Light and Telescopes

In the second half of this morning's activities with the 3-4 graders, we discovered some things about light and telescopes.  I handed out diffraction gratings and we looked at the spectrum of the Sun and of the fluorescent lights in the room, discovering that white light is actually composed of many colors. We also looked at discharge tubes filled with different elements, with mercury and helium being the stars.    We found that each element emits a unique "fingerprint" of spectral lines.  To see a great 2-minute video of everything the kids saw, check this out. This is how we know what stars and other planets are made of.

We then discussed how the colors always appear in a certain order in a rainbow or a diffraction grating: red, orange, yellow, green, blue, violet.  Could there be any light which appears before red?  Yes, it's called infrared, and we can build cameras to see it even though our eyes can't.  I showed this nice video demonstrating the properties of infrared light.  Could there be any light which appears after violet?  Yes, ultraviolet, and after that would be X-rays and finally gamma rays.  We talked about X-rays for a while because some kids were worried about it being dangerous.  (Like many other things, they are safe if used properly, but dangerous if not.  A yearly dental X-ray is ok, but how do we protect the parts of our bodies which don't need to be X-rayed?  And how do we protect the workers who administer dozens of X-rays each day?) I extended that discussion to the ultraviolet and sunlight.

All this was a springboard for discussing telescopes, which is one of the last astronomy standards I hadn't covered yet.  Specialized telescopes are built to look at all kinds of light, from gamma rays to the infrared and radio. I showed pictures of some of the big telescopes I have used in my research, and that led to all kinds of interesting questions. We ran out of time, so I may start next Friday by answering more telescope questions.