Question about Planck's constant

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Planck's constant is crucial in distinguishing between classical and quantum mechanics, as it sets the scale at which quantum effects become significant. The discussion highlights confusion regarding its role, with one participant asserting that quantum models apply when actions are comparable to Planck's constant. However, another contributor points out that the Planck scale is vastly different from atomic scales, suggesting ambiguity in the original question. The conversation reflects a broader misunderstanding of how fundamental constants influence physical systems. Ultimately, clarity on the relationship between Planck's constant and the transition from classical to quantum mechanics is essential for accurate comprehension.
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I was talking to my friend (who's a physics major) about the difference between quantum and classic mechanics. Planck's constant came up somehow and my friend said that you could use it to determine with a system can be described by classical or quantum mechanics. I thought he was crazy since it's just a constant, how can it determine anything? That's like saying the speed of light can determine how fast a system is moving... it doesn't make sense. Anyone have any comments? Is he right or making everything up?
 
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Methinks your friend meant that quantum mechanical models are for atomic phenomena & are to be applied when the action is of the order of Planck's constant. Regards,
Einstone.
 
einstone said:
Methinks your friend meant that quantum mechanical models are for atomic phenomena & are to be applied when the action is of the order of Planck's constant. Regards,
Einstone.

Even that can't explain it since Planck scale is many OOM from the atomic scale. It seems too ambiguous to determine what the OP meant...
 

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