en "base units" of the SI measuring system are: metre (length), kilogram (mass), second (time), ampere (electric current), kelvin (thermodynamic temperature), mole (amount of substance), and candela (luminous INTENSITY)In actuality, the fundamental quantities are (1) the second, defined as exactly 9,192,631,770 times the period of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. We can't accurately define the second by the rotation of the earth because it is not completely constant. For example, a large earthquake changes the length of the day, and the axis of the earth's rotation precesses every 23,000 years, etc.(2) The speed of light has an exact value of 299,792,458 meters per second. It is exact because by international agreement (3) a meter is defined to be the length of the path travelled by light in vacuum during a time INTERVAL of 1/299792458 second, and the second is extremely precisely defined as above.The standard for the kilogram is a platinum-iridium cylinder manufactured in 1889 and kept under carefully controlled conditions; however, its mass fluctuates by about 50 micrograms, and cannot be perfectly accurately defined. Thus the definition of the kilogram is a secondary measure.The standard of the gravitational constant G is notoriously uncertain, as physical constants and standards go, and since its first measurement by Cavendish in 1798 has only slightly improved in accuracy. However, the more useful number is the GM product for the Earth, GM⊕ = ( 398,600.4415 ± 0.0008 ) km^3/sec^2 ; and for the Sun, GM⊙ = ( 1.327124400 × 10^11 ) km^3/sec^2, which is known far more accurately.An important goal is to find absolute and unchanging standards and definitions for all the physical constants and units. There are 19 fundamental independent physical constants, and 5 "natural units" not based on any human construct: the Planck length, Planck mass, Planck time, Planck CHARGE, and Planck temperature.I hope this will help youIf not then COMMENT me