Welcome TMJ,
My DD6 is also very intense about food (and lots of other things). We too have had gravity questions, and all sorts of other "strange" dinner conversations with her since she could talk at age 1. My favorite dinner conversation however, was when Pluto got "down graded" to a planetoid, DD was so upset she couldn't eat - "it's not fair, you can't tell him he's not a planet anymore, it will hurt his feelings." How do you explain that to others?
I'd recommend you read James Delisle's book
Parenting Gifted Kids: Tips for raising happy and successful children. (book link) it was a great help to DH and I when we first realized we didn't have the typical little girl.
