"Weaver could say something about the sun, though. In principle, the sun pours onto Earth enough energy--vastly more than enough--to provide all humanity with the necessary 128,000 calories a day. "If solar energy could be utilized with full efficiency, the United States alone could sustain, energy-wise, a population over 40 times the present total population of the planet." The global population then being about 2 billion, Weaver was suggesting that in terms of energy the theoretical carrying capacity of the United States was about 80 billion people."