Are there reflections in the fourth dimension?

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Discussion Overview

The discussion centers around the concept of reflections in the fourth dimension, exploring the nature of such reflections and the implications of dimensionality in physics. Participants question the meaning of "reflection" and the characteristics of a fourth dimension, as well as the theoretical constructs that might allow for such reflections.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants inquire about the nature of reflections in the fourth dimension and what such reflections might look like.
  • One participant questions the meaning of "reflection" in the context of the fourth dimension, suggesting a need for clarification.
  • Another participant introduces the idea of a "phase conjugate mirror," proposing that it could reflect electromagnetic radiation in a way that appears to reverse time, leading to potential invisibility effects.
  • A different perspective defines reflection as a linear map that alters the sign in one dimension while keeping others fixed, asserting that this definition applies regardless of the number of dimensions involved.

Areas of Agreement / Disagreement

Participants express varying interpretations of reflections and the fourth dimension, indicating that multiple competing views remain without a consensus on the definitions or implications of these concepts.

Contextual Notes

There are unresolved questions regarding the assumptions behind the definitions of reflection and the nature of the fourth dimension, as well as the practical implications of theoretical constructs like phase conjugate mirrors.

hydrostaticequil
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If so what does the reflection look like?
 
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hydrostaticequil said:
If so what does the reflection look like?
Physicists refer to three dimensions of space and one of time usually. I am not sure what you mean by "reflection."
 
What do you mean by the fourth dimension?
 
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hydrostaticequil said:
If so what does the reflection look like?
How will you make the mirror?

A "phase conjugate mirror" might reflect EM radiation, back the way it came, in effect backwards in time. That would cause things that reflect light or radar to cancel with themselves, becoming invisible. There has been military research into the field of making things invisible, but I don't think there has been any real success.
https://en.wikipedia.org/wiki/Nonlinear_optics#Optical_phase_conjugation
 
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hydrostaticequil said:
If so what does the reflection look like?
I would define a reflection as a linear map that changes the sign in one dimension and keeps all other dimensions fixed. This is independent of the number of dimensions.
 
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