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

by Andrew Fraknoi (Foothill College), George Greenstein (Amherst College), Bruce Partridge (Haverford College) and John Percy (University of Toronto)
[December 28, 2001]

INTRODUCTION

A small, but vocal, minority of religious individuals has been urging a major revision of how evolution is taught in U.S. schools. Based on their personal beliefs, they find fault not only with biological evolution, but also with modern astronomical ideas about the age, expansion, and evolution of the universe. They have been actively pressing their case in the political, media, and educational arenas, and their loud arguments sometimes drown out other perspectives, including science.

Many good books and articles have been published for teachers on the scientific basis of evolutionary ideas in biology. But rather little is available to help teachers explain to their students how we know that the galaxies, stars, and planets are really old. In this special edition of The Universe in the Classroom, we want to give you some of the background on how scientists have been able to measure ages so vast that human history is a mere blink of an eye in comparison. We also provide some references to classroom activities you can do with your students, and resources for further exploration of some the astronomical ideas we discuss.

As part of our discussion, we want to emphasize the methods by which scientists study cosmic age and evolution, and how this relates to the interwoven structure of scientific knowledge. We note that science and religion deal with different aspects of human existence. For example, science cannot answer such questions as why there is a universe or what happened before the universe as we know it existed. What science is very good at, however, is searching out physical laws that describe the behavior of matter and energy in the universe, and seeing how such laws make stars, planets, and 7th grade students possible.

There has been much concern, in both the educational and scientific communities, about attempts to abolish the teaching of evolution in our schools. Astronomers share this concern because the term evolution - which just means change with time - is an underlying theme in all of science. Not only is evolution a unifying concept in biology but it also describes the way in which the planets, stars, galaxies, and universe change over long periods of time.

Evidence from a host of astronomical observations, which we will discuss below, strongly supports the great age of these objects, as well as the fact that they change significantly over the billions of years of cosmic history. Students should be given the chance to learn about these changes and what they mean for the development of life on Earth.

Concerned by the tendency to de-emphasize the teaching of evolution, the President and Council of the American Astronomical Society issued a formal statement on behalf of the astronomical community in 2000. The Society, which is the main body of professional astronomers in the U.S., includes men and women from a wide range of ethnic, cultural, and religious backgrounds. The statement reads in part:

"Research . . . has produced clear, compelling and widely accepted evidence that astronomical objects and systems evolve. That is, their properties change with time, often over very long time scales. Specifically, the scientific evidence clearly indicates that the Universe is 10 to 15 billion years old, and began in a hot, dense state we call the Big Bang.

Given the ample evidence that change over time is a crucial property of planets, including our own, of stars, of galaxies and of the Universe as a whole, it is important for the nation's school children to learn about the great age of, and changes in, astronomical systems, as well as their present properties. . . .

Children whose education is denied the benefits of this expansion of our understanding of the world around us are being deprived of part of their intellectual heritage. They may also be at a competitive disadvantage in a world where scientific and technological literacy is becoming more and more important economically and culturally.

Sincerely,
President Robert D. Gehrz
on behalf of The American Astronomical Society"

Let's take a look at the scientific discoveries that lie behind the Society's statement.

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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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