INTRODUCTION

What is Astronomy?

The word `astronomy' comes from the Greek roots `astron', meaning `star', and `nomos', meaning `law'. Although astronomy, as we use the term today, includes the study of stars, it also includes the study of other celestial objects.

Astronomy is the science which studies:

  • interstellar gas and dust
  • comets
  • asteroids
  • moons
  • planets
  • Stars
  • clusters of stars
  • galaxies
  • clusters of galaxies
  • the Universe as a whole

What is Science?

Science is generally broken down into separate fields: Physics, Chemistry, Biology, Astronomy, Geology, and so forth, but this division is somewhat arbitrary, of course. Studying astronomy requires knowing a lot of physics and a bit of chemistry, for instance. Science is nothing more than the systematic study of the universe. You study the universe every day just by walking around and looking at it. Professional scientists do the same thing, at a slightly more sophisticated level. The process by which scientists systematically study the universe around them is generally called the scientific method. The scientific method works something like this:
  • Observe a phenomenon, and gather facts about it.
  • Guess an explanation for the phenomenon: this guess is called a hypothesis.
  • Test your hypothesis by gathering more facts.
  • Modify the hypothesis if necessary to explain the new facts. (Or if the hypothesis is totally helpless, scrap it entirely.)
(This bloodless description of the scientific method makes it sound rather pompous and formal. In fact, we use the scientific method every day. For instance, I opened my refrigerator door one day and observed that the inside light didn't go on. I guessed that the light bulb had burned out. I tested my hypothesis by buying a new bulb, screwing it in, and looking to see whether it lit up. Since it remained dark, I modified my hypothesis, and guessed that the wiring was loose. And so on, with additional testing, until the light was fixed.)

When a hypothesis has been thoroughly tested, and becomes widely accepted by scientists, it is referred to as a model or theory. (The terms `model' and `theory' differ slightly in their meaning. Usually a `model' describes how one particular object or phenomenon works, while a `theory' is able to describe how many different objects or phenomena work.) Note, however, that a model or theory can never be proved absolutely. There is always the possibility, no matter how many tests it passes, that it will fail the next test.

In science, THERE IS NO ABSOLUTE PROOF. The best we can hope for is ``proof beyond a reasonable doubt''.

Since there is no absolute proof, and every theory is subject to future modification, there will always be not one, but two main questions asked. Not only will we ask:

(1) What do astronomers know?

we will also ask:

(2) How have they learned it?

Although the facts printed in any textbook may prove in some cases to be wrong, the process of how science works (how astronomers learn) remains the same, and is important to know. If nothing else, it will help you to figure out which scientific claims you read in the newspaper are plausible, and which are a large load of dodo guano.

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