Time traveler's cheat sheet


Have you ever fantasized about traveling back in time a few hundred or thousand years and giving civilization a boost? Here's a poster for you in case your fantasy comes true. You can even get it on a T-shirt.

UPDATE: Some commenters have kindly pointed out that this poster was created by Ryan North of Dinosaur Comics. Thank you, kind commenters!

Time traveler's cheat sheet (Via Bits & Pieces)


  1. This was made by Ryan North of Dinosaur Comics (Qwantz.com). Or, at least, it’s been sold by him for almost a year now.

    Please give credit where it is due.

  2. It’s a good start, but they left out reminding me which stocks to invest in, which lotto numbers to pick, and which sporting events to bet on.

    1. That would be too much information for a cheat sheet, except for traveling to a very specific time. Also keep in mind that going back in time and making lots of good bets and investments, not to mention “inventing” all this stuff, is itself going to profoundly change history, so tips from our timeline would only be useful for a short time anyway.

  3. Hey, it’s me, Ryan! I made this poster. Glad you like it, Mark!

    You’re linking directly to the image, but if you want to see it in context, here’s the print page:


    (You can also get it on a shirt!)

    Thanks for the link!

  4. I don’t suppose anyone will care, but the explanation of flight is incorrect. Airfoil shapes cause streamline curvature, which gives rise to a force normal to the streamline. The statement about slower moving air having more pressure is just wrong, wrong, wrong.

    1. Pressure is related to the normal force you are talking about–and the slower moving air exerts a larger force than the faster moving air. The boundary layer is not mentioned either, but we have to leave some intrigue for future scientists. Don’t every brilliant mind there ever was just because you’ve mastered space-time.

      1. There primary problems with this argument is this: there is no justification for assuming that a fluid parcel traveling over the top of the wing is moving faster than one traveling under the wing – hence you cannot appeal to the Bernoulli eqn (move faster = lower pressure) for pressure guidance. It’s all related, of course, and there is no “real” simple explanation of lift, but streamline curvature explanation (Euler-n eqn) doesn’t require any transit-time assumptions.

    2. Slower air does, in fact, have higher pressure. It’s counterintuitive, but true. That’s not to say this is the only reason airfoils work, but it is an important one.

  5. LOL, I’m reading the Grantville Gazette IV right now, part of the huge shambling Ring of Fire alternate history series, and this totally reminds me of that…

    For the unfamiliar, the first book (“1632” by Eric Flint) posits a small West Virginia mining town scooped out of the y2k-era earth and deposited in the middle of the 30 Years War in Germany, and how the modern villagers use their modern knowledge, the contents of their library, and surviving parts of their technology base to transform 17th century Europe.

    1. “Conneticutt Yankee in King Arthur’s Court” by Mark Twain hooked me on this kind of stuff when I was a kid. To be honest, I read the “Classics Illustrated” version.

      Thanks to you, I just ordered “1632” from Amazon.

  6. Awesome! Reminds me of my favorite day dream when I was a kid. I would spend hours thinking about how to explain all the technology in my home and the science I knew to Leonardo da Vinci. I figured he would get it quickly if I gave him the opportunity. If I went back in time, I’d certainly want the original two-volume set of the The Way Things Work (far better than the modern version)(http://www.amazon.com/Way-Things-Work-Illustrated-Encyclopedia/dp/0000913154/ref=sr_1_4?ie=UTF8&s=books&qid=1263416899&sr=1-4), plus something like Asimov’s Intelligent Man’s Guide to Science series with modern updates… any suggestions?

  7. He appears to have left out how to invent intellectual property so you can ‘take the credit’.

    Apparently people from the future do things to ‘take the credit’ rather than solve difficult problems.

    Perhaps then it should include the invention of TV talent shows?

  8. I learned to fence in college since I knew that swords were around a lot longer than guns. I learned archery in high-school for the same reason.

    1. I would have imagined that the skills that go with fencing swords are quite different from, say, those required to proficiently wield a claymore or a katana.

      (Another high school archer here!)

  9. This should only be necessary for amateur time-travelers; anybody smart enough to invent a time machine already knows these things and doesn’t need such “cheat-sheet” reminders.

  10. I’m 30 years old and I don’t think I’ve ever spent a day of my life where I didn’t think about what I could possibly make / invent if I went back in time. For some reason, this has always struck me as VERY IMPORTANT. Oddly, this poster matches up quite well with the running list in my head.

    Although, to be truthful, sometimes I think it may also be useful for deserted islands and post-apocalyptic futures, but most days its for the off chance that I should find myself in the past.

  11. I was always a little worried by including Penicillium notatum. There are lots of Penicillium, they all look like that, and they’re not all safe, or you could cure yourself by eating nearly any moldy meat or cheese.

  12. First: This is a rerun: http://gadgets.boingboing.net/2009/04/15/time-travel-cheatshe.html

    Second: This only provides general concepts. If you don;t understand the underlying principles, the mechanics, the biological aspect of these this data is only useful for a game of trivial pursuit. The profile of a wing, for instance, is only useful to you if you have a lightweight engine and the knowledge that a propeller shares the same profile as the wing.

  13. It’s always a fun game to try and work out what would be the best things to “invent” if you went back in time. Assuming, of course, that you aren’t aware that you’re about to be zapped back and so don’t have time to take a Nuclear Physics course and carry enough Plutonium and lab equipment to make a working nuclear power plant or whatever.

    In the good boom Lest Darkness Fall, the guy is able to invent the still and the printing press.

    I always thought that stirrups would be an amazing and very easy thing to invent (they completely revolutionized horse warfare). I bet I could also get by as a doctor better than most actual doctors before, say, 1700.

    I also always imagined going back and trying to teach the Greek mathematicians the Arabic number system.

  14. Ryan North read this post, then, using his time machine, went back a year to create the ‘original’ and claim credit for it – cunning.

  15. I’d also appreciate knowing how to make bricks and dynamite or some other fairly stable but simple explosive. Both of those have seemed to go down pretty well in terms of history. Gunpowder might be nice to know how to make, just to be able to rile the Chinese a bit.

    1. Bricks: dig up some dirt. Put it in a sealed clear container and shake until thoroughly dissolved. Let sit motionless until the dirt precipitates back out; it will deposit into three layers comprising sand, clay, and organic detritus. The more clay the better, the less organix the better, the more sand, the higher the temperature required to bake the bricks solid. Too much organic stuff or too little clay and it won’t make a useable brick at all. Rummage around until you find a nice deposit of mostly clay. Dig a big hole, fill with water, add removed soil back into water whilst stomping like a vintner’s ugly daughter, and throw in some of whatever you’ve got that has good fibers, like straw for example, chopped into more-or-less brick-length. Mold mud bricks by hand onto a drying board, let them dry. If you can figure out ways to wire-cut them to uniform size or perforate them to speed drying and minimize kiln explosions do so. Once they are utterly dry, fire them until they are as bricky as you desire. If they are insufficiently dry they will explode during this process, so watch for that. You should be able to get a 21st century grade brick in about a week of experimentation with no more information than I’ve provided. More explicit information would be useless since your local clay composition will introduce variables.

      Gunpowder: Black powder is 75% saltpeter, 15% softwood charcoal, and 10% sulfur by weight. Saltpeter can be found in yellow crystals under dungheaps. Sulfur is a common mineral that looks and smells like egg yolks. Softwood charcoal is made by covering a fire made of deciduous tree wood with turf, leaving only a small smokehole at the top; smothered, incomplete combustion makes charcoal. Grind the ingredients to powder, mix them wet, and grind the resulting paste into powder after it dries. Expect to get blown up during that last step. You will increase your chances of survival if you don’t grind your powder anywhere near your powder store. Smokeless powder: Dude, don’t even think about it. If you already know how to make guncotton you can consider cordite, but I’d just go for nitroglycerin and call it a day, myself.

      Hope that helps.

      1. Wow! Yes, I have wasted many hours thinking about time travel and gunpowder does rise to the top. I love that flight gets top honors–but if you’re gonna mention nuclear power it’s not like you’re avoiding military applications as a matter of principal.

        Remember–every genius gets hired by the military first!

        What’s even better is how saltpeter is made from urine. Both a colorful story and a hugely important discovery. I am unrepentant that I have spent many hours fantasizing about how pissing on a heap of cow manure could have changed the world.

      2. Actually I spent a good long time figuring out how to synthesize smokeless powder if I were shot back into, say, any time period after the invention of batch distillation and lime kilns. It’s difficult, but not at all impossible.

        If you’re interested, the basic ingredients you need for two-component smokeless powder are a stabilizing medium (say, petroleum jelly or baking soda) and the two explosives, typically nitroglycerin and guncotton. The first is relatively easy to obtain, the second and third must be synthesized.

        Glycerin can be obtained from the glycerin-rich bottom layer of a soapmaking or, alternatively, biodiesel reaction. The fat should be easy to obtain; olive oil or tallow will both do fine. Strong basic catalyst can be obtained through caustic lime from a lime kiln.

        Similarly, base can be used to strip the lignins off of any lignocellulosic plant fiber by heating in water for a day or so.

        Strong acid can be formed by burning raw sulfur and combining with steam in a glass container to produce a mixture of sulfurous and sulfuric acid. Distillation can be used to bring it up to whatever concentration is desired. Add potassium nitrate from urine/feces mounds, or alternatively add chilean saltpeter (sodium nitrate) and you get nitric acid, which lets you synthesize both nitroglycerin and guncotton from the aforementioned processes.

        Take you a few months but very doable, the closer to the 1800s you get the better.

  16. “Congrats… you’ve just invented pasteurization”

    … and you’ve also just killed off much of the good stuff in there, too — e.g., beneficial enzymes and nutrients. Pasteurization is useful in certain contexts, but it does reduce the nutritional value.

    There is a lot of health info on this sheet, but perhaps not the best info, IMHO, to send back into time. Many would argue that, for example, we *over*-vaccinate now — or that we *over*-treat with antibiotics. Why start this trend way back in time? You may actually be killing off the present! (For example, if over-use of antibiotics leads to super-bugs that wipe out humanity. Thus, introduce this, and we may no longer exist.)

    Also, diabetes is curable by diet. Shocking to many, yes, but check out the “Movement to Reverse Diabetes Naturally” (Google it) and you’ll see *numerous* examples of people who’ve kicked insulin 100% after changing their diet. Why kill off tons of dogs and pigs when you can simply eat healthier?

    Super-cool idea, though. I’m just not a mainstream guy when it comes to health.

    1. (For example, if over-use of antibiotics leads to super-bugs that wipe out humanity. Thus, introduce this, and we may no longer exist.)

      The only thing “super” about super-bugs is antibiotic resistance, so if you don’t have any, all diseases are essentially super-bugs. Mankind hasn’t been wiped out yet, and modern diseases haven’t come closer than some of the great epidemics of the past.

    2. “I’m just not a mainstream guy when it comes to health.”

      Sweet. Start with that, and everything you say is a useful counter-argument. Start with your actual beliefs and you’re not that different from a christian scientist.

      Incidentally, if a doctor talks about the whole vaccine conspiracy it is now officially legal malpractice. It is illegal for a doctor to suggest that vaccines are linked to autism (or insert your wacko idea here).

      However, as long as your beliefs selectively creep into the mainstream where they hold, I’m totally happy and agree you’re doing a public service.

    3. Type II, sometimes. No diet will return the insulin producing cells my immune system killed. That website looks pretty scammy.

    4. I don’t think you know the difference between type1 and type2 diabetes.

      Type 1 (Insulin Injections): Body does NOT generate insulin. This is caused by a deficiency or failure of the pancreas. Injections are required and while a proper diet will help, it will NOT remove your insulin dependency.

      Type 2 (Pill/Diet Controlled): Body does not use insulin properly, this is normally controlled by a pill that helps the body use it’s own insulin. Not only can obesity be a cause for

      Type 2 diabetes, but a proper diet and weight loss can actually reverse the condition.

      My father as Type 1 Diabetes and while there are some experimental procedures being worked on, there is currently NO cure. Until there is a medical breakthrough, Type 1 Diabetes sufferers will Please do not give medical advice about conditions you are only familiar with from random googling.

      More Info: http://en.wikipedia.org/wiki/Diabetes_mellitus

  17. Just browsing through this, I must take issue with the mention of Polaris at the north star. Due to the precession of the earth on its axis (think of the wobbling that happens when you spin a top or a gyroscope) the stars in line with our axis to the north migrate from our perspective, so there could be another polestar. The best thing to do is stare at the sky at night and look for the one that doesn’t move- tough, I know, but that’s how they did it 600 years ago.

    Plus, what if you wind up in the southern hemisphere?

  18. I’d be sure to memorize the various manufacturing methods (modern and older) for a number of basic but important materials, and understand how to make cruder versions of the devices used in the manufacturing process. You might have to go all the way back to methods for refining ores, but it would increase the range of centuries you’d feel comfortable getting dropped off in.

    Also memorize timeless witty remarks, which are great in a jam.

  19. I have never fantasised being, say, in the Middle Ages or before. People need to know the truth of living in the past. Highwaymen were thugs, people stank and the Church held too much influence and dealt in FEAR. And my sister would not have survived her eye infection due to lack of penicillin.

  20. You should make sure your cheat sheet is fireproof since you’ll probably end up being burned as a witch.

  21. Great idea, Ryan. Well done. Okay got that over with. Issue with the longitude and London blurb. Sailors were already doing the London-time thing. Trouble was roiling seas upset the accuracy of shipboard clocks. That big prize was to find a clock whose inner movement was unperturbed by sea movement – the chronometer.

  22. I have the T-shirt. So far the only person to compliment me was a Target cashier.

    I’ll show you all!

  23. If you go back in time, aren’t you almost certain to end up in empty space?

    Going back in time could be easy, but maintaining your position relative to the earth, sun, solar system, galaxy, etc. seems much more difficult.

    In other words, never step foot in a time machine, even if you know (especially if you know!) it works… unless it’s a Delorean of course.

  24. If you get a Tshirt, can you get the text printed upside down so you can read it when you are time-traveling?

  25. I just realized this earlier today: If time travel becomes possible, and people can go back in time, wouldn’t somebody have killed Hitler?

    So either time travel to the past is never invented, or everybody in the future is a Nazi.

  26. Max–I figure if time travel exists in the future, it’s probably heavily regulated, and there’s probably some rule in place that’s like Star Trek’s Prime Directive of non-interference, except for time periods instead of planets.
    Or, alternately, picture a timeline in which the Holocaust doesn’t happen, but some other horrible thing happens. Someone from the 53rd century or something goes back to prevent that awful thing, but inadvertently causes the Holocaust. It could be that no matter how many awful things get fixed by future-folks, the unpredictabilities of the timestream are such that creating a timeline free of atrocities is impossible.

    1. The thing is, if time travelers came back here and changed history, how would we know? If even someone from today traveled back and killed Hitler we wouldn’t assume something incredible happened (it’s not like we would have “remembered” the future that did not get to occur– from our point of view that murder would have always been a part of “real” history), so in theory time travelers could have changed history a million times and we would not even notice (unless, perhaps, WE were the parties that did the changing and would remember the alternate history.) For example, how do we know that JFK’s assassination was not performed by time travelers who witnessed him (let’s say) go nuclear in Vietnam and start WW3, and sacrificed him to save the world? (HA! take that Jim Garrison!)

  27. Holy crap, this guy read my mind. I’m always thinking about this stuff, and half the time this is why I’m on wikipedia. I suppose this could also serve as T3H OFFICIAL CIVILIZATION REBOOT MANUAL in case of a zombie apocalypse or something. I’m also pleased at least one of you mentioned soap-making. How to make cement, the Watt steam engine and subsequently the internal combustion engine (which is arguably a greater obstacle to flight than understanding the finer details of aerodynamics), and the Bessemer process for making steel would also be useful additions.

  28. I’m not so sure killing Hitler would have stopped the Holocaust.

    If a leads automatically to b, then maybe, but German politics in the 20s and 30s had a lot more going on, and Hitler was an opportunist. But, hey, just read modern German history and learn about contexts and links, and you’d really have to knock a lot of people off to get WW2 to not happen.

    And if you did, WW2 would happen anyway in a different time (delayed by 3 years perhaps), and you might want to actually kill Stalin. imho he was a bigger phucker, he just didn’t deliberately publicly target certain types of people, record it so meticulously, and go on rants that were completely looney. Oh, and not start a war on 2 fronts, and think you are the boy-genius from Germania. And not be so, well, right-wing. Stalin is a bit more PC I guess.

    Maybe you would slip into the room on 20 July 1944 when the bomb exploded to kill Hitler, and move it back to its place, then leave. Then the bomb actually kills him.

    Or you might work within the KPD of the early 30s and kill the policy of ‘social fascism’, and work together with the SPD, so Ernst Thälmann would not stand. Hindenburg would not have made Hitler Chancellor, and 1933 would have possibly been the same as 1932. With the NSPAD just a large group of phucktards.

    And all the cool shit going on in Berlin would have continued, and we wouldn’t have the awful ode to garishness as the Sony Centre in Potsdammer Platz these days.

    But, thanks to the NSDAP, Germans of the oneties (2010s) are quite anti-militaristic, and show the west for being as authoritarian as always. When you’re the loser bigbigbigbigtime, you learn!

    But my time-travel plan is to build/subcontract a timetravel machine that can carry arnaments, go back to Sydney late Nov 1787, make friends with the Eora tribe of Sydney, teach them to handle guns. So when the whiteys come 2 months later, well, they blast them out of the water. Those who survive, well, they have to live by the existing law that existed.
    So long as I would be able to quickly do up some vaccs for the smallpox of 1789, things would be fine for the locals, and worse for the invaders (how many would be left…)
    Or something like that

    Ah, time travel how I like it: all political ….

  29. As someone already pointed out, the explanation of how a wing works is dead wrong and won’t help you build a flying machine.

    Also, chemical formulas like “C5H5NO2” and “C20H26O2” will not help you make superglue or contraceptives one bit. There are millions and billions of molecules with exactly the formula “C20H26O2”, and even if you knew which one, you have no idea what stuff to mix together to make it. It’s wasted space on this sheet.

    The penicillin thing at least gives you some vague instructions (but it’ll still take probably years of trial and error to make penicillin, if you’re lucky and get access to the resources you need).

    Hmm, making a sheet like this, but only including stuff that’s actually useful, might be an interesting project…

    1. The explanation of the wing is not actually “dead wrong.”

      I know lots of people learned in high-school that the reason wing generate lift is because the top surface is longer, and so the air has to travel further to get to the end, and so it has to travel faster. Faster = low pressure, so Bernoulli etc.

      Then everyone learned that this was wrong, and that just because the top is longer doesn’t just by itself imply that the air has to move faster. Myth disproved. So far so good.

      But then everyone reads explanations of wings that involve air pressure and jump in and say “wait! wrong! classic misconception, bozos!”

      But Bernoulli and air pressure are still important concepts for airfoils.

      A good part of the wing’s lift comes from deflecting the air downwards. Yes. But the angle of attack, coupled with the airfoil shape, does cause there to be higher pressure on the bottom surface of the wing than the top.

      The angle of attack causes the air below the wing to “bunch up” beneath it (because it’s hitting the underside). The airfoil shape, in turn, causes the top surface to spill up above the surface of the wing. This then causes a low pressure “gap” above the wing. This difference in pressure provides a second upward force.

      Here’s a good website that shows the myths of the commonly taught wing theory, and it’s these myths that everyone is thinking of when they shout “wait!” But you’ll note that the “correct” explanation is entirely consistent with Ryan’s diagram and description. Ryan just happens to omit the second reason for lift, the downward-deflected air.

  30. …the explanation of how a wing works is dead wrong and won’t help you build a flying machine.

    What? You are wrong, then, too.

    The point is to build something that flies, not to be pedantically correct. Often an explanation that has been simplified to the point of being incorrect is perfect for physical design work.

  31. A few took issue at my suggestion that diebetes can be profoundly treated via diet. I guess I gave a secondary source for that instead of a primary one. Instead of googling “reversing diabetes naturally,” google the work of Dr. Gabriel Cousens. He’s an M.D. in Arizona and has written many amazing books on nutrition, including a few focused on his research into treating diabetes. The secondary source was a web site that promotes a documentary called “Simply Raw” in which they took a group of diabetics and put them on a special raw foods protocol, then showed the (amazing) results after 30 days.

    @DarwinSurvivor Yes, I know the difference. I just wanted to keep my comments brief. For the long explanation, check out Dr. Cousen’s research. I think it’s incredibly inspiring.

    @teufelsdroch Don’t know exactly what you’re saying to me, but I’m *proudly* not mainstream medical. If someone uses that as a “counter-argument” against my ideas, that’s their problem, not mine. I’m here neither to argue nor to proselytize. Just sharing opinions like everyone else.

  32. Pfft. . . where is the valuable information for those of us that traveled FORWARD in time?!! This magical computing box has me flustered, dagnabbit!

  33. It’s even more funny to image some average individual using this when going back in time, and then being imprisoned and/or executed by order of some king because the time traveler couldn’t properly invent what they claimed they could.

    Terry Gilliam should jump on this, there are laughs abound I tell you…

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