Doppler Shift Interactive (70.0K)
Astronomers use the Doppler Effect to determine the motion and speed of galaxies and other distant objects. This Interactive shows you what the Doppler Effect is: how the frequency and wavelength of light or sound waves change as the source or the observer (or both) move relative to each other. Click on the buttons to make the Observer, the Source or Both approach, and observe the waves on the graph. Or take matters into your own hands by clicking and dragging on the spaceship to change its velocity.
Here we will use radio waves to study the motions of nearby objects, in this case the rotation of planet Venus, always hidden from direct visual observation by a thick veil of sulfurc acid clouds. But radio waves can penetrate the map the surface.
Since 1995 we have used the Doppler Shift to detect planets orbiting other stars. The first instance of this, the finding of a "hot Jupiter" orbitting 51 Pegasi, rocked the scientific establishment.
Few principles in science are applied on as varied a scale as the Doppler Principle. Since vast clouds of dust hide about 90% of the Milky Way from us visually, we must rely on radio observations of Doppler shifts in the hydrogen clouds to map the layout of the spiral arms of the galaxy.
Few principles in science are applied on as varied a scale as the Doppler Principle. In the 1930's Edwin Hubble and Milton Humason used it to discover the expansion of the universe, setting the stage for the Big Bang Theory.