I almost referenced that same section of Feynman. However, he mentions that there is a number and that number doesn't change.
Well, for an open system, that number DOES change. I fear referencing Feynman will, in their minds, reinforce constancy.
I did not have the video link. That is nice.
I thought about sharing the av8n link. However, I referenced a UM physics professor that at one point told a local hs group that the idea of constancy = conservation was one of the student ideas that are a big pet peeve of his. The group I am talking to thought this might be him 'trying to make a name for himself.' So if they would easily dismiss a singular physics professor, I imagine they would easily dismiss a single website that (please, I really intend no offense) does not appear to have any institutional association.
I am trying to find a reference that clearly addresses conservation =/= constant for an open system. I can't seem to find any.
Modeling physics addresses this, however, the group claims modeling physics is one of the sources of this incorrect and non-useful physics.