Astronomy belongs to everyone. The Universe is here for all of us to see. Its study is not just the province of astronomers, with their expensive telescopes and strange, unfamiliar mathematics. In this chapter, we are concerned with astronomy that you can do with your naked eye.

Some of the most universal aspects of our lives are influenced by astronomical phenomena. Imagine, for instance, a world in which day did not turn into night, or one in which there were no seasons! As we think about these, we will quickly realize that they are more subtle than perhaps we had thought. Indeed, even so simple a thing as the daily path of the Sun across the sky was historically explained in several different ways.

So too with eclipses and the phases of the Moon, the measurement of time and the drifting of the Sun along the zodiac – we begin our voyage through the Universe with these, some of the most fundamental aspects of our everyday environment.

Rising and setting: the rotation of the Earth

Perhaps the most basic of all astronomical observations is the simple fact that day turns into night and then day again in a never-ending cycle. This perpetual alteration, caused by the passage of the Sun across the sky, is so familiar that we hardly ever stop to pay attention to it. But in fact there is more to it than many people think.

Let us begin our study of astronomy with this, perhaps the simplest of all astronomical observations: the study of the Sun’s path across the sky. To perform this study you will need no advanced scientific equipment. Simply step outside just before dawn, face east, and watch what happens. What you see depends on where you live: we will concentrate on the view of the sky from the mid northern hemisphere.