I'm imagining a world where time travel is a part of day to day life. Technically speaking, a sealed chamber (imagine it being about phone booth sized) would be linked to it's past and future instances of itself. This gets around issues like "the Earth is moving through space so if you travel to the EXACT same space in the universe you won't be on Earth you'll be floating in the cosmos" because instead of being in the EXACT same space in the universe you'll be in that chamber wherever it is.

There's no affect of constant time traveling other than extreme instances of "jet lag" (time lag?). There aren't diseases or ailments that arrive from over use.

Anything within the chamber is moved through time with the person, air and all. To facilitate this, the "receiving end" of the time travel jump needs to be a vacuum. Cargo can be sent without a human passenger as the chamber is operated by somebody outside of the chamber.

Given that the machine is functioning normally without any damage, it's safer than a flight by today's standards. However, a collision could occur when time is mismanaged and two people exist inside the chamber at the same time (whether it be somebody arriving just as another is departing or that two people arrive too close to the same time). This kind of collision usually results in the death of the people or at least destruction of property if only cargo is transmitted due to overlapping atomic structures and increased pressure of the chamber (there's 2 chambers worth of matter in the chamber at the same time).

There are public stations similar to today's bus stations or airports where the public can travel time if they've bought a ticket. Time keeping is kept very strict to prevent collisions in the chambers. There are also private stations operated by businesses or governments for their own uses.

What kind of laws or restrictions are there that would help reduce paradoxes? How might the people in charge of the stations organize arrivals and departures when arrivals could come from either direction (forward or backward in time)? How might individuals and workplaces use time travel? I can imagine a research company repeatedly looping their scientists so they re-live the same day over and over to produce results from their research (relatively) faster in the grand scheme of the timeline. Are their personal uses for time travel? How can age be regulated? Being born in the year 2000 but spending 20 years of your life repeating 2007-2010 for a job or some other reason means that in 2011 you're not necessarily 11 years old. Other than fear, would their be any reason to avoid time travel? How is the economy impacted if goods can be jumped in from a time when their production was cheaper?

Ultimately this comes to one question: how can cheap, safe, easy to use time travel be used, governed, and managed?

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Jan 25 '15 at 1:20

I'm making the assumption that you're being serious about this idea. Or rather, the story is not meant to be one of pleasant absurdity, à la Hitchhiker's Guide to the Galaxy. I'm also assuming you're time traveling along the same timeline.

What kind of laws or restrictions are there that would help reduce paradoxes?

The best law to prevent a paradox would be "There shall be no time travel." Seriously, any free use of time travel would be a disaster and by the laws of time travel it would happen immediately. The instant you turned on the machine, a drunk version of yourself would step out and let you know that you're the a**hole who destroyed civilization. Then comes a hungover version apologizing for drunk you/him, though admitting he's right, and telling drunk you/him to go drink some water. The hungover version then says things will be alright and leaves you with a tight-lipped smile that says nothing will be alright.

How might the people in charge of the stations organize arrivals and departures when arrivals could come from either direction (forward or backward in time)?

The future-most booth simply keeps a record of all departures and arrivals and disallows simultaneous travel. You have knowledge of all time, just use it.

How might individuals and workplaces use time travel? Are their personal uses for time travel?

In the most varied an imagination stretching ways. Society, as we know it, would because instantly unrecognizable. Things wouldn't evolve to crazy. Crazy would come in from the future would be on us instantly.

How can age be regulated?

Implanted clocks. Simply count age with subjective time. Certainly peers would be harder to come by except through careful intention.

Other than fear, would their be any reason to avoid time travel?

Preservation of mystery. Most other answers seem to come down to fear, fear of the unknown, fear of meddling, fear of robots, etc.

How is the economy impacted if goods can be jumped in from a time when their production was cheaper?

You've got bigger issues than that. You have paradox manufacturing. Simply send back a widget to yourself before you made it. Now send that one back to before you received it, but since that means you had two to send back, send both, but since you did that you had three to send back, etc. From your perspective, or one of your perspectives, this thing you designed (or you got the design from a past you) shows up in crates. Good luck trying to sell anything though, anyone can dupe items, currency, gold, etc. in this way.

The only thing I can imagine selling/trading would be first-hand experiences. Especially if the sales pitch came from future you, saying "you should totally do it".

Ultimately this comes to one question: how can cheap, safe, easy to use time travel be used, governed, and managed?

Perhaps by a single individual this could be accomplished. It would take careful planning and limited use. I can see no conceivable future where a large group of people, let alone the public, the unwashed masses, could use such power with wisdom and safety.

The two assumptions I started with (serious and same timeline) may guide you in averting the numerous issues with your idea as I understand it. That is, you should be whimsically time travelling to uncannily similar universes, where as it turns out, you just happened to leave (this, as it happens, is how instantaneous travel occurs in Old Man's War, called a skip drive. It solves lots of problems.)

  • $\begingroup$ Duping items like this sounds like a massive multiplayer online RPG hack. The first time machine would be a proto-type and one would assume much larger...future time machines could be significantly smaller after miniaturization gets to them...anything stopping you from using this duplication process to create an infinite number of time machines? $\endgroup$ – Twelfth Jan 21 '15 at 21:13
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    $\begingroup$ @Twelfth No reason not to, highly likely in fact. It seems that such a device couldn't be moved through time once activated. If it's always linked to its past versions then it's always the same machine and one would only need to send them back in time and turn it on. Likely then, the first cargo would be a large set of time machines to simply receive (as quickly as they can be unloaded) the endless stream of machines that will be the infrastructure all of time demands. Machines would be unloading and flying off into interstellar space to land and activate on future colony planets. $\endgroup$ – Samuel Jan 21 '15 at 21:24
  • $\begingroup$ You'd really only need 2 time machines...one large one, send back a mini version of it. Go off in the future in the mini one, dissemble the large one, bring it back to the past in the mini one, reassemble...now you have two large ones. Go forward in time in any of them) disassemble the second large one and repeat the process until there is a time machine for every person. $\endgroup$ – Twelfth Jan 21 '15 at 21:34
  • $\begingroup$ @Twelfth This is getting complex. Disassembling a machine means it no longer exists in its future. You could only travel as far as to when you disassembled it. If the disassembly occurs at the end of time, then sure, no big deal. $\endgroup$ – Samuel Jan 21 '15 at 21:53
  • $\begingroup$ no more complex then some jackass sending a bomb to the start or end of time. Or even a misc crate to the start of time to conflict with everything. $\endgroup$ – Twelfth Jan 21 '15 at 22:15

I think the best way to deal with time travel is to assume that since you made the machine and know it works, then time travel not only is possible, but has happened for all of time without destroying the entire space-time continuum. There are two explanations for this:

1 - This is the best of all possible universes. In an infinite multiverse, it is very possible that the vast majority of universes that invented time travel were utterly destroyed by some paradox. We may be the only ones who survived, because all the quantum particles spun exactly as they needed to so we could make all the right choices that led to time travel working perfectly.

2 - There is an all-powerful entity that constantly stops us from destroying the universe during time travel. It doesn't have to be intelligent, it just has to have a bunch of sophisticated algorithms for ensuring the continued existence of the universe. For how this entity could have been created, see option #1.

These options lead to the assumption that to a certain extent, once we invent time travel we are no longer in control. Events will occur because they already have occurred. The future is fixed because the past is fixed, and the present is just the past of the future, and the future of the past. As far as I can tell, this basically means that time travel is self-governing. When you turn on the first machine, people from the future will send you instructions on how to operate the machine without error until you get the next set of instructions (or, alternately, you discover that no matter what you do, everything works out perfectly and paradoxes are impossible to create). Most time travel engineers will commit suicide, but some will accept their lack of free will in exchange for the massive amounts of money they will get for what should be an incredibly easy job (after all, you just need to follow instructions).

When you get to the consumer level, this can all be hidden away. People will still buy tickets because to simply hand out the tickets to the people who will need them would cause mass hysteria, and probably lead to no one actually using the time machines (thus it did not and therefore cannot happen). Some will get denied passage because they would have killed their grandfathers, or created some other kind of paradox. We can't know what they'd have done, but we know we don't let them do it.

This doesn't leave much room for error, but like I said you can hide it from most characters. Ultimately, so long as they don't successfully rewrite time or cause paradoxes, it should all work out.

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    $\begingroup$ A very Panglossian answer :) $\endgroup$ – Samuel Jan 22 '15 at 21:55

Um, how to say this. What you are proposing is impossible even on a logical level.

I'll start with this

I can imagine a research company repeatedly looping their scientists so they re-live the same day over and over to produce results from their research (relatively) faster in the grand scheme of the timeline

it 'sounds' neat but if you think through what you are talking about logically you'll this is crazy.

I finish a day of work at a company. I get sent back in the morning to yesterdays morning. I go to work to find myself already there about start what I worked on yesterday. I'll need different equipment to continue with what I was doing. If I tell my earlier self what I did, then I'll cause a paradox if I decide not to do one of the failed experiments. The next morning we'd both be sent back and now there would be 3 of me...

You don't really 'relive' the same day over and over.

What would be the point of sending cargo? The only way to know what is needed where is after the fact and you would then be changing the timeline.

  • $\begingroup$ The only way I can imagine this would work is if certain paradoxes don't exist. Instead of being conundrums, they just work. Like the Grandfather paradox not being a paradox because the grandson just continues to live. What if that's just the way it is? I imagine a lot of knowledge will be bootstrapped. Also, instead of changing the past, what if the past is fulfilled? I'm not so happy with that because that implies a pre-determined future even though it does solve the paradox. $\endgroup$ – Corey Ogburn Jan 21 '15 at 18:22
  • $\begingroup$ @CoreyOgburn Well if you want to use the time travel that Jasper Fforde uses in the Thursday Next series no problem that is kind of what you are referring to, but then your just telling a story and time travel is just a gimmick that doesn't really follow rules. (and time travel doesn't work like Groundhog day). $\endgroup$ – bowlturner Jan 21 '15 at 18:26

The key issue here is humans perception of time. Time isn't linear, but we perceive and insist that it is linear...and this perception allows us to envision a past instance that's 'saved' awaiting for our arrival, which allows for idea's like this one to be created. But it's false. Negative velocity in time does not mean travelling back to a saved version of the past.

The number of paradox's that arise in this scenario are absolutely stunning and there is simply no way to resolve it outside of fracturing time lines all over the place. Governments/law only exists with that gov't, and the only real truth about any government is they eventually collapse.

It is great to send a scientist back in time, but they still must sleep. That scientist would go home, find thousands of himself sleeping and preparing for the next day work, no?

This would make an interesting story, but fails in any serious reality check scenario. Time is not linear.

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    $\begingroup$ I'm still stuck on 'what happens if someone breaks in and send a large crate back to a conflicting time near the start of the booths existence?' Would this interfere with a past traveler (resulting in that person death), and would they be able to clean it up quick enough before the next person came back in time (basically causing a chain reaction of failure/conflicting time travel for that booth) $\endgroup$ – Twelfth Jan 21 '15 at 19:15

I think this is a bit iffy logically and paradoxically, but I'll try to ignore those and address the question.

Some immediate issues I see:

  1. Crimes. How do you handle crimes when you can have multiple instances of the same person at the same point? Who goes to jail, and who committed the crime and should be punished? What about people framing an earlier/older version of themselves? How do you make someone serve time for a crime when they can just skip ahead?
  2. Contracts. Contracts are generally for a set duration - how do you handle it when that duration is in the past? What happens if I take a contract, ignore it for 10 years and then go back and complete it - is that a breach, or is everything ok because I did it "when" they wanted me to? And jeez, think about marriage - you could have several versions of the same person legally married to different people all at the same time.
  3. Laws. These generally go into effect as of a certain time - does that mean I can go back in time and do something that's currently illegal? If I take a legal drug in the past and then move forward to a point where it's outlawed, am I in trouble?
  4. Property. I own a phone. If future me comes back, does he also own that phone? Or is it stealing if he takes it?

One way around some of these would be if everyone had some sort of unbreakable, unhackable clock that indicated their exact age, and you would use that to differentiate all laws and contracts. So maybe Alice-21 gets 5 years in prison - that effectively means that Alice-21 through Alice-26 all need to be in jail. It doesn't matter what year they show up in, they should be in prison for those years.


You may want to review the Guide to SF Chronophysics and decide what kind of timeline you want to deal with.

If, for example, you decide to use a type one (Deterministic) timeline, legislation on grandfather-type paradoxes wouldn't be necessary; they're impossible. If it's possible to intentionally create closed loops, on the other hand, that might cause problems. Any economic disturbances would be only temporary because at some point any new value would need to be sent back, or any value sent forward would reappear.


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