Back in my Sr year in high-school (1959/60) I took a college freshman level physics class. The teacher made the point (strongly) that to start a Foucault, one has to pull it to the side thus establishing the plane of swing (vertical per earth gravity and also passing through the low point of the swing and the bob's present position). However, since the starter is standing on the earth, s/he is imparting rotation to that plane of swing. In other words, the plane of swing will continue to rotate with the earth, thus nulling the intended effect. My teacher insisted that all real pendulums are given a reverse push to actually "show" the principle.

Currently I'm reading "The Prism and the Pendulum" by Robert P. Crease a popularization of ten "beautiful" experiments in the history of science. He describes Foucault's setup including the use of a cord to hold the bob to the side until extraneous motions cease and a candle to burn through the cord so the bob is released without extraneous motions. The cord was attached to the earth, thus was changing the plane of swing to be.

That seems to contradict my high-school teacher. Intuitively I expect that the plane of swing is also influenced by Newton's laws of motion, hence would maintain the push from the earth it got when the bob is released.

Any resolution to this apparent contradiction?

Appreciations,
Gene