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 birthday party, apparently 30 years in the past.

After going through the original disbelief, questioning of his sanity, and similar issues he resigned himself to accepting this is his world now and chose to utilize his knowledge of the future to live a better life. Early on he finds himself enjoying being seen as a prodigy for how quickly he 'mastered' his early school subjects, though as he reaches high school and college he reaches a point where he can no longer depend on his past education to score easy A's and finds himself not enjoying the disappointment he gets for 'not living up to his potential' as the prodigy he was presumed to be as a child.

However It's when he is graduating with his new degree in computer engineering that he finally gets informed why he is traveling in time, and that it will continue to happen. His time travel will obey the following rules:

  • He will go back in time when he goes asleep after his 35 birthday, which occurs on oct 2020, and wake up on his fifth birthday
  • He will experience a minimum of 10 of these repeat lifetimes, and potentially far more
  • Eventually the repeats will stop and time will continue as usual after the 35 birthday. He will know when the lifetime starts that it's his last repeat.
  • He will not forget past lifetimes, despite the subjective centuries. This doesn't mean his memory during a lifetime is any better or he will be any better at recalling something from a past lifetime then he would have been at the end of that lifetime.
  • Despite his mental age his thought processes are still is affected by having a child's body and mind. In his youth he will still enjoy 'childish' activities, struggle with controlling emotion & patience, and generally still have the temperament of a child despite his increased knowledge. Likewise he won't feel much in way of romantic or sexual attraction until puberty, and he gets to enjoy all the hormonal fun of puberty each lifetime.
  • The butterfly effect is in full force. While he can use his knowledge of the future to predict, and change, events at first as soon as he makes a significant change the future will be altered significantly enough to make it hard to anticipate what will happen next.
  • It is possible to pick small items to take back in time with him. The size and amount of items he can carry back is limited by both weight and physical dimensions, but with repeated lifetimes he will grow capable of transporting more back in time with him.
  • At the end of his first repeat he can carry back something around the size of a thumbdrive, by his third lifetime he could carry a laptop, the size of things he can store will continue to grow linearly with lifetimes (possibly slowing down after he reaches a sufficiently large carrying capacity)
  • Items he takes back in time will exist in a sort of Hammerspace until he needs them, preventing other's from asking questions about why a preschooler has an advanced laptop.
  • If he dies during a lifetime he will wake up as a 5 year old again at the start of a new lifetime. Death is still quite traumatic, and he may lose access to items in his hammerspace when it happens, so it's best to avoid it.

Personality wise you can also take the following for granted:

  • His family lives int he USA and is a non descript upper middle class family; well off but with no special resources or connections.
  • From personal experience he has decided he doesn't like being seen as a child prodigy, since he can't live up to the expectations later in life, nor does he like the spotlight of media attention. Thus he doesn't want to use his future knowledge to become too famous or rich or be seen as a child prodigy. He is not opposed to being seen as smarter then average or being successful, so long as he doesn't attract too much attention.
  • He is a generally decent person who doesn't want to utilize his knowledge to harm, manipulate, or exploit others. In fact he'd like to use it to help people and improve the human condition if possible; though he isn't a saint either and won't dedicate all his time to helping others.
  • After numerous lifetimes he is going to start struggling with boredom, impatience, and generally going mildly stir-crazy, particularly during his childhood when expected to spend most of his life in school relearning things he long since mastered.

The Question

Our protagonist has decided that one of the things he wants to do is to make 'future' knowledge generally available in the 'past' once he repeats. By uplifting our knowledge by 30 years he hopes both to improve and save lives via making advanced technology available sooner, and to decrease his own boredom by making more modern technology, games, etc available sooner for him to enjoy. He hopes for a compounding effect, with each lifetime making new discoveries thanks to the bootstrapping of having access to his past lifetimes discoveries.

I'm looking for the best strategy he can utilize for transporting knowledge backwards, and sharing the knowledge with the general public.

Even with a few 'lifetimes' of experience our hero won't come close to knowing everything, thus he is mostly going to be dependent on carrying knowledge back by bringing something back in his 'hammerspace'.

Luckily he could fit gigs worth of documentation on his thumbdrive even at the end of his first repeat, unluckily he won't have a machine capable of reading a thumbdrive's data for decades. He's going to have to think carefully about what to bring back in time to trade off storage capacity with availability of technology to read the medium at first.

In terms of distributing the knowledge he needs to figure out a way to making the knowledge publicly available to everyone in a mostly pre-internet world of 30 years ago, all while somehow ensuring his own anonymity to avoid drawing the very attention he's learned he does not enjoy.

Finally he has to convince people of the knowledge's authenticity. How does he convince people this is not a practical joke and this stuff is real? Yes Higgs-Bison is real, you can clone animals and rewrite DNA with CRISPR, and everyone should be expected to be carrying around a 'supercomputer' in their pockets, that they mostly use to play floppy birds. While his claims can be validated with research, how does he provide sufficient evidence to both convince people of authenticity enough that they will take time to validate it, and how can he help them validate things as quick as possible so they can skip ahead to using it to building cool toys for him to play with.

I'm looking both for original strategies to bring back knowledge, when he can carry little back in time and needs to figure out how to bootstrap things, and eventual strategies for once he can carry more backwards in time, and had enough time to watch and perfect the information sharing techniques, that he can just carry back a perfectly built society uplifting tool with him to the past.

My final solution:

I ended up deciding I liked the idea of asking questions and making other's do the work of figuring out how to do things for me so much my character could do it to. He takes back as much as he can per the original accepted answer, but he does a poor job of picking and choosing what data is most important to bring back the first time.

Luckily he brought back enough to convince other's he was legit, and he had the forethought to preface it with a description of what was happening and a request for help designing a better process for his next leap back. By the third leap large non-profits start to be created dedicated solely to designing the uplift package he should take back on his next leap. He just has to pay for the uplift hardware they designed, upload the data they deemed worth transporting, and carry that back.

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    $\begingroup$ +1! Very thought out and very good question. $\endgroup$
    – fartgeek
    Commented Oct 30, 2020 at 19:49
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    $\begingroup$ It looks like you're asking about the decisions your protagonist will make in a particular scenario in a world you've already created. Such a question depends entirely on the specifics of your protagonist and the specifics of the world that you are building. $\endgroup$
    – sphennings
    Commented Oct 30, 2020 at 19:54
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    $\begingroup$ @sphennings even if so some of the top questions on this site are like that $\endgroup$
    – Topcode
    Commented Oct 30, 2020 at 19:57
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    $\begingroup$ Popularity has never been a good metric for what is and isn't a good fit for this site. $\endgroup$
    – sphennings
    Commented Oct 30, 2020 at 19:58
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    $\begingroup$ @sphennings considering none are removed or closed, and all have good answers, i disagree that they cant be a good fit $\endgroup$
    – Topcode
    Commented Oct 30, 2020 at 20:08

7 Answers 7


It's 1990, so the home computer revolution has just went beyond 8-bit era. Good. Get an ESP8266 module, it is very basic (by current standards) computer (forget the wifi), but it has an SPI interface that can be used to connect an SD card. The crucial thing is the NTSC output - the 8266 is fast enough to directly modulate VHF signal on its data pin, and there are already libraries for text and video. You also need a keyboard - fortunately, 8266 has enough input pins and the work has been already done. Back in 1990, you just need a simple matrix keyboard - just re-solder any scrap computer keyboard you find, or build one from say doorbell buttons.

This will give you a rather modest (by 1990 USA standard) computer system directly connectable to a common TV set. Until you compare the CPU speed and access the data on your SD cards, then its beyond wildest imagination.

Now for communication, so that you would not have to copy the screen manually - 8266 is capable of serial UART communication, which was commonplace in IBM PC (AT) of 1990s. You need to interface the different voltages, but that's not a big problem. Or use common Centronix parallel port - easier to connect electrically, but needs some more coding (in my misspent youth, I did exactly this - connected a vintage 8 bit computer to a 286 IBM PC AT via parallel port and achieved something like 40KB/s transfer speed).

If by "thumbnail" sized you mean something slightly bigger, like Raspberry Pi, then you have much better possibilities (built in MicroSD slot, full Linux environment etc.) but it takes away half of the fun.

So, establish yourself as a child prodigy with keen interest in electronics (i.e. HAM radio), get some basic tools and a computer, build a power source and keyboard interface for your ESP8266 and you are done.

For the content of the (micro)SD card(s) you take with you, standard procedures for time travelers apply - dump of Wikipedia, selected patents etc.

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    $\begingroup$ Workable, but imho too much work. SPI interface would require some work (soldering) to make it connect with an SD card. On the other hand, SD-UART adapters like this one would require much less work, since we still need a 1990 computer to connect to. $\endgroup$
    – Alexander
    Commented Nov 2, 2021 at 16:45
  • $\begingroup$ How would you manage to address say a 64GB SD card formatted in NTFS with an 8 bit 8266? $\endgroup$ Commented Nov 23, 2022 at 21:05

I don't think taking back data and disseminating it would be all too difficult. Here's how your protagonist could do it:

  1. Load up a couple 1-tb microSD cards with all scientific papers, journals, reports, patents, and whatever written between 2000 and 2020. I'd avoid non-scientific literature as if you include a copy of Wikipedia or contemporary news, governments around the world would start up pre-crime divisions and that could be distrubing. Also bring a thumbnail-sized USB microSD reader.
  2. Travel back in time with reader and microSD cards
  3. You're a 5-year-old. Enjoy it and wait for USB flash drives and their protocols to be invented
  4. You're 15 years old, Y2K just happened, and the internet is starting to be a thing. Use your 2020 hacking skills (you can easily be the best hacker on the planet if you include zero-day exploits and hacking software in your microSD cards) to easily break into the primitive, security-through-obscurity internet systems that have been established by universities and governments.
  5. Upload all your data onto university and government servers. This may require you to break into a university, get a job at a telecom hub, or something similar to access a high bandwidth connection. Alternatively, burn data onto floppy disks or CDs/DVDs and mail them to universities (obtaining money shouldn't be difficult if you can convince your parents to buy stock or lottery tickets)
  6. Sit back and enjoy while universities and governments around the world discover a trove of future-dated documents. Yes, there will be skepticism at first but the amazing part of science is that it's experimentally verifiable and very soon, this data will be used by other researchers to write papers. By disseminating this data to many places, you ensure that it can't be hidden or suppressed. People who refuse to use the data will be left in the dust by those who do.
  7. Rinse and repeat.

Unfortunately, it's almost impossible to pull this off and stay anonymous. Even if you do avoid getting shanghai'd by the government through your superior hacking skills, the investigation on who you are won't end with the time-jump. People, particularly trained government agents, are very smart and would undoubtedly bury encrypted, obfuscated, or disguised intel for themselves in published research papers, anticipating that when 2020 rolls around, you'll be grabbing up all the data and going back again.

At the start of each timeloop there will be an unknown race going on in the background to see which intelligence agency trips over the messages they've hidden for themselves in the data first. Once they find it and decrypt all their future-intelligence, a covert WWIII will be kicked off as one agency/nation will suddenly have an unprecedented multi-decade intelligence and technological advantage over all the others.

  • $\begingroup$ I'd advise figuring out how to get on ARPANET early. $\endgroup$
    – Malady
    Commented Oct 30, 2020 at 21:28
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    $\begingroup$ The protocols for today's USB drives and SD cards will be different in the next universe, so they'll be unreadable without major hacking effort. Tim Pratt's short story Impossible Dreams used this as a plot device: escapepod.org/2018/10/25/… $\endgroup$
    – lirtosiast
    Commented Oct 31, 2020 at 3:54
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    $\begingroup$ @lirtosiast Op never states that the protagonist is going to alternate universes, just time traveling. Also, even if they are different, a competent programmer who put in the prep work should be able to write a driver from scratch $\endgroup$
    – Dragongeek
    Commented Oct 31, 2020 at 9:02
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    $\begingroup$ @Dragongeek It is not about parallel universes. It is because the butterfly effect has 10 years to unfold. For the same reason I would not expect the lottery thing to work. Stocks maybe. $\endgroup$
    – M. Winter
    Commented Nov 2, 2020 at 12:16
  • $\begingroup$ Will definitely need some time to brush up on those skills. After 15 years of not being able to write any code (partly because the languages weren't invented yet) I think most of the details would have gone. I've had languages I haven't used for a couple of years and have to remind myself of the basics of those and I've just been writing in a different language for a bit. $\endgroup$ Commented Nov 2, 2020 at 17:23

30 years of groundhog loop back from NOW, and he can carry a compact usb drive with him?

No problem with accessing the drive in the past, just take along a ide-to-usb interface. (no, not the common usb to ide, its inverse. rare, but they exist). Once he can manage an actual hard drive, the storage ability is effectively infinite.

The strategy on the first loop would be to bring political, military and financial data. Initial world state will be utterly predictable, so he can easily go and win 5 lotteries in the first week, invest it all in stocks that just happen to surge the next week, and I absolutely guarantee that by the third week the world will have noticed the newest Billionaire. Be a bit "loud" about using it, and get snatched by the appropriate supersecret government department. Not pleasant, yes, but they will provide the means to disseminate the future knowledge rapidly and efficiently. They can also be 'trained' to respect the traveler's privacy and rights. "If you mistreat me, then next time I am not contacting you, neener-neener-neener!". For better results, also use the equivalent services in many other countries. worst case scenario, he is killed or the world is blown up. Then next loop just don't trust that same agency, or contact them in a different way. After even just a couple of loops, he should have knowledge of means to inject the future knowledge to these organizations without them having the faintest clue who he is.

The person himself does not need to do, or invent anything himself. Sit back, enjoy life. Look for opportunities that are easily exploitable. Look for ways to better use the loop.

With highlevel government involvement, and careful planning of the (ever improving!!) amount and quality of data he is looping back, global tech should be advancing by about 20 years further on each 30-year cycle.

Meanwhile, accumulate a "private" file and plan for the known-to-be-final loop, the only one where he cannot afford to take any chances.

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    $\begingroup$ Becoming filthy rich would lead to the media attention and publicity he explicitly does not want to experience again, having experienced that in his first repeating loop after becoming a 'child prodigy' and hating everything about the media attention of being in the spotlight. As a lesser issue this strategy would likely result in the government hording his knowledge for political gain rather then making it publicly available to other countries, he would rather it be made available to everyone so more can benefit from it and improve upon it faster. $\endgroup$
    – dsollen
    Commented Oct 30, 2020 at 20:02
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    $\begingroup$ He would only nee to do so ONCE, to get the needed connection info to the relevant agencies. If he insists on remaining anonymous and invisible, his maximum effect and rate of improvement will be many, many magnitudes less. $\endgroup$
    – user79911
    Commented Oct 30, 2020 at 20:06
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    $\begingroup$ On the first trip take a spindle of burnt CD's. 90's computers could read those. Include everything needed to implement USB, flash memory, etc. Next time you will be able to bring more data. You could repeat that a couple times to increase the bandwidth of future trips, but really once you have microSD cards and readers you are pretty good on capacity. $\endgroup$
    – Atog
    Commented Oct 30, 2020 at 20:18
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    $\begingroup$ Spindle of cd's is hella bigger than the allowed "thumb drive size" for first trip $\endgroup$
    – user79911
    Commented Oct 30, 2020 at 21:38
  • $\begingroup$ Ahh missed that $\endgroup$
    – Atog
    Commented Oct 30, 2020 at 21:59

First contact math

Wikipedia says that thumb drives were first sold in 2000, and SD cards around that time. Assuming that the protagonist can communicate discreetly and anonymously, or gets good enough grades by the age of 15 to get in touch with a mathematician at the local college that they can confide in, perhaps they can bring a solution to the problem that the mathematican was working on. Such knowledge can be verified without access to lab equipment, and so that researcher can confirm that the protagonist is from the future. The protagonist can then use that academic as a front, using their connections to nudge technological progress.


I was suggesting this in another answer, but for the self-use this might be even simpler. If you go -30 years from now, your protagonist at that time might not have the corresponding connectors for USB or SD cards yet. But they would have film.

So either use microfilm / microfishes rolled together to be small enough, or just use 135 film. Then, develop instructions on how to make a external-SCSI (or whatever) converter to USB, plus the actual thumb drive. This might be tricky. Very tricky. But I am unsure, if the SD card is much better.

But the general idea is to bring the time when the card is readable closer by bringing instructions on building an adapter with it. The instructions should be readable, before the card is.

The next problem is the file system. A larger card might have exFAT, NTFS and what not. Good luck reading this on a C64!

Notice, however, that "large UNIX machines" were there for a lot of time. So, probably, some UFS or something might be writable nowadays with FreeBSD and is still readable in the late 80s on some Sun workstations. But good luck getting access to one of the USD 10k+ devices as a 5 year old! And good luck obtaining some BSD derivate without internet in 1993!

The easiest way is just to put the information you need on film. It would be much more limited, but the access is much easier.

As for the "layered" solution: paper notice -- film -- digital storage -- ..., it is easier, when the recipient knows, what to do with it. Is it not the case, you would need to provide instructions on the previous layer on how to read the next.


It may be easier if the protagonist would accept the role of prodigy and could spearhead the scientific research from an early age. However, if he must remain anonymous, he must find ways to disseminate the future information.

For the first iteration, I assume, the protagonist wouldn't have a chance to pack anything, let alone a machine-readable data storage. So he must write down as much as he remembers, before the details would fade away from child's memory. Depending on what he studied, this information may become very useful in 1990s world, or not usable at all.

The second iteration is becoming more interesting. One small item can be brought back. He can take a modern USB drive and wait for some 10 years until it would become readable, as @Dragongeek had suggested. Or, he can take something like Mini CD with him. Pro: it's readable everywhere right in 1990. Con: it contain only 210 MB of information.

210 MB is tiny by today's standards. However, if limiting the media to text only, this can pack a small library. Moreover, zip file archiver was already available in 1990, so the amount of information could be easily doubled. What our protagonist needs to do is to carefully select what to pick. I suggest picking scientific and engineering articles, patent documentation and any blueprints if he's able to get them. The design of Apple A14 processor, for example, is nice, but the details of how to make 5 nm fabrication process work would be nicer.

Thus, I further suggest that our protagonist would spend his iterations burrowing into corporate secrets and engaging in technical espionage (as legal as it's possible).

Anonymous dissemination of information in 1990 would be considerably more difficult than in 2000, but it's still possible. In 1990, the world (and USA, in particular) already had email and bulletin board systems. Those systems, however, were often disjointed and providing only limited outside access. Here I second @Dragongeek's suggestion of hacking. Our protagonist can hack university's email server and send the information to the particular scientist (or, at the time, a student), who years later would perform that groundbreaking research.

On second iteration, as more baggage can be carried, our protagonist can take with him modern USB storage as well as custom adapter (like ide-to-usb interface mentioned by @MarvinKitfox). And again - collect more nitty-gritty technology details which are not found in research papers and patent applications.

Rinse and repeat, until he carries the whole "2020 for the dummies" blueprint back to 1990.


I know its an older question but its something I've been thinking about for a long time.

For starters you will buy the best storage capacity you can before oktober 2020 and store the data you want on it. Alongside it you buy a foldable data link that can connect to an 1990 PC of your choice, have one specifically made for the purpose if necessary. You could even skip this and order a microPC instead.

Key however is that you can access a series of text documents first and print them. Each document contains a date and adress so you know when to send them. These documents contain many many things:

  • they create persona's and businesses that only exist on paper.
  • you lend and spend money using these persona's to play the market early on before the butterlfy effect moves too far.
  • as your money grows you also send out letters to hire people and give them tasks, like being the face for your businesses and let you lend money that would require showing a face. Similarly you can buy existing companies and give them tasks as a legitimate group for you to perform.
  • hire people to win loteries, including the Powerball. It may take a few tries to find suitably trustworthy people who would make sure the money goes to you (a threat and a small payout of the money could help), but this will net you a great deal of money (some powerball wins went into the billions).
  • now play the market hard, use every nook and cranny of the law, foreknowledge of people's likely choices and likely market changes to earn billions more.
  • again, this is done all by paper mail early on. You'll likely create seperate folders, load these on a PC and give these to a group of hired hands who's only task it is to print the data, put it in envelopes with the right adresses and send it at the right time. That means that practically you could have thousands of letters being send every day without lifting a finger, controlling your empire through guesswork, learned lessons from previous lives and whatever supercomputer you could hire up until september 2020 to do predictions for you.

That is just the preperatory work. As with that money you now start to buy up technologies and companies that you will need and want.

The problem is that much of that technology will require increasing amounts of data. You wont be storing the complete detailed plan of construction and material properties of an F35 on one thumb drive. So what you do is set the researchers to create Minimal Reference Points (MRP's). These MRP's are the smallesr possible account required for the researchers to create a particular material or technology. So you can cram many technologies into one drive and have researchers invent them plus create all the data sheets and crap needed to work with it, as they invent it another group is already working on a technology that requires juuust that piece of tech which they just so happen to receive. Chief among these would naturally be low-cost and easy to create tech which boosted our capabilities but took years for us to discover.

Now this will help you create general technologies, but some lives you will focus on a particular technology. For example you may buy all airship tech and spend billions on creating and testing airships, just so you can create an MRP for it and build working prototypes in a fraction of the time.

A more important thing would be biotechnology. If you have the perfect CRISPR techniques (or superior to CRISPR) in detail either on your thumbdrive or in your mind, you could have someone create it very early in your life (they may not know what they did but still produce decent quality). This could let you improve both yourself and people around you, say the (future?) researchers working for you. With the right technique you could make yourself smarter, eliminate certain genetic disorders or simply improve your own life.

With this in place, you can create and fund a technological empire that can have technologies that wouldnt otherwise be economical to create. Think the aerospike thrusters for space ships, functional and efficient airship technology and other such things.


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