Discussion Overview
The discussion centers around the nature of photons, particularly how relativity affects their perception in terms of time and space. Participants explore concepts related to the experience of time by photons, their behavior in spacetime, and the implications of their masslessness on their 4-velocity. The conversation includes theoretical considerations and mathematical reasoning.
Discussion Character
- Exploratory
- Technical explanation
- Conceptual clarification
- Debate/contested
- Mathematical reasoning
Main Points Raised
- Some participants assert that photons do not experience time, while others question the appropriateness of this statement, suggesting that it may not be suitable to say photons "don't experience time" as there is no frame of reference for them.
- There is a discussion about whether photons are "outside" spacetime, with some arguing that they are not outside but rather that their time dilation approaches infinity as they travel at the speed of light.
- One participant explains that every system in spacetime has a 4-velocity of 1, and that a photon, having no rest mass, allocates all of its 4-velocity to spatial dimensions, leaving none for time.
- Another participant raises the question of whether there are physical entities that have 100% of their 4-velocity in the time dimension and 0% in the space dimension, noting that in a sublight object's rest frame, this is indeed the case.
- Some participants discuss the dual nature of photons as both particles and waves, suggesting that coherence length may play a role in this characterization.
- There is a technical discussion regarding the normalization of 4-velocity for photons, with some confusion about why a normalized 4-velocity for a photon is not Lorentz invariant.
Areas of Agreement / Disagreement
Participants express differing views on whether photons experience time and the implications of their masslessness. There is no consensus on the nature of photons in relation to spacetime, and the discussion remains unresolved regarding several technical aspects, including the normalization of 4-velocity.
Contextual Notes
Limitations include the dependence on definitions of time and spacetime, and the unresolved nature of certain mathematical steps regarding the normalization of vectors in the context of Lorentz transformations.