Why lists of worldwide bird species disagree

How many species of birds are there in the world? It depends on whose count you go by. The number could be as low as 10,000 or as high as 18,000. It's tough to standardize lists of species because the concept of a "species" ...

When foams collapse (and when they don't)

Researchers from Tokyo Metropolitan University have revealed how liquid foams collapse by observing individual collapse events with high-speed video microscopy. They found that cracks in films led to a receding liquid front ...

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