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His Legacy
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Newton's Dark Secrets homepage
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Sir Isaac Newton's accomplishments border on the uncanny, as does his
image in the world of science. As the historian Mordechai Feingold has written,
"With time, the historical Newton receded into the background, overshadowed by
the very legacy he helped create. Newton thus metamorphosed into science
personified." So what is that legacy? What were those accomplishments? Here,
familiarize yourself with Newton's greatest contributions.—Peter
Tyson
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Invented the reflecting telescope
The standard telescope of Newton's time, the refracting telescope, was not
ideal. Its glass lenses focused the different colors inherent in light at
different distances. This resulted, at the edges of any bright objects seen
through the telescope, in colored fringes that rendered those objects slightly
out of focus. Newton solved the "chromatic aberration" problem by using mirrors
instead of lenses. His original reflecting telescope, which he built himself in
1668, was just six inches long. This modest device not only eliminated the
colored fringes but magnified whatever it focused on by 40 times, which, as
Newton noted at the time, "is more than any 6 foote Tube can do." After
presenting his scope to the Royal Society, the then-unknown Newton was proposed
for membership; he later served as its president for 24 years, until his death
in 1727.
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A replica of the six-inch
reflecting telescope that Newton presented to the Royal Society in 1671
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Proposed new theory of light and color
Not long after he donated his telescope to the Royal Society, Newton delivered
a paper to that august body about his novel theory of light and colors. Using
prisms and his usual very exacting experimental technique, Newton had
discovered that sunlight is comprised of all the colors of the rainbow, which
could not only be separated but recombined into white light. "[T]he most
surprising and wonderful composition was that of Whiteness," he wrote. "I have
often with Admiration beheld that all the Colours of the Prisme being made to
converge, and thereby to be again mixed ... reproduced light, intirely
[sic] and perfectly white." Though he made his experiments on light as
early as 1666, when he was only 24 years old, he didn't publish his classic
Opticks, which summarized his findings on light and color, until
1704.
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"Newton Investigating Light,"
from The Illustrated London News, June 4, 1870
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Discovered calculus
When Newton began to muse on the problem of the motion of the planets and what
kept them in their orbits around the sun, he realized that the mathematics of
the day weren't sufficient to the task. Properties such as direction and speed,
by their very nature, were in a continuous state of flux, constantly changing
with time and exhibiting varying rates of change. So he invented a new branch
of mathematics, which he called the fluxions (later known as calculus).
Calculus allowed him to draw tangents to curves, determine the lengths of
curves, and solve other problems that classical geometry could not help him
solve. Interestingly, Newton's masterwork, the Principia, doesn't
include the calculus in the form that he'd invented years before, simply because he hadn't yet
published anything about it. But he did combine related methods with a very high level of classical
geometry, making no attempt to simplify it for his readers. The reason was, he
said, "to avoid being baited by little Smatterers in Mathematicks."
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The first page of Newton's "How
to Draw Tangents to Mechanicall Lines" (November 8, 1665), from his "Waste
Book" manuscript
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Developed three laws of motion
Newton's Principia is difficult to comprehend on two levels, even for
experts: in its original form, it is written in Latin, and it uses very challenging mathematics. Yet
one thing that comes out very simply and very clearly to all is his three laws
of motion:
Law of inertia: Every object persists in its state of rest or uniform
motion in a straight line unless it is compelled to change that state by forces
impressed upon it.
Law of acceleration: Force is equal to the change in momentum (mV) per
change in time. For a constant mass, force equals mass times acceleration, F
= ma.
Law of action and reaction: For every action, there is an equal and
opposite reaction.
To these Newton added, in the Principia, two general principles of space
and time, many careful explanations, and much else besides. All of this went
into his classic explanation of how the universe works, otherwise known as
Newtonian mechanics. (Mechanics developed into a branch of physical science that deals with
energy and forces and their effect on bodies.).
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Newton's first and second laws of
motion, in Latin, as they appear in the original 1687 edition of the
Principia
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Devised law of universal gravitation
Newton said shortly before his death that it was seeing an apple fall in his
mother's garden that set him thinking "that the power of gravity ... was not
limited to a certain distance from the earth but that this power must extend
much farther than was usually thought. Why not as high as the moon ... and if
so that must influence her motion and perhaps retain her in her orbit." This
brainstorm (which some scholars suspect Newton may have invented late in life)
ultimately led to his law of universal gravitation. The law says that all
particles of matter in the universe attract every other particle, that
gravitational attraction is a property of all matter. The law explained many
things, from the orbits of the planets around the sun to the influence of the
moon and sun on the tides. And it held sway as the accepted description of
terrestrial and celestial mechanics for almost 200 years—until Einstein
came along and rocked the boat with relativity.
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As an old man Newton
claimed the idea of universal gravitation came to him while watching an apple
fall in the garden of his mother's house at Woolsthorpe (above, as it appears today).
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Advanced early modern chemistry
Newton spent untold hours of his life practicing alchemy. Like other
alchemists, he sought to turn base metals into gold, find a universal cure for
disease, and secure the elixir of life, which promised perpetual youth and
eternal life. In his garden shed outside his rooms at Trinity College,
Cambridge, in the midst of phials and furnaces, mortars and pestles, Newton
pored over ancient texts and performed endless experiments. Yet while he never
found what he and other alchemists sought, and while he only published one
short paper that grew out of his alchemical experiments (a two-page speculation
on acids), his work was not for naught. As the historian Jed Buchwald has said,
"As historians have shown in the last several decades, there was a much more
profound element to the practice of alchemy which really makes it deserving of
being called early modern chemistry." Through his meticulous efforts, Newton
greatly furthered the practice and techniques of chemical science.
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The work of
alchemists, depicted here in a painting by the 19th-century artist William
Fettes Douglas, helped lay the groundwork for modern chemistry.
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Became father of modern science
Newton essentially invented many elements of the modern scientific method. His paper on the properties
of light that he presented to the Royal Society in the early 1670s shows all
the hallmarks of the method he would use throughout his long life: conducting
experiments and taking very careful notes on the results; making measurements;
conducting further experiments that grew out of the initial ones; formulating a
theory, then creating yet further experiments to test it; and finally,
painstakingly describing the entire process so that other scientists could
replicate every step of the way. This method governs how all science is
conducted today. Newton once famously said, "If I have seen further it is by
standing on the shoulders of Giants." Many scientists today would argue that
the greatest Giant of all in the world of science was Isaac Newton himself.
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"Newton," painted by William
Blake in 1795
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