256 n yesterday, Today, and Tomorrow: Time Travel hero system 6th edition TEMpORAL MECHaNICS aND CONSEQUENCES f the many ideas raised in Science “Time is an illusion. Fiction stories, few have captured REAL-LIFE MECHANICS Lunchtime doubly so.” the imagination as thoroughly as In recent decades, time travel has made several time travel. The idea of being able —Ford Prefect O big jumps toward possibility, as physicists (many to journey to the past or future has fueled philosophizes in The of them Science Fiction fans) played around with many novels, television shows, and movies, Hitchhiker’s Guide To The concepts of modern cosmology to find shortcuts and it’s fraught with scenario ideas and plot Galaxy, by Douglas Adams through time. According to physicist Steven hooks for gaming. Unfortunately, it also Hawking, a rotating black hole distorts spacetime creates some problems in a gaming context. in such a way that one can go backward or forward This chapter looks at the methods and uses of in time by selecting the appropriate trajectory for time travel in Star Hero games. a close pass. Of course, the tidal forces involved Time travel was invented as a concept the first in close encounters with a black hole can exceed time somebody wished they hadn’t done some- tens of gees across a single meter, and a spaceship thing. In literature, the idea of visiting another must be going an appreciable fraction of the speed time was once solid fantasy, as in Mark Twain’s A of light for such maneuvers. But a physicist would Connecticut Yankee in King Arthur’s Court. With call those mere engineering details. the rise of physics models of “spacetime,” in which Another method is the possible creation of time is considered as essentially a fourth “dimen- a “wormhole” connecting two places that are sion,” the idea of moving about in time got a bit separate in spacetime. Starships could also use more scientific respectability. In his first novel, wormholes for faster-than-light travel (page 227). H.G. Wells dressed up the notion of time travel in Current theories require staggering amounts of technological trappings, sending his protagonist to energy to create them, along with the need for the future aboard a “time machine” and drawing “negative energy” to keep them open. But again, an analogy between a balloon moving in three those are matters for the engineers. dimensions and the machine moving in four. In point of fact, any method of going faster For more information about time travel and than light must necessarily be a way to travel in time travel campaigns, see Time Travel Hero. time as well, since outpacing light leads to viola- tions of causality. Time travel is an idea that brings into play GAME MECHANICS immense possibilities, but it lies at the margin of In the HERO System, physically visiting other hard sf. Are paradoxes inevitable — or can you times is an application of the Power Extra-Dimen- really shoot your grandfather and still survive? sional Movement (see 6E1 220-23). If the power There is a considerable body of sophisticated has a Focus or is built into a Vehicle, then you’ve 9 theoretical research devoted to probing whether got a Time Machine. Communication between physics can in principle exclude time travel, different times is best simulated by the Clairsen- and the jury — after many physics papers tience Power, with the Transmit and Dimensional about faster-than-light particles (tachyons) and modifiers. wormholes in space-time — is still out. Nearly all physicists are very doubtful. —from Gregory Benford’s essay “Real Science, Imaginary Worlds” in The Ascent Of Wonder: The Evolution Of Hard SF, edited by David G. Hartwell and Kathryn Cramer star hero n Chapter Nine 257 The biggest problem with time machines is TIME TRAVEL METHODS AND EFFECTS that characters are obsessed with protecting their JARGON ride home (and understandably so). This makes it hard for the GM to involve them in plots and Time Travel is a hard The [Very Slow Time Machine] was the size of goings-on in the past. A related problem is that concept for human minds a small caravan; but it had the shape of a huge the time machine imposes limits on where and to grasp, so the technical lead sulphide, or galena, crystal[.] ... It perched when the explorers can go. Is there room on the vocabulary relating to the precariously — but immovably — on the base deck of the Marie Celeste for the Time Pod? How subject is complex and square, the four lower hexagons bellying up and about aboard the Hindenburg? Unless the device includes lots of shorthand out towards the waist, where four more squares has really effective camouflage, time missions will terms. here is some (oblique, vertically) connected with the mirror- have to arrive in deserted or wilderness areas (or, standard lingo for the image upper hemisphere, rising to a square as on Doctor Who, accept the consequences of time travel business: north pole. Indeed it looked like a kind of world sticking out like a sore thumb). Causality: The idea that globe, lopped and sheared into flat planes[.] DOORS INTO SUMMER things happen in a partic- —a description of the Very Slow Time Machine from Time gates are another popular option, and one ular order. If a causes “The Very Slow Time Machine,” by Ian Watson with more than a smidgen of possibility. The char- B, then a has to happen acters go through the gate and come out some- before B. If for some when else. Gates may be permanent or temporary. reason B happens before Regardless of the scientific justification, in Since a gate isn’t very large, it can appear almost a does, causality has a game the “special effect” of how one actually anywhere, making it possible for the Player Char- been violated. Marrying travels in time has a tremendous influence on the acters to slip aboard Lenin’s train to Russia in 1916 your grandmother structure of the campaign. or arrive backstage at Ford’s Theater in 1865. and becoming your TIME MACHINES A time gate means the travelers are limited to own ancestor violates just what they can carry themselves, and they’re causality because you have to exist before you [T]here in the laboratory we beheld a larger likely to be very paranoid about getting separated from the gate. Since the gate is presumably gener- can exist. seeing some- edition of the little mechanism which we had thing before it happens is seen vanish from before our eyes. ... ated from the Time Institute, the characters can’t mess with causality unless the directors (and the also a causality violation. “Upon that machine,” said the Time Traveler, “I GM) agree. Paradox: a self- intend to explore time.” The size and permanence of the time gate can contradicting causality —the Time Traveler shows his friends his time be very important. If the gate can only stay open violation. shooting your long enough for the explorers to pass through, machine in The Time Machine, by H.G. Wells grandfather before he then it’s more like time jumping, described below. can sire your father is a A permanent gate means anybody can wander paradox (in fact, it’s the When most people think of a time machine, from one time to another, creating the possibility famous “grandfather they think of a vehicle or device that one rides of abundant paradoxes and causality violations. paradox”) because you into the past or the future, like getting into a Human-sized gates are most appropriate for an have prevented yourself car and riding to the store. This method gets rid exploration-centered adventure, but one can from ever existing. If you of cumbersome explanations about how to get imagine time gates big enough for trains or even don’t exist, then you can’t home — you get back in the machine and shift supertankers. This could allow large-scale trade have shot Grandpa. Which into reverse — and it makes it easy to send a small (or warfare) between different times. means you will exist, and group and a moderate amount of equipment to TIME JUMPING can do it after all. and another time. so on. If the characters control the vehicle themselves, Time travel might be akin to teleportation. the GM must give serious thought to how easy it is You switch on the time machine or step into the time loop: a to operate and how much power it has on board. If booth, and suddenly you’re in another time. (The special paradox very precise time-hops are possible, the characters temporal transporters of Star Trek work this way.) in which a time may be tempted to fix problems by going back The big question is how you get back. If the time traveler does half an hour and redoing their mistakes. On the jump is generated by a “time belt” or some other something 9 other hand, imprecise controls make it hard to hit device carried by the traveler, then getting back which leads specific historical events. or visiting some other time is simply a matter to his traveling in A time machine which the travelers don’t of adjusting the controls and making sure the time in the first place. control themselves is one option: Mission Control batteries are charged. Loops include becoming back in their original time operates the time If teleportation requires some huge machine your own ancestor, giving machine, and the explorers go where their bosses back in the jumper’s home time, getting home can future technology to the send them, much like modern-day astronauts.