Teacher Enrichment: 1 February 2006

The goal of science is to understand the world around us. In astronomy, since we are dealing with the whole universe, we cannot perform direct experiments on many of our subjects. But the basic method for exploring our questions about the universe is the same across all branches of science. Keep in mind, however, that the list below is merely a guideline: sometimes the question comes first, which leads to the observation. Sometimes a model is developed to explain one thing, which prompts questions about something else.

Observation. First you see something that makes you curious. This leads to:
Questions. What could cause this effect? Can I see any other systems that behave in a similar manner? Is this event rare or common? Is the effect similar to something I have seen before? These, and other questions, form the basis for an:
Hypothesis. A description for how you think the system behaves, or how the event occured. This often involves a mathematical model of the system. With your hypothesis in hand, you now need to make more:
Observations/Models. In most sciences, the next step would be to perform an experiment to test your hypothesis. Astronomy deals with objects that are so big, and time-scales that are so long, that experiments are not feasible. So you have to examine the predictions your hypothesis makes and make more observations or computer models to:
Test/Check. Do the predictions of your hypothesis match what you see? Have you found something new that cannot be explained by your hypothesis? Can you revise your hypothesis to reflect your new findings, or must you reject it and come up with a new one? With your new or revised hypothesis in hand, go back to step four and make more observations.

This is not the end of the process, by any means. The first hypothesis made often does not match what is later observed. Science is a dynamic process: scientists are constantly asking new questions, and new observations are requiring changes to old hypotheses. As I stated above, less that 100 years ago, we did not have any idea what made stars shine. It required many developments in nuclear physics in the 1920s and 1930s before Bethe came up with a hypothesis that matched our observations.

Notice that I have not yet used the word theory. A scientific theory is something that has survived many iterations of this process, and is the best explanation for the observed facts. This does not mean a theory cannot be revised! If new observations are not explicable by a given theory, some new hypothesis must be developed that explains not only the new observations, but all old observations where the previous theory was successful.

Forming the solar system

A good project for a grad student: form a solar system and report on its properties and how it differs from ours. You have two months...

How would we go about determining how the solar system formed? Now is your chance to try out the scientific method! For each observation, ask some questions and see if you can come up with a hypothesis that explains that observation. Your hypothesis should naturally make some predictions: what kind of observations would test those predictions?

Astronomy for Teachers, 4th session: 1 February 2006

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The Scientific Method

Forming the solar system