Galileo and the Origins of
the Modern World
David Banach
Department of Philosophy
Galileo and the Origins of
the Modern World
David Banach
Discoverer of new worlds
Proponent of New Theories
Saint for Science
Galileo at Arcetri
Galileo and Milton at Arcetri
Galileo and Milton at Arcetri
Galileo at Arcetri
Galileo at Arcetri
Galileo
Discourse on the Two New Sciences (1638)
Galileo and Scientific Method
1602-Pendulum experiments.
 1604- Inclined plane experiments of
natural acceleration.
 1607-Systematic manipulation of shapes
and weights of wax balls to study
flotation.
 Investigation of projectile motion.
Discovery of parabolic character of
projectile motion.

Science and the Modern World


Scientific Method as a model for Reason: The new method
of knowledge introduced by Galileo and the Scientific Revolution
increased the confidence in the power of human reason and its
ability to transform civilization. The hundred or so years
following the Scientific Revolution (the 1700’s, the
Enlightenment) saw an unprecedented revision of the forms of
human government and culture on the basis of the application of
this new method. The Post-Modern world will ask whether
Science can deliver on the promise of objectivity and whether a
society can be ordered on the basis of reason.
The Mechanistic world view: The Scientific revolution
introduced a radically new view of the world as a mechanism
composed of inert parts, whose configuration and mechanical
relations determine all of its properties. The Post-Modern world
will ask whether human values and the human soul can find a
place in this mechanistic world. This is the real conflict between
science and religion.
The Scientific Method



Science does not trust the senses. It
mistrusts and re-interprets them.
Science does not aim at understanding the
particular, but at isolating how nature acts
under ideal conditions
Scientific discovery involves more than merely
looking in the right place. It requires uncovering
the hidden order within appearances.
The Scientific Method


Purifying the Appearances
Separating the Relative from the Absolute
Separating Relative and Absolute:
The Copernican Revolution

The senses tell us that the sun is moving.
Using our minds we can see that the
motion of the sun in the sky is really our
motion, merely relative to us.
Copernicus’s Revolution: The Motion
we see outside us in the Sun
Is not in the sun but in us;
Is not real but merely relative
The Laws of Terrestrial Motion


1. Free fall: Aristotle believed heavy objects fell faster than light objects,
since they had more earth than air or fire or water in them. Galileo saw
that all objects fall at the same rate. The senses supported Aristotle.
Galileo’s experiments aimed at purifying the senses and isolating only
the effects of weight from all the other causes involved such as air
resistance, friction, and buoyancy.
2. Inertia: Aristotle thought that an object in natural motion moved to its
natural place and stopped and that to keep it moving in violent motion
required energy. Galileo formulated the law of inertia: that an object in
motion tends to stay in motion. The senses supported Aristotle. Only
Galileo’s purification of the senses in experiments proved him to be
correct.
Aristotle on Terrestrial Motion:
Natural Place
Purifying the appearances
Simple unified motions often arise from an impure conglomeration
of forces such as friction and air resistance. The scientific method
systematically manipulates properties to isolate the real source of
phenomena.
Only in a vacuum do objects fall at the
same rate
The Law of Inertia


The senses tell us that objects require force to keep them
moving and eventually slow down.
Only under ideal conditions does an object in motion tend to
stay in motion
Three Experiments


1. The Pendulum: Used to demonstrate the law of inertia and
that heavy and light bodies fall at the same rate. Galileo also
discovered the mathematical laws governing the length of the
string, the period of the motion, and the amplitude of the swing.
2. The Inclined Plane and the Rate of Acceleration: Galileo
used the inclined plane to slow the motion of falling objects
enough to accurately measure how their speed increased.
3. Projectile Motion: Galileo also used the inclined plane to
control the speeds and heights of projectiles in order to discover
the mathematical properties of their paths.
1. Pendulum
Pendulum


"...repeat many times the fall through a small height in
such away that I might accumulate all those intervals of
time that elapse between the arrival of the heavy and
light bodies respectively at their common terminus, so
that this sum makes an interval of time which is not only
observable, but easily observable."
"...two balls, one of lead and one of cork, the former more
than a hundred times heavier than the latter, and
suspended them by means of two equal fine threads, each
four or five cubits long. "This free vibration repeated a
hundred times showed clearly that the heavy body
maintained so nearly the period of the light body that
neither in a hundred swings nor even in a thousand will
the former anticipate the latter by as much as a single
moment, so perfectly do they keep step."
Galileo
Pendulum

Momentum is conserved
Pendulum



1. Robust Regular motion remains
independent of impurities in
environment.
2. Demonstrates regular fall of bodies
and law of inertia.
3. Allows mathematical study of
dependence of motion on string length
and mass of pendulum.
2. Inclined Plane
Inclined Plane
"...in such a plane, just as well as in a vertical plane, one may discover how bodies of different weight behave..." Galileo
Inclined Plane
"...in such a plane, just as well as in a vertical plane, one may discover how bodies of different weight behave..." Galileo
Inclined Plane
"...in such a plane, just as well as in a vertical plane, one may discover how bodies of different weight behave..." Galileo
Total distance traveled is proportional to the square of time.
Inclined Plane
Slows down motion to enable the measurement of
mathematical relationships.
Corrects for the effects of air resistance.
Simplifying and purifying the appearances
allows discovery of first mathematical law of motion.
3. Projectile Motion
Projectile Motion

Purifying the appearances:
Separating and Analyzing the Components
of motion.
All Projectile paths are Parabolas
Parabola is a Conic Section
Vertical motion can be separated from
the horizontal motion
Projectile Motion
The apparent single motion is actually
composed of two different motions
Which function independently even
when united
Separating the Relative and the Absolute
Projectile Motion
Purifying the appearances allows the
different components of motion to be
separated and describe mathematically.
 The Scientific method is reductionistic. It
breaks down complex things into their
simple parts.

Primary and Secondary Properties
The Assayer 1623

Separating the relative from the absolute

2°
feeling
1°
real
properties of
matter
All our sense perceptions are relative to
the five senses
Sensible properties are relative

Once we separate the relative from the
absolute within our perceptions, we find
that most of the properties we found to be
indicative of unities that required a single
nature as their source are really not in the
external world at all, but are the effects
that the primary qualities of objects have
on our constitutions.
Sensible properties are relative

1. Primary properties are the properties really
in the object such as the size, shape, number, or
speed of the atoms or particles of matter.
2. Secondary properties are the effects that
the object has on us and exist only in us, not in
the object itself. (E.g. the tickle of the feather.)
Galileo saw that all sensible qualities such as
color, sound, warmth, taste, and smell were
really only in the mind.
The world is made of numbers


Galileo in The Assayer
“Philosophy is written in this grand book, the
Universe, which stands continually open to our gaze.
. . . It is written in the language of mathematics, and
its characters are triangles, circles, and other
geometric figures without which it is humanely
impossible to understand a single word of it.”
May God us keep/ From single vision, and Newton's
sleep! (William Blake)
Galileo and the Modern World
1. Science is a model for how impartial
human reason works. Science is objective.
It forms the basis for our hopes of a
rationally organized society. (Jefferson)
 2. We are no longer at home in the world
revealed by science. Science unweaves
the rainbow. There is no room for the
human spirit in the purified appearances.
(Beethoven)

1. Science as a model for human reason

Science is objective. Purifying the
appearances and separating the relative
from the absolute means that science
eliminates us, our biases, our prejudices,
our point of view, from the appearances.
The Scientist separates the relative from
the absolute
The Scientist separates the relative from
the absolute
Does the Scientist separate themselves
from their humanity?
The Mad Scientist
2. Mechanistic Reductionism and the
Human Soul
Mechanism: The World is a Machine. The
world consists of matter in motion and the
mathematical laws that govern its motion.
 Reductionism: The qualities of complex
objects, such as squirrels, persons, or
countries, can be explained completely by
an examination of the basic forms of the
components that make them up and the
scientific laws that govern them.

Mechanism
Reductionism
May God us keep/ From single vision, and
Newton's sleep! (William Blake)
Do not all charms fly/ At the mere touch of cold philosophy?/
There was an awful rainbow once in heaven:
We know her woof, her texture; she is given/ In the dull
catalogue of common things./ Philosophy will clip an Angel’s
wings,
Conquer all mysteries by rule and line,/ Empty the haunted air,
and gnomed mine –/ Unweave a rainbow…
(John Keats)
Two Questions


Is Science objective? Do Science and Reason
really give us absolute and complete knowledge
of the world? Can all questions be solved
scientifically through the application of the
scientific method? Are humans capable of being
completely objective?
Does Science leave room for the human
spirit? Does Science oversimplify and rob the
world of its beauty and grandeur? Are human
beings more than machines, and are there
limitations to the applicability of the views and
methods of science? Is science a savior of
mankind, or are the pervasive applications of
Galileo’s methods an enemy to human values.