Vie development of a society and the growth ofenergy consumption have always been closely inter-related. Currently the world's production of primaryenergy sources in 9 billion tons of equivalent juelannually. When recalculated to coal, the transporta-tion of this quantity of fuel requires 150 million rail-road cars. Such a train could circle the globe 60 timesalong the equator or cover the distance to the moonand back three times.
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