Slashdot Mirror
Measuring Gravity in Your Basement
Jack Durian writes "John Walker, the founder of Autodesk/co-author of AutoCAD has some fun playing pretend experimentalist, measuring gravity in his basement."
← Back to Stories (view on slashdot.org)
← Back to Stories (view on slashdot.org)
For your information, it's metric (cgs).
Check out "Gravity" by Chuji Tsuboi.
S /G RAV/NOTES/gravunits.html
He describes the International Geodetic or Gravimetric Network or something, they have gravimeters about the surface of the Earth or measured readings to get an idea of the varying gals of gravity. A gal is a unit of gravity. Over the surface of the planet it is something like around 980 gals, varying by tens to more of milligals. Normally people think the acceleration of gravity is 9.8 m/s^2, or, -9.8 m/s^2.
http://www.mines.edu/fs_home/tboyd/GP311/MODULE
The Earth is a spheroid oblate. The southern hemisphere is negligably, barely, thicker through the latitudes. Maybe the center of gravity of the galaxy is to the south, or, maybe just this part of the galaxy.
You want to see what Gabe Luther and and William Towler,current "holders" of Big G, used to measure it ? Here's a great shot of the torsion balance device from this short summary .
Here's a link to the press room at LANL Look for "17) Measuring the Gravitational Constant ("Big G") -- In the Lab of Gabe Luther, Los Alamos scientist. Sound bite on methodology." - no link but an interesting page of resources.
"Whoever would overthrow the liberty of a nation must begin by subduing the freeness of speech."--Benjamin Franklin
The reason he used dynes and stuff (part of the cgs - centemeter, gram, second - system) and not the SI (formerly the mks - meters, kilograms, seconds) system is that most of his measurements would have been different by many orders of magnitude. Who wants to see something with a force of 0.0000001 newtons (kg*m/sec/sec) when you could see 0.01 dynes (gm*cm/sec/sec)?