Factors Affecting Gravitation Constant: Understanding G in Cavendish Experiment

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Discussion Overview

The discussion revolves around the gravitational constant (G) and its determination through the Cavendish experiment. Participants explore the nature of constants in physics, particularly whether G depends on any factors or is truly independent as a constant value.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant asserts that the gravitational constant has been determined experimentally and is always a constant, questioning what factors it might depend on.
  • Another participant argues that a constant, by definition, does not depend on any factors, seeking clarification on the original question.
  • A third participant agrees, stating that the gravitational constant defines the magnitude of mass effects on gravitational force, but notes that the exact nature of gravity's creation remains unknown.
  • There is a challenge regarding the interpretation of experimental determination, suggesting that constants may depend on the terms used in their measurement.
  • One participant emphasizes that the value of G is approximated through measurement and that the exact value is unknown, drawing a parallel to measuring mass.
  • Another participant uses the example of resistance in an electrical circuit to illustrate that while measurement requires certain conditions, the constant itself does not depend on those conditions.

Areas of Agreement / Disagreement

Participants express disagreement on whether the gravitational constant can depend on factors related to its measurement. Some maintain that it is a true constant, while others suggest that experimental determination implies some dependency.

Contextual Notes

Participants discuss the implications of defining constants and the challenges in measuring them accurately, highlighting the complexity of understanding physical constants in experimental contexts.

DrChem
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gravitation constant has been determined experimentally by cavendish. Its value has been found to be always a constant. The expression for G is given as G=Fd*d/Mm. I would like to know-
on what factors does gravitation constant depend?
 
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Hi DrChem, welcome to PF!

I don't understand your question. Something which is constant, by definition, does not depend on any factors.
 
I concur. The gravitational constant simply defines to what magnitude mass effects the gravitational force.

By "factors", do you mean to ask how natures form of creating gravity has the specific magnitude of the gravitational constant? Unfortunately, no one really knows.
 
if a value is determined experimentally will that not mean that it depends on those terms which were responsible for its determination.
does this mean that any constant is independent of any factor.
 
The value is not determined experimentally, it is only approximated by measuring it. We don't (and probably never will) know the exact value of G.

Just like you can measure your mass (or weight). Your mass does have an exact value, but you will never know it exactly, you can only measure it and determine an approximate value for it.
 
DrChem said:
if a value is determined experimentally will that not mean that it depends on those terms which were responsible for its determination.
No. For example, consider determining the resistance of an ideal resistor. In order to determine its resistance we must apply a voltage across it and measure the current. Then we can take the ratio of the voltage over the current and we have the experimentally measured resistance. We can apply a different voltage, measure the new current, and get the same ratio. Despite the fact that you need to apply a voltage in order to experimentally determine the resistance we still say that the resistance does not depend on the voltage because we can apply any voltage and measure the same value for resistance.

Mathematically V=IR defines resistance and says that we need a voltage and a current in order to measure resistance. In contrast, dR/dV=0 says that the resistance is constant (wrt V) and therefore its value does not depend on the voltage. Does that help?

DrChem said:
does this mean that any constant is independent of any factor.
Yes, again, that is the definition of the word "constant".
 
Last edited:
thank u
 

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