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This article raises the question of how oxygen levels have changed over the past 2 centuries, when carbon dioxide has been increasing. John MillsDecatur, Ala. There is a problem in this interesting article. The graph of oxygen content versus time doesn’t agree with the text. Specific example: “About 255 million years ago … the oxygen […]
- Earth
Changes in the Air
Changes in the atmospheric concentration of oxygen through geologic time, some gradual and some drastic, have strongly shaped evolution among many types of creatures.
- Math
Surface Story
Mathematicians have zeroed in on a new type of minimal surface based on a double helix.
