An Ancient Universe: How Astronomers Know the Vast Scale of Cosmic Time

THE UNIVERSE: AN OVERVIEW

Telescopes

Astronomy is increasingly recommended as an integral part of the school science curriculum. The study of astronomy is deeply rooted in culture and philosophy. It harnesses our curiosity, imagination, and a sense of shared exploration and discovery, and it is also an area of great interest to people of all ages -- especially children. With new and better telescopes on the ground and in space, astronomy is one of the most exciting and rapidly-growing sciences today.

We live in a wonderful universe. It has inspired artists and poets through the ages, from ancient Greece to today's Star Trek television series. Astronomy, the study of the universe, reveals a cosmos that is vast, varied, and beautiful. The sky is our window on this universe. The universe is there for all to see on any clear night, and it is all around us.

When astronomers talk about the universe, they mean everything that is accessible to our observations. The universe includes all that we can survey or experiment on, from the moon that orbits our own planet out to the most distant islands of stars in the vastness of space. Since we cannot visit most of the universe, we rely on the information it can send to us. Fortunately, we receive an enormous amount of cosmic information all the time, coded into the waves of light and other forms of energy that come to us from objects at all distances. The main task of astronomy is to decode that information and assemble a coherent picture of the cosmos.

Saturn with Some Moons

Locally, our planet is one of nine that orbits the pleasantly energetic star we call the Sun. The solar system (Sun's system) also includes dozens of moons and countless pieces of rocky and icy debris left over from when the system formed. Astronomers now have many samples of these other worlds to analyze, including the rocks the astronauts brought back from the Moon, the meteorites (chunks of rock) that fall from space, including a few that were blasted off Mars long ago, and the cosmic dust we can catch high in the atmosphere.

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An Ancient Universe - Table of Contents

Home | Introduction | The Universe: An Overview | The Process of Science | The Ancient Universe - The Age of the Expanding Universe - The Age of the Oldest Stars - The Age of Light From Distant Galaxies - The Age of the Chemical Elements | The Changing Universe - Changes in the Solar System - Changes in Stars - Changes in the Universe | Science and Religion | Resource Guide | Activities

© Copyright 2001, American Astronomical Society. Permission to reproduce in its entirety for any non-profit, educational purpose is hereby granted. For all other uses contact the publisher: Astronomical Society of the Pacific, 390 Ashton Ave., San Francisco, CA 94112.

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