HTMLThe dream of time travel probably arose out of a desire to go back and correct one's past mistakes or to visit the future and subsequently return to take advantage of foreknowledge. The concept intrigues historians and archaeologists for obvious reasons. Science fiction has explored the possibility of time travel many times, as well as the pitfalls of visiting the past and impacting the future.
Technically, time travel of the "into the future" sort is within the realm of possibility. In fact, it happens all the time just on such a small scale that no one notices. Given that a starship engine could be developed that accelerates a ship to relativistic speeds at which time dilation occurs, time travel can be achieved simply by achieving 90% of the speed of light for a short time, then returning to one's point of origin. For every minute you spend flying at 90% the speed of light, 2.3 minutes pass everywhere else. Travel at relativistic speeds long enough and you could return to a time predating the rise of human civilisation!
Travelling into the future isn't a very useful ability if one has no way back which is where the concept of travelling into the past breaks down. The principle of causality rather logically argues that an effect cannot occur before its cause meaning, in this case, that one cannot arrive in the past via the use of a time machine before that time machine is invented.
The time machine is perhaps more dangerous than any other technology that manipulates space and time. Not only can unscrupulous people use it to wreak havoc in the past and take advantage of knowledge from the future, but a single misstep could forever alter the course of history.
Trips through time are exercises in causality. Travelling into the past might set in motion a chain of actions culminating in different major historical events. Characters might return to the present to discover that the Roman emperor Caligula used intercontinental ballistic missiles to conquer Europe and the Middle East. Conceivably, history could be altered in a way that prompts the Soviet Union to invade and conquer North America. Perhaps the characters can't even return to their own time because the person who invented the crucial component of the time machine was never born, for some reason. In short, the permutations of cause and effect can be infinitely mind-boggling.
Temporal paradoxes are liable to stall the development of time travel until someone can prove either that (a) actions in the past by people from the present have, in fact, already happened (and that it was those actions that led to the current state of affairs), or (b) actions in the past that affect the present can be detected and averted by sending someone else into the past to prevent those actions from happening.
Another potential side-effect of time travel popularised in literature is the alternate reality. The timestream in which time travel is invented continues to exist. Situations that create significant changes or temporal paradoxes serves as the locus or intersection point where realities diverge.
The time travellers might encounter worlds very similar to or different from their own. This creates a rich diversity of settings where the established "facts" and "rules" are no longer sure. The nefarious villain recently defeated in a different reality might be a trustworthy ally in this one. A temporal adventurer might encounter a dead companion who did not die in this alternate reality. The possible permutations are infinite.
Time machines that do not actually move are at the mercy of topographical changes and other changes in the locations in which they appear. Never mind that one couldn't construct a time machine in New Mexico and use it to visit Jerusalem in the year A.D. 33.
Travelling into the past might deposit you in the middle of a rushing river or under thousands of tons of glacial ice. Travelling into the future, you might find that the position occupied by your time machine now resides in the basement of a futuristic skyscraper or in the middle of a radioactive wasteland covered by ice the result of an extraordinarily heavy and sustained nuclear bombardment.
Modern language is loaded with slang, jargon, and colloquialisms that would mean nothing to people who lived in the 19th century. Their slang, jargon, and colloquialisms, by the same token, would mean nothing to those who lived in the 18th century. Go back another thousand years, and the words you are reading right now would be all but incomprehensible to the average English- speaking person assuming he or she could read. Your speech would be equally incomprehensible. Go forward a thousand years, and the English of the new millennium will barely resemble the English of this millennium. Without a Speak Language or Read/Write Language skill for the appropriate era, communication could more closely resemble a game of charades.
Those who travel in time age normally within their own localised time. So, while eons may pass in the eye blink it takes to travel through them, the time traveller feels none of the effects of ageing. However, this can work against the traveller. If he were to spend twenty years in his own timeframe exploring the centuries, then return to his starting point, he would, in fact, be twenty years older than he was when he left.
Temporal displacement drives colloquially known as "time machines"do not exist until Progress Level 8. The first time machines are faintly reminiscent of the brass, ivory, and quartz machine invented by H.G. Wells in his novel The Time Machine, though made of lightweight aluminium and resembling something more like bathyspheres. Those that follow are constructed as fixed tunnels leading to nowhere, while those mounted in starships turn the entire ship into the time machine.
Time Sphere (PL 8)
Time spheres are small, two-seated modules designed to withstand any reasonable amount of buffeting that might occur when the machine finally comes to rest in a different time period. At the very least, the self-contained atmosphere should give the occupants time to "reverse course" should they discover that conditions outside are too hostile to disembark. The time sphere carries sensors designed to test outside conditions immediately upon arrival.
The temporal displacement mechanism itself is arranged around the inside of the sphere, giving the occupants full access to the electronics in case of emergency. The main computer has all programs necessary to operate the machine and is crammed with historical and linguistic information, electronic encyclopedias, and any other information that might be necessary to survive in a different time. Operation of the time sphere is quite simple for characters familiar with computers. One simply sets the desired date and time and presses the "Go" button.
Time spheres are not sold commercially. In fact, doing so is illegal, but the plans to construct them are quite common. The components have a total purchase DC of 36. Building a time sphere chassis takes 12 hours and requires a successful Craft (mechanical) skill check (DC 25). Building and filling the time sphere's computer (a much more daunting exercise) takes 120 hours and requires a successful Craft (electronic) check (DC 35).
Time spheres have the following statistics:
Crew: 2
Passengers: 0
Cargo: 120lbs
Defence: 6
Hardness: 5
Hit Points: 24
Size: Huge
Purchase DC: 65
Restriction: Illegal (+4)
Temporal Drive Generator (PL 9)
Like the D-drive generator, which is designed to carry starships across dimensional boundaries, the temporal drive generator (or "T-drive generator") carries starships through time. The drive can be mounted in a starship of any size and turns the entire ship into a time machine.
Purchase DC: 60
Restriction: Military (+3)
Time Bridge (PL 9)
Doing away with the issue of portability, the time bridge opens a portal to both other times and other places. The time bridge also has the advantage of not leaving a fragile piece of vital equipment lying about while its operators go exploring.
Instead, the travellers use a simple "message-drop" system to communicate with their base of operations: Upon arrival, they conceal a small transmitter somewhere near their point of embarkation. They then have a prearranged amount of time to explore and return to the location to catch the next appearance of the time bridge. If they do not return, an operative from their base emerges to search for the transmitter.
Assuming he finds it, the operative records a message on the transmitter, letting the explorers know when the bridge will reappear again, or he collects any recorded message the explorers might have left indicating where and when to pick them up. The process repeats until the explorers are brought back safely.
Travel through the time bridge is comparable to walking through a tunnel. Operators at the base set the temporal and physical coordinates at the other end, and a team of travellers walks into the tunnel and seems to vanish. For the travellers, the point of origin simply becomes less "real" as the destination becomes more real. The bridge is large enough to accommodate vehicles up to Huge size.
Purchase DC: 71
Restriction: Illegal (+4)
