Discovery

Explore the Universe Musically

Take a musical jaunt into the realms of astronomy with AstroCappella, a teaching resource developed by astronomers and professionally recorded by an a cappella group, The Chromatics. The team has produced an engaging CD of music and a book of related activities, funded by the NASA-based Initiative to Develop Education through Astronomy and Space Science (IDEAS). This resource is available free to teachers (while stocks last), and can be accessed off the Internet.

The six songs cover a range of space-related topics including high-energy physics, solar convection and radio telescopes, each with a selection of activities to explore concepts further. Here's an excerpt from Doppler Shifting:

Now Susan's standing by the side of her car
(show me your licence, you're in big trouble)
Trucks blowing right by her but she's not going far
(they're still cruisin', Susan's losin')
She's been caught by a speed trap, and now she can hear
(here comes the physics, you're in for it now)
Sound of the Doppler shift right in her ear
Eeeeeeeeeeeeee-owwwwwwwwww That's the Doppler shift -- you've heard it I know
The Doppler shift -- first it's high then it's low

The booklet describes how students can investigate the Doppler shift for themselves. Take a pure tone electronic noise-maker (available from places like Dick Smith) and insert it into a plastic ball. The activity talks about a "splash-out" ball, but any ball which can be opened and which has holes that allow the sound to be heard clearly would work.

Attach a cord to the ball and then have someone swing it around above their head. The sound will change as the ball moves towards and away from an observer. This Doppler effect can occur with both sound and light, because both sound and light reveal wave- like behavior. If a source of light was a star moving relative to an observer on Earth, this would cause the star's spectrum to be shifted toward the red (going away) or toward the blue (coming towards) end of the spectrum.

Discussion questions for this topic include:

Does the person swinging the Doppler ball assembly hear the Doppler shift? Why or why not? Can the red/blue shift technique be used for objects other than stars? Can you tell which way an emergency vehicle is traveling by the pitch of its siren?

The AstroCappella Web page is at http://www.pagecreations.com/astrocappella/
Or email astrocappella@athena.gsfc.nasa.gov
Or write to Dr Padi Boyd, Code 662, NASA/GSFC, Greenbelt MD 20771, US