How Do We Know...? takes a fresh look at the world around us, examining in detail what is normally taken for granted. This book looks at why we call a kilo a kilo, who dreamt-up the metre, and who thought angles could be obtuse. It examines the origins of the sixty-minute hour, the 12-inches foot and the 1000-gram kilogram. Starting with the earliest civilisations, with their digits and spans, and ending with today's metric world, this book will prove irresistible to anyone curious about all types of measurement.