Why Planck's Constant Has Dimensions and a Unit?

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Discussion Overview

The discussion centers around the nature of Planck's constant, specifically why it possesses dimensions and a unit despite being classified as a constant. Participants explore the implications of dimensionality in constants and compare Planck's constant to other physical constants.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants assert that Planck's constant is a dimensional constant, similar to other physical constants like the gravitational constant.
  • One participant questions the assumption that constants cannot have dimensions or units, citing the speed of light as an example of a constant that does have dimensions.
  • Another participant expresses confusion over the definitions of constants, suggesting that some examples provided are not physical constants but merely numerical values.
  • A later reply clarifies that a constant can either have dimensions or be dimensionless, providing examples such as the fine structure constant, which is dimensionless.

Areas of Agreement / Disagreement

Participants generally disagree on the definitions and implications of constants having dimensions. There is no consensus on the initial claim that constants do not have dimensions or units, as multiple viewpoints are presented.

Contextual Notes

Some participants reference educational sources that may have led to misunderstandings about the nature of constants, indicating a potential limitation in the definitions being discussed.

Nader AbdlGhani
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Despite being a constant, It has both dimensions and a unit, can someone kindly explain why ?
 
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Planck's Constant is a dimensional constant. Energy= Planck's Constant. * frequency . It is not the only constant that has dimensions , many other physical constants also has dimensions , like gravitational constant.
 
Nader AbdlGhani said:
Despite being a constant, It has both dimensions and a unit, can someone kindly explain why ?

This question is puzzling. Are you saying that the property of a "constant" includes NO dimensions and NO units?

"c", the speed of light in vacuum, is a constant. It has "dimensions and units". Why are you not asking about that as well?

Zz.
 
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ZapperZ said:
This question is puzzling. Are you saying that the property of a "constant" includes NO dimensions and NO units?

"c", the speed of light in vacuum, is a constant. It has "dimensions and units". Why are you not asking about that as well?

Zz.
Actually I intended to ask generally, but then I went for the example spontaneously, I have just studied units and dimensions and they told me that constants don't have dimensions and units, for example, number one itself, angle of measure 60° etc, and what came in my mind are constants which are in many relations in physics
 
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Nader AbdlGhani said:
Actually I intended to ask generally, but then I went for the example spontaneously, I have just studied units and dimensions and they told me that constants don't have dimensions and units, for example, number one itself, angle of measure 60° etc, and what came in my mind are constants which are in many relations in physics

This makes very little sense. Who are these "they" that you are referring to?

The examples you cited are NOT "constants" in physics. These are simply numbers associated with some quantity. Again, look at "c". Do you think this constant has NO dimensions and NO units? This one constant itself falsify any claim that a constant has no dimension and no units.

Zz.
 
Nader AbdlGhani said:
Actually I intended to ask generally, but then I went for the example spontaneously, I have just studied units and dimensions and they told me that constants don't have dimensions and units, for example, number one itself, angle of measure 60° etc, and what came in my mind are constants which are in many relations in physics
As zapperz has pointed out, you are confusing terms. The examples you site are not physical constants, they are just numbers. If used in an equation, they can be called constants as far as math is concerned, but that has nothing to do with physical constants like c
 
Simple answer: A constant may either have dimensions (i.e. units), or it may not.

Examples:
The fine structure constant alpha = 1/137.035... is a dimensionless physical constant.
And, as pointed out already in this thread, Planck's constant and the speed of light are constants that have units.
 

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