Isaac Newton, a name synonymous with genius, is a paramount figure in the Scientific Revolution who transformed our understanding of nature and the cosmos. He is the author of gravity, the inventor of calculus, and formulated the laws of motion. From his humble upbringing in the English countryside, Newton’s accomplishments as a scientist and mathematician, encapsulated in the groundbreaking book, “The Mathematical Principles of Natural Philosophy”, brought him renown during his lifetime. Outside of science, Newton served as a Member of Parliament and was Master of the Mint, prosecuting counterfiers with zeal including levying the death penalty. He was also an alchemist, keeping his involvement secret for fear of compromising his reputation, and was an unorthodox Christian who believed in God but rejected the Trinity, a controversial stance given that his position as a professor at Cambridge required accepting holy orders from the Church of England. Upon his death in 1727, an inscription on his tomb called him “an ornament of the human race” while the poet Alexander Pope wrote, “Nature and Nature’s laws lay hid in night. God said let Newton be! And all was light”.
Why doesn’t the Earth fall into the Sun?
Why doesn’t the Earth fall into the Sun given the Sun’s massive gravitational force? The answer lies in the balance between the Earth’s forward momentum and the Sun’s gravity. Consider an analogy with a baseball. When you throw a baseball, it doesn’t fall straight to the ground. Instead, it follows a curved path because of its forward motion before gravity finally pulls it down.
Now imagine throwing the baseball harder and harder. If you throw it with enough speed, it will travel so far that it escapes the Earth’s atmosphere. At this point, the baseball continues to follow a curved path due to Earth’s gravity, but if it’s moving fast enough, it will essentially “fall around” the Earth rather than back to its surface. This is because the Earth’s gravity pulls it toward the ground while its forward motion counteracts this pull, keeping it in a stable orbit.
If the baseball’s speed (known as orbital velocity) is less than the required speed to maintain orbit, it will fall back to Earth. If it exceeds this speed, it might escape Earth’s gravity entirely and head into outer space.
The Earth behaves like this baseball but on a larger and more complex scale. Its forward momentum keeps it in motion around the Sun, while the Sun’s gravity pulls it inward. According to Newton’s First Law of Motion, an object in motion will remain in motion unless acted upon by an external force. Because space is a near-perfect vacuum, the Earth experiences no resistance (and thus no friction) from air molecules as it moves forward. The only significant force acting upon the Earth is the Sun’s gravity, which pulls it inward. This creates a delicate balance: the Earth’s forward velocity ensures it doesn’t fall into the Sun, while the Sun’s gravity prevents it from flying off into space.
This balance is what allows the Earth to continue orbiting the Sun. During the formation of the Solar System, a rotating cloud of gas and dust collapsed under gravity, creating angular momentum that set the Earth and other planets into motion.
It’s remarkable to think about how the Earth’s orbital velocity and the Sun’s gravitational pull are in perfect harmony. If the Sun’s gravity were stronger, the Earth would spiral inward; if it were weaker, the Earth would escape into space. I can thus understand why people of faith might interpret this balance as evidence of God, which Newton himself believed in.