Imagine that we have invented time machine. Now we can go back in time okay?

Now if we go back in time and teach our ancestors thing which were discovered or invented thousands of year later after that time.

As an example, think that the mobile phone was invented in 2000 CE (just an example don't over think when it was discovered), now using time machine we go to 1000 CE and teach the people of that year how to make and use the mobile phone (cellphone). Do this with all modern technology of the year 2000.

This means now our ancestors will be 1000 years ahead in technology, than they were, instantly.

This means our future will also be thousand years ahead and we will have some extra inventions when we go back to 2000 CE.

Now if we repeat this a few thousand times, our technology will advance millions of years ahead in technology in a short period of time, the time it took to use the time machine thousands of times

Is this theoretically possible? If yes then all scientists of world should start to attempt to invent a working time machine, right?

For the above theory, assume that old people are positively taking up your knowledge without resistance.

Everyone took my example so seriously and talked about how medieval people would react to new knowledge so I made a new example. Forget that mobile phone one.

New example: Teach things of 4000 CE to 3000 CE people. They will be well developed and will understand technology.

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    $\begingroup$ What you describe is a very well documented class of scenarios in time travel mythos, with literally thousands upon thousands of pages devoted to it, if not millions. Two questions: 1) have you read any works on timetravel which deal with paradoxes or researched them on wikipedia and 2) Which flavor of time travel are you using. This is such a well documented region of timetravel that there are actually many different ways to resolve it, depending on which author is writing. Forking Timelines, Novikov self-consistency, timelines degenerating, these all have their own solutions here. $\endgroup$ – Cort Ammon - Reinstate Monica Oct 25 '15 at 16:48
  • $\begingroup$ Here is an introduction to some of the models of time travel used in fiction. $\endgroup$ – 2012rcampion Oct 25 '15 at 18:42
  • $\begingroup$ What does "make and use mobile" mean, exactly? $\endgroup$ – WhatRoughBeast Oct 25 '15 at 20:48
  • $\begingroup$ Produce mobile in factory and then use them to call and everything else lol $\endgroup$ – Kesh Oct 26 '15 at 4:29
  • $\begingroup$ This is a bit of a side note, but technological progress isn't necessarily constant, and isn't necessarily linear. There's all sorts of societal pressures that can drive, prevent, and suppress technological progress. It's entirely possible that by introducing technology from the year 4000 AD to the ignorant savages of 3000 AD, you will destabilise their society to the point of collapse, leading to a dark age of lost knowledge that takes more than 1000 years to recover from. (This could happen very quickly if the technology you introduced was the Y4K equivilent of a nuclear bomb, for example.) $\endgroup$ – user867 Oct 26 '15 at 6:54

1000 years ago, that was the middle ages. In other words, before you have the chance to pass on even a small amount of your knowledge, you'll be identified as a heretic and burned on the stake.

So you think you can prove your knowledge by doing things that people of that time can't do? Well, that's just further proof that you're in league with the devil and deserve the burning.

  • $\begingroup$ I said it was an example didnt i? Forget tht example and try this. Teach things of year 4000 to year 3000.. They will be ably to understand right? $\endgroup$ – Kesh Oct 25 '15 at 15:12
  • $\begingroup$ This does not answer the question though, as it is not tagged reality-check. $\endgroup$ – timuzhti Oct 25 '15 at 23:34

Assuming time travel were possible, there are several issues here, it seems to me.

Assuming we're going back to middle-ish ages, then:

1. Poor understanding by people of the time would greatly limit what could be reasonably taught. Remember, the vast majority of people were illiterate.

2. Poor infrastructure of the time would greatly limit what could be developed. You're dealing with pre-industrial iron/steel working.

3. Unfavourable social structures would make any approach very dangerous, if not impossible (you would need to be known to acquire resources and that would bring you on the radar of groups like the Catholic Church).

[note: it could be argued that going back 1000 years from A.D. 3000 --> A.D. 2000 would be even more dramatic and difficult because the process of technological change is that much faster from 2000->3000 than from 1000->2000]

more generally...

4. The pace of technological change needs to be balanced by the rate of social change or the society risks collapsing (too much tech -> society literally self-destructs, too little tech -> society stagnates).

5. If it was possible, it's already happened. i.e. if time travel is a reality and such backward travel possible, then time is essentially linear and the process you're speaking of has already happened (unless you work very hard to make up a reason why it couldn't happen - like maybe getting some ideas from the 10th dimension group on YouTube re: all times exist simultaneously).

6. If it was possible, it's already been factored into the timeline -> similar to 5, however... this could mean that someone travelling back, creates a branching timeline so that their original timeline is not affected (yes, something like Back to the Future). In this way, travelling back to the same point in time would only create a vast number of different futures that would not build on each other.

Furthermore, to get constructive reinforcement of time changes from (6), not only would travellers have to go back to times after the previous traveller's changes have taken hold, but they would have to go back from the newly changed timeline. i.e. in this scenario, one could not change their own timeline at all, let alone by repeatedly sending travellers back.


Your experience is going to be that of building a tech tree, as seen in computer games such as Civilization, Age of Empires etc. Before you can build a mobile phone, you will need to build hundreds (perhaps thousands) of other technologies, most of which use previous technologies in the tree.

As a simple example, think of a wire of the thickness used in a phone. That's one of the simplest components and yet it would be impossible to make with medieval technology: they can't create a hair-thin wire and coat it with plastic. Even to make that wire is going to take a substantial tech tree. Then, think about a CPU, which is hugely more challenging.

So, the best that you could do is guide, and hasten, the creation of this tech tree. With the benefit of hindsight, it will be much quicker than it took historically for mankind to stumble and experiment their way through. But, it will still take a very long time - perhaps centuries. Alongside the tech tree will need to be a lot of infrastructure, ranging from universities to roads.

If you had unlimited money/gold, you could perhaps found a small country, or city state, where you could develop all of this technology in a small focussed way. You're then going to attract a lot of political attention, and will probably end up having to use some of your technology to repel people wanting to steal it.

It's not a simple job.

  • $\begingroup$ They don't even have plastic, so you'd have to use some other insulator. Plastic only became possible when we started extracting oil from the ground, but even then it wasn't a given that it would be developed. $\endgroup$ – a CVn Oct 26 '15 at 12:08
  • $\begingroup$ @MichaelKjörling yes, that is certainly one of the problems that the time traveller would face with my example, and an example of a part of the tech tree for "hair thin wire". $\endgroup$ – Max Williams Oct 26 '15 at 12:11
  • $\begingroup$ Oh, I didn't make that comment to try to refute your point. In fact, quite to the opposite, I think it reinforces the point you make. Not only couldn't they make the hair-thin electrical conductor in the first place even if told about it, they also don't have what we'd normally use to coat it to add insulation against other wires! $\endgroup$ – a CVn Oct 26 '15 at 12:14

There are two completely different cases in your question.

In first case, you are going to pre-scientific (or pre-industrialization) time. In this case, best way to go about it is to teach people Scientific Method itself. That means experimentation and free disclosure of information. The problem is, at the time, many powerful groups of people were against free disclosure (eg. religion). So you would be fighting uphill battle.

Second case is going to post-scientific world. In this case, it is as simple as taking results of experiments and bringing them back in time, so those experiments don't have to be done. For example, imagine you took current LHC data and brought them before LHC was built : "We found Higgs Boson, here is the data." Then, LHC probably wouldn't be built and all that money would be used for different kind of experiment. This would also dramatically cheapen any progress in engineering, because expensive mistakes would be avoided and better tools would be made thanks to better understanding of our world.


I assume you realize that this is a site for building fictional worlds?

Time travel is not possible with technology as we know it. The scheme you are proposing relies on time travel paradoxes, and the fictional technology of your setting will have to answer how it deals with those paradoxes. e.g.

  • Each travel into the past might create an alternate timeline for the future.
  • Time travel makes things happen as they were supposed to happen.
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    $\begingroup$ Plus, there's another very serious issue. There would be two copies of the same matter. One that exists and the other that would exist in the future but is still existing now. $\endgroup$ – Youstay Igo Oct 25 '15 at 15:10

I agree: assuming Novikov self-consistency principle (and I find it the most logical approach to the problem) and no legal or technical restrictions on time travel, we could develop almost everything that can be developed. Even if the people from the past resisted for unknown reason, we could in the worst case kill them all and become our own ancestors, but we could also go even earlier and colonise the world before any people appeared. In such a world, there were actually no progress ­– every knowledge that the humanity possesses would go with the first people that used time machine to colonise prehistory (maybe Cambrian, maybe Precambrian, maybe time shortly after the Big Bang, if a way to survive without planets can be discovered (that automatically means that it is known)).

Of course, we do not know time travel now, so this is not the case. Maybe time travel is not possible at all, maybe one can not go before the time machine is invented and maybe giving informations from future to present time is illegal.

Besides, maybe when many useful things are known, some unknown things are not discovered, even though they could be if people were accustomed to discovering.

  • $\begingroup$ Well may be it would be possible in year like 22000 ad, we dnt know yet .. It might be illegal to give knowledge to past people but many people do illegal work without anyone knowledge right? May be Einstein, newton had some knowledge from future people but we dont know it.. Just a thought $\endgroup$ – Kesh Oct 25 '15 at 15:16

In essence, what you are accomplishing is to multiply the length of time the human civilisation exists. Should time travel be possible (It isn't, as far as we know), this is a perfectly valid way of speeding up development.

To avoid the difficulty of teaching (rather stubborn) medieval people modern science would be a large challenge though, and it will be far more preferable to travel to a time before significant civilisation, so that there isn't troubler getting a foothold. Until you have significant climate control technology, you're limited to times where your ecosystem can survive.

Not all scientists, however, will be willing to study temporal mechanics. Just like how people choose to be artists or writers, each field also has subfields, that are not very mutually compatible. Only a small subset of mathematicians and physicists can work on the task.

You can be sure they'll get sufficient funding though, if time travel is indeed possible.

  • $\begingroup$ All scientist which r interested in time machine field.. And killing past people is not wise idea, i mean we might kill our own ancester and we wont even exist then lol, so we ll go to another example as above teach year 4000 thing to year 3000, cause they will be understanding techs $\endgroup$ – Kesh Oct 25 '15 at 15:19
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    $\begingroup$ @Kesh, by altering the past, we will have already irreversibly changed the present. People that may get married may not even meet each other. $\endgroup$ – timuzhti Oct 25 '15 at 23:40
  • $\begingroup$ We need to change the future thts the point, but not by killing by knowledge $\endgroup$ – Kesh Oct 26 '15 at 4:28

There are several issues which could occur depending on which models of time travel you follow, but the most important one regardless of the model or method of time travel is simply that the tools to make the tools don't even exist.

You would be trying to teach concepts that literally cannot be proven or understood with the science and technology of the day (even if you find someone very receptive, like a Leonardo da Vinci), and even the basic tools of understanding (the scientific method, standardized units of measurement and even accurate clocks) are completely lacking. Most of your time won't be teaching the theory of integrated circuits, but how to do things like make accurate measurements or maps, and refinements of basic metallurgy (which is still a very empirical process in the time you are describing; the periodic table of elements hasn't been discovered yet)...

As mentioned there will be a huge social and political resistance to your innovations, not just because of the Church, but wherever you go your "new" methods will totally overturn the existing social, political and economic order, much to the fury of those who benefit from this. Not only the Lords and merchants be after you, but even things like the guild of weavers will have a stake in keeping cloth making the way it is. If you are successful, then you will probably ignite revolutions and counter revolutions, which will have much the opposite effect that you are looking for (think of the Luddites burning textile mills in England, then multiply by 1000...)

As for how that will play out 1000 years in the "future", my opinion is that you will have created a new time line, so in "our" timeline you disappeared with a library of "how to" books, and disappeared forever. We would see no changes at all.


Is this theoretically possible?

No. Time travel is not possible. There is quite a bit of argument as to why it is impossible, but the simplest is that it hasn't happened. If time travel were possible, we'd see time travelers all over the place.

Of course, this forum is devoted to the development of fictional worlds. So our normal approach is to assume that your premise is possible in your fictional world. So here we'd start by assuming that in your world, paradoxes are not a problem for time travel. It just works. We could speculate as to why it works, but I don't know that it matters for this question.

Teaching advanced science

I think that you are overestimating the ability to teach advanced science. It's not as simple as just sending one person back. You'd have to send back an entire school system's complement of teachers.

Even if you only go a hundred years from 2015 to 1915, things changed a lot. In 1915, they still used slide rules. In 2015, we use handheld computers. What will we use in 2115? Maybe it's just more powerful computers. Or maybe it's something as different from an Android tablet as the tablet is from a slide rule. Do you know how to teach modern science with a slide rule? I certainly don't.

Moving the example to 4000/3000 doesn't fix this. It just hides it since we have no idea of what technology would be like in those years. For all we know, technology would regress during that period because civilization collapses in 3300.

Is this the best approach?

I'm not sure that lack of knowledge is the big reason for lack of progress. Consider what happened around the time of Christ. They stopped funding basic research. Changing that would have far more of an impact than sharing knowledge.

What would have happened if the Roman empire had become more democratic rather than more autocratic? Skip the Dark Ages entirely.

How I'd do it

Hand out time machines to everyone. People could do their research and then send the results back to themselves prior to when they started. That would save time individually and would speed research times going forward. Perhaps develop a short research cycle just to be able to reproduce the results. No need to go back hundreds of years -- days or months at a time is plenty.

Consider Edison's ten thousand ways not to make a light bulb. That took his people ten thousand attempts. What if they sent their research back. Skip the ten thousand attempts and go right to the working one.

Need to choose between two options? Pick one randomly, send the results back, pick the other, and send back both sets of results. Instant research! True A/B testing, as even death is reversible. Repeat the research with the same exact subjects but switch the choices. Or keep the choices and see if you get the same results.

Just the elimination of accidental deaths would speed up research. No car accidents or murders cutting promising careers short. Future Death division will take care of it (think about how Minority Report's Future Crime would work if they could predict all death).

The danger

Of course, the danger here is that someone will try a full on conspiracy to put themselves in power by changing the past. Of course, you have time travel too...


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