels to Earth because at the end of the novel, he travels back in time and brings himself to Earth. I'm sorry that it's a little confusing. ...
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10answers
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Time traveling Bitcoin buying

One of the most common answer tropes to the "start-your-life-over-at-x-age-with-all-your-current-memories"-question is people saying that they'd buy Bitcoin or invest in Stock XYZ that they ...
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18answers
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How could a lost time traveller quickly and quietly determine they've arrived in 500 BC France?

A time machine malfunctions and spits a traveller from ~2015AD out in 500BC northern France. With nothing but the clothes on his back, and minimising contact with the locals (as that may risk altering ...
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4answers
391 views

How could medieval nobles standing improve by having someone from 2021 as an accountant?

I remember reading in another question about Time Travel here on the forum, with the subject of your being stuck in medieval time. That if you where lucky, you could have a good life serving your ...
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1answer
106 views

A SWAT van with Raptors attacking it? [closed]

I want to know if a SWAT Lenco BearCat van that got teleported to a different world where a group of a few dozen raptors starts attacking the van. Would the van be able to survive about eight hours ...
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6answers
468 views

battleship vs pirate ships [duplicate]

So I was thinking of a scenario where a fleet of 5 warships got sucked into a portal that dumps them in a glitch in time. They were dumped into an ocean world where pirates of the Caribbean-ish keep ...
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6answers
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Robbing the past to pay the future: Where do the resources go? How to balance the books?

In the future, the world is in a parlous1 state. Earth people of the future (let us call them Futurians as in the answer by DWKraus) are desperate but they still have a number of time portals in ...
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4answers
198 views

How much trouble would a great depression era rural county have with settling a late cretaceous Montana/Wyoming?

I have a very specific setting in mind that can be pretty much summed up as "Wild West with Dinosaurs". However, I'm still trying to figure out the details of just how the people native to a ...
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8answers
2k views

Is it murder if I stop a person's parents from meeting?

Suppose time-travel is common. There is someone who I want to eliminate for nefarious purposes of my own. If I go back in time and kill that person, then surely it's murder, but what if I go back and ...
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14answers
4k views

Safely preserving a manuscript for 700 years [closed]

The problem: My time travelling hero has travelled from the present, back to 14th century France (think 100 years war) to retrieve the mcguffin, a manuscript. He cannot take any physical objects back (...
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1answer
216 views

Lifetime Groundhog-Day Loop... For Everyone (UPDATED) [closed]

Four and a half years ago, IchabodE asked a very famous question about what would happen if everybody experienced a single-day loop like the one in Groundhog Day. Recently I saw the question again (I ...
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10answers
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Why is mind control tech a common consumer product in 2050? [closed]

Several time travellers from the 2050s arrive in a single-use time machine and disappear into society. They have 30s years of future knowledge, the clothes on their backs, and a backpack of future ...
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2answers
145 views

Ways to make the time travel aspect of FTL to be as hard as possible? [duplicate]

As I understand it, thanks to the General Relativity it is absolutely impossible to have both relativity and FTL without the latter opening you a way to get into your past thanks to the relativistic ...
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18answers
12k views

Why can't modern fighter aircraft shoot down second world war bombers?

It's September 1940, the Luftwaffe is launching the blitz over the UK. One squadron of night bombers (either Henkiel He 111 or Junkers Ju 88) is flying over the English Channel when they are somehow ...
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9answers
4k views

What person/group can be trusted to secure and freely distribute extensive amount of future knowledge in the 1990s?

This is another attempt at helping my previously mentioned time traveler to distribute a significant amount of 2020 knowledge in 1990. This time we're assuming 2-3 loops have happened and he can ...
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4answers
287 views

How can a time traveler ensure he can't be traced when posting data to BBS in 1990?

Numerous answers to my last question suggested the best way to anonymously share future data was to hack the limited protection of early 90s internet. I know the first publicly available BBS had just ...
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8answers
4k views

30 year Groundhog day: Surviving High School over and over with sanity intact (ie how to avoid the repetitiveness of school life?)

Our protagonist is repeating the last 30 years of his life, from the age of 5 years old, over and over again. Read the 'premise' section of this question for all the details. As mentioned in the last ...
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6answers
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30 year groundhogs day: how to increase the world's technology

The premise: Our protagonist was a intelligent, good natured, programmer who just tucked himself in bed at the end of celebrating his 35th birthday, only to wake up as a child on the day of his fifth ...
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2answers
129 views

People moving through time in different directions: Do they run into each other more than once?

This is a question about the relationship between a character moving backward through time and her relationship with characters who move forward through time. The character [Cate] travels backward ...
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1answer
430 views

How would a person from the different eras in the past react to our society and technology? [closed]

In Doctor Who and some other sci-fi stories (like the Navigator) we often see people from the past mostly from medieval times traveling to our time line. So lets say we take people all the way back ...
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17answers
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Does this time travel delivery service cause paradoxes, and if so how can I avoid them?

After the time travel designs from the CASH WHEN YOU NEED IT YESTERDAY business was stolen by a corporate spy, Amazon now has time travel capabilities. Of course, saying that they could deliver the ...
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21answers
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How would a preemptive crime fighting group prove they stopped a criminal?

In my world, there is a government agency that stops crimes before they happen, kind of like in Minority Report. However, in this case, they swoop in as early as possible, sometimes waiting outside ...
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15answers
3k views

How can I allow bidirectional time travel in a deterministic block universe?

I am working with a setting in a block universe that is deterministic. Starting from an initial garden of Eden configuration at time t = 0 every configuration of ...
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2answers
107 views

How to keep my past self from freaking out when I go back to see him? [closed]

Utilizing 17 9v batteries, a large speaker, a series of rotating magnets and some weird alien technology that landed in my yard, I have created a time machine! (I'd tell you how it works, but the only ...
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23answers
8k views

How can an average person prepare themselves to verify their future time-traveler self's identity?

I'm just an average person. I'm not a millionaire with thousands of dollars to spare. I don't have any kind of special power. I'm not currently affiliated with anyone working on anything grand. I'm ...

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