The Population Reference Bureau has projected that in 2011, the planet Earth will be home to more than seven billion living humans. At current growth rates, we'll top 9 billion in 2050. By that year, the population of Africa is expected to double, and that of Asia to grow by 1.3 billion.
The world's population is growing unevenly too, the projection states. In a continuing trend, economically developing countries are growing faster, while the populations of developed nations are aging, and their workforces diminishing relative to their elderly populations.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.