Proof Earth orbits the sun

To the editor:

On Dec. 14, Mr. Drietz also suggested that Earth doesn’t orbit the sun. Another challenge accepted.

Suppose you were standing beside a railroad track when a train went by blowing a whistle. You would hear a high-pitched (short wavelength) tone sliding down to a lower pitch (long wavelength) tone. Christian Doppler first studied and reported this effect using sound. The Doppler Shift of wavelength is also present in light.

We can hear Doppler Shifts caused by a moving source of sound or a moving observer. It is necessary to spread out light with a prism to create a spectrum to measure the shift in the frequency of the light. A spectrum is the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet, or ROYGBIV. Scientists examine photographs of spectrums call spectrograms to measure the Doppler shift of light.

A light source moving toward us will have its light shifted toward the blue end of the spectrum (short wavelengths). A source moving away from us has its light shifted towards the red end of the spectrum (long wavelengths). The same effects are present if the observer is moving toward or away from a stationary light source.

If Earth and the stars are stationary, there would be no Doppler shift in the light coming from any star over any period of time.

If Earth revolves around the sun, at some point in the earth’s orbit, it will be moving straight toward some star. The light from that star will show a shift toward the blue end of the spectrum. Six months later, the earth is on the other side of its orbit, and traveling in the opposite direction. Now the light from our chosen star will show a shift toward the red end of the spectrum.

When we examine spectrographs made six months apart, we do see the expected red and blue shifts. This proves that Earth orbits the sun.

Harold Shuckhart