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Introduction:
The velocity of light C in vacuum belongs to a small
group of the fundamental constants; however, it occupies an outstanding
position even within this group. First of all, it is encountered in very
different branches of physics. It will come as no exaggeration if one says
the story of the determination of the velocity of light is a concise history
of physics. And this story has not come to an end yet.
From the ancient Greeks down to the Middle ages, the
speed of light was believed to be infinite. Aristotle believed that light
propagates instantly!. In the eleventh century, an Arabic scientist Alhassan
suggests that light travels at a finite speed. Galileo (1600) tried this
speed but he Eailed saying that light is extraordinarily rapid(l). Roemer
(1676) was the first measuring C using the eclipses of the Jovian satellite
Io. He obtained an inaccurate value of C (215000 km/s) because the diameter
of the earth's orbit was not known exactly.
Starting from 17th century, experiments show the progress of methods and techniques in the determination of the speed C as indicated in the following table (1). table 1
Froome's value was considered to be the most accurate for a long period until 1983 when the modulated laser radiation interferometers were applied for the determination of C with great precision.
According to the US National Bureau of Standards(3): C = 299792.4574 + 0.0011 km/
and according to the British National Physical Laboratory C = 299792.4590 + 0.0008 km/s
A basically new definition of the metre wasaccepted in October 1983 at the 17th General Conference on Measures and Weights(3):
"The metre is the length of the path travelled by light
in vacuum during a time interval of
1/299792458 of a second".
The Fixation of the value of C after the formation of the new definition of the meter does not mean yet the end of the story of this fundamental constant C. There are numerous other questions dealing with the realtion between this multifarious, enigmatic constant C and the theory of Relativity.
Recalling the second postulate of the special theory of relativity declared by Albert Einstein (1905):
"The velocity C of light in vacuum is the same in all inertial frames of reference in all directions and depend neither on the velocity of the source nor on the velocity of the observer".
Pauli(4) (1958) said that the data on binarystars allowed us to consider this postulate of the constancy of the velocity of light to be almost certainly correct.
According to Einstein's general theory of relativity (1917), the law of the constancy of the velocity C of light in vacuum can not claim any unlimited validity because the curvature of rays of light can only take place when the velocity of propagation of light varies with position!. Einstein(4) himself solved this contradiction between special and general relativity declaring in his paper written (1917):
"The results of the special relativity hold only so long as we are able to disregard the influence of gravitational fields on the phenomena".
This validity condition of the second postulate of special relativity is considered in the present work because the constancy of the velocity C needs absolute space (vacuum). To attain vacuum in the Einstein's sense of this word. it is not: sufficient just to eleminate from a volume of space every atom, molecule and particle, it is necessary also to get rid of the gravitational field. Therefore we have screened out the effect of the solar gravitational field on the geocentric orbital motion of the moon, which is considered here, according to the applied Quranic equation; as a standard measure reference for evaluating the greatest cosmic speed described in the Holy Quranic verses.
Lunar Orbital Motion described in
Quran:
Fourteen centuries ago, the QURAN(5), i.e. .the Holy
Book of Islamic Religion, was directed from GOD to all humanity through
Prophet Mohammad, who lived in the Arabian Peninsula.
The ARAB people use the lunar system in their calculation of time. The Quran addressed them in the only language they could understand without upsetting their habits. GOD (in Arabic ALLAH: the ONE and Only GOD, the CREATOR) says in the Quran:
"GOD is the ONE who made the sun a shining glory and the moon a light and for her ordained mansions, so that you might know the number of years and the reckoning" (10:5)
The lunar year is twelve months, the month is defined recently as the time of one revolution of the moon in its orbit around the earth. God hints at such orbit in the Quran:
"GOD is the ONE who created the night, the day, the sun, and the moon. Each one is travelling in an orbit with its own motion" (21:33).
Here an essential scientific fact is clearly stated, namely, the existence of the earth's, sun'so and moon's orbits; besides, a reference is made to the travelling of these celestial bodies in space with their own motion! A new concept had therefore been established in the Quran, hundreds of years before it was discovered by modern science(6-7)
Today the concept of the lunar year is widely spread and, as we know, the moon is our nearest neighbour in space, and a companion to our planet. It is often said that the earth and moon form a twin-planet. As the moon orbits around the earth, the change in the relative positions of the moon, earth and sun cause the moon to show its phases(8-9). The time between consecutive new moons is 29.53 days and is called the synodic month. During this time, however, the earth, and consequently the moon's orbit, have travelled some way around the sun, so the position of the moon against the background of stars is different. 'l;he time for the moon to return to the same position in the sky as viewed from earth is called the sidereal month (27.32 days) which represents the actual real net time of one revolution in the moon's orbit. This orbit is almost circular having an average radius r=384264 km.
Fig. 1 describes the moon's motion during a lunar month. Position A1 shows a new moon. Position B (about 2 weeks later than A1) illustrates the following full moon. Position A2 the moon has orbited the earth once (with respect to an apparently fixed star). Thus one sidereal period (27.32 days) has elapsed since position A1. The next new moon does not occur until position A3 where the moon has once again lined up with the sun. Thus one lunar synodic period (29.53 days) has elapsed since position A1.
Referring to the Quranic verse (10:5), we notice that it discriminates between the apparent synodic period for knowing the number of years and the real sidereal period for reckoning in scientific calculations. These two systems of measuring time are now given in the text books of Astronomy as indicated(l¡) in table 2:
Table (2) Lunar month and terrestrial:day