What size do particles start to get a quantum effect

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Discussion Overview

The discussion revolves around the size at which particles or objects begin to exhibit quantum effects, exploring the transition from classical to quantum physics. Participants consider various scales, from individual particles to macroscopic systems, and the implications of these scales in different contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that quantum effects typically dominate around small to medium molecule scales, but this is context-dependent.
  • One participant argues that individual particles, atoms, and molecules generally require a quantum description, while larger systems may often be described classically.
  • A participant introduces a more technical perspective, mentioning the significance of the de Broglie wavelength and its derivative in determining quantum behavior.
  • Another participant points out that macroscopic systems, such as Bose-Einstein condensates and superconductors, can exhibit genuine quantum behavior, indicating no absolute size threshold exists.
  • A claim is made that quantum mechanics effects are believed to become relevant around 10^14 atoms, with a specific experimental limit noted at 430 atoms, referencing a study on superposition in interferometry.
  • One participant provocatively states that quantum mechanical effects exist at all scales, suggesting the relevance of these effects is subjective and based on the observer's interests.

Areas of Agreement / Disagreement

Participants express a range of views regarding the size at which quantum effects become significant, with no consensus reached. The discussion reflects multiple competing perspectives and highlights the complexity of the transition from classical to quantum physics.

Contextual Notes

Participants note that the transition between classical and quantum descriptions is not clearly defined and may depend on specific conditions and contexts. The discussion includes references to experimental limits and theoretical considerations that remain unresolved.

Dammes
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Im wondering at what size particles/object start to get a quantum effect? At what size does classical physics stop and at what size does quantum physics start?
 
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Well, as far as I understand we typically talk about quantum effects starting to dominate around the small-medium molecule scales. However, this really depends on what you are trying to figure out or discuss. The difference between two electron states in a large polymer probably requires quantum mechanics, but that polymers behavior in a material may or may not.

Personally I would say that individual particles, atoms, and molecules generally require a quantum description, while large systems of these objects can be described by classical physics in most situations we deal with. I just don't think it's a clear cut between the two.
 
when hbar starts looking a little less non-zero
or more accurately speaking when the derivative of the de brodglie wavelength with respect to the coordinates stops being << 1
 
There are even macroscopic systems which show genuine quantum behavior like bose-einstein condensates, superconductors, superfluids, ...; even a single pair of entangled particles shows quantum behavior. There is no absolute size in terms of length scales or number of particles
 
Dammes said:
Im wondering at what size particles/object start to get a quantum effect? At what size does classical physics stop and at what size does quantum physics start?

it is believed that over 1014 atoms begins macrorealism.quantum mechanics effects, actual experimental limit, 430 atoms:
http://www.nature.com/ncomms/journal/v2/n4/full/ncomms1263.html

...PFNS10 and TPPF152 contain 430 atoms covalently bound in one single particle. This is ∼350% more than that in all previous experiments...
...in our experiment, the superposition consists of having all 430 atoms simultaneously 'in the left arm' and 'in the right arm' of our interferometer, that is, two possibilities that are macroscopically distinct. The path separation is about two orders of magnitude larger than the size of the molecules...
 
How long is a piece of string?

There are quantum mechanical effects at all scales. Whether they are large enough that you care about them is a statement about what you care about, not anything physical.
 
Thanks for all the replies, I understand know.
thanks
 

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