In modern life, we take for granted so many numbers describing the world around us. But how do we know them? What technology is needed to measure them? And can we trust them? Take, for example, how smartphones routinely tell us where we are on Earth to within a few meters: this technology relies on extremely accurate timing provided by atomic clocks in orbit (with corrections made possible by Einstein). Three hundred years ago, the invention of another kind of accurate clock arguably led to a more fundamental advance in estimating geographic position, because sailors were finally able to measure their longitude and safely navigate the oceans.

In this course we will look at the history, science and technology of measurement. We will learn how we know such basic numbers as the size, age and temperature of the Earth, and the clever tricks that science has contrived to estimate them. We will study how measurements are made across a vast range of scales, from the sub-atomic to the galactic, and how in some cases (such as observation of gravitational waves) both are important at the same time. We will discover that many of the numbers we see and trust, like the strength of a typhoon or the magnitude of an earthquake, have only recently been measured accurately and require global instrumentation to make such measurements possible. At the end of the course, we will have a much better appreciation for the certainty and uncertainty inherent in the fundamental data that guides our lives.