The Hertzprung-Russell diagram, created in the early 1900s by Ejnar Hertzsprung and Henry Norris Russell, was a major step towards understanding "the life cycles of stars". Unfortunately, many students think that the H-R diagram is some sort picture or map that shows the locations of stars. They don't seem to understand that it is a way to CLASSIFY stars based on two criteria; brightness and temperature. To help them understand how it works, try using something that they do understand (food).
Draw a grid on the board like the one shown here, and then explain that they are going to classify various foods, based on two criteria; taste and nutritional value. Call on students to name foods that would (based on their opinion) be placed in various locations within the rectangle. CLICK HERE to see a more detailed description as well as an example that shows how I would classify certain foods.
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