दिल्ली में चीनी नागरिकों के लिए टैक्सी नहीं, एसोसिएशन ने किया बैन
दिल्ली के टूर एंड ट्रैवल एसोसिएशन ने चीनी नागरिकों को अपनी सेवाएं देने से इनकार कर दिया है. टैक्सी...
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Readers ask about positronium, wild bees and more
Dance of the doomed particles Scientists are puzzled by an unexpectedly large gap in the energy levels of an exotic “atom” called positronium, which consists of an electron and a positron, Emily Conover reported in “ Positronium result baffles physicists ” ( SN: 9/12/20, p. 14 ). Reader Lee Skinner asked why the electron and its antimatter counterpart, the positron, don’t just annihilate each other when they collide. Eventually, the electron and positron do annihilate one another, Conover says. As a result, positronium doesn’t stick around forever. “The two particles do a little orbital dance with each other for a period of time before they meet up and annihilate,” she says. “That’s actually part of how the researchers made the measurement, though I didn’t have the space to include those details in the story.” The team measured how long it took electrons and positrons to annihilate, which depends on the atoms’ energy level. “Timing that annihilation revealed whether the positr
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