Experts vs Imitators

This is adopted from an article on farnam street on how to tell an expert from someone who merely talks like an expert but may not have the deep down knowlege - an imitator

An expert can answer questions about details, deeper reasons why, or non standard situations.
An expert can explain to a child, or someone in simple language without using jargon.
Experts have failed at multiple points in the past
Experts know the limits of their information, and are usually not afraid to tell you, whereas imitators may want to give the impression they know everything.
There is s difference between a popularizer article or book and an actual expert in a field.