The older you get, the more you realize that facts aren't nearly as fixed as you thought they were. For decades Pluto was a planet. However, if you were part of the generation that ingested that tidbit during grade school and recited it today, everyone would mock your ignorance. Or what about the continents? Some people say there are seven continents, whereas others say the planet only has five. Suffice it to say some of the fundamental facts you learned in your younger years can shift at a moment's notice.
One of the oldest pieces of info I can recall teachers and School House Rock insisting I learn was the difference between consonants and vowels. Not to get too Grandpa Simpson, but back in my day, "r" used to be classified as a consonant. According to the brilliant YouTube channel Storied and their hit show Otherwords, I found out that "r" is more versatile than previously imagined.
