seeing is believing: Watching fights make male crayfish docile. Researchers in an experiment put two males into a fighting arena and a bystander was allowed to watch. After seeing the fight, the observer was placed in another arena with a new opponent. Crayfish that previously observed an encounter rarely initiated fights. They also took longer to end fights, which escalated slowly, and lost more often.

mapping dark matter: Astronomers have mapped the largest structure of dark matter. They have detected a web spanning 270 million light-years, or more than 2,000 times the size of the Milky Way. The results are a major leap forward since the presence of a cosmic dark matter web that extends over such large distances has never been observed before. Around a fifth of the universe is believed to consist of dark matter.

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