Wisdom of a 5-year old

A portion of conversation between V and a neighbor boy that was over tonight: They are making a fort with a blanket draped over various chairs and an ottoman. To keep the blanket from drooping in the middle, V puts weighty items on top of some chairs to hold the blanket in place. Neighbor boy (J) wonders why she leaves one chair empty. V tries to explain to him that the blanket was not sliding off that chair so therefore there was no need. He tests her statement himself and finds she is correct. J: "Oh, there's something holding it down, down down." V: "Yeah...gravity."