Up and Down the Ladder of Abstraction. In real life, you would never use a ladder that only let you go up.
Likewise, when creating abstractions, stepping down is as important as stepping up. Here, we take the abstraction from the previous section, and overlay a concrete representation on top of it. That is, we draw the trajectory that represents all time, but we also draw the car at some particular time. Quantum Levitation. Why Can’t We Drink Sea Water? Imagine you’re stranded on a desert coastline… Namibia’s, perhaps.
The searing heat drains your body of fluids and your mind slows to a snail’s pace. Forget food, forget sunburn, forget your coordinates; your biggest danger here is dehydration. If you don’t find water soon, you’ll perish, simple as that.