Answer:
Mercury's orbit—up close to the Sun—has a blip in it that Newton's laws can't explain.
Step-by-step explanation:
"Newton's rules explain a lot, from falling apples to most planets’ orbits. But his laws don't work perfectly. In high-gravity zones, Newton's ideas don't jibe with what scientists observe. For example, Mercury's orbit—up close to the Sun—has a blip in it that Newton's laws can't explain." Newton's laws may usually explain everything, but this one just had something weird, so Einstein wanted to work to find why he had that feeling, and he eventually did. This was the answer he got when he figured it out.