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Weighing An Attogram
Roland Piquepaille writes "Researchers at Cornell University have reached a new level of precision by measuring objects with a mass of less than an attogram (10^-18 gram). They used a silicon cantilever oscillator to measure small dots of gold. But their real goal is to detect and identify viruses. The team also wants to reduce the size of the cantilever, extending the sensitivity well into the zeptogram (10^-21 gram) range. This summary contains more details and an image of a small gold dot resting on the silicon cantilever they used to achieve this breakthrough."
Au: 197g/mol
10E-18 / 197 = 5.076x10E-21 mol
5.076x10E-21 x 6.022x10E23 = 3056.8 gold atoms.
At that scale, influences like Van der Waals forces become far more powerful than gravity. Reading the pull of gravity with all the EM-related forces at work seems like a very, very difficult job.
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Your question reveals some confusion, perhaps produced by the wording of the article.
They are not "weighing" anything. They are measuring the mass of the gold. These are two different things. Gravity is not involved in the latter.
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About 1.4x10^-11 microns/zL on the highway, 8x10^-12 or so in the city. Although I think that mileage is more commonly measured in zeptolitres per 100 Angstroms these days.
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