At 42:18 minutes, when Daniel Lathrop is demonstrating his rotating core model, the narrator says: "The experiment is fraught with danger, because Dan plans to fill his core with molten sodium metal - a highly volatile element - and then spin it at up to eighty-five miles an hour."
Only the speed of linearly traveling objects can be measured in miles per hour.
The speed of rotating objects is measured at revolutions per minute.