Electrons and Electric Fields

The famous Millikan oil-drop experiment involved observing suspended minute oil-drops falling under gravity and then under an applied electric field which stopped the downward motion. There are quite a few descriptions of the experiment on the Internet, this being one of many.

There is a wee, ever so minor problem with the experimental setup and assumptions. This wee problem is the assumption that with the experimental electric field turned off, the only force acting on the oil-droplets is gravity.

What about the ambient electric field of the Earth itself?

None of the descriptions of the experiment make any mention of the Earth’s electric field, but do stress the presence of the far weaker gravitational field, and of course the far stronger electric field induced by the experiment design to stop the oil-droplets from falling under gravity.

About Louis Hissink

Retired diamond exploration geologist. I spent my professional life looking for mineral deposits, found some, and also located a number of kimberlites in NSW and Western Australia. Exploration geology is the closest one can get to practicing the scientific method, mineral exploration always being concerned with finding anomalous geophysical or geochemical data, framing a model and explanation for the anomaly and then testing it with drilling or excavation. All scientific theories are ultimately false since they invariably involved explaining something with incomplete extant knowledge. Since no one is omniscient or knows everything, so too scientific theories which are solely limited to existing knowledge. Because the future always yields new data, scientific theories must change to be compatible with the new data. Thus a true scientist is never in love with any particular theory, always knowing that when the facts change, so too must he/she change their minds.
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