Einstein.

Someone asked Einstein and said: "You are an unprecedented figure in the world of physics. Why do you need to study tirelessly? Why not rest comfortably?" Einstein did not answer immediately. Instead of asking this question, he found a pen and a piece of paper, drew a big circle and a small circle on the paper, and said to the young man: "Under the current circumstances, in the field of physics, I may be the best one." I know a little more than you. As you know this small circle, what I know is this big circle. However, the entire physical knowledge is boundless for the small circle, and its circumference is small, which is related to the unknown field. With a small contact area, he feels that there is little he doesn't know; and with the circumference of the circle being in contact with the outside world, he feels even more that there are many things he doesn't know, and he will work harder to explore."