Definition:Universal Gravitational Constant

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Physical Constant

The universal gravitational constant is the physical constant which is the constant of proportion in Newton's Law of Universal Gravitation.

Its value in SI units is referred to as $G$ and is approximately equal to $6.674 \times 10^{-11} \, \mathrm N \, \mathrm m^2 \, \mathrm{kg}^{-2}$.


Symbol

The symbol for the universal gravitational constant is $G$.


Dimension

The universal gravitational constant has the dimension $\mathsf {M^{-1} L^3 T^{-2} }$.


Units

The SI unit for the universal gravitational Constant is given as newton square metres per kilogram squared:

$\mathrm {N \, m^2 \, kg^{-2} }$


Value

The value of the universal gravitational constant is:

\(\ds G\) \(\approx\) \(\ds 6 \cdotp 67430 \, (15) \times 10^{-11}\) $\mathrm {N \, m^2 \, kg^{-2} }$ \(\quad\) in SI units
\(\ds \) \(\approx\) \(\ds 6 \cdotp 67430 \, (15) \times 10^{-8}\) $\mathrm {dyn \, cm^2 \, g^{-2} }$ \(\quad\) in CGS units
\(\ds \) \(\approx\) \(\ds 3 \cdotp 32 \times 10^{-13}\) $\mathrm {lbf \, ft^2 \, lb^{-2} }$ \(\quad\) in FPS units


Also known as

The universal gravitational constant can also be seen referred to as the gravitational constant, but this is ambiguous.

The more wordy term universal constant of gravitation can also be seen.


Also see

  • Results about the universal gravitational constant can be found here.


Gravitational Constant: $G = 6.67 \times 10^{-8} \, \mathrm{cm}^{-3} \, \mathrm{gm}^{-1} \, \mathrm{sec}^{-2}$ is a track by Type O Negative on their $1991$ album Slow, Deep and Hard. It is about committing suicide.

As well it might be. If I'd had to express the physical constants in CGS units when I'd been in college, I doubt I'd have found a reason to stay alive myself.


Historical Note

When Isaac Newton formulated his Law of Universal Gravitation, he did not know, and had no immediate means to determine, what the universal gravitational constant $G$ actually is.

The value of $G$ was determined in $1789$ by Henry Cavendish in what is now known as the Cavendish experiment.


Sources

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