Has Newton gravitational constant really been proven Universal?

Answer 1

The gravitational constant is perhaps the most difficult physical constant to measure. In SI units, the 2002 CODATA recommended value of the gravitational constant is

G = \left(6.6742 \plusmn 0.0010 \right) \times 10^{-11} \ \mbox{N} \ \mbox{m}^2 \ \mbox{kg}^{-2} \,

= \left(6.6742 \plusmn 0.0010 \right) \times 10^{-11} \ \mbox{m}^3 \ \mbox{s}^{-2} \ \mbox{kg}^{-1} \,

Another authoritative estimate is given by the International Astronomical Union (see Standish, 1995)
So far so good, it works. Therefore it is proven 'Universal'.

Answer 2

The Newton gravitation constant G is called universal because Newton called his theory Universal Gravitation. This law seems to work everywhere we can observe, except at the quantum scale. Lots of theoretical work is going to try to unify Newtonian, relativistic, and quantum physics. The best known are the various superstring theories and Quantum Gravity.

"All living humans breathe" is a universal law until someone finds an exception, like perhaps someone on an artificial lung.

Answer 3

what a great question! I'm pretty sure a lot of physicists have wondered it, as well.

although no one really knows for sure (though it is generally assumed that it is), i think that it is universal. here's my argument for why!

so, newtonian gravitation has proved remarkably useful, and we can use it to describe how stars work! (as gas collapses in on itself gravitationally, it heats up and gets pressurized, and so if it gets hot enough it triggers nuclear fusion which makes stars shine!) if we could imagine that the gravitational constant could be changed, making it HIGHER would mean that there would be higher pressures and temperatures inside stars, and so they would burn brighter and bluer; alternatively, if the gravitational constant was lower, there would be less pressure on the inside of stars, and they would burn dimmer and cooler!

okay, so, it's reasonable to assume that over any (large enough) volume where you have a bunch of stars, they will have similar mass distibution: the percentage of stars with sun-sized masses will be the same in any population...

so if, in some region of space, the gravitational constant is HIGHER than in ours, even though we'll can expect that in that region the stars all have a mass distribution comparable to the ones we're used to, because the gravity is stronger, a HIGHER percentage of stars than we are used to seeing will be burning really hot and brightly! alternatively, if the gravitation constant is LOWER somewhere else, we'll see a LOWER percentage of stars which burn hot and bright!

anyway, the moral of the story is that i'm pretty sure that no matter where astronomers look in space, the percentage distribution of hot-bright stars is about what we'd expect it to be. alternatively, it means that if there was a difference in G, we'd be able to see it by doing careful observations. I'm pretty sure that no one's seen anything like what i've described, but if they do, we'll know what it means (thanks to your question!)

Answer 4

It has worked so far for this whole solar system for launching spaceprobes and such.

Answer 5

nothing can be proven. all theories are just that until something better comes along.