After a mixed record as a high-school level student, Newton proved himself dreadful at farming and overseeing his family's affairs, though he may have failed intentionally so that he wouldn't have to carry that responsibility [source: The Newton Project]. His failure allowed him to continue his education. He eventually went on to study at Cambridge, paying his way through school by acting as a servant to wealthy students and starting a small loan business.

While at Cambridge, Newton paid scant attention to the required curriculum, instead following his own intellectual whims. Because of his lack of success there, the Cambridge faculty thought that he showed little promise. But Isaac Barrow, a noted scholar and mathematician, discovered Newton's talents and mentored him.

From 1665 to 1667, Newton left Cambridge after an outbreak of the plague closed the university. Popular conception has it that he made many of his most important discoveries during one year in this period -- sometimes called his annus mirabilis, or "year of miracles." It's more likely that at least some of these major discoveries came later, over an extended period of time and with important subsequent breakthroughs and revisions of his original ideas [source: MathPages]. But the great man himself probably propagated this myth of the year of miracles. When Newton became involved in various conflicts with other scientists over claims of discoveries, it was to his advantage to claim that he had made these breakthroughs years before.

As a fellow at Cambridge's Trinity College, Newton was known as obsessively devoted to his work, rarely allowing himself any time for relaxation. His lack of sleep wore him down, but he wasn't a complete shut-in. He actively corresponded with other scientists and counted a select few among his friends.

Newton is highly regarded not only for his discoveries but also for the quality and rigor of his experiments. He was incredibly precise, took careful notes and paid close attention to evidence. He concocted theories from the information at hand and then created reasonable experiments with which to test them. He was also far ahead of his time in how he considered data, for example, by calculating averages when he had several different measurements for the same phenomenon. Believe it or not, this wasn't a common practice then. His scientific method became the standard from which future scientists would draw.

­Now that we've laid some of the groundwork for who Newton was as a person and as a scholar, let's consider some of his major accomplishments.

Newton didn't attempt to publish some of his early discoveries, such as his work on the shape of orbits. Modesty and controversy made him hesitant to share his theories. His claim that all of natural philosophy -- the forebear to the natural sciences -- could be explained through mathematics was both groundbreaking and highly controversial when introduced in 1670 [source: The Newton Project]. That same idea formed the basis of his first masterwork, the Principia.

­Eventually Newton's genius came to be widely known. His three laws of motion -- inertia, acceleration, and action and reaction -- remain a cornerstone of modern physics. His law of universal gravitation laid forth the theory that all particles in the universe exerted some gravitational force. In Newton's view, gravitational force was everywhere, from an apple falling from a tree to the moon being kept in orbit by its mutual attraction with Earth. While imperfect -- his law was later altered significantly by Einstein's theory of relativity -- Newton's conception of universal gravitation dominated physics for more than two centuries.

In his student years, Newton performed experiments in optics examining the nature of light. He found that normal, or "white," light is actually made up of a spectrum of colors. He used prisms to break apart white light into a rainbow of colors and recombine the disparate colors into white light. Despite his breakthroughs in optics, Newton didn't publish his conclusions until 1704, in "Opticks," which was considered his second great scientific treatise [source: The Newton Project].

Isaac Barrow, Newton's mentor, was instrumental in presenting one of Newton's major inventions to the scientific community. The refracting telescope commonly used during the period often couldn't produce clearly focused images. Newton replaced the mirrors of the refracting telescope with lenses. His new telescope, the reflecting telescope, was one-twelfth the size of conventional refracting telescopes and had more powerful magnification powers. Barrow's presentation of it to the Royal Academy earned Newton membership.

­Newton also created calculus as a response to the insufficiencies in mathematics of the time. Originally called the fluxions or the "method of series and fluxions," calculus provided methods for solving complex problems about orbits, curves and other issues that classical geometry couldn't solve [source: The Newton Project]. Calculus is particularly suited to these challenges because it produces information about things that are continually changing -- like the speed of a falling object. In calculus, Newton laid the basic framework for understanding these problems and for making the calculations described by his laws of motion and gravitation.

­Newton wasn't always good at accepting criticism, and intense clashes with the British physicist Robert Hooke and others spurred him to retreat from the scientific community for much of the 1670s. These traumas, combined with the death of his mother, caused Newton to isolate himself during this period. He published little and devoted himself to religious and alchemical studies.

Alchemy was a popular subject back then. In some ways, it can be considered an early form of chemistry. While today there is much stigma against alchemy, many of Newton's contemporaries were involved in it. Practitioners of alchemy, Newton included, thought that common metals could be turned into gold. Other alchemists held similar mystical ideas, such as believing that immortality-granting elixirs could be created. But alchemy was a wide-ranging discipline, encompassing more legitimate practices, like creating paints.

To Newton, alchemy represented a riddle, steeped in ancient Greek myths and the work of past alchemists, whom he studied closely. Deciphering this riddle could allow him to control nature. He even believed that he was potentially part of a line of great men chosen to receive hidden, ancient wisdom [source: NOVA]. Newton so devoted himself to alchemy and its mystical practices that he created a special name for himself: Jehovah Sanctus Unus. It translates, from the Latin, to Jehovah, the Holy One [source: NOVA].

Like many others before him, Newton attempted to produce the mythical philosophers' stone [source: NOVA]. The stone was thought to be a substance that could turn metal into gold, cure diseases and perform other powerful effects.

Newton didn't publish his work on alchemy, in part because he was rather secretive about it. He thought that he made progress on some of alchemy's great challenges, like the philosophers' stone, so he wanted to keep his work to himself. Alchemy was also illegal until just before Newton's lifetime, and by the end of his life, with his reputation well-established and the Enlightenment in full swing, there was great stigma against the practice, particularly for someone as celebrated as Newton.

Some of Newton's texts on alchemy may have been destroyed.­ Others are so full of riddles, code names and vague details as to be difficult to decipher. But many of his texts are available for study and provide an interesting perspective of a complicated, mystically inclined, highly ambitious genius, who wanted to understand the universe in any way he could.

­Early in his career, Newton was often reluctant to publish his work, despite encouragement from some of the preeminent minds of his day. His own modesty (which didn't last f­orever), combined with some of the criticism he received about his early discoveries, caused him to keep some ideas to himself. But eventually, with the support of Barrow and others, Newton began to write and publish widely.

No publication of Newton's is more important than "Principia Mathematica." In this document, the full name of which is "Philosophiae Naturalis Principia Mathematica," Newton defined his three laws of motion. He described how elliptical orbits work and how bodies in motion exert force upon on another. The work also contained his findings about fluids and mechanics.

Begun during his intensely productive years at Cambridge in the mid-1660s, the Principia, as it's often called, was published in 1687. It represents a transformational work, one of the world's most important scientific treatises. It quickly vaulted him to the elite ranks of scientific theorists.

The Principia provided a physical and mathematical basis for how basic elements of the universe work and how celestial bodies move and interact with each other. No longer were vague stories or conjectures enough to explain the world. From then on, a scientist could not say that the sun revolved around the Earth or make some other declaration without using the mathematical processes (namely, calculus) and rigorous scientific method laid out by Newton.

The work did involve some contributions from Newton's contemporaries and forebears. For example, German scientist Johannes Kepler found that planets had elliptical orbits. He also made other observations about the radii of orbits and how long revolutions took. But he couldn't come up with a mathematical justification of why and how, which is what Newton accomplished, conceiving a universal theory of gravitation that could apply to all celestial bodies, from the smallest moon to the largest star.

­Despite its revolutionary content, scientists found the Principia very difficult to understand. Many of the era's scholars couldn't decipher it, including, for a time, Leibniz and Huygens­, two of Newton's great contemporaries. This gap in understanding existed in part because there were few people in the world studying mathematics at such a high level. And the work seemed very theoretical, difficult to apply in the real world.

­While studying in university, Newton found himself drawn to religion and began a lifelong study of religious history and theology. At that time, he wrote a list of all the sins he had committed, which seemed minor by most standards (such as breaking the Sabbath by baking pies). As a scientist, his religiosity informed his research and motivated his belief that rational forces dominated the world. Newton thought that the universe must abide by calculable rules and laws because a rational, logical force -- God -- had created them.

Newton also had some eccentric theological opinions that came to be shared by the devoted following that developed around him after the publication of the Principia. He thought, for example, that his scientific discoveries were actually recovered "ancient wisdom" from pre-Christian civilizations. In his view, these pre-Christian civilizations understood the laws of the universe, but they encoded these ideas in myths, monuments and religious sites.

Newton also believed that mainstream Roman Catholicism, Anglicanism and Calvinism were heretical and corrupt. He thought that the Holy Trinity, one of the main doctrines of orthodox Christianity, wasn't in line with the beginnings of early Christianity. He was influenced in this regard by an obscure theological notion called Arianism.

Arianism states that Jesus, while created by God, was not divine. Believers in Arianism, Newton included, feel that the Holy Trinity actually represents a heresy that the Council of Nicaea, in the 4th century, mistakenly made part of Christian dogma. Critics of Arianism have said that it encourages polytheism, since it casts Jesus as less than divine but still deserving of worship [source: Britannica].

The Council of Nicaea attempted to do away with Arianism by proclaiming Jesus' divinity and the sanctity of the Holy Trinity. It didn't survive much beyond the 7th century, except in altered form and in the occasional adherent, such as Newton.

Despite his thorough research into theological matters, Newton did not publicize much of his religious inquiries. For him, it was largely a personal effort to get back to the true foundations of his religion [source: Snobelen]. His beliefs were also highly controversial at the time, only a few decades after heretics in England were burned at the stake. So Newton mostly kept his beliefs to himself, for fear of becoming an outcast or losing his university position.

­After he died, Newton's relatives concealed most of his writings on religion and alchemy because they could have severely damaged his reputation. Most of these papers only became available to scholars when they were released on microfilm in 1991.

­Although he was one of history's great geniuses, Newton certainly capitalized on the work of his predecessors. For example, Galileo had already figured out aspects of two of the basic laws of motion [source: Einstein]. He knew that an object would continue moving unless some outside force acted upon it. He also discovered that a free-falling object's velocity increases over time. But Newton added to these ideas by figuring out that the key to all of these phenomena is mass. Each mass, he determined, influences each other, based on the theory of universal gravitation. Consequently, even the smallest atoms exert gravitational force on one another.

Newton, however, may have wanted his contemporaries to believe that his genius was his alone. Take the well-known apple story. This popular tale finds Newton lying in a garden, considering how the moon orbits the Earth. Suddenly, he sees an apple fall to the ground and has an epiphany -- the same force that caused the apple to fall also kept the moon in orbit around the Earth. But many think that the story is a bit too convenient [source: NOVA]. After all, Newton didn't complete his theory of universal gravitation until 1686. Yet, he later helped to propagate the story as true [source: The Newton Project].

Other stories have been inflated by historians or rumors. Much has been made of Newton predicting the second coming of Jesus in the year 2060, but the date was only Newton's idle speculation [source: Snobelen].

Similarly, it's often said that Newton was born the same year Galileo died, somehow implying a cosmic connection between the two. This claim is based on a mistake produced by using the old Julian calendar for Galileo's death and the modern Gregorian calendar for Newton's birth. In fact, when using the same calendar, Newton's birth and Galileo's death fall almost a year apart.

Newton's deliberate striving toward greatness took its toll on him. Newton once stared at the sun with one eye until he could hardly see anything besides reds and blues. His eyes later recovered.

­It wasn't just his eyes that were sensitive. Newton suffered two nervous breakdowns, and he subsequently gave up scientific research after the second one in 1693. Three years later, he accepted a position with the Mint. Most officers of the Mint had traditionally done little, instead enjoying the title and income that come with such positions, but Newton threw himself into the role and went after counterfeiters.

In his own time, Newton's ideas changed the world, and the publication of the Principia brought him into contact with most of the great minds of his age. He corresponded, debated and shared ideas with many of them.

Edmond Halley, he whom the famous comet is named after, was a vocal backer of Newton in the scientific community, but Newton also had many rivals. He had intense arguments with Robert Hooke, who accused Newton of stealing from his work. Even so, he corresponded and exchanged ideas with Hooke.

Gottfried Leibniz, a German philosopher, mathematician and scholar of many fields, was also one of the pioneers of calculus. There was a tremendous rivalry between the two men as to who invented calculus. The two had corresponded about their work, and Newton claimed that Liebniz stole some of his calculation methods, even though Leibniz had conceived of some of the basic ideas of calculus on his own.

As old men, the two great thinkers frequently and publicly fought about their contributions to calculus. In scientific journals and letters, they rallied their supporters to their respective causes.

Newton was aggressive in trying to discredit his rival. By then well respected and quite powerful, Newton used his position as president of the Royal Society to anonymously draft a report claiming that he was the inventor of calculus. The rivalry continued until Leibniz's death.

Astronomer John Flamsteed's observations of comets contributed to some of Newton's breakthroughs about gravitation. But Flamsteed felt that Newton didn't adequately acknowledge his contributions to the Principia. He may have been justified: Newton removed all references to Flamsteed in the second edition of the Principia.

Albert Einstein revered Newton. He especially admired Newton's ability to create empirical methods that could verify the speculations of Descartes, Kepler and other thinkers, going back to the ancient Greeks. He also wrote about how Newton's innovations provided the basis for numerous subsequent discoveries: James Clerk Maxwell and Michael Faraday's work on optics and electrodynamics, electromagnetic fields, conservation of energy and thermodynamics.

It wasn't until the early 20th century and the development of quantum and theoretical physics that scientists began moving out of Newton's long shadow. Einstein's theory of general relativity dramatically departed from Newton's ideas, but they remain important and applicable to numerous aspects of science and the physical world. His legacy as the founder of the modern scientific method, as an inventor, innovator and brilliant scholar, remains assured.

­Keep reading for more information about Isaac Newton, scientific breakthroughs and other related topics.