Four Indistinguishable Phenomena?

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Discussion Overview

The discussion revolves around the comparison of four phenomena in nature that some participants suggest may be indistinguishable from one another: crossing beyond an observer's cosmic horizon, crossing the event horizon of a black hole, accelerating toward the speed of light, and approaching absolute zero. The scope includes conceptual understanding and exploratory reasoning regarding the nature of these phenomena and their observational effects.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant proposes that the four phenomena are indistinguishable, drawing a parallel to the equivalence of gravity and acceleration.
  • Another participant counters that the phenomena are not physically equivalent, specifically noting that while 1-3 share similarities, 4 is fundamentally different.
  • A third participant emphasizes that having a common feature, such as "redshifting into invisibility," does not imply that the phenomena are indistinguishable, as they lack other shared characteristics.
  • There is a discussion about the interpretation of "redshifting" in relation to a black body spectrum approaching absolute zero, with one participant suggesting that this interpretation is overly generous.
  • One participant highlights a practical difference between the phenomena, noting that for 1-3, small lab experiments detect nothing unusual, while for 4, significant precautions are necessary.
  • A later reply points out that the "redshift" associated with a black body approaching absolute zero is not due to a Doppler effect, questioning the validity of calling it a "redshift."

Areas of Agreement / Disagreement

Participants express disagreement regarding the indistinguishability of the phenomena. While some acknowledge similarities among the first three, they assert that the fourth phenomenon is distinct. The discussion remains unresolved with multiple competing views on the nature of these phenomena.

Contextual Notes

There are limitations in the discussion regarding the definitions of "redshift" and the conditions under which these phenomena are observed, which may affect the interpretations presented.

Ontophobe
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It seems to me, and so I'm really just checking to see if I understand it all correctly, that there are four phenomena in nature that are indistinguishable from one another: (1) crossing beyond an observer's cosmic horizon, (2) crossing the event horizon of a black hole, (3) accelerating toward and nearly reaching the speed of light, and (4) approaching and nearly reaching zero degrees Kelvin. In all four cases, an observer in an inertial frame of reference would see you redshift into invisibility ( I say "you" as if "you're" the one accelerating beyond the observer's cosmic horizon, or the black hole's event horizon, etc). I'm just starting to wrap my head around these concepts, so I'm just checking to see if I understand these four phenomena correctly by (a) venturing a hypothesis; i.e., these phenomena are as indistinguishable from one another as gravity is from acceleration, and I'm (b) testing that hypothesis; i.e., I'm asking y'all if it's true.
 
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They are not indistinguishable (as in physically equivalent). Although 1-3 have certain similarities, 4 has nothing to do with the others.
 
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Ontophobe said:
these phenomena are as indistinguishable from one another as gravity is from acceleration

Gravity is not indistinguishable from acceleration.

For your phenomena, none of them are indistinguishable from the others. (1), (2), and (3) do happen to have one common feature, which you describe as "redshifting into invisibility". (On a sufficiently generous interpretation of "redshifting", one could argue that (4) has that property as well; but the interpretation has to be generous.) However, having one common feature does not make them indistinguishable; that would imply that they had all possible features in common, which they don't.
 
PeterDonis said:
On a sufficiently generous interpretation of "redshifting", one could argue that (4) has that property as well; but the interpretation has to be generous.
Average wavelength of a black body spectrum? That is generous ...
 
The big difference is that for 1-3, small lab detects nothing unusual, while for 4, the lab scientists need very good coats.
 
Since the "redshift" of a black body approaching absolute zero isn't caused by a Doppler effect, I see why it's a stretch to call it a "redshift."
 

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