It is true that Sir Isaac Newton developed his laws of motion and universal gravitation long before the concepts of space-time and general relativity were introduced. Newtonian physics, also known as classical mechanics, was developed in the late 17th century and served as the prevailing theory of motion and gravity for over two centuries.
Newton's equations, such as his laws of motion and the law of universal gravitation, are incredibly accurate within the context of the systems they were designed to describe. They provide accurate predictions for a wide range of everyday phenomena, including the motion of objects on Earth, the orbits of planets, and the behavior of projectiles. These equations are still widely used today, especially in situations where the speeds involved are much smaller than the speed of light and the gravitational fields are not extremely strong.
The reason Newton's equations are so successful in many cases is that they provide an excellent approximation of reality within their applicable range of validity. Newtonian mechanics accurately describes the behavior of objects under normal conditions and at low speeds. It is a simplified model that neglects certain factors, such as relativistic effects and the curvature of space-time.
However, as our understanding of the universe deepened, it became apparent that Newton's equations are not entirely complete. In the early 20th century, Albert Einstein's theory of general relativity provided a more comprehensive and accurate description of gravitation. General relativity incorporates the concept of space-time curvature, where gravity is seen as the curvature of the fabric of space-time caused by mass and energy.
In situations involving extremely high speeds, strong gravitational fields, or when dealing with phenomena at the cosmic scale, the predictions of general relativity differ significantly from those of Newtonian physics. For example, near the event horizon of a black hole or during the early stages of the universe, the effects of general relativity become prominent, and Newton's equations break down.
So, while Newton's equations are remarkably accurate in many practical scenarios, they are not the complete picture. Our understanding of the universe has advanced with new theories and observations, leading to the development of more comprehensive models like general relativity that better describe the behavior of objects and the nature of space-time in extreme conditions.