A recurring theme in society is that of food shortage. Thomas Malthus is now mainly known for his theory that population growth would outstrip food supply. [0]

As it turned out, human beings are good at making lots and lots of food. [1] But the question is still interesting; what’s the absolute maximum capacity of the Earth?

1. Energy

How might we calculate this number?

One possibility is this: energy consumption. If a human being needs 2000 kCal/day to survive at a normal level, that energy must come from somewhere; but where?

The sources of energy on the Earth itself can be used up; coal gets burned, oil is spent, uranium is fissed. Almost all new incoming energy must originate from the Sun, the Sun produces 1.740×10¹⁷ watts of power. [2]

Google thus identifies the maximum number of people we could ever support with only the earth: 1.79655832 × 10¹⁵ people. [3] This doesn’t take into account crowding or energy efficiency, but we can know with absolute certainty that without a change in the human species or space colonization, it is impossible to get past this number, which is incidentally about a million times the current population of Earth.