Why is the length of the sidereal year for 1900.0 so important?

The orbital period of our Earth around the sun is a unique measure of time that has challenged the greatest minds of human civilizations to create a calendar system, which will keep in tune with the solstices and equinoxes for thousands of years to come. Obviously, rock solid evidence exists that ancient calendar-makers accomplished a high degree of perfection. Such perfection has not even been attained again until the end of the dark ages, when in 1582 A.D. the Church of medieval Europe was forced to reform the calendar of its Roman ancestors for a religious rather than scientific reason (the slipping of the Holy Easter Days throughout the years). After the Church "recanted" its flat-Earth and geo-centric worldview, science in Europe was able to emerge. As nations competed with each other to explore and investigate nature's secrets and mankind's past, uncovering the riches of ancient Egypt for instance became a fashionable occupation. While some explorers took home material treasures, others eventually discovered scientific treasures. Time became more essential.

Already by 1820, a commission of French scientists proposed to define the unit second as the 86400th part of the mean solar day. Since the period of the actual solar day varies due to the elliptical orbit of the Earth around the sun, the term mean is based on a hypothetical sun travelling at an even rate throughout an orbit of 360 degrees.

At the turn of the last century, the ingenious western astronomer Simon Newcomb determined the tropical year of 31,556,925.974 seconds, already recognizing the fact that mean solar time can be more precisely defined in terms of Earth's very stable orbital motion. Since Newcomb applied the precession of the longitude in his calculations, he needed the stars as a frame of reference.

Nowadays, the uniform time scale of atomic clocks allows us to measure sidereal time with utmost precision. By synchronizing atomic time to the fundamental reference frame of inertial space (the most distant quasars and galaxies), modern astronomers would even prefer to describe the rotation of the Earth independently from its orbital motion.

Historically, the term sidereal always refers to motions relative to the sphere of the fixed stars or inertial space. Already since antiquity the sidereal day is regarded as an invariable measure for time. In the late 1940's, accurate quartz clocks became available and it was possible to determine the exact period of the mean sidereal day and consequently the precise length of the sidereal year. By 1952, the sidereal year for 1900.0 was determined to be exactly 31,556,925.97474 seconds.

Because of the notion that lunisolar precession must exist, the sidereal year or Earth's complete 360-degree orbit period around the sun was considered to be about twenty minutes longer than the tropical year. It appears when scientists discovered that the actual length of the sidereal year is essentially equal to the time interval upon which our calendar is based, they realized that the original theory of precession could no longer be valid.

The "good old" sidereal day, which can be easily measured with respect to the fixed stars, was re-defined as "measured" with respect to the moving vernal equinox. But the equinox is an imaginary point in the sky and therefore impossible to measure and verify without using complex formulas and pre-calculated astronomical tables based on sidereal time. This only proves that simple things can be made complicated.

In 1955, in a seemingly clever semantics game, the International Astronomical Union (IAU) substituted the time interval of the tropical year for 1900.0 for the sidereal year for 1900.0. The IAU called this a "minor correction", but it was actually a deceitful manipulation. It might have gone undetected, if it was not for the fateful mistake in 1952 to document the fact - though only in French - that the "l' année sidérale pour 1900.0" had been originally proposed as the fundamental unit of time to define the second.

Substantiated data on the length of the sidereal year for 1900.0 is therefore a crucial piece of evidence to demonstrate that the IAU had manipulated scientific data and has been deliberately misleading the public on an important scientific fact regarding the phenomenon of Earth's precession.

The question is why do National Science Institutes intentionally withhold information on such important scientific data? One could be led to believe that there is a tacit agreement among the authorities not to discuss this issue - a "conspiracy of silence".

Uwe Homann