The typical rubber sheet bowling ball analogy to "explain" gravity visually in layman's terms always seems to be two space dimensions. Why don't we use one dimension of space and the other of time? Both are curved by mass and everybody takes Eucledean/Cartesian type flat graphs of, say, x and t as a matter of course. Is it too much to imagine such a traditional layout deformed/curved? Or is there a fundamental flaw in an x,t curved representation that is worse than the typical representation?