Download Humanities 3 V. The Scientific Revolution

Humanities 3
V. The Scientific Revolution
Lecture 20
The Trial Of Galileo
Outline
• The Astronomical Revolution
• Galileo and the Church
• Letter to the Grand Duchess Christina
Copernican System
• 1543 Publication of Copernicus’ On the
Revolutions of the Celestial Orbs
• Heliocentric theory: Earth revolves around
the sun and rotates on its axis
• Copernicus’ picture modified by Johannes
Kepler (1571-1630) based on observational
data of Tycho Brahe (1546-1601)
Galileo and the Telescope (1609)
Significant Telescopic
Observations
• Face of the Moon: indicates that the Moon was
affected by geological variations (mountains,
craters) just like the Earth
• Sunspots: similarly show that the Sun is not a
perfect, unchanging celestial body
• Moons of Jupiter: indicate that the Earth was not
the only center of motion
• Phases of Venus: indicate that Venus must be
located between the Sun and the Earth (as the
Copernican model predicted)
Galileo, Moons of Jupiter
Galileo, Letter on Sunspots (1613)
Do Galileo’s Observations
Disprove Aristotle’s Theory?
• Not necessarily: an opponent could discount the
reliability of observations made with the telescope
• In response, Galileo had to (a) show the telescope
offered reliable results up to the limits of the
observable (e.g. distant towers); (b) argue there was no
reason to think the telescope is less reliable in the case
of celestial phenomena than terrestrial phenomena
• What’s at stake: is the distinction between the
terrestrial and celestial “realms” a fundamental
assumption of cosmology, or a hypothesis subject to
observational test and refutation?
Galileo’s Rise to Fame
• 1609: Observations of moon, moons of Jupiter,
sunspots, stars (10x as many as with naked eye)
• 1610 Publication of The Starry Messenger
(Siderius Nuncius). Appointed “chief philosopher
and mathematician” to the Grand Duke of
Tuscany, Cosimo de’ Medici
• 1613 Publication of Letter on Sunspots
• 1615 Denounced to the Inquisition for support of
the Copernican theory, called to Rome to defend
his views
What’s at Issue?
• Galileo points out that Copernicus himself was a
priest and his book received papal approval.
• Some in the Church were prepared to accept
Copernicus’ theory on instrumental grounds, as they
had Ptolemy’s theory.
• But Galileo’s observations were evidence of the
truth of Copernicanism. The Church could not
accept this.
• In 1546 the Council of Trent had decreed that the
Church alone had the authority to interpret the ‘true
sense and meaning” of scripture.
Condemnation of 1616
(1) The Sun is the center of the world, and is
completely immobile by local motion
Censure: All agree that this proposition is foolish
and absurd in philosophy and is formally heretical,
because it explicitly contradicts sentences found in
many places in Sacred Scripture according to the
proper meaning of the words and according to the
common interpretation and understanding of the
Holy Fathers and of learned theologians.
Condemnation of 1616
(2) The Earth is not the center of the
world and is not immobile, but moves as
a whole and also with a diurnal motion
Censure: All agree that this proposition
receives the same censure in philosophy;
and in respect to theological truth, it is at
least erroneous in faith.
Passages from Scripture
• “The sun rises, and sets, and returns to its place,
from which, reborn, it revolves through the
meridian, and is curved toward the North”
(Ecclesiastes 1:5)
• “You fixed the earth on its foundations” (Psalm
104:4)
• “God made the orb immobile” (1 Chronicles 16:30)
• “Heaven is up, the earth is down” (Proverbs 30:3)
• “He suspended the earth above nothingness, that is,
above the center” (Job 26:7)
Consequences for Galileo
• Galileo is forbidden from discussing or defending
the Copernican theory
• Later, under a new pope, Galileo is assured that he
can continue to examine the theory as a
mathematical hypothesis
• In 1615, prior to the condemnation, Galileo had
composed a detailed response to the Church’s
position, his Letter to the Grand Duchess
Christina, which was not published until 1636 but
circulated widely in manuscript copies
Letter to the
Grand Duchess Christina
• Galileo’s main claim: the Bible cannot be used to
disprove scientific claims
• Each is an authority in its own sphere: the Bible
with respect to salvation; science with respect to
the order of nature (doctrine of double truth)
• Both express God’s will: the phenomena of nature
execute God’s commands, and our sense
experience and reason allow us to understand the
immutable order of nature
“I think that in disputes about natural
phenomena one must begin not with the
authority of scriptural passages, but with sense
experience and necessary demonstrations. For
the Holy Scripture and nature derive equally
from [God]…. After becoming certain of some
physical conclusions, we should use these as
very appropriate aids to the correct
interpretation of such Scriptures and to the
investigation of the truths they must contain,
for they are most true and agree with
demonstrated truths.” (pp. 116-7)
“[T]he Holy Spirit did not want to teach us whether
heaven moves or stands still…. But, if the Holy
Spirit deliberately avoided teaching us such
propositions, inasmuch as they are of no relevance
to His intention (that is, to our salvation), how can
one now say that to hold this rather than that
proposition on this topic is so important that one is a
principle of faith and the other erroneous….. Here I
would say what I heard from an ecclesiastical
person in a very eminent position (Cardinal
Baronio), namely, that the intention of the Holy
Spirit is to teach us how one goes to heaven and not
how heaven goes.” (p. 119)
What to Do When Scripture
Appears to Contradict Science?
• The Bible is not a science textbook: its purpose is not
to teach about nature. Natural events are described in
a way that common people will understand.
• Thus, biblical descriptions of nature cannot be taken
literally.
• Science becomes the authority on how to interpret the
Bible: when it is and is not to be read literally.
• Yet this conflicts with the Church’s claim to be the
sole authority on the meaning of scripture.