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The night sky seen from Mauna Kea in Hawaii. The feature extending across the sky is the Milky Way, consisting of hundreds of billions of stars. The Milky Way is the galaxy in which we reside.
Astronomy and the Universe
LEARNING GOALS
By reading the sections of this chapter, you will learn
| 1–1 | What distinguishes the methods of science from other human activities |
| 1–2 | How exploring other planets provides insight into the origins of the solar system and the nature of our Earth |
| 1–3 | Stars have a life cycle—they form, evolve over millions or billions of years, and die |
| 1–4 | Stars are grouped into galaxies, which are found throughout the universe |
| 1–5 | How astronomers measure position and size of a celestial object |
| 1–6 | How to express very large or very small numbers in convenient notation |
| 1–7 | Why astronomers use different units to measure distances in space |
| 1–8 | What astronomy can tell us about our place in the universe |
Imagine yourself looking skyward on a clear, dark, moonless night, far from the glare of city lights. As you gaze upward, you see a panorama that no poet’s words can truly describe and that no artist’s brush could truly capture. Literally thousands of stars are scattered from horizon to horizon, many of them grouped into a luminous band called the Milky Way (which extends up and down across the middle of this photograph). As you watch, the entire spectacle swings slowly overhead from east to west as the night progresses.
For thousands of years people have looked up at the heavens and contemplated the universe. Like our ancestors, we find our thoughts turning to profound questions as we gaze at the stars. How was the universe created? Where did Earth, the Moon, and the Sun come from? What are the planets and stars made of? And how do we fit in? What is our place in the cosmic scope of space and time?
Wondering about the universe is a key part of what makes us human. Our curiosity, our desire to explore and discover, and, most important, our ability to reason about what we have discovered are qualities that distinguish us from other animals. The study of the stars transcends all boundaries of culture, geography, and politics. In a literal sense, astronomy is a universal subject—its subject is the entire universe.
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