Why Is This Night Different From All Other Nights?

"Netilat Yadayim" is a ritualization of hand washing practiced in traditional Judaism. In the days of the Holy Temple, we Jews used to perform the netilat yadayim ritual before eating vegetables, fruits, grains, or their derivatives, unless the food had never come into contact with moisture. Since the destruction of the Temple around 70 AD, we only do netilat yadayim before eating bread. Except at the Passover seder, that is. On Passover, we eat a vegetable before the meal (this vegetable, called "karpas", must be dipped in salt water), and we perform the netilat yadayim ritual in preperation for eating the vegetable.

Why is this night different from all other nights?

Why do we do netilat yadayim in preparation for a vegetable? For that matter, why do we eat this vegetable before the meal, and why do we dip it in salt water?

My own personal answer will appear in a later post. Meanwhile, Dear Reader, please comment with your answer.