Friday, 25 September 2020

gravity - Is 4piG the true most fundamental gravitational constant?



Newton's law of gravitation is:


F=Gm1m21r2


It looks simple and natural.


But that's only in 3 dimensions. Let's look what happens in n dimensions:


n=2:F=2Gm1m21r

n=4:F=2πGm1m21r3
n=5:F=32π2Gm1m21r4
n=6:F=4π2Gm1m21r5


Oh no! Newton's force law becomes cluttered with unintuitive constants! But by defining G=4πG Newton's law of gravitation can be reformulated as such:


F=Gm1m214πr2



Immediately we recognize that 4πr2 is simply the surface area of a sphere of radius r.


But that's only in 3 dimensions. Let's look what happens in n dimensions:


n=2:F=Gm1m212πr

n=4:F=Gm1m212π2r3
n=5:F=Gm1m2183π2r4
n=6:F=Gm1m21π3r5


2πr is the surface area of a 2 dimensional sphere of radius r.


2π2r3 is the surface area of a 4 dimensional sphere of radius r.


83π2r4 is the surface area of a 5 dimensional sphere of radius r.


π3r5 is the surface area of a 6 dimensional sphere of radius r.


Newton's law of gravitation in n dimensions is:


F=Gm1m21Sn


Where Sn is simply the surface area of a n dimensional sphere of radius r. From this, it seems like G would be a nicer definition for the gravitational constant.





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