Which of Albert Einstein's accomplishments further undermined Newtonian physics?

Question

Quizplus · Accepted Answer

Einstein's theory of special relativity further undermined Newtonian physics by showing that time and space are not fixed and absolute, but rather relative to the observer's motion and gravity. This challenged Newton's laws of motion and the concept of absolute time and space. Einstein's discovery of quanta (A) was a major contribution to quantum mechanics, but did not directly undermine Newtonian physics. Similarly, his discovery of the radioactive properties of radium (C) and successful test to split the atom (D) were significant contributions to nuclear physics, but did not contradict or undermine Newton's laws of motion.

Which of Albert Einstein's Accomplishments Further Undermined Newtonian Physics