“This all goes back to the idea of ‘carrying capacity’,” Sutton adds. “You can only put so many goldfish in a tank before they’re killed by their own wastes, and you can only raise so many livestock on a certain size of land.” Humans are in a unique position, he says, because Earth’s carrying capacity for us depends intimately on how we choose to live and use technology: Billions of bicycle-riding, solar-panel-building vegetarians will produce a different planet than billions of Hummer-driving, coal-burning carnivores. Thus, the influence of technology on Earth’s carrying capacity is difficult to predict and discern. “Some cultures will use technology to increase their environmental impact; some will use it to decrease it,” Sutton says. “But nighttime satellite imagery may offer a good proxy for its use now.”