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Timeline-Altering MacGuffin

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"Sixty years from now, it will be a child's toy. But today, it's the most powerful weapon on earth."
Vandal Savage, about a laptop, Justice League, "The Savage Time, Part 2"

The reverse of the Butterfly of Doom, the Timeline-Altering MacGuffin is a nondescript item from the future that, if left in the past, will bring about an Alternate Timeline. This can be something that contains information about the future, such as a history book, for instance. It could also be a future technology that someone in the past decides to reverse engineer. The item will probably become a MacGuffin pretty quickly.


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    Anime & Manga 
  • Full Metal Panic!: The "Whispered" are privy to "Black Technology" — devices they should be unable to design for decades or even centuries. It's extended their Cold War clear into the 21st century.
  • Negima! Magister Negi Magi:
    • Possibly used when Chao Lingshen produces what may or may not be a future copy of the Springfield family register as the ultimate party-breaking item. Whether it was real or not is irrelevant, since it was destroyed shortly after. She did, however, bring a number of real pieces of information and technology from the future as well.
    • In chapter 349, it makes a return later and is revealed to be... blank. The future was changed, so the family register has yet to be filled out.
    • Negi is shown to be married in at least one timeline, to one of the girls who peeked at the original book. It's entirely possible that she was the girl he was married to the entire time.

    Comic Books 
  • The Sandman (1989): People are digging up a bunch of those from an archaeological dig in Crete. Sadly some of them are explosive.
  • Superman: In Pre-Crisis stories, it was well-established that changing the past was impossible. One issue of World's Finest, however, saw the time travelling villain Chronos acquire the means to "interactively" time travel, so he could change the past. Fortunately, he never gets the chance. Instead, Batman gets sent back in time to the night his parents were murdered, tempting him to Set Right What Once Went Wrong at the expense of the future he knows. Fortunately, he resists the temptation, and Superman is able to bring him back to the present.

    Films — Live-Action 
  • Back to the Future:
    • In the first draft of Back to the Future, Marty revealed to 1955 Doc that all his crazy inventions could be cheaply powered with Coca-Cola (It Makes Sense in Context... well, almost), so when he traveled back to 1985 he actually ended up in an alternate reality where everything was a Zeerust '50s rendition of the future, with hovering cars and robots everywhere powered by Coca-Cola. The dystopic part? No Rock and Roll!
    • The former Trope Namer is the Gray's Sports Almanac in Back to the Future Part II, which allowed Biff Tannen to become wealthy by placing bets on the outcomes of sporting events when his future self gave it to him in 1955. What makes it work is that the ripple effect ensures that the almanac will recursively update to reflect the changes in outcomes as a result of his prior betting, meaning it'll always be accurate. He then uses the money to become a Corrupt Corporate Executive and ruin the lives of Marty and everyone else in Hill Valley, forcing Marty and Doc to go back in time and stop it.
  • The Jet Engine in Donnie Darko — also an example of an (Un)Stable Time Loop and a Temporal Paradox. Probably one of the soonest "futures", though — less than one month later.
  • The Cell Medals become this in OOO, Den-O, All Riders: Let's Go Kamen Riders. After Ankh accidentally leaves one in 1971, it falls into the hands of Shocker, who use it to create a monster strong enough to defeat Rider #1 and #2, allowing them to change history and Take Over the World.
  • Star Trek:
    • In Star Trek IV: The Voyage Home, Scotty teaches the 20th century plastic maker how to make "transparent aluminum", justifying it with the argument, "How do we know he [the person to whom he gave the formula] wasn't the one who invented it?" (The man himself explicitly points out that working out the details to turn Scotty's sketch into an actual product is going to take years of research.) The original script had Scotty saying that he knows that the manager would eventually go on to "invent" it, therefore giving him the formula created a Stable Time Loop.
    • Star Trek (2009):
      • Played with the trope by a future Spock showing Scotty an equation that he would eventually create — however, earlier in the film, the reason that future Spock is there is explicitly stated to be an Alternate Universe, not a Stable Time Loop. Scotty had not only already invented the formula, but had tested his theory before. It went wrong, leading to his assignment at the remote outpost we see, but this could be part of the Alternate Universe. Spock only shows Scotty a revised version of his theory, bringing his own discovery earlier into the timeline.
      • The nigh-unstoppable warship belonging to the villain is also an example. In its own time period it is merely a mining vessel, but it's powerful enough compared to Federation ships of the past that it can lay waste to whole fleets of them. Its ability to blow up planets is due to something that they stole from Spock.
  • The Terminator: The arm and CPU from the first Terminator, left behind in the 1980s, brought about the rise of SKYNET. Well, sometimes. In any event, since the Terminator was sent back in time by SKYNET, this is also a Stable Time Loop... until it's broken by the destruction of the items in Terminator 2: Judgment Day, which doesn't stop SKYNET from rising again in Terminator 3: Rise of the Machines (where the novelization even implies that, despite the destruction of the items, what had already been researched was apprehended by the military, leading to SKYNET's creation). Yeah, Timey-Wimey Ball.
  • Hot Tub Time Machine: The Grays Sports Almanac version was parodied, where Lou initially makes a ton of money betting on the 1986 AFC Championship Game between the Denver Broncos and the Cleveland Browns. Unfortunately for Lou, the Butterfly of Doom (in the form of a squirrel that Lou had vomited on) kicks in to derail John Elway's game-tying Miracle Rally in the fourth quarter. And extra unfortunately for Lou, the terms of the bet were that not only does he give up all his earnings to the other guy, he now has to give Nick oral sex — and the guy he made the bet with has a gun and won't take no for an answer.

  • The 1632 series is about a small town from West Virginia sent back to the central Germany during the Thirty Years' War, so almost every object in the town is a Timeline Altering MacGuffin, particularly books telling of events beyond the point at which they arrived in seventeenth century Europe. The protagonists eventually take advantage of this by ensuring that only inaccurate transcriptions of uptime books circulate outside their territory, causing the royal houses of Europe to make some drastic miscalculations such as attempting to settle the Florida Everglades looking for gold.
  • A Connecticut Yankee in King Arthur's Court by Mark Twain. It goes from Lighter and Softer to Darker and Edgier in a serious Mood Whiplash, thanks to the author's personal issues at the time.
  • In the Dragonlance Twins novels, Caramon bringing a volume detailing events back from a very dark future was the reason Krynn did not falter into an Alternate Continuity where it was utterly destroyed.
  • A subversion in Driftless Wormhole — a cell phone accidentally taken to a society with Dieselpunk technology levels would be really useful, but they can't reverse-engineer it. It's so far advanced that they even have trouble gleaning ideas from it that they can use.
  • Harry Turtledove's The Guns of the South has an unusual application of this trope, as the timeline is already altered by time-traveling Afrikaners who arm the Confederates with AK-47s so they can win The American Civil War, and the MacGuffin comes afterwards. Through various circumstances, Robert E. Lee ends up with The Picture History of the Civil War, an elementary history book which the Afrikaners brought back with them for research. Through it, he learns that the men lied about the future being a constant race war between black and white, and also that the South's hopes of being Vindicated by History came to nothing thanks to their holding slaves being viewed as morally repugnant by future generations. This leads to the Confederates severing ties with the Afrikaners, who wanted to build a strong nation that supported "white power", and Lee (after being elected President) passes a bill calling for the gradual, compensated emancipation of black slaves.
  • The Harry Harrison novel A Rebel in Time subverts this. A racist colonel, Wesley McCulloch, goes back in time with Troy Harmon, a black officer, following him, assuming the man is going to give modern weapons to the Army of Virginia and thus help the South win the Civil War. He's confused when Perry instead plans to arm small groups to seize key Union towns. In their final confrontation, the colonel asks why Perry would do this when John Brown tried and failed. Perry's dying words: "Who's John Brown?" Going over his effects later, the colonel realizes that Perry (who barely passed high school and a horrible student of history) just happened to be basing his entire plan on the one book on the Civil War that didn't mention John Brown or the raid on Harper's Ferry.
  • Lewis Padgett's "Mimsy Were the Borogoves": A scientist doing an experiment in Time Travel realises he doesn't have anything to send back, so he grabs some of his children's educational toys and sends them back to 1943 (when the story was written) where they educate a brother and sister how to move into another dimension, which they do before their father's horrified eyes.
  • Occurs in "Mr. Was" where the main character previously wrapped a sandwich in newspaper. This newspaper had stocks from the future on it when he went to the past. The man who later became his grandfather found this paper and used it to get rich.
  • This trope is played around with in The Pendragon Adventure. Generally, taking an item from one territory to another is said to cause disaster and allow Saint Dane to win. This first occurs in The Merchant of Death, the very first book, when Bobby ignores this warning and gives the Milago tribe all the necessary parts to make an atomic bomb. Saint Dane is sometimes shown as doing this as well, such as in Black Water where he uses a poison from another territory to try and poison the locals, but in the very same novel, the protagonists use the antidote from the same territory as the poison to foil his plot. It goes so far as to have Bobby give the people of Ibara weapons from Quillan to defeat an army of Quillan dado robots, who themselves were attacking Ibara on skimmers from Cloral.
  • Done in Alfred Bester's Time and Third Avenue. A young lawyer accidentally gets a copy of the almanac from the far future year of 1985 and a timecop stops him before he opens it. The lawyer says all right, you can have the almanac: using it to speculate on stocks or bet on elections would be cheating, and I'm sure I can have a great career without cheating... only, I wish I could have some reassurance that the world won't end in a nuclear holocaust. So the timecop gives him a hundred dollar bill, one of the 1980 series. He can't spend it in his time, but he feels that he's well paid when he reads the name of the Secretary of the Treasury from the bill... and it's him.
  • In To Visit the Queen, a spin-off of the Young Wizards series, a book on modern-day engineering gets sent back into an Alternate Universe Victorian England, enabling the British Empire to rapidly develop many forms of modern-day technology. Including nukes.
  • In the Past Doctor Adventures novel The Roundheads, a children's history book from the TARDIS threatens to become this after the TARDIS crew lose track of it, but they're able to retrieve it before any permanent damage is done.
  • Subverted in Just War. Benny's history book, which details the entire course of World War II, falls into the hands of a Nazi officer. At first he dismisses it as a fraud intended to demoralize, then accepts its validity as the events it describes keep coming true — but he is unable to get his superiors to listen to his warnings, and watches helpless as the Third Reich rolls on toward its historical end.
  • In Pastwatch: The Redemption of Christopher Columbus, while studying the life of Christopher Columbus, a Pastwatch researcher ends up stumbling on the scene of Columbus washing up on a shore after a naval battle. Then he sees a vision of God telling him to sail west. Except the researcher sees the vision too, recognizing it as a hologram, probably projected by a small device. It becomes clear that this (our) timeline, in which Europeans colonized the Americas was no the original one. From what they can theorize, in the original timeline, Columbus never sailed west. Instead, he led a disastrous crusade against the Muslims, which left the European nations in financial ruin. Meanwhile, in North America, the Aztecs were conquered by their Tlaxcala enemies, who were even more bloodthirsty but accepting of new technology (the Aztecs were more conservative in that respect) and used it to take over both Americas. When the continent was finally visited by a Portuguese ship, the sailors were captured and tortured for information, revealing the secrets to building oceangoing ships and firearms. The vast resources of the Americas were used to build a huge armada of warships, which sailed east and easily crushed any resistance the impoverished and disorganized Europe could mount. Thus, the Tlaxcala managed to actually Take Over the World. Fast-forward a century or two, their descendants also developed Pastwatch technology and discovered that their civilization was doomed. So, they sent a holo-recording to the past, in order to create our reality. Unfortunately, they didn't do enough, and the current civilization is also on the verge of ruin. It takes sending three actual people into the past to fix things so that humanity remains prosperous.
  • In The Leapfrogged Console Wars, A Nintendo DS, along with it development kits and design documents, as well as copies of Pok√©mon Diamond and Pearl and Platinum, are sent to Nintendo at the beginning of 1990. This leads to Nintendo forming an alliance with Apple and ARM to develop the technology to release the DS in 1996. This would change the face of gaming, pop culture and the rest of the world forever.

    Live-Action TV 
  • Doctor Who: In "The Long Game", Adam attempts to leave one of these for himself in the past by recording historical information from 197,988 years in the future on his mother's answering machine. The Doctor finds out. He's not happy. Ironically, Adam himself ends up at risk of becoming one. He has his own brain upgraded in the future, to interface with the computers of the time. Now, whenever someone snaps their fingers near him, a little port on his forehead opens up. The Doctor mentions that Adam has to lead a quiet life and not draw attention to himself, or he risks being dissected for the future technology in his skull. At the end of the episode, his mother snaps her fingers while talking to him.
  • In The Hanged Man episode of Journeyman, a digital camera that Dan accidentally left in the early 1980s causes technology to leap far forward when he returns to modern times— including a family member being wiped from existence because of a "nanotech accident" on the day of his conception.
  • Legends of Tomorrow:
    • In the second episode, Vandal Savage finds a piece of the 21st-century Atom suit in 1975 Norway. Realizing its importance, he orders his people to reverse-engineer it, killing a scientist who claims that it'll take too long. Back aboard the Waverider, the "Legends" find out that this development will allow Savage to move up his Take Over the World schedule by a century or so, showing a picture of Central City on fire in 2016. Fortunately, the team recovers the tech before Savage can make use of it.
    • In a later episode, Professor Stein almost becomes a living example of this, as he's captured by Savage's Soviet allies, who want to make use of his knowledge to create an army of Firestorms that they can conquer the world with, as the Waverider shows via an image of Star City being invaded in 2000. Again, the team manages a rescue before the effect to the timeline becomes permanent.
    • In yet another episode, when returning Julius Caesar to his own time, Nate allows the Roman to see a book on the history of the Roman Empire. Caesar snatches the book without Nate realizing it. Upon returning to the Waverider, the Legends are shocked to find out that, with the book's help, Caesar was able to avoid his assassination and used the lessons in the book to ensure an unending reign for the Empire, which managed to conquer the entire world by the 21st century. Naturally, the book is recovered and Caesar is mind-wiped.
    • A Furby-like toy called Beebo ends up being transported into the 10th century Viking colony in North America called Vinland. The Vikings form a Cargo Cult, treating Beebo as a god and interpreting its preprogrammed phrases as calls to war and conquest, resulting in all of North America to be New Valhalla in the new timeline (effectively conquering it centuries before Columbus stumbles on the continent). Mick ends up roasting Beebo with his flame gun, convincing the Vikings that Beebo is not a god.
  • In Lois & Clark, after the first time Tempus was defeated, he was left in the past, where he wrote a diary that a man would eventually use to become wealthy by investing in oil, plastic, and computers. Later, that man's unfavorite son used the diary to blackmail Superman into stealing from the man's other son. According to this Villain of the Week, Tempus was either a man from the future or a fortuneteller good enough to put Nostradamus to shame.
  • Misfits has an episode where an elderly Jewish man with time travel powers tries to go back and kill Hitler. That ends badly, but Hitler manages to retrieve the man's cell phone from him before the man gets sent back to his time, leading to a future where the Nazis have taken over Britain due to technological superiority. Why the man went back in time with both his cellphone and a letter explaining he was going back in time to kill Hitler (instead of leaving the letter behind in case he failed to return) is not explained.
  • The Outer Limits (1995): In "Gettysburg", this is attempted but fails. Andy Larouche and Vince Chance get sent back in time to the Battle of Gettysburg. Andy, a Confederate sympathizer, tries to show a book called Great Battles of the Civil War to Colonel Angus Devine and his men to prevent Pickett's Charge and win the Battle of Gettysburg for the Confederacy. Vince stops him and hides the book in a house that Devine and his men occupied. The woman who owns the house later finds the book and is horrified by it. However, she secretly returns it to Vince without asking any questions as she is grateful to him for delivering her baby and saving his life when his umbilical cord became wrapped around his head.
  • Star Trek:
    • A non-time travel version occurs in the Star Trek: The Original Series episode "A Piece of the Action": A pre-Prime Directive starship 100 years prior had inadvertently left behind a book on Chicago gangs of the 1920s, which caused the civilization in question to develop into the original Planet of Hats, with a culture based around 1920s gangsterism. After the crew has fixed the entire planet, McCoy leaves his communicator behind, alarming Kirk who worries that this trope will take effect. "In a few years they could be demanding a piece of our action!"
    • One of the comics actually referenced the events of "A Piece of the Action", when various representatives were at Admiral Kirk's trial including one from that planet, with the only result being that the representative simply gives it back to McCoy after saying how he'd left it behind. (They had still kept their original gangster society, though the profits had been invested in things like schools, libraries, and hospitals. What Kirk hadn't anticipated was that, as the new boss, they had saved 10% of the take as Kirk's personal cut.)
    • The Deep Space Nine writers at one point considered doing an episode that revisits the planet from "A Piece of the Action" and finds that all the inhabitants are now dressing up as Kirk and Spock. This episode was to be a Star Trek 30th anniversary celebration, and was dropped in favour of "Trials and Tribble-ations". Considering how good "Trials and Tribble-ations" turned out, they probably made the right choice. The concept was later picked up in a comic.
    • The 1989 tie-in book The Worlds of the Federation had the same idea. When contact was re-established sometime around Star Trek: The Next Generation time period, the entire planet had restructured their society around TOS-era Starfleet and extrapolated enough technology to build a working starbase and apply for Federation membership.
    • The NES Star Trek: 25th Anniversary game starts out with the Enterprise being pulled into unknown space by a wormhole. When they finally reach Federation space again, they figure out that the wormhole was a side effect of the gangster planet blowing itself up. The last mission requires you to go back in time to retrieve the communicator and prevent the explosion/wormhole.
    • There was also The Next Generation comic issue "A Piece of Reaction" which follows the same plot (more or less).
    • Star Trek: Voyager:
      • "Future's End" has a 29th Century timeship that was sent back to 1967, although this results in a Stable Time Loop, since the technology boom of the late 20th century turns out to be thanks to the reverse-engineered tech from the timeship. Interestingly, the 29th century technology helps create the "holo-emitter" that the Doctor uses for the rest of the series, so the timeship was a Timeline Altering MacGuffin to the 24th Century as well.
      • The final episode leaves the possibility of this trope rather alarmingly dangling overhead. Future Janeway comes back over a decade to bring the crew home, decking out the ship in all kinds of future tech and eventually infecting the Borg Queen with a super nasty future virus. Now, given the Borg's ability to adapt, one can speculate that if they manage to overcome that virus, they would then have adapted to technology and programming that the Federation hasn't yet invented. Not only that, but they had already assimilated her shuttle from the future by then, including the armor and the torpedoes. In the Expanded Universe novels, specifically Star Trek: Destiny, this comes back to bite them.
    • In Star Trek: Enterprise, when stranded in the 29th century, Archer finds a book about the Romulan Star Empire. Luckily, Daniels is there to stop him from reading it. When they finally encounter the Romulans in a later episode (but do not see them), Archer mentions the book title.

  • In the Doctor Who audio drama "Colditz", it's discovered that their accidental appearance at Colditz Castle goes horribly wrong, and Nazis from the 1960s reveal that they got the TARDIS. The twist is that the Timeline Altering MacGuffin isn't the TARDIS, but a CD player which leads to them getting to the concept of lasers quicker than they were supposed to, thus having them win the rocket race, making the V missiles more deadly than they were and eventually letting the TARDIS end up in their hands.

    Video Games 
  • The Elder Scrolls:
    • The eponymous Elder Scrolls themselves. While not exactly a mundane item from the future, they are scrolls of unknown origin and number, referred to as "Fragments of Creation", which simultaneously archive past, present, and future events; all that has happened, all that will happen (usually in the prophetic form of "if X happens, then Y and Z will happen, in that order"), all that could have happened. They require immense training in order to read and actually interpret anything useful, and have a high probability of causing blindness and madness in their readers. (Even those who merely study the nature of the Elder Scrolls, never actually reading one themselves, are driven to complete madness with alarming regularity.) The Scrolls have been used by the various Imperial Dynasties throughout history to help guide the Emperor in making decisions.
    • What's more, they are absolutely and utterly immutable, such that they can change history, just by being read. In Oblivion the ultimate Thieves' Guild quest involves stealing one in order to break a Daedric curse. (Yes, even the power of a Daedric Prince pales in comparison to the power of the Scrolls.)
    • In Skyrim the player gets to read one for the first time. If opened near a temporal rift known as the "Time Wound", the Scroll lets you see an important piece of the past. If used anywhere else it, temporarily strikes you blind. The only reason why it only temporarily strikes them blind is because the Dragonborn's soul technically exists outside of time also. (Several more Elder Scrolls play into the plot of the Dawnguard DLC, though you'll only need to gather them there. A Moth Priest will read them for you, and his blindness is permanent.)
  • In the Legacy of Kain series, the Soul Reaver plays this role several times. This is not because of any property of the Reaver, but because every time someone travels through time, they bring their present-day version of the sword with them, and go to another point in time where the sword exists. Having the same item be present twice at the same point in space-time causes a paradox, which derails You Can't Fight Fate.
  • Another non-time travel version is in Predator: Concrete Jungle. The game starts in 1920s Chicago, where the Predator accidentally leaves some of his technology behind. Cut to modern-day, and the technology has become way advanced, with Hollywood Cyborgs and flying cars and all that fun stuff.
  • In SD Gundam G Generation DS, the cast of ∀ Gundam travels back in time to try and prevent the apocalyptic "Dark History" from coming to pass. Unfortunately, Gihren Zabi gets his hands on the Dark History data, which allows him to produce an army of super-mecha equipped with knockoffs of the Turn A's Gray Goo weapon.
  • The Sims 3: Into The Future features at least half a dozen ways to influence the future neighborhood of Oasis Landing. The two that play this trope straightest are introducing a Future Musical instrument to the present, or "pioneering" the design of future robots. All you get for either accomplishment is a statue of yourself.

    Western Animation 
  • Justice League villain Vandal Savage sends a laptop containing the history of World War II and schematics for advanced war machines to himself in the 1930s. With this knowledge, WW2!Savage easily outwits the Allied forces, deposes Hitler and sets his sights on world domination. The present!League, minus Batman (everyone but him was given Ripple-Effect-Proof Memory by being protected by Green Lantern's power when the laptop went back), must go back in time to prevent this.
  • In a Super Friends episode, the Superfriends are able to find the Legion of Doom by traveling to the year 7000 and finding a future almanac, which they simply look up the year when the Legion of Doom took over the future (the past?) in the year 3984. By the end of the episode they keep it.
  • One episode of American Dad! had Stan go back in time to prevent Jane Fonda from ruining Christmas (in his opinion). A tape of disco's greatest hits is accidentally left behind, where it's discovered by the past version of Roger the Alien, who becomes insanely rich and then goes broke riding the rise and fall of the disco trend. The net effect wasn't really noticeable, but at the end of the episode, the family complains that Roger is whining about disco, again (something he never did before in the series.)
  • Beast Wars features the Voyager Disk, which initially only helped Megatron find Earth, but was eventually revealed to contain both photos from the planet's present, in the future, which is the past, and a message from G1 Megatron ordering future Decepticons to go into the past to change the present. Both were used in attempts to Make Wrong What Once Went Right, with varying degrees of success.
  • In Transformers: Rescue Bots, Doc Greene's robot, Dither, ends up being one of these. Doctor Morocco gets his hands on Dither in 1939, which leads to a Bad Future.
  • Big Guy and Rusty the Boy Robot: When BGY-11 was accidentally sent to the past, it was found by English soldiers who learned how to control it. They renamed it "Iron Jack" and used it to stop The American Revolution. Because nobody knew everything needed for its maintenance, it eventually blew up but the damage was done. As a result of this, nobody developed BGY-11 or anything else that could have stopped the alien invasion BGY-11 did at the beginning of the series in the original timeline. Dwayne Hunter and Rusty then had to travel back in time to recover it and set history right.
  • Gargoyles: Xanatos' claim that he is a self-made man is apparently very, very true; when he and several others end up transported back to ancient Scotland (it's a confusing tale), Xanatos takes a moment to take a single coin of the time period, seal it in an envelope, and date it to be delivered to himself when he would be a young man in the future. He would then use said coin to invest and grow into what would become his future extremely powerful multinational company. Which would raise the gargoyles. Who would end up with the Phoenix Gate. And he'd end up traveling back in time with them. To send himself a coin.
  • Oddly averted in King Arthur & the Knights of Justice: In one "today's moral" clip, the knights are motivated to give items to the poorer members of the castle and kingdom, including items they brought with them when they were summoned from the future. While the letterman jackets and footballs could pass as (very) foreign objects, several of the knights are shown carrying textbooks. Beyond the normal content of freshman to senior textbooks, at one point Lance explicitly stated he was studying medicine, in case the football thing didn't work out. But there never seem to be any ripple effects from the information the books would contain, from Newtonian physics to mathematical systems such as calculus, developed well after the middle ages.

Alternative Title(s): Grays Sports Almanac