"Apart from the question of food, there is the question of energy. It seems clear that, if it were financially worth while, fairly economical methods could be discovered by which more use would be made than at present of energy from the sun. And in theory there is no calculable limit to what can be got out of atomic energy. When people have discovered how to turn hydrogen into helium, sea-water will become their raw material, and it will be a long time before this source of supply is exhausted. Speaking of less specific possibilities, we have to reflect that man has existed for about a million years, and scientific technique for at most two hundred years. Seeing what it has already accomplished, it would be very rash to place any limits upon what it may accomplish in the future. Scientific knowledge is an intoxicating draught, and it may be one which the human race is unable to sustain. It may be that, like the men who built the Tower of Babel in the hope of reaching up to heaven, so the men who pursue the secrets of the atom will be punished for their impiety by providing by accident the means of exterminating the human species, and perhaps all life on this planet. From some points of view such a consummation might not be wholly regrettable, but these points of view can hardly be ours. Perhaps somewhere else, in some distant nebula, some unimportant star has an unimportant planet on which there are rational beings. Perhaps in another million years their instruments will tell them of our fate, and lead them to agree on an agenda for a conference of foreign ministers. If so, man will not have lived in vain."