# Displacement experiment help

1. Oct 11, 2004

### omin

The magnitude of G is the same as the magnitude of the force between two masses of 1 kilogram each, I meter apart: 0.0000000000667.

Where does 0.0000000000667 come from?

G is an acclerlation rate. The experiments in my text from Henry Cavendish and Philip von Jolly. Both experients seem to only show a displacement rather than the time the displacment occurs. Wouldn't they have to know in the experiment the time the displacement occurs to get the constant G? If they didn't test for the time, how did they get it from the experiment?

2. Oct 11, 2004

### chroot

Staff Emeritus
Well, not to be pedantic, but the numerical value of G is simply a result of mankind's arbitrarily-chosen units of distance, time, and mass. In many situations, physicists use natural units in which G (and other constants) are simply unity.

- Warren

3. Oct 11, 2004

### HallsofIvy

To be even more pedantic: G is not an "acceleration rate", "g" is.

4. Oct 12, 2004

### omin

That really helpfull. I sit in a better place now. Thanks for the wonderfull explaination.

5. Oct 13, 2004

That is a good question. Why is G the value it is?

Maybe it is the only conceivable value possible that would lead to a stable Universe where thinking lifeforms could evolve and wonder why G was that value!

Maybe in other Universes it has a different value?
It is one of the least accurately measured constants - only 6 significant figures I think...

6. Oct 13, 2004

### omin

I have misled things unintentionally in my first quesiton.

Humans have chosen distance, mass and time constants. These constants are used to define G, 0.0000000000667.

Is there an accessable to the laymen way, and brief way, to step through how we use our constants to arrive at 0.0000000000667?

7. Oct 14, 2004

### Staff: Mentor

It is found by application of Newton's law of gravitation. Perhaps http://www.npl.washington.edu/eotwash/gconst.html [Broken] will help.

Last edited by a moderator: May 1, 2017