What the work claims
The experiment claims to measure the elementary electric charge and establish that all observed charges are integer multiples of a single base value, which the authors identify as the magnitude of the electron’s negative charge.
How it was done
Millikan and Fletcher observed charged oil droplets between parallel metal plates in 1909. With no electric field, they measured terminal velocity to infer droplet radius and mass. Then they applied a voltage to create an electric field and adjusted it until droplets hung motionless — balancing electrical and gravitational forces. Using the known field strength, they calculated each droplet’s charge.
What holds up
The method reliably yields charges that are integer multiples of a base value. That value — 1.5924(17)×10⁻¹⁹ C — is reproducible from the described procedure and matches the modern electron charge within 0.6%.
What does not
It does not prove electrons exist as particles. It measures charge quantization on macroscopic droplets. The inference that the base unit is the electron’s charge rests on interpretation, not direct observation of electrons.
Why it matters beyond the lab
It ended the debate over whether charge is continuous or atomic. At a time when subatomic particles were not universally accepted, it gave concrete, numerical weight to the idea of the electron as a fundamental unit.
Is it worth your time
Yes. It is the first direct, quantitative demonstration that electric charge is quantized — not continuous — and anchors the electron as a discrete physical entity with a measurable charge.