1+ day, 6+ hour ago   (372+ words) Here's something I've wondered about before: are there good mnemonics for chemical element symbols? Some element symbols are based on Latin or German names and seem arbitrary to English speakers, such as K (kalium) for potassium or Fe (ferrum) for…...

1+ week, 5+ day ago   (749+ words) One of my daughters gave me a Klein bottle for Christmas. But is a Klein bottle real? My Christmas present is a real physical object, so it's real in that sense. Is a Klein bottle real as a mathematical object?...