Equivalence Principle and Rindler Horizons

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Discussion Overview

The discussion centers around the concept of Rindler horizons in the context of standing on a massive body like Earth and whether this situation generates a Rindler horizon directed towards the ground. Participants explore the implications of the Equivalence Principle and the nature of spacetime in relation to acceleration and gravitational fields.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Meta-discussion

Main Points Raised

  • Some participants propose that standing on Earth, which involves acceleration, might generate a Rindler horizon directed towards the feet.
  • Others argue that Rindler horizons are specific to flat spacetime, and the equivalent phenomenon in a gravitational field is an event horizon.
  • A participant questions the assertion that Rindler horizons are a flat spacetime phenomenon, seeking sources for this claim.
  • There is a discussion about the relationship between acceleration and light signals in curved spacetime, with one participant suggesting that a Rindler horizon-like effect could occur in large, fairly flat regions of curved spacetime.
  • Several participants express differing views on the necessity of mathematics in discussing physics concepts, with some advocating for plain language and others emphasizing the importance of mathematical rigor.
  • Concerns are raised about the effectiveness of teaching physics concepts without mathematics, with anecdotes shared about educational experiences that highlight the challenges of understanding without a mathematical framework.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether standing on a massive body generates a Rindler horizon. There are competing views regarding the nature of Rindler horizons and the role of mathematics in understanding physics concepts.

Contextual Notes

Participants express uncertainty about the implications of warped spacetime on the existence of Rindler horizons and the conditions under which such effects might be observed. The discussion also reflects a range of educational backgrounds and preferences for how physics should be communicated.

  • #31
vanhees71 said:
It is, at least as far as I can imagine, impossible to discuss the topic of this thread, i.e., Rindler coordinates and Rindler horizons to locally describe the region close to an event horizon in GR, without using the adequate math.
The question was if a Rindler Horizon forms when you stand on a massive body. The answers can be yes, no, or nobody knows, and none of those answers require math, nor was math desired.
 
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  • #32
vanhees71 said:
This is the 30th posting within this thread, and we've not achieved anything to answer the question yet.
I disagree. The question has been answered, and at a B level, without math.
 
  • #34
sbaker8688 said:
The answers can be yes, no, or nobody knows, and none of those answers require math, nor was math desired.
That's disingenuous.

You got an answer like this, immediately challenged it by demanding a source, and then complained that the source used "technobabble".
 
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  • #35
The weak-field approximation for time dilation is Td = 1 + 𝜙/c². The Rindler horizon occurs when 𝜙 = -c²; in a 1 G field, that is about 1 light year "below" you. At that point, the formula gives Td = 0, i.e. time stops running.

In SR, the Rindler horizon actually exists, because the linear equation is exact. But for gravity, it's only the first order approximation. The actual equation is Td = exp(𝜙/c²). [Einstein 1907] Time never stops unless 𝜙 goes to minus infinity. So there is no Rindler horizon. (There may still be black hole event horizons, etc.)

The Einstein equivalence principle says that gravity and acceleration are locally indistinguishable. Here "locally" means "over short enough distances that the linear approximation is good and you can't see higher order terms". It doesn't say that they are globally indistinguishable. They're not.
 
  • #36
sbaker8688 said:
The question was if a Rindler Horizon forms when you stand on a massive body.
As @Dale has already pointed out, this question has been answered. The answer is no.

Thread closed.
 
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