STELLA: NASA's DIY educational gadget for measuring plant health

On her morning walk to school, a high schooler notices a patch of greenery in her neighbor's yard. But the plants don't look quite as green and healthy as she thinks they should. To see if she's right, she puts down her backpack ...

Q&A: Urban doom loop—what it is and how cities can stop it

Recent images of downtown San Francisco—emptied of office workers now dialing in remote and filled with wandering homeless people—has struck fear for the future of urban areas. A Columbia University professor coined the ...

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