on gravity as a weak force

[acroyear]

Changing Standards of Mass : Uncertain Principles:

This [the "standard" 1kg cylinder's mass seems to be changing] is not a new problem-- it was old news when I was a student at NIST, and people at NIST and elsewhere have been working on alternatives to the physical kilogram standard for decades. The physical kilogram standard is really an artifact of a past age-- all the other major standard measures have been redefined in terms of more universal interactions, as explained by Physics Buzz.

Attempts to redefine the kilogram have yet to yield anything, though. The problem, as always, is the gravity is so damnably weak.

Gravity may not seem like a weak force, but it is. The simplest illustration of gravity's weakness is the old "rub-a-balloon-on-your-hair-and-stick-it-to-the-ceiling" trick. When you do that, the attractive force of maybe ten billion extra electrons on the balloon is enough to hold it up against the gravitational pull of the entire Earth pulling on a billion trillion atoms in the balloon. Gravity is preposterously weak compared to the electromagnetic force.

This is a nice feature for those of us who like to play basketball, but not such a good thing if you're trying to come up with a standard for mass. Tiny electric and magnetic fields are enough to throw off any attempt to measure mass by measuring the gravitational force, simply because of the huge disparity in the strengths of the two forces.

As one physics prof noted, it takes gravity 30-something seconds to get you to fall a certain number of stories from the roof of a building...and electro-magnetism a fraction of a fraction of a second to stop you.