By looking at the Earth’s orbit from the above its orbit appears to be much more elliptical.
The next step involved measuring the radical velocity the star Arcturus in the solar neighborhood. The star Arcturus is relatively close to the Sun hence its temperature is slightly different from that of the sun. Zooming into the small regions of the spectrum of individual stars, similar absorption lines are observed. The little offset in wavelength is as a result of movement of Arcturus.
Since we have obtained the value of the earth’s velocity as 129.74 km/sec, and the period of its orbit is known to be one year, we can calculate earth’s radius (in astronomical units) using the formula
5. The apparent color of the Arcturus changes with the radical velocity. If the object is close to the observer only a single edge of shifting to the other but if the object is far away they will appear as a small dot of light. Incase the observer is moving quickly, the interference of wavelengths will result in spreading of individual lines, a condition known as rotational broadening (Richmond