Astronomy for Teachers, 4th session: 27 November 2006

The Sloan Digital Sky Survey

The Sloan Digital Sky Survey (SDSS) has developed several labs for classroom and personal use. In class, we began exploring the scavenger hunt, which is a great way to familiarize oneself with the SDSS tools. There are several more advanced labs available, as well as some very simple ones for kids which involve making sketches and interpreting drawings.

The Universe lab is also a good one to help get a grasp on the scale of things. It includes making a model universe with a balloon, and a discussion about how astronomers measure distances.

The nature of science (as it pertains to astronomy)

The most exciting phrase to hear in science, the one that heralds new discoveries, isn't 'Eureka!' but rather 'hmm....that's funny.' -- Isaac Asimov

Tantulus
Greek myth about a man who stole the secrets of the gods. As punishment, he was placed in a pool with fruit over his head. The fruit receded when he reached for it, and the water drained when he bent to drink.
The Tantulus principle
We can look, but we can't touch.

The goal of science is to understand the world around us. In most sciences, one performs controlled experiments to help understand the thing being studied. In astronomy, since we are dealing with the whole universe, we cannot perform direct experiments on most 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.

  1. Observation. First you see something that makes you curious. This leads to:
  2. 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:
  3. 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:
  4. 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:
  5. 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 inital hypothesis rarely matches what is subsequently observed. Science is a dynamic process: scientists are constantly asking new questions, and new observations are requiring changes to old hypotheses. 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 Hans 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. Bethe's explanation for the shining of the sun is now a very well tested theory, but for many years, it made predictions that were not observed. In the end, his theory was right, but we needed to revise our understanding of fundamental nuclear processes! This was refered to as the Solar neutrino puzzle, and it was only solved in 2001!

For a more in depth discussion of the scientific method, and what constitudes scientific proof, I direct you to: Talk.Origins Archive: Scientific Proof?