B Fundamental Constants: How Do We Know They're Constant?

AI Thread Summary
The discussion centers on the constancy of fundamental constants like the Gravitational constant (G) and Planck's constant (h), questioning whether they change over time. Various experiments, including precise measurements using pulsars, suggest that any potential change in G is negligible, with a measured value indicating consistency with zero change. The distinction between the gravitational constant (G) and gravitational acceleration (g) is clarified, emphasizing that g varies based on Earth's mass and radius. The conversation also touches on the implications of these constants in the context of dark matter and cosmic observations. Ultimately, ongoing research and measurements continue to verify the stability of these fundamental constants.
PumpkinCougar95
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How do we know that constants in nature like the Gravitational constant or plank's constants are actually "constant" and don't actually change over time? What sorts of experiments have been done which verify these things?
 
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You could try Googling "Measuring G" or "measuring h" and see that such quantities are frequently 'checked'. Somebody could make a real name for themselves if they managed to find that G is increasing. Dark Matter was introduced to explain weird recession speeds of distant galaxies.
 
PumpkinCougar95 said:
How do we know that constants in nature like the Gravitational constant or plank's constants are actually "constant" and don't actually change over time? What sorts of experiments have been done which verify these things?
You can just check the BIPM definitions of the SI. These constants are not “in nature” they are in the SI. In other unit systems they may or may not even exist.
 
Shadow89 said:
The gravitational constant of earth is roughly 9.81m/s2.
That's not the gravitational constant. It's the gravitational acceleration g (lower case) on Earth and it depends on the Mass of the Earth and the radius.
G (upper case) is constant in
g = MG/d2
Shadow89 said:
Source: This is common, undisputed knowledge.
Whoops! That was really sticking your neck out to say something like that on PF. :wink:
 
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PumpkinCougar95 said:
How do we know that constants in nature like the Gravitational constant or plank's constants are actually "constant" and don't actually change over time? What sorts of experiments have been done which verify these things?
Only time will tell if some constants change over time.
 

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