At approximately 3:20 it explains that solder is a mix of tin and lead and through some quirk no-one understands, this causes it to melt at least 100c lower tha

At approximately 3:20 it explains that solder is a mix of tin and lead and through some quirk no-one understands, this causes it to melt at least 100c lower than either of those two elements on their own. We don't understand how, but we understand how to exploit that. Do we now understand why that happens? (edit: minor side-rant about high definition 16mm films being preserved at 480p mpeg.)