What is the largest size for identical particles?

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Discussion Overview

The discussion revolves around the concept of identical particles, exploring the size limits of such particles, ranging from fundamental particles like electrons to larger entities such as atoms, molecules, and even macroscopic objects like cars. Participants examine the implications of identicality at various scales and contexts.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the size limit for identical particles, suggesting they could range from atoms to much larger objects, including cars.
  • Another participant clarifies that at the particle level, two particles of the same kind are considered identical, but complexity increases at the atomic and molecular levels due to arrangements.
  • A participant references a quote about the indistinguishability of fundamental particles, asserting that all electrons are identical and cannot be marked or differentiated.
  • In response to the idea of identical cars, one participant agrees that they can be considered identical if they are in the same "quantum state."
  • Another participant argues that the concept of identicality breaks down at macroscopic scales, noting that even highly ordered structures like crystals have flaws, and achieving flaw-free macro-scale substances is a significant challenge in materials science.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the concept of identicality to macroscopic objects, with some agreeing that identicality can apply under certain conditions while others argue that it breaks down at larger scales. The discussion remains unresolved regarding the implications of identicality across different sizes and contexts.

Contextual Notes

The discussion highlights limitations in understanding identicality, particularly at the transition from microscopic to macroscopic scales, and the dependence on definitions of "identical" in various contexts.

scope
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hi,

I would like to know how big can be 2 identical particles?
can they be atoms, molecules, or even much larger than this?

in the extreme case, can they be 2 identical cars for example?

can we also say that any 2 electrons in the universe are identical particles?

I would be grateful for your reply!
 
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Your question is a little confusing. However on the particle level, any 2 particles of the same kind are identical. When it comes to atoms, etc. these are combinations. As long as the constituents are the same, they are identical. However at the molecular level things get more complicated, since arrangements matter.
 
scope said:
can we also say that any 2 electrons in the universe are identical particles?

In regards to this part of your question, I think there is a quote from David Griffith's (or was it Schroeder) that I'll paraphrase:

It does not make sense to talk about this electron or that electron. The best we can do is talk about an electron.

All fundamental particles one anyone type are entirely indistinguishable from one another. There is no way to "mark" one electron to set it apart from the others.
 
scope said:
in the extreme case, can they be 2 identical cars for example
Yes, provided they are in the same "quantum state".
 
scope said:
in the extreme case, can they be 2 identical cars for example?
The identicality of a substance breaks down pretty quickly before even you get out of microscopic scales.

Even crystals, the most highly ordered of macro objects, are full of flaws at the microscopic level. And regular materials such as even the thinnest of metals are much more disordered than the most disordered crystals.

It is the Holy Grail of Materials Science to produce macro-scale substances that are virtually flaw-free.
 

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