A university student attending lectures on general relativity in the morning and others on quantum mechanics in the afternoon might be forgiven for concluding that his professors are fools, or have neglected to communicate with each other for at least a century. In the morning the world is curved space where everything is continuous; in the afternoon it is a flat space where quanta of energy leap.
The paradox is that both theories work remarkably well. Nature is behaving with us like that elderly rabbi to whom two men went in order to settle a dispute. Having listened to the first, the rabbi says: “You are in the right.” The second insists on being heard, the rabbi listens to him and says: “You’re also right.” Having overheard from the next room the rabbi’s wife then calls out, “But they can’t both be in the right!” The rabbi reflects and nods before concluding: “And you’re right too.”
—from Seven Brief Lessons on Physics (translated by Simon Carnell and Erica Segre)