generate about fifty watts, this means that it would take 150 slaves, working eight-hour shifts each, to peddle you to your current lifestyle. (Americans would need 660 slaves, French 360 and Nigerians 16.) Next time you lament human dependence on fossil fuels, pause to imagine that for every family of four you see in the street, there should be 600 unpaid slaves back home, living in abject poverty: if they had any better lifestyle they would need their own slaves. That is close to a trillion people.
