The Doppler effect explains changes in the length of light waves or sound waves as they move toward you or away from you.

VOA: special.2009.04.29

Running,walking or playing sports causes physical changes that make you feel better.

VOA: special.2009.03.24

Knowing what your skin looks like will help you recognize any changes.

VOA: special.2010.07.06

Or whether you take a very hard line against them to try to force changes coming in from below within the government.

VOA: standard.2009.08.14

How do you do? Next weekmy schedule changes, so I can...

VOA: standard.other