"Airplanes, elephants, and plankton – three beautiful 'machines.' Weights + Measures compares proverbial apples and oranges, in order to probe a system of relative values. Take any two of the three creatures in the system: in water, airplanes sink while elephants swim. Elephants and airplanes both release methane, and both have been instruments of transport and war. Airplanes produce carbon dioxide (CO2), while plankton consumes it. As the largest land mammal, elephants are at the top of the terrestrial food chain, and microscopic plankton is at the bottom; yet without phytoplankton, the oceans would starve."