When light of a particular color is emitted from the surface of the sun, it has a definite wavelength, similar to how a note from a musical instrument can have a certain pitch. When this light enters the corona, it is scattered (bounced) off of electrons there.

    This shifts the wavelength of the light slightly to higher and lower wavelengths depending on whether the electron (a given particle of light) hits are coming toward you or going away from you. This is similar to how a note from a train whistle will sound higher or lower depending on whether the train is approaching you or going away.

    Once this light leaves the corona, it will have a variety of wavelengths which can be measured. The more that the light is scattered in the corona, the more wavelengths it will leave the corona with. So any given wavelength in the light from the solar surface is spread out when it bounces around in the corona.

    By comparing the light that leaves the surface of the sun (at just one particular wavelength) and light that leaves the sun's corona (at a variety of wavelengths), scientists can measure how much the light is scattered in the corona, and learn how hot each point in the corona is.

    The corona's temperature is also being measured in other ways, such as with instruments on the Solar and Heliospheric Spacecraft (SOHO), and these eclipse measurements can be compared with the spacecraft measurements to tell even more about the structure of the corona.

The Williams College Eclipse Expedition is set up and training for eclipse day!

    Tim McConnochie practices tracking the sun in the experiment to track oscillations in the corona of the sun. This is the only system that has to be tracked manually and Tim has been practicing in the hot Aruba weather.