The exagram (Eg) is a unit of mass in the metric system. It is equal to one quintillion (10^18) grams. The exagram is an extremely large unit of mass and is primarily used in scientific contexts when dealing with colossal quantities of matter, such as in astrophysics or geology.
To give you an idea of the scale involved, one exagram is equivalent to 1,000,000,000,000,000,000 grams or 1,000,000,000 metric tons. This unit is rarely encountered in everyday life but is valuable when measuring the mass of massive celestial bodies, geological formations, or other incredibly large objects in the universe.
The kilogram (kg) is the base unit of mass in the International System of Units (SI). It is defined as the mass of the International Prototype of the Kilogram (IPK), a platinum-iridium cylinder kept at the International Bureau of Weights and Measures (BIPM) in France.
Until May 20, 2019, the kilogram was defined by the physical prototype, but as part of the redefinition of the SI units, the kilogram was redefined in terms of fundamental constants. Since that date, the kilogram is defined by fixing the numerical value of the Planck constant (h) to be exactly 6.62607015 x 10^-34 joule-seconds.
This redefinition ensures that the value of the kilogram is now based on a constant of nature rather than relying on a physical object that could potentially change over time. It allows for a more precise and stable definition of the kilogram and other SI units.