Is the Newtonandtheapple story true? Does anybody really understand the
Principia? Was Newton a nice guy? In this interview, Dr. Jed Buchwald, an
historian of physics and professor of history at the California Institute of
Technology, answers these and other provocative questions about the man many
consider to be the greatest scientist who ever lived.
The real Newton
NOVA: Everybody has an image of Newton, the guy who got hit on the head with an
apple and dreamed up the universal law of gravitation. Is there any truth to
this?
Buchwald: I doubt that an apple is what stimulated him to get the idea. The
story behind it, of course, is that he was lying in the garden there, and
instead of thinking about girls, he was thinking about the moon and how it goes
around the Earth and so on. And an apple falls, and the story goes that
bang, he suddenly has the idea that the same thing that's making the
apple fall is what's holding the moon in its orbit. Then he does a calculation
to see whether the mathematical behavior, the acceleration, as it's known, of
the moon as it orbits around the Earth would fit with the fall of the apple if
you assume that it falls at a certain rate. In other words, he's already got
the whole ball game in his hands. I don't believe it.
NOVA: So how do you see Newton? I mean, who was Isaac Newton?
Buchwald: Well, these were, of course, the very early years in which science
itself was forming as a discipline. The idea of doing experiments, the idea of
taking measurements and what you did with them afterwards, what a laboratory
was and what you should do in one, and how you should put it all together with
mathematics were really in many ways new. Not that there weren't elements long
before that. You can go back to antiquity and find Ptolemy, the great
astronomer, handling things mathematically and doing observations. But there
were a lot of new things about Newton.
For instance, it's pretty clear that he had the most sophisticated way of
handling data, at least that I know about, in the 17th and early 18th
centuries. He treated data very much the way scientists much later treated
data. To give you an example, if you're an astronomer and you observe the
position of a star and you observe the position of a star again, you're going
to get different numbers every time because people aren't perfect. Well, what
do you do with all those different numbers? Nowadays, really since the end of
the 18th century, you take what's called an average. You put them all together
with this mathematical procedure.
But almost nobody did that until the middle of the 18th century except Newton.
He was extremely sophisticated in the handling of data. This is a major part of
the novelty and the difficulty of his science, because he puts that together
with a deep and profound understanding of how to build a mathematical
structure. Almost nobody at the time was able to penetrate deeply into what he
had done there, in part because he never really talked about it. These are the
kinds of things that he did but never really discussed.
So the way I see it, he is the exemplar of a profoundly new way [of doing
science]—mathematically based, grounded in the generation of laboratory
data, and the handling of complex data in a very concerted way. You can
recognize a lot of the present in Newton, and you can't in most other people in
the 17th and early 18th centuries. So to me he represents in some ways the
birth of the very ethos of quantitative science.
Inventing calculus
NOVA: You started to talk about calculus. For the uninitiated, what exactly is
calculus and what does it allow one to do? And what was Newton trying to solve
that brought him to invent the calculus?
Buchwald: Newton was interested in solving mathematical problems that had
gripped people. This was a guy who adored computation of every kind. Among the
things that you can see if you open his manuscripts, for instance, is there are
places where you'll find he's calculated logarithms out to 50 places and things
like that. Not because he needed it, but because he liked doing it. I mean, it
was a pleasure to him to do that sort of thing. He was an unusual sort,
obsessive, but gripped by the power and the beauty of sheer computation. I
think that was a driving force behind what he did.
“Once he was onto something, he worked at it and worked at it and
worked at it until he could solve it or until he had to give up.”
And when he hit a problem he couldn't solve, he bounced it off other related
problems and saw relationships between them that other people had never seen
before. So the mathematical structure really emerged in that sense within the
boundaries of what were already intrinsically interesting mathematical
problems. Not because he needed something to solve the orbits of the
planets.
NOVA: But calculus has very practical uses today. In what way does it?
Buchwald: Well, calculus is about finding the behavior of continuously changing
things. Like, for example, when a rock falls, its speed is continuously
changing, and you may want to find out the distance that it's traveled or how
fast it's going at a given point. The calculus is adapted to continuous
change—not jumps, but continuous change—and that raises a lot of
philosophical questions that people addressed as well. But it has practical
application in the sense of being useful for the solution of problems of that
sort.
Now, preeminently, problems of that sort are the problems of mechanics, and
among the problems of mechanics are, of course, the motion of the planets. When
Newton produced the Principia, he deployed a form of the calculus in
order to figure out the relationships between the orbits of the planets, the
forces that keep them in their orbits, and indeed what kind of paths they could
use. In the absence of the calculus, these problems are, if not unsolvable,
close to being unsolvable. So he needed that structure in order to produce the
famous Newtonian mechanics itself.
His motivations
NOVA: When he did his alchemy, was he doing it to gain knowledge for
knowledge's sake? Or was there some driving quest to understand truth or
whatever? Did he have an aim in this, do you think?
Buchwald: Well, he was a complicated man, and you can't reduce things to single
motivations. Lots of things clearly motivated him. For instance, once he was
onto something, he was gripped by it and he worked at it and worked at it and
worked at it until he could solve it or until he had to give up. In other
words, it was the quest to reach a solution, to break the problem, that gripped
him. It's the same kind of thing that motivates scientists today in very much
the same way, only he was maybe more extreme and successful than many.
NOVA: But when you say solve this thing, what is it?
Buchwald: Well, there were many different things. In the case of the
mathematics, he wanted to solve the problems that were out there that other
people had treated and that he saw relationships between. When he found that
the shape of the sun in the prism wasn't what it should be, [he asked] why is
that so? He was driven to figure this out, to probe it, to push, to monkey
around, whether he was playing around with prisms in a laboratory or whether he
was sitting there with his quill pen and his paper and trying to calculate.
This was really the same kind of activity. It was a quest to solve whatever
problem it was that he came upon in his voluminous and voracious reading,
things that were floating in the air. Same in the alchemical laboratory. He was
seeking for methods of transmutation, of course, and he thought he could make
progress where other people hadn't. In the end he didn't, but he spent an awful
lot of time trying.
NOVA: Were there connections between his scientific accomplishments, his work
in early chemistry, and his work in religion? Or were these all separate
endeavors?
Buchwald: No, no, I think they were connected but in complicated ways. I think
that, first of all, they were connected at a certain level in the way he
thought about how to handle information—how to deal with it, how to work
with it. His techniques of working on these things were all the same. There was
also an underlying belief that all of these things must be connected, because
the world was, after all, created by God. God is not irrational. There had to
be a logic underlying all of these things. That was a profound belief that he
had, a belief derived from a deepseated religious conviction. Now, there were
plenty of others around, particularly by the 19th century, who didn't need that
religious conviction to believe that a rational order underpins the universe.
But Newton did.
Setting the standard
NOVA: Why is the publication of the Principia held to be such a crucial
event?
Buchwald: Well, the Principia is objectively a work of profound
mathematical insight. And I would argue that anybody in the late 17th century
who was capable of reasoning at that level (and there weren't many but there
were several) would have recognized the brilliance of what he had done, even
though they might quarrel with the basis of the mechanics underlying it, as
both [the Dutch mathematician Christiaan] Huygens and [the German mathematician
and philosopher Gottfried] Leibniz, his two greatest contemporaries, did. Here
he had put together the mechanics of the world with the most profound and
advanced mathematics available.
“Except in the rarified world of general relativity, the Newtonian
system still reigns.”
It set a standard and a structure that anybody choosing to work in that area
subsequently had to meet. It was an almost impossible standard to meet, but it
was nevertheless something that did set a structural standard. After, say, 1710
or 1715, you would no longer get people who would be taken profoundly
seriously—that is, who would invent stories, so to speak, about the
world—without attempting to bind it in some way to a mathematical
structure that led to results that could be compared with observation. This was
something that the Principia provided and that ever after was a
desideratum, something that is necessary for scientists to work towards.
NOVA: Did many people even understand the Principia?
Buchwald: Very few people could understand what this thing was about, but a lot
of people could see that there was something important in there. Even some
really smart people couldn't figure out the novelty of what was being done in
there. In particular Huygens and even Leibniz, when they first ran into this
thing, didn't really understand what he was doing. Now, they would argue with
him later on about other things in it, and eventually they did understand it,
but very few people could.
You know, there weren't tens of thousands of students taking calculus at
universities in those days. It was very hard to understand, and moreover, this
was very arcane stuff. I mean, after all, what was the point here, right? What
were you going to do with this stuff? It was purely abstract. Eventually it had
some practical results, and Newton had some in mind eventually. But initially
it was very abstract.
Newton's legacy
NOVA: What is Newton's legacy today? Why are we still interested in him 300
years later?
Buchwald: Well, I think it's reasonable to say that Newton both represents and,
in fact, was the founding father in a certain sense of the form of
experimental, quantitative science that has ever since become the way in which
we do things. He's not the only one; there are many others as well. But I think
the dimensions of his accomplishment are really in almost every respect
unparalleled in all of these various aspects.
Now, you could find people who did magnificent things in other areas, and even
areas that Newton worked in, like Huygens or Galileo. But I think that in terms
of the influence that he had, the impact, the way in which it eventually
changed the practice of science, both for good and some might say for bad as
well, are a part of Newton's legacy. Certainly in England at the Royal Society
and elsewhere as well, science did change very radically under Newton's
tutelage.
Of course, since really the 1920s and 1930s, we have had an image of a certain
basic divide in science—well, really in physics—between what we
call the classical world and the quantum world. Interestingly enough, the
classical world, if you ask physicists today, usually includes relativity, and
the quantum, or nonclassical world, is about the strange behavior of
particles.
But it's also generally thought that there is a major divide between mechanics
as done before Einstein and mechanics after relativity, after, say, 1905 or
thereabouts. That divide is often expressed as being represented by the
difference between the Newtonian world and the Einsteinian world. And there is
some truth to that, that is, that Einstein's innovations do make many of the
claims that you might have made in using the mechanics before Einstein
incorrect.
“Was he a nice guy? No, he probably was not.”
On the other hand, it is also the case, as historians of relativity will tell
you—especially general relativity, the theory of gravity—that one
of the most important factors in what lead to the particular form of general
relativity that Einstein produced was the necessity of figuring out how to get
Newton's world out of it.
NOVA: That's not the way we usually think about it, I guess.
Buchwald: No. No, but what I mean is it was an essential requirement that by
choosing certain specific values for all of the various parameters that went
into the general relativistic, complicated equation, you had to be able to get
the Newtonian system out. And in that sense, the Newtonian system, except in
the rarified world of general relativity, which doesn't have that much of an
effect on most things, the Newtonian system still reigns. (Although it is the
case that we've become so accurate today with GPS systems that they must take
account of general relativity—nonNewtonian effects—so our world
today is in a fair number of effects quite realistically nonNewtonian.)
Challenging childhood
NOVA: Final question: Newton was not always a nice guy, I guess you could say.
Can you tell me about that? What was he like?
Buchwald: Well, that's a very interesting question. Of course, it's trying for
a historian to try and get behind that. There were all sorts of stories that
would emerge later on about Newton. Was he a nice guy? No, he probably was not.
He led a very selfconfined, solitary existence. He didn't seem to care that
much, at least in his youth, about other people. He certainly didn't, at least
until the 1690s, have any significant relationships with anybody else.
A book written by a now deceased historian, Frank Manuel, tried to probe the
psychology of Newton. [See A Portrait of Isaac Newton, Da Capo Press,
1990.] Manuel was convinced, maybe not incorrectly, that Newton's whole persona
was formed when his father died before he was born and he was then brought up
for three years by his mother. And his mother then married the Reverend
Barnabus Smith. He was an older man, I believe in his 60s at the time, and
Smith did not want the little boy around the house. So Newton had to stay back
at Woolsthorpe Manor, taken care of by his grandmother, I believe, while his
mother would see him relatively infrequently. Eventually, Barnabus Smith died
and she came back.
But Manuel would argue that this had a very profound effect on the young
Newton. It must have had some effect on him because, after all, he was a
threeyearold boy when his mother vanished from his life all of a sudden. That
cannot have had a good effect on him. And he was not an easy young guy, so the
story goes, later on in life. But this is speculative. These psychological
things are very difficult to know. But I think there's enough evidence to show
that this was not, generally speaking, a man who at least until the 1690s you
wanted to spend an evening drinking with. I think there's no doubt about that
whatsoever—not that he didn't drink, because he did. But he could not
have been very pleasant company on the whole.

Jed Buchwald (right) says that, for him, Isaac Newton
"represents in some ways the birth of the very ethos of quantitative
science."
 
Buchwald has a straightforward response to the popular notion that Newton
came up with the theory of universal gravitation all at once after seeing an
apple fall in his mother's garden: "I don't believe it."
 
Newton's manuscripts are riddled with
mathematical calculations, which he appeared to do, at least some of the time,
for the pure pleasure of it.
 
To help determine the paths of the
planets and the forces upon them, Newton needed a more sophisticated
mathematics than was then available. So he invented calculus.
 
In "The Alchemist in Search of the
Philosophers' Stone" of 1771, the painter Joseph Wright of Derby captures the
intense passion that many alchemists, including Newton, had for their work.
 
Newton's death mask, crafted from a
cast of his face made at his death
 
Newton's marble tomb and monument in
Westminster Abbey
 
