Earth Around the Sun

In 1916 Einstein wrote a book, “Relativity: The Special and General Theories”. In Chapter 5 he gave two specific measurements of the motion of the earth around the sun: aberration and Doppler shift. Below are several of the experiments available to Einstein at the time.


In 1725-1727 James Bradley discovered an unexpected shift in the position of stars that varied in direction throughout the year. It was determined that the shift was due to the earth’s velocity and direction in relation to the light. Specifically, the amount of the shift is equal to the ratio: (velocity of earth in orbit / (velocity of light). The amount of the shift is called the “constant of aberration”. James Bradley measured the aberration of many stars and came to a figure of 20.5 arc seconds for the constant of aberration. See Bradley’s 1727 paper listed below.

By 1910 the value for the constant of aberration was measured to be 20.4(45) arcseconds. See Encyclopaedia Britannica 10th edition linked below. The current measurement is 20.49551 arc seconds. The article on aberration in all Encyclopaedia Britannica editions back to 1771 is included below.

Stellar Aberration was initially published in 1727, Einstaion was born in 1879, 152 years after it was first discovered. See the links to Encyclopaedia Britannica with articles on aberration starting with the first edition in 1771. Aberration was a well-known phenomenon long before Einstein was born.

Doppler Shift

In progress.

William Huggins, 1868

Henry Draper, 1872

Pickering, 1889