Arrival
The end of a traversal. Arrival is an event on the destination timeline. See also destination.
Branching Timelines
The chronoverse starts as a single timeline, and changing the past causes a new timeline to split off from the original.
Causal Time
Time as experienced by the entire multiverse. It could also be called chronoversal time or multiversal time. Its main purpose is to allow us to follow the flow of causation in events. Outside of causal loops, an effect always comes after a cause in causal time. Unlike universal time and proper time, causal time cannot ever go backward. Also unlike universal and proper time, causal time doesn’t have an obvious reference to work from. Universal time can be pegged to a calendar date, proper time can be pegged to the age of the object, but causal time needs to be given some arbitrary starting point and scale.
Chronodynamics
The study of time travel and the movement of time.
Chronology
The ordering of events. Often used synonymously with timeline, but not in the context of time travel. Rather, it’s more like “reconstructing the timeline of events”. Despite its name, it is not actually the study of anything.
Chrononaut
A time traveler. Any object that undergoes time travel.
Chronoportation
The method of travel through time. This describes the effect of time travel on the time traveller.
Chronotopology
The shape of time. Generally refers to the structure of the timeline and how the universe reacts to time travel.
Chronotraversal
Technical term for time travel. Time travel is the phenomenon of elapsed time measured by a traveling object (i.e. proper time) differing from the elapsed time measured by an outside observer (i.e universal time). A single time travel trip could be called a traversal for short. In general, a traversal is composed of a departure event and a corresponding arrival event.
Chronoverse
The chronoverse is the collection of all the different timelines. Since different timelines are themselves separate universes, the terms multiverse and chronoverse can be synonymous in certain contexts.
Departure
The beginning of a traversal. Departure is an event on the source timeline. See also source.
Destination
The destination of a traversal is the spacetime location a time traveler ends at. This is an arrival event on the destination timeline. See also arrival.
Dynamic Timeline
The timeline can be changed. There is only one timeline, and it can be overwritten. This results in a litany of issues when reconciling with modern physics, but it is popular in science fiction as a way to add direct consequences to meddling with time.
Elastic Timeline
Historical inertia is the idea that the past is resistant to change; you can change the past, but only to a certain extent. The timeline will stretch and shift back into how it “should” be. Such a topology is an elastic timeline. See also historical inertia.
Event
Any single point in spacetime. The combination of time and place is enough to specify anything as an event, but we will often describe it by what happens during an event–e.g. July 25, 2015 at Griffith Park is an event, but we might instead describe it as “Jimmy’s 5th birthday party”.
Historical Inertia
Historical inertia is the idea that the past is resistant to change; you can change the past, but only to a certain extent. The timeline will stretch and shift back into how it “should” be. Such a topology is an elastic timeline. See also elastic timeline.
Horology
The general study of time.
Multiverse
The multiverse is the collection of all the different universes. Since different timelines are separate universes, the terms multiverse and chronoverse can be synonymous in various contexts.
Object
For our purposes, any concrete thing is an object. A ball is a kind of object; a person is a kind of object; even a radio signal could be a kind of object in the right context. Since we are talking about physical effects of phenomena, “object” will generally be used to refer to the affected party.
Prochronotraversal (PCT)
Forward time travel. Specifically, time travel in which the departure universal time is earlier than the arrival universal time.
Proper Time
Time experienced by an object in their own reference frame. Could also be called personal time. Generally corresponds to the age of the object.
Retrochronotraversal (RCT)
Backward time travel. Specifically, time travel in which the departure universal time is later than the arrival universal time.
Source
The source of a traversal is the spacetime location a time traveler leaves from. The beginning of a traversal is a departure event on the source timeline. See also departure.
Spacetime
Instead of treating space and time as two separate things, we put them together and call the combination spacetime. A spacetime location is simply another way of referring to a specific time and location (i.e., an event). The spacetime continuum is all the infinite points of spacetime, also called the fabric of spacetime. This isn’t just a mathematical abstraction, mind you. Einstein’s relativity tells us that space and time are actually physically linked as a single hyperfabric.
Static Timeline
The most common modern scientific interpretation of a timeline’s topology. The past can’t be changed, history is immutable. Spacetime forms one big fabric that will always remain unchanged.
Temporal Mechanics
The study of all the technical workings of time. We will often use this term interchangeably with chronodynamics.
Time
We can consider time to be the measure of how far apart events are in nonspatial terms, i.e., not including distance. It is a measurement of duration. Fundamentally, time is really its own dimension, much like up, down, forward, back, left, and right. These are the dimensions of space, sometimes called height, width, and depth; or x, y, and z. Time complements them as a fourth dimension. Any event can be specified by these 4 coordinates.
Time Travel
Time travel is the phenomenon of elapsed time measured by a traveling object (i.e. proper time) differing from the elapsed time measured by an outside observer (i.e universal time). Also known as chronotraversal.
Timeline
All of the spacetime of a single universe, from one end to the other, from the beginning of time to the end of time. A timeline can be looked at as a series of all of the events in a universe, one after the other. We will often use the terms timeline and universe interchangeably.
Timestream
Extratemporal “space”. The Timestream is the hyperspace outside of the timeline. Generally, when travelling through time, we consider the Timestream to be the medium the traveler travels through.
Traversal
Short for chronotraversal. Generally refers to a single trip through time. In general, a traversal is composed of a departure event and a corresponding arrival event.
Universal Time
Time experienced by the universe. Generally measured using calendar dates/times (e.g. September 3, 2018), so it could also be called calendar time.
World Line
A world line is the path an object takes through spacetime. It is the collection of every place, every event, that the object has been through.