engel’s note

"Millions of years may pass, hundreds of thousands of generations may be born and die; but inexorably the time approaches when the declining heat of the sun will no longer be able to melt the ice advancing from the poles; when humanity, crowding closer and closer together, will no longer find even at the equator the warmth necessary for life; when gradually even the last trace of organic life will vanish; and the earth, an extinct, frozen globe like the moon, will circle in deep darkness and in an ever-narrowing orbit around the equally extinct sun, and at last fall into it." Frederic Engels - Dialectics of Nature , New York, 1942, s. 20