Smolin: Lessons from Einstein's discovery....

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Discussion Overview

The discussion revolves around Lee Smolin's paper "Lessons from Einstein’s 1915 discovery of general relativity," specifically focusing on the concept of background independence and its implications for the search for a fundamental theory of nature. Participants explore the relationship between relational degrees of freedom and symmetries in physical laws, questioning how these ideas might guide theoretical development in physics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants discuss the principle of background independence, suggesting that it implies a lack of fundamental symmetries in the laws of nature as one approaches a more complete theory.
  • Others argue that diffeomorphism invariance in general relativity indicates a reduction in symmetry compared to special relativity, which has additional global symmetries.
  • One participant expresses uncertainty about the implications of restricting to relational degrees of freedom and its connection to symmetries.
  • Another participant references Leibniz's principle of sufficient reason and the identity of indiscernibles, suggesting that these principles challenge the existence of global symmetries in cosmological theories.
  • Some participants critique Smolin's ideas, comparing them to a meal that is initially satisfying but leaves one wanting more, indicating a perceived lack of depth or completeness in his arguments.
  • There is a suggestion that if a theory reveals no symmetries, it could lead to any statement being considered a law of nature, blurring the distinction between laws and specific facts.
  • One participant proposes that the presence of symmetries in theories may indicate a need for a more fundamental description, while another counters that the absence of symmetries does not necessarily imply a lack of meaningful laws.
  • There is a discussion about the nature of symmetry and asymmetry in systems, with one participant suggesting that entropic systems inherently display asymmetry.

Areas of Agreement / Disagreement

Participants express a range of views on the implications of background independence and the role of symmetries in physical theories. There is no consensus on whether the restriction to relational degrees of freedom necessarily leads to fewer symmetries in a fundamental theory, and several competing interpretations of Smolin's arguments are present.

Contextual Notes

Some arguments rely on interpretations of Leibniz's principles and the nature of symmetries in physical theories, which may depend on specific definitions and assumptions that are not fully resolved in the discussion.

  • #31
Here's a quote from his book "The Singular Universe and the Reality of Time" written with with Roberto Unger Cambridge University Press 2015

"Relationalism offers a strategy that can take over at the point that reductionism fails. The properties of the elementary particles can be understood as arising from the dynamical network of interactions with other particles and fields. A property of a particle or event that is defined or explained only by reference to the network of relations it is embedded in can be called a relational property; its opposite, a property that is defined without reference to other events or particles, is called intrinsic. The ambition of a purist relational approach would be satisfied if all properties of elementary particles and events are relational." p380

He mentions a guy named Chew and collaborators from the 1960s "bootstrap approach" to understanding the observed hadrons as kind of pioneers of the view. I am just into the chapter on this now. He's working up from Liebniz' "principle of differential sufficient reason" and "principle of the identity of the indiscernible" - I'm struggling with it to be sure (and the whole chapter). It seems like a valiant but hopeless defense against infinite regress... I'm hoping it convinces me of some new way of ignoring that.
 
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  • #32
Jimster41 said:
Here's a quote from his book "The Singular Universe and the Reality of Time" written with with Roberto Unger Cambridge University Press 2015
"Relationalism offers a strategy that can take over at the point that reductionism fails." ... It seems like a valiant but hopeless defense against infinite regress.

I would say reductionism fails where there is intrinsic complexity that cannot be avoided or bypassed on the way to a theory. Then if you try to sum a quantity over terms that are more and more complicated, you may get an infinity that cannot be eliminated. Is that the idea?
 

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