"Are you Sirius?"

Critics argue that scientific observations, some apparently made before the birth of Christ, do not support the notion that our solar system is in orbit with Sirius. Someone even suggested that Sirius has not moved the required distance of about 30°, as measured relative to the most distant stars over the last 2000 years.

Who is supposed to have measured this? Or does one refer to apparent positions of stars marked on maps that until 400 years ago were still based on a geo-centric worldview with a flat earth and no celestial equator? In order to make any valid statements on this subject one would require photographic images that specifically targeted the region around Sirius. Even if such images were available and one could piece together the astrometric information from a number of different sources, the information would only date back to the last 100 years or so. Before any assumptions can be made on the exact position of Sirius in the past, one must agree upon which 360-degree orbit period of the Earth is the fundamental sidereal reference time for such measurements; i.e. 365.25636, 365.2425, 365.25 or 365.24219878 mean solar days?

The conclusions regarding Sirius are based on repeatable observations of its transit times (mean transit period), as well as on the indisputable mathematical relationship that exists between Earth's periods of rotation and Earth's actual 360-degree orbit period around the sun - the tropical- or sidereal year for 1900.0.

Scientists agree that the speed of rotation is subject to periodic and non-periodic variations, some miniscule others of significant amplitude. Undoubtedly, such variations - irrelevant of their cause - directly affect Earth's period of rotation; i.e. the solar day and the sidereal day. However, the difference between these days remains constant regardless of any variations, including nutation and the assumed slowing trend in Earth's speed of rotation. All of these variations are contained in the term 'mean', except for precession! In our reckoning of time, precession affects therefore only the mean sidereal day and not the mean solar day.

Given the fact that the Earth does not precess relative to the position of the sun, as it does relative to inertial space, and that the tropical- or sidereal year for 1900.0 is Earth's true 360° orbit period, one can conclude that our sun is in orbit with a point in space to which the axis of the Earth remains aligned. Most astronomers think it is the imaginary "vernal point" (some are foolish enough to believe that the rotation time difference relative to the precessing vernal point is about 3.34 s per day). Other researchers* have suggested that perhaps a still undetected companion of our sun is the cause for the phenomenon of precession. However, as observations have shown the system of Sirius remains the most likely candidate.