Doppler and Sound • When sound waves are made they spread out evenly in all directions like ripples on a pool of water • A stationary train sounds the same from all directions.
When the train making the sound or the listener are moving there is an apparent change in frequency. • Higher frequency when moving towards each other. • Lower frequency when moving apart.
Doppler and Light • The Doppler effect occurs with light waves and other energy wave types. • In the area of astronomy the Doppler effect helps explain the red shift in stellar objects.
Red Shift • Stars emit light in specific patterns called spectral lines. • Stellar objects found outside of our galaxy all had spectral lines that had shifted towards the red end of the spectrum.
Red light has lower wave frequency which means the objects are moving away from the earth.
Big Bang • The red shift shows every galaxy is moving away from the Earth. • This supports the concept of an expanding universe . This in turn supports the Big Bang theory.
Links • www.pbs.org/wnet/hawking/strange/html/untitled_14_stuff.html webphysics.davidson.edu/Applets/Doppler/Doppler.html www.colorado.edu/physics/2000/applets/doppler.html www.colorado.edu/physics/2000/applets/doppler2.html lectureonline.cl.msu.edu/~mmp/applist/doppler/d.htm