She grows and falls over a lot and maintains her orange coiffure and reads books and is generally precocious. The veganism and the aversion to salt and lipids persist.
Her fifth basketday approaches.
"Happy basketday," says Lynn, presenting Astrid with a plate of fruits arrayed in a cake-like shape, with coconut oil frosting and some brightly colored candles.
"Eee," giggles Astrid, and she sets about eating up her fruit with little dabs of frosting on each piece (not too much; coconut oil is vegan but it's still an oil).
Lynn smiles, and then says, "I neglected to get you balloons, I'm afraid. Do you want balloons?"
"Hmmm. To be bright, cheer up a room, and be different from how other things work due to quirks involving physics and weight."
"Yup! Like airships. Or dirigibles, if you'd like to show up my students with your knowledge of vocabulary."
"Dirigibles," repeats Astrid. "Why do people go in airplanes instead of airships? Airplanes aren't floaty."
"Well, first because airplanes are faster, but also because they're safer and less fragile. In a dirigible, if there's a hole in the balloon and it loses enough helium, it will lose its ability to float."
"Mm, not quite. Would you like me to try and explain the reasoning why it doesn't work that way verbally, or for me to make a quick trip to the store so I can get the materials to explain it visually along with verbally?"
"All right," says Lynn, brightly. "Then finish up your enhanced fruit cake and we can go get some balloons."
"Okay," she says, "first, do you know why balloons float?"
"Exactly right," she agrees. "To be more specific, the helium in the balloon is lighter than regular air. So, when something is light enough in comparison to how much helium it has, it can carry it. Makes sense?"
"Possibly," snorts Lynn. "But you have lots of things inside of you, and there wouldn't be room for helium if they stayed. And you need to keep those things in you, they're what keeps you alive and walking about."
"True, but I don't recommend trying it, there are lots of things in you that do more than just let you walk around." Lynn pokes her nose affectionately.
"So!" says Lynn, and she retrieves a pin to pop the balloon. "When the helium isn't there anymore to make the balloon lighter..." Pop! Whzzz, hsss, flop, goes the now deflated balloon. "It sinks to the ground."
"Well, because the balloon was keeping all of the helium bottled up under pressure inside it. So the minute the helium saw an opening, it rushed out because it - didn't want to be under pressure and trapped anymore."