Understanding Units and the SI System

This lecture introduces the concept of units by comparing different lengths using ropes, leading to the necessity of a standard unit. It explains the need for a coherent system of units and delves into the history and development of the International System of Units (SI), based on universally true constants. The lecture discusses the base units and prefixes of the SI system, as well as the importance of defining units based on physical phenomena, artefacts, and constants. It highlights the recent shift towards defining units based on physical constants rather than physical artefacts, emphasizing the fundamental differences between the old and new SI system.