Measurement of the Earth’s rotational speed via Doppler shift of solar absorption lines
Schematic view of the Earth-Sun geometry looking South. is the observer’s speed due to terrestrial rotation and is the solar hour angle.
Portion of the solar spectrum as imaged by the spectrograph. The upper band is properly focused while the lower, brighter band is out of focus; this is caused by a flaw in our self-built instrument.
Intensity profile of the spectral portion shown in Fig. 2.
Correspondence between wavelength and position for 24 atmospheric oxygen lines (crosses) and 8 solar iron lines (circles). This graph is important to verify the correct identifications of all spectral lines.
Wavelength residuals after subtracting the optimal quadratic fit to the atmospheric lines (crosses). The solar lines (circles) show a blueshift of 0.016 Å.
Plot of the measured radial velocities. The slope gives the Earth’s rotational speed while the vertical offset indicates an additional constant velocity, in this case directed towards the sun, due to the Earth’s orbital eccentricity.
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