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"Impossible" Colors: See Hues That Can't Exist

People can be made to see reddish green and yellowish blue—colors forbidden by theories of color perception. These and other hallucinations provide a window into the phenomenon of visual opponency

By Vincent A. Billock and Brian H. Tsou

Fixing the Global Nitrogen Problem

Humanity depends on nitrogen to fertilize croplands, but growing global use is damaging the environment and threatening human health. How can we chart a more sustainable path?

By Alan R. Townsend and Robert W. Howarth

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