In chemistry, all the elements of a "sort through" in Mendeleev's table. In biology, all life is distributed by Carl Linnaeus in the genera, species, family, etc. In grammar, all words are neatly divided into parts of speech and the sentence. And that Physics? Only elementary particles in the twentieth century was laid in, and this has led to new discoveries. A routine physical quantities, which innumerable and enjoyed by millions of people in everyday life – for them the system is not. All known sr – is not a system, it is simply an international agreement on what units of measurements considered essential (kilogram, meter, second, and four more units), and all the rest is on them. Guide creation of the si one: it was convenient and relatively cheap to measure. And when ordering must be guided by the laws of nature, even if it is inconvenient and expensive.
Now physics reminiscent of an army victoriously rushing forward and are gaining more and more new frontiers. But in the baggage of the army and its statutes carefully preserved all that was reached two and even three centuries ago, with the same names and with the same symbols. Although much has long been obsolete, needs to be revised in line with new developments. And then it becomes clear that the mass measured in kilograms, is the principal value only at the earth's velocity and terrestrial equipment. And at speeds close to the speed of light, the same mass estimate is in units of energy. Hence, the energy in nature is the main variable.