Doppler Effect

The Doppler effect does not just affect sound; it also affects how astronomers study the light from stars. If they could see the frequency of a star increasing from where it normally should be, then they could tell that the star or object is approaching Earth. The emission or absorption lines of stars reveal certain elements of the star or object and its movement. By comparing the light of the star and its spectrum to the position of the elements that it contains, astronomers can see a shift in the position of the wavelength.

If a star is approaching, it will show a shift toward the blue end of the spectrum because the frequencies of the waves are increasing and the waves are getting closer together. This shift to the blue end of the spectrum is called blueshift. Blueshift tells astronomers if an object is approaching Earth. The opposite occurs in a redshift, in which the object recedes and shows a shift toward the red end of the spectrum with the wave frequencies decreasing and the waves being farther apart. Astronomers can then measure how much the specific element signatures have moved in order to determine the speed of that movement.

The Doppler effect helps prove that the universe is expanding -- a notion that scientists have used to support the Big Bang Theory. Doppler effect is a valuable tool for understanding how stars and galaxies interact with one another. This brings up several questions that astronomers are trying to answer: If the universe is expanding, where is it going, where are humans located in the universe, and will it continue to expand or will it all come back together?