Lorentz Transformation via Rotation

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Discussion Overview

The discussion centers on the derivation of the Lorentz transformation, particularly through the lens of using rotation in a space-time framework. Participants explore the implications of assuming the equality of spacetime intervals and the conditions under which this approach is valid, especially in relation to flat versus non-flat spacetimes.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant proposes that the Lorentz transformation can be derived using rotation, considering one dimension for space and another for the product of time, the speed of light, and the square root of minus one.
  • There is a suggestion that the equality ds^2 = ds'^2 is justifiable under the assumption that the speed of light is constant in both frames of reference, leading to the implication that ds^2=0 results in ds'^2=0.
  • Another participant questions the general validity of the equality ds^2 = ds'^2 and whether alternative methods are necessary to derive this relationship.
  • A later reply notes that the proposed method is only applicable to flat spacetimes.
  • One participant mentions that the use of ict has fallen out of favor due to its limitations in general relativity and its complications in relativistic quantum mechanics.
  • Another participant acknowledges the limitation of ict in non-flat spacetimes, suggesting it could lead to a complex ds^2.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the rotation approach to the Lorentz transformation, particularly regarding its validity in flat versus non-flat spacetimes. There is no consensus on the necessity of finding alternative methods to establish the equality ds^2 = ds'^2.

Contextual Notes

Participants highlight limitations related to the assumptions of flat spacetime and the implications of using complex numbers in the context of spacetime intervals.

snoopies622
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To me the easiest way to arrive at the Lorentz transformation is by rotation, using one dimension for space and the other for the product of time, the speed of light and the square root of minus one. This seems justifiable to me if one starts with the premise that ds^2 =ds'^2. I can see how if one assumes that the speed of light is the same in both frames of reference then ds^2=0 implies ds'^2=0 (and vice versa). But I don't know why ds^2=ds'^2 in general. Must one find the Lorentz transformation in some other way in order to arrive at this equality?
 
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snoopies622 said:
To me the easiest way to arrive at the Lorentz transformation is by rotation, using one dimension for space and the other for the product of time, the speed of light and the square root of minus one. This seems justifiable to me if one starts with the premise that ds^2 =ds'^2. I can see how if one assumes that the speed of light is the same in both frames of reference then ds^2=0 implies ds'^2=0 (and vice versa). But I don't know why ds^2=ds'^2 in general. Must one find the Lorentz transformation in some other way in order to arrive at this equality?
Whatever works easiest for you!
But notice that this only works for flat spacetimes.
 
ict was popular 100 years ago. It has lost fashion, because it can't be extended to GR, and it complicates relativistic QM, with two different i's.
 
Thanks to you both. I didn't realize that ict wouldn't work for non-flat spacetimes, but I guess it would yield a complex ds^2 (and who wants that?).
 

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