Time Travel #2: The Rules
These are the rules I have outlined for my campaign setting. Rules 1 through 5 provide a consistent outcome to any situation, while Rule 6 assures game balance. You can modify these rules for your own campaign, but I will offer a reason for each of them that you should first consider.
Rule #1: The two ends of a time portal always exist at the same time relative to each other.
Example: The front end of a portal always exists exactly 50 years ahead of the back end. If Alice walks through a portal at midnight, January 1, 2050, she will walk out the portal at midnight, January 1, 2000. If she then hangs around for a while and reenters the portal at 5:05 PM, February 3, 2000, she will exit the portal at 5:05 PM, February 3, 2050. Different portals can have different jumps in time.
Purpose: To give the players a real sense of urgency. If Alice is in January 1, 2000, and she knows something bad will happen on January 2, 2050, she will only have one day to get to the future and prevent it. She won't have the luxury of waiting around for a few months until she feels like heading off to 2050.
Rule #2: The actual structure of a time portal is indestructible, but they can be moved.
Example: The portal from the previous example is at the bottom of a 20 foot hole. With sufficient construction equipment, Alice can uproot the portal in 2050 and take it to her house. The portal will still go to the same hole in the ground in 2000, but Alice can dig up that one too.
Purpose: To gloss over the fact that since the planet is flying through space, the two ends of a portal are never really in the same place at different times.
Rule #3: Time machines work similarly to portals, except they're not just two-way.
Example: A time machine may have a dial with five settings: -100 years, -50, 0, +50, and +100 years. If the dial's on the 0 and Alice turns it to -50, the time machine will go 50 years back. If Alice then turns the dial to +100, the time machine will go +150 years forward.
Purpose: Same principle as the portals, except with more flexibility.
Rule #4: The world has only one timeline. If the past is changed, the present and future are rewritten. There are no alternate universes.
Example: Alice is living her life in 2050. Bob goes back in time to when Alice is a newborn, and he convinces Alice's parents to name her Carol instead. The timeline is now rewritten so that Alice is named Carol, and Alice will believe her name was always Carol.
Purpose: To emphasize to the players that they can't simply wash away their mistakes by going to an alternate universe where they didn't make those mistakes. It also prevents the players from meeting up with their alternate selves. You might have a difficult time, however, explaining to a player that her character's name has suddenly been changed to Carol, and that she thinks her name was always Carol.
Rule #5: When a person or object goes back in time, it is not actually moving through time. Rather, the object is annihilated, and an exact copy of the object appears in the past or future. This new event, the appearance of the object, cannot ever be prevented.
Example: Bob is in the year 2050. He jumps in the portal to 2000. Bob in 2050 vanishes, and a new Bob, let's call him Bob2, appears in 2000. Bob2 appears as a copy of how Bob was when he disappeared, and Bob2's appearance in 2000 cannot be prevented by other time travelling shenanigans. In a way, Bob2 has "saved his game," since nothing can ever change the way Bob2 was when he appeared.
Purpose: To resolve the grandfather paradox. If Bob2 goes and kills his grandfather, Bob will never be born. Bob2 can still live out his existence, and he will remember sitting on his grandfather's knee as a child. There might not be a place for Bob2 anymore, since nobody in 2050 will remember who he is.
Rules 4 and 5 appear to contradict each other. Can the players' pasts be changed, or not? Think of it this way. As a player, you are assured that everything you remember about yourself is constant, up to the last time you time travelled. Anything that has happened to you since the last time you jumped through a portal may be changed by other time travellers, and you will think those changes have always been that way. This is the most difficult and confusing point to drive home.
Rule #6: Every living thing and magical item gives off a unique signature aura. Additionally, every living thing and magic item has an "internal clock" that starts at birth/creation and keeps ticking forward. If two objects with the same aura ever exist at the same time, the one that has spent the most time existing will cease to exist.
Example: Bob in 2050 goes back to 2000 and becomes Bob2. Bob2 waits a day, finds a different portal and goes to 2040, when Bob has been living his life. Bob2 will cease to exist as soon as he walks through that portal.
Another Example: Bob in 2050 goes back to 2000 and becomes Bob2. Bob2 decides to live out his life in 2000. Assuming Bob2 never does anything that prevents Bob from being born, Bob2 will vanish off the face of the earth in 2025, at the instant when Bob is born.
Yet Another Example: Bob in 2050 goes back to 2000 and becomes Bob2. Bob2 does something in 2000 that prevents Bob in 2050 from discovering time travel. Bob2 then goes to 2070. In 2070, Bob vanishes off the face of the Earth as soon as Bob3 steps out of the portal.
Purpose: This rule assures that no person or magic item will ever be in two places at once. It prevents the players from creating copies of themselves or their +5 swords. The players will have to be concerned with messing with their own backstories and bumping into themselves in the future. The DM might want to cut the players some slack with this, and offer a wise NPC that alerts them when they might have messed up the past. Nobody wants to be playing a game only to find out that they suddenly don't exist anymore.
Incidentally, this rule also clarifies what happens when the back end of a portal catches up to the front end. For every portal, you will need to decide not only how far apart the two ends are, but also when the front end and back end were created.
This set of rules hopefully creates a scenario that is as easy to understand as possible, while still ensuring game balance. While things might not always make sense for the players, the DM still has a simple line of cause and effect and can follow events as they happen. I apologize if something doesn't make sense. Please feel free to ask me to clarify anything.
In the next article, I will discuss the world itself, and how you can use time travel to create a unique setting and plot for your players.
Rule #1: The two ends of a time portal always exist at the same time relative to each other.
Example: The front end of a portal always exists exactly 50 years ahead of the back end. If Alice walks through a portal at midnight, January 1, 2050, she will walk out the portal at midnight, January 1, 2000. If she then hangs around for a while and reenters the portal at 5:05 PM, February 3, 2000, she will exit the portal at 5:05 PM, February 3, 2050. Different portals can have different jumps in time.
Purpose: To give the players a real sense of urgency. If Alice is in January 1, 2000, and she knows something bad will happen on January 2, 2050, she will only have one day to get to the future and prevent it. She won't have the luxury of waiting around for a few months until she feels like heading off to 2050.
Rule #2: The actual structure of a time portal is indestructible, but they can be moved.
Example: The portal from the previous example is at the bottom of a 20 foot hole. With sufficient construction equipment, Alice can uproot the portal in 2050 and take it to her house. The portal will still go to the same hole in the ground in 2000, but Alice can dig up that one too.
Purpose: To gloss over the fact that since the planet is flying through space, the two ends of a portal are never really in the same place at different times.
Rule #3: Time machines work similarly to portals, except they're not just two-way.
Example: A time machine may have a dial with five settings: -100 years, -50, 0, +50, and +100 years. If the dial's on the 0 and Alice turns it to -50, the time machine will go 50 years back. If Alice then turns the dial to +100, the time machine will go +150 years forward.
Purpose: Same principle as the portals, except with more flexibility.
Rule #4: The world has only one timeline. If the past is changed, the present and future are rewritten. There are no alternate universes.
Example: Alice is living her life in 2050. Bob goes back in time to when Alice is a newborn, and he convinces Alice's parents to name her Carol instead. The timeline is now rewritten so that Alice is named Carol, and Alice will believe her name was always Carol.
Purpose: To emphasize to the players that they can't simply wash away their mistakes by going to an alternate universe where they didn't make those mistakes. It also prevents the players from meeting up with their alternate selves. You might have a difficult time, however, explaining to a player that her character's name has suddenly been changed to Carol, and that she thinks her name was always Carol.
Rule #5: When a person or object goes back in time, it is not actually moving through time. Rather, the object is annihilated, and an exact copy of the object appears in the past or future. This new event, the appearance of the object, cannot ever be prevented.
Example: Bob is in the year 2050. He jumps in the portal to 2000. Bob in 2050 vanishes, and a new Bob, let's call him Bob2, appears in 2000. Bob2 appears as a copy of how Bob was when he disappeared, and Bob2's appearance in 2000 cannot be prevented by other time travelling shenanigans. In a way, Bob2 has "saved his game," since nothing can ever change the way Bob2 was when he appeared.
Purpose: To resolve the grandfather paradox. If Bob2 goes and kills his grandfather, Bob will never be born. Bob2 can still live out his existence, and he will remember sitting on his grandfather's knee as a child. There might not be a place for Bob2 anymore, since nobody in 2050 will remember who he is.
Rules 4 and 5 appear to contradict each other. Can the players' pasts be changed, or not? Think of it this way. As a player, you are assured that everything you remember about yourself is constant, up to the last time you time travelled. Anything that has happened to you since the last time you jumped through a portal may be changed by other time travellers, and you will think those changes have always been that way. This is the most difficult and confusing point to drive home.
Rule #6: Every living thing and magical item gives off a unique signature aura. Additionally, every living thing and magic item has an "internal clock" that starts at birth/creation and keeps ticking forward. If two objects with the same aura ever exist at the same time, the one that has spent the most time existing will cease to exist.
Example: Bob in 2050 goes back to 2000 and becomes Bob2. Bob2 waits a day, finds a different portal and goes to 2040, when Bob has been living his life. Bob2 will cease to exist as soon as he walks through that portal.
Another Example: Bob in 2050 goes back to 2000 and becomes Bob2. Bob2 decides to live out his life in 2000. Assuming Bob2 never does anything that prevents Bob from being born, Bob2 will vanish off the face of the earth in 2025, at the instant when Bob is born.
Yet Another Example: Bob in 2050 goes back to 2000 and becomes Bob2. Bob2 does something in 2000 that prevents Bob in 2050 from discovering time travel. Bob2 then goes to 2070. In 2070, Bob vanishes off the face of the Earth as soon as Bob3 steps out of the portal.
Purpose: This rule assures that no person or magic item will ever be in two places at once. It prevents the players from creating copies of themselves or their +5 swords. The players will have to be concerned with messing with their own backstories and bumping into themselves in the future. The DM might want to cut the players some slack with this, and offer a wise NPC that alerts them when they might have messed up the past. Nobody wants to be playing a game only to find out that they suddenly don't exist anymore.
Incidentally, this rule also clarifies what happens when the back end of a portal catches up to the front end. For every portal, you will need to decide not only how far apart the two ends are, but also when the front end and back end were created.
This set of rules hopefully creates a scenario that is as easy to understand as possible, while still ensuring game balance. While things might not always make sense for the players, the DM still has a simple line of cause and effect and can follow events as they happen. I apologize if something doesn't make sense. Please feel free to ask me to clarify anything.
In the next article, I will discuss the world itself, and how you can use time travel to create a unique setting and plot for your players.
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