Worldviews, by Richard Dewitt
Chapter 18:  Problems facing the Aristotelian Worldview

Accepting the heliocentric model of the universe was to conclude that an enormous amount of common knowledge was actually false.  Phenomena that were well-explained on a geocentric Aristotelian worldview now became completely mysterious.  These included:

•	Why do objects fall rather than go zinging off the face of the earth?
•	What keeps the earth moving about the sun?
•	Why do objects thrown upward come back down in your hand?
•	Why is the incredibly fast motion of the earth completely undetectable? 
•	Considering the absence of stellar parallax, how big is the universe?  Is it infinite? 
•	What happens to the celestial sphere and the perfection of the heavens?
•	What even constitutes an explanation in such a strange place?

Chapter 19:  Philosophical and Conceptual Connections in the Development of the New Science

The size of the universe

The stellar parallax argument for the stationary earth was very strong simply because for parallax to be unobservable, even with the naked eye, the universe would have to be unimaginably huge.  Accepting the heliocentric universe meant embracing this hugeness, only more so, because the telescope sharpened our observational abilities considerably, and still no parallax was observed.  

Your book contains a nice discussion of the size of the universe, and it is a good consciousness raising exercise to go through.  Most people today understand that the universe is pretty big and that there are quite a few more stars out there than they can see, and when asked to guess how many more will usually express it in terms of millions or even billions. Most college educated people also know what a galaxy is and that we live in one called the Milky Way.  However, only a very small percentage of people living today know that according to current science there are about 100 billion stars in a galaxy, and probably about 100 billion galaxies.   

Within galaxies the distance between stars is completely ridiculous.  Your author asks you to imagine a scale model of the universe in which the earth is represented as being the size of a basketball.  Our sun would be 80 miles away, and the next closest star would be 50,000 miles away.  Another way to try to come to grips with this is to contemplate the fact that if two galaxies, filled with 100 billion stars a piece “collide” they would almost certainly pass right through each other without a single one of their 200 billion or so stars coming into contact.  

Infinity

Aristotle had a conception of infinity, but he did not believe it made sense to speak of an actual infinite, i.e., a thing, like the universe itself, that is actually infinite in size.  This is intuition is not foreign to us.  Even if you think that it makes sense to speak of space as infinite, you probably do not think it makes much sense to speak of the universe as containing an infinite amount of matter.  Even if the container is infinite, the amount of stuff inside, it seems, must be finite.

But scientists were now faced with compelling evidence that the universe is unimaginably bigger than previously believed, and that humans take up an incredibly insignificant part of it.  This tended to challenge the comforting wisdom that the universe is made for humans, but it also meant that the creator of such a universe would have to been truly awesome.

Scientific revolutions of this magnitude often require something more that scientific argumentation to be completed.  People need to be able to see how it is possible for life to remain interesting and meaningful under the new way of looking at things.  For example, today the main reason that many ordinary people still balk at the theory of evolution by natural selection is that it seems to imply that human existence is a complete accident.  Intelligent design theorists, etc. still make what sound to ordinary people like compelling scientific arguments against it, but they are very much like people who clung to the Tychonic view after Newton.  If it weren’t for the problem of meaning, no one would really be taking their arguments seriously.

The heliocentric universe changed our understanding of the size of the universe so drastically, that it invited a reinterpretation of its meaning, and this was supplied by the suggestion that the universe is actually infinite in size. If you think about this, it is really going off the deep end.  Why not just conclude that it is huge, but not infinite?  One possible answer is that it gives us a new perspective on our creator.  God is no longer just a spectacularly powerful being, but an infinitely powerful one.  (It’s worth noting, that this in itself is a kind of de-humanizing influence.  An infinitely powerful entity could not possess human characteristics, like beliefs, emotions, etc. which seem to arise from our finitude.)

Atomism

Before Aristotle a pre-Socratic philosopher named Democritus had articulated the theory that the ultimate constituents of reality are atoms and that absolutely everything in the universe is the result of different ways in which the atoms are configured.  Atoms were understood as populating the void, which is essentially just empty space.  This view is no less problematic than the Aristotelian four-elements view, and in fact was entirely metaphysical, since atoms could not be experienced in any way, and did absolutely no work in explaining specific phenomena.  However, it did supply an alternative to the teleological/ essentialist framework, one that seemed more compatible with the heliocentric view.

From an atomistic point of view, movement is just what atoms do.  To take your author’s example:  Consider a single atom moving along through an infinite space.  What would you expect it to do?  What reason would it ever have to stop?  What does it even mean for a single atom to be moving?  These are the sorts of questions that gave rise to the scientific revolution.

Overview of the Newtonian Worldview

In addition to the Copernican revolution, certain mathematical developments were key, specifically calculus, which was independently developed by Isaac Newton and Gottfried Leibniz.  The calculus is essentially the mathematics of change, and nothing much of the new physics could have been accomplished without it.

Newton’s colossal work Principia Mathematica Philosophiae Naturalis is where a great deal of the revolution took place, and today we summarize its significance in Newton’s three laws of motion and the law of gravity.

Newtons Three Laws

1.  The law of inertia.
•	Objects in motion remain in motion in a straight line and objects at rest remain at rest until acted upon by an outside force.

2.  F = ma
•	A change in the motion of an object (acceleration) is proportional to the force applied and occurs in the direction of the force.

3.  Reciprocal action
•	For every action, there is an equal and opposite reaction.

Universal Gravitation

As your author points out, the concept of gravity begins not as a universal principle, but rather as a particular force that attracts objects to earth.  Understood in this way, it’s a magical, or at least very unique property of the earth itself, so it bears some of the earmarks of the Aristotelian worldview.

The key move in the Principia occurs when gravitation is universalized.  It is used not only to explain bodies falling toward the earth, but also the behavior of the moon, as well as the moons of Jupiter, and then of the planets themselves as falling bodies.  The mathematical equation that represents the universal law of gravitation is

F = Gm1m2
				r2

At this point gravity is still an incredibly mysterious force.  Its mysteriousness is captured by the phrase “action-at-a-distance”.  Even today, most people feel that we have some intuitive understanding of causation insofar as it involves physical contact.  However, gravity defeats this idea entirely.

Your author tries to give you a sense of this by imagining that someone were to ask you to move the pencil on your desk without touching it, or disturbing it’s environment (by blowing, tilting the desk, etc.) in any way.  It’s likely that you would regard this as a request to perform some kind of magic trick, but gravitational attraction is that magic trick.

Again, most people think of gravity as some kind of downward attraction, since this is the ordinary perspective one has on falling bodies.  But gravity has nothing to do with up and down, falling or rising.   It is only about the mutual attraction of bodies.  The force pulling the apple to the earth is also pulling the earth to the apple.  The earth moves only minutely, however, because it is by far the larger of the two masses and the greater the mass, the larger the force required to overcome its inertia.

The machine metaphor

Newtonian science had no use for the Aristotelian teleological framework.  The animated notion of motion, based on an analogy with human desire, was replaced by a mechanistic notion of motion, based on an analogy with a machine.  (Of course, if you think about this, it doesn’t make that much sense as an account of the shift, since Aristotle would presumably have thought of a machine in animated terms.)

Mechanistic explanation also had no real place for God.  On the Aristotelian framework, the perennial motion of the planets was understood as born of an essential desire to emulate the perfection of the Gods.  But there was no longer any need for this view.  Long after Newton, in the early 1800’s, a great French mathematicians and astronomer named Laplace wrote a very sophisticated book on celestial mechanics which made no reference whatsoever to God.  When Napoleon asked him about the deletion, he is said to have replied:  “I have no need of that hypothesis.”

Of course, this is not to say that people stopped believing in God.  Some people did, but the concept of God started morphing.  Rather than the sort of being that would constantly intervene in human affairs, many philosophers started thinking of God as the designer of the great machine we call the universe.  (This, it’s easy to see, is not really the sort of God one would expect to answer prayers.)

Laplace characterized the Newtonian worldview by imagining a demon that had absolutely perfect  knowledge of (1) the starting conditions of the universe, and (2) all the laws of the universe.  Given these two extraordinary bits of knowledge, the Laplacean Demon could predict absolutely anything that would ever occur in the universe.  This is what we call a deterministic worldview.

Your author also notes that the Newtonian worldview had a very powerful egalitarian effect on society and politics. On the Aristotelian picture, it was very natural to think of people having essentially different stations in life.  Slaves, were born to be slaves; kings were born to be kings, soldiers were born to be soldiers, etc. (This view obviously still has a great deal of literary appeal.) But Newton’s laws don’t really give a rat’s ass who you are, because they don’t care about anything at all.   Apples, kings, and slaves are all made of the same basic stuff, and consequently all fall at the same rate.