Introduction

Before physics can be introduced as a subject in its own right, it helps to ask a broader question: what is science itself, and where did the impulse to study nature systematically come from?

The English word science traces back to the Latin scientia, simply meaning "to know." In Tamil, the equivalent term is Ariviyal (அறிவியல்), which carries a slightly different flavour -- "knowing the truth." Both point at the same underlying human trait: people have always been curious about the world around them -- the motion of bright objects in the night sky, the regular turn of the seasons, why a rainbow appears after rain -- and have looked for patterns and explanations behind these everyday and not-so-everyday phenomena.

That curiosity is the real origin of science, long before the word 'science' existed. In fact, the term itself is comparatively recent -- it only came into use in the 19th century. Before that, the pursuit of systematic knowledge about nature was called natural philosophy, and it stretches back into deep antiquity: ancient civilisations were already practising astronomy, chemistry, human physiology, and agriculture well before they had a single word for the enterprise as a whole. Knowledge in that era travelled by word of mouth, since writing systems had not yet been developed everywhere. Among the earliest known contributors to this tradition were the Egyptians, whose observations spanned fields from astronomy to medicine. India has its own deep roots in this story too -- scientific and mathematical thinking on the subcontinent can be traced as far back as the Indus Valley Civilization (roughly 3300-1300 BCE).

Out of this broad, ancient project of systematically understanding nature, science eventually organised itself into distinct disciplines depending on what kind of "nature" is being studied. The branch that studies non-living things is called physical science (physics and chemistry fall under this umbrella), while the branch that studies living things is called biological science (botany, zoology, and related fields). Physics -- the subject of this unit -- is one half of that physical-science pairing, and its own specific meaning and place among the sciences is taken up next.