Does Spacelike Worldlines Exist?

  • Context: Undergrad 
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Discussion Overview

The discussion centers on the terminology used in the context of spacetime, specifically whether the term "worldline" can be applied to spacelike trajectories or if it is reserved for timelike paths. Participants explore the implications of these terms and their usage in theoretical contexts.

Discussion Character

  • Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants assert that a worldline is the path followed by something through spacetime and can be timelike or null, but not spacelike until tachyons are discovered.
  • Others argue that spacelike lines, such as lines of synchronization, should not be referred to as worldlines, suggesting they should simply be called "lines."
  • A participant expresses a preference for using the term "curve" for spacelike trajectories, indicating that "worldline" implies a representation of a particle or object’s position.
  • There is a reiteration of the preference for the term "curve" over "worldline" for spacelike paths, emphasizing the distinction in meaning.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the terminology, with multiple competing views regarding the use of "worldline" for spacelike trajectories and the implications of such terminology.

Contextual Notes

The discussion reflects varying interpretations of the term "worldline" and its applicability, highlighting the dependence on definitions and the context in which these terms are used.

kent davidge
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I'm writing some notes and I don't know if the term "worldline" is used only for timelike paths. When referring to spacelike trajectories, I have been using the word "curve" so far. Can I use "worldline" too?
 
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A worldline is the path followed by something through spacetime. It can therefore be timelike or null. Until we discover tachyons, it can't be spacelike.
 
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Trajectories you say gives me a false image that particles goes along it. So space like lines, e.g. lines of synchronization, should be called just "lines" with no world-, trajectory or orbit.
 
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kent davidge said:
When referring to spacelike trajectories, I have been using the word "curve" so far. Can I use "worldline" too?
I would continue using curve. Worldline implies that the curve represents the position of some particle or object.
 
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