An appeal by IUA and
UNESCO: “… the citizens of
the world rediscover their
place in the Universe through
the day- and night-time sky
observation, and thereby
engage a personal sense of
wonder and discovery… .”
Talk by:
Surajit Sen
Physics Department
G C College
Silchar
`Papal Doctrine’ in medieval
age
 2. Galileo: Biographical Timeline
 3. Power of equation
 1.
 i) Evolution of Mechanics
 ii) Law of Falling Bodies
 iii) Laws of Kinematics
 iv) How Galileo’s was an inch away from
Newton’s laws of motion.
 4.
Other major discoveries
 5. Power of Telescope
i) Galilean Telescope
ii) Momentous astronomical
discoveries
 6.
Telescope versus Church
 7. End of Papal Doctrine
 8. Why Galileo is regarded as the
`Father of Modern Science’?
 The
Vatican considered `Ptolemaic
and Aristotelian Thought’ as a
`Papal Doctrine’ and the civic
society accepted it without any
experimental demonstration.
“Heavier bodies fall faster than the lighter
bodies”, i.e., “Objects falling under gravity
is proportional to their mass”.
ARISTOTLIAN `THOUGHT’
t1  M 1
M1
M2
Galileo asked:
t2  M 2
Is it correct ?
t1
M1


t2 M 2
(1589)
M1>M2
t1<t2
S
U
N
Pla
net
EARTH
“Sun, moon and all planets (up to Saturn)
move around the Earth in circular path in
the backdrop of fixed stars”.
Copernicus asked:
Is it correct ? (1514)
 GALILEO
GELILEI established the
pivotal role of `EXPERIMENT’ as the
`SCIENTIFIC
METHOD’ which
is
essential to validate of any scientific
proposal or thought.
 Using
`TELESCOPE’
he
further
established
Copernicus’
`HELIOCENTRIC
THEORY’
which
compels the Vatican to correct its stand
on the `GEOCENTRIC THEORY’.
1564
February 15
• Born at Pisa, Italy
• Father: Vincenzo Galilei
• Mother: Giulia Ammannati
1581
• Entered University of Pisa to
study Medical Science, but
left because of poor economic
condition
1583
• Discover
isochronous
character
of
pendulum
watching the lamp of the
cathedral of Pisa.
1586
1588
1589-92
• Discovered Hydrostatic
Balance
• Obtained
position
of
Professor of Mathematics at
University of Pisa
• Conducted
some
experiments `On Motion’
1592
• Obtained
position
of
Professor of Mathematics at
University of Padua
1604
• Conducted famous `Inclined
Plane Experiment’ to obtain
`Law of Falling Bodies’.
1604-07
• Discovered Pump to lift water,
Military
compass,
Thermoscope etc.
1608
• The Dutchman, Hans
Lipperhey discovered
socalled `spyglass’ to
see distant object.
1609
• Built up the replica of
Telescope
started
observing sky.
Einstein
Newton
Other Major Players
Galileo
Lagrange
Hamiltonian
Jacobi
De Alembert
MECHANICS
(Science of objects
in motion)
F=0
KINEMATICS
(Galileo)
F =/= 0
DYNAMICS
(Newton)
V=L/T
V=L/T
V=L/T
V=L/T
V=L/T
Equal Distance
Uniform velocity=
Equal Time
Uniform Motion =>No Acceleration
V1=
L1 / T
V2=
L2 / T
V1
=
L1 /
T
V3=
L3 / T
V2=
L2 / T
Velocity
Acceleration=
Time
Non-uniform Motion => Uniform Acceleration
Velocity
Acceleration=
Time

Galileo’s famous experiment from the
Leaning Tower of Pisa demonstrates that,
`The time of fall of different bodies is
independent of their mass’.
ARISTOTLE `THOUGHT’
M1
M2
t1  M 1
M1
M2
t  M1
t2  M 2
t1
M1


t2 M 2
M1>M2
GALILEO `EXPERIMENTED’
t1<t2
2
t 1M 2
1
 M 1  M 22
2
2
s
t

s
t
 Absurd!
M1>M2
t1=t2
 Theorem
of Uniform Motion: “If a
moving particle, carried uniformly at
constant
speed,
traverses
two
distances, the time intervals required
are to each other in the ratio of these
distances.”
t1
s1

t2 s2

s1 s2

t1 t2
s
 v
t
 Theorem of Non-uniform Motion: “If
two particles are moved at a uniform rate, but
with unequal speeds, through unequal distances,
then the ratio of time intervals occupied will be
the product of the ratio of the distances by the
inverse ratio of the speeds.”
 Uniform
rate means the Uniform Acceleration:
v1
v2
t1
v1
a
and a 


t1
t2
t2 v2
(1)
 For
non-uniform velocity we obtain from
the law,
t1 v2 s1
(2)

t 2
v1 s2

Eliminating velocities from Eqs.(1) and (2)
gives most important Law of Kinematics;
same as the law of falling bodies:
s1 t

s2 t
2
1
2
2
 s  t
2
“The spaces described by the bodies falling
from rest with a uniformly accelerated motion is
equal to the ratio of the squares of the time
intervals employed in traversing these distances.”
s1 t

s2 t
2
1
2
2

 s1  t and s2  t
2
1
Thus we obtain famous `Law of Falling
Bodies’:
s  t
2
2
2
Time
Distance
Velocity
Acceleration
0 Sec
0 meter
0m/sec
-9.8 m/Sec^2
1 Sec
-4.9 meter
-9.8 m/sec
-9.8 m/Sec^2
2 Sec
-19.6 meter
-19.6m/sec
-9.8 m/Sec^2
s
2


4.9m
/sec
2
(t)
3 Sec
44.1 meter
-29.4m/sec
-9.8m/Sec^2
Time (In Sec)
Acceleration
(m/sec^2)
Velocity (m/sec)
Distance (m)
i) Concept of uniform motion:
s  s0  ut
ii) Concept of acceleration for non-uniform motion:
v  u  at
iii) Law followed by the accelerated bodies:
1
s  u t 
at 2
2
iv) Eliminating time one obtains an auxiliary relation:
v  u  2as
2
2

Galileo’s Law of Inertia: “Imagine any particle projected
along a horizontal plane without friction; then we know . .
. that this particle will move along this plane with a
motion which is uniform and perpetual, provided the
plane has no limits.” “A body at rest remains at rest and
a body in motion continues to move at constant velocity
along a straight line unless acted upon by an external
force”

Newton’s Law of Inertia: “Every body continues in its
state of rest, or of uniform motion in a right [straight] line,
unless it is compelled to change that state by forces
impressed upon it.”.

Galileo : “Acceleration is directly
proportional to the motive force and
inversely proportional to the volume of
the body”.
1
a  F, a 
V


F
a
V
Newton’s second law: “The change of
motion is proportional to the motive
force impressed and is made in the
direction of the force”.
dp
F
 F,  a 
(m=constant)
dt
m








i) Isochronous character of Simple
Pendulum
ii) Pendulum based clock
iii) Parabolic Path of Projectile
iv) Determination of specific gravity by
Hydrostatic Balance (1586)
v) Water lifting pump
vi) Thermoscope (Earlier version of
Thermometer)
vii) Military compass
viii) Improved Microscope

“Philosophy is written in this grand book the
universe, which stands continually open to our
gaze. But the book cannot be understood
unless one first learns to comprehend the
language and to read the alphabet in which it
is composed. It is written in the language of
mathematics, and its characters are triangles,
circles and other geometric figures, without
which it is humanly impossible to understand a
single word of it; without these, one wanders
about in a dark labyrinth.” – Galileo (1622)
Telescope
(Device that brings
distant objects
closer)
Momentous
Astronomical
Discoveries
Win of Rational
Thought over
Authoritarianism
.
.
.

Galileo was the first person to use the
refracting telescope, now known as
Galilean Telescope, for astronomical
observation.
Galileo’s Telescope
Hubble space Telescope
Galileo’s diagram
Modern observation
Galileo’s diagram
Modern observation
Galileo’s diagram
Modern observation
Galileo’s diagram
Modern observation
Galileo’s diagram
Modern observation
1. Developed and improved Telescope for
astronomical observation (1609)
2. Phases of Venus
3. Satellites of Jupiter
4. Mountain in the moon
5. Stars as the composition of the Milky
Way
6. Sunspot and its movement
7. Strange feature of Saturn
8. Established the Copernican thought of
heliocentric universe.
In 1609, Galileo developed and refined
`Telescope’ and make it suitable for
astronomical observation
Discovered of the phases of the Venus,
mountains in the Moon and the satellites of
Jupiter and starry composition of Milky Way.
Discovered the Sunspots and noted their
movements. Established of the Sun and the Moon
as the imperfect bodies contrast to Church’s belief.
All these discoveries convinced Galileo to
become an ardent proponent of the
Copernican theory.
In `Letter on the Sunspots’, Galileo
unequivocally mentioned that Copernicus is
correct and Ptolemy was wrong.
Galileo visited Rome for first time to meet Pope
and explain him about `Power of Telescope’.
Church ordered the heliocentric theory of
Copernicus as a “foolish and absurd and formally
heretical” and asked Galileo to give up the theory.
Galileo argued, “The primary purpose of the Holy Writ
is to worship God and save souls. …The Bible tells us
how to go to Heaven, not how the heavens go… ”.
Galileo emphasized, “in disputes about natural phenomena,
one must not begin with the authority of scriptural
passages, but with sensory experience and necessary
demonstrations.”
Galileo declined to accept Papal Order and
continued his support to the Copernican theory.
Published masterpiece `Dialogues concerning Two
Chief World Systems’ to establish the Copernican
theory. It was later banned by Vatican.
Vatican from Rome summoned him for second
time and ordered to accept Ptolemaic doctrine
renouncing the Copernican theory publicly.
Galileo declined again and faced `Inquisition’.
After the trial he was kept house arrest for
disobeying the Vatican.
Behind the grill Galileo wrote `Dialogues of
Two New Sciences’ which summarizes his all
great discoveries.
Galileo became gradually blind, his health
deteriorated and finally he died on 8th January,
1942.
In October 2, 1992,
Pope John Pal II has
withdrawn
`Papal
Order’ on Galileo.
Established
prime role of
Experiment
in Science
Established
Copernican
theory
Rescued physics
from metaphysics
Any natural
phenomena is
comprehensible
as a Laws of
Nature
 “Pure
logical thinking cannot yield us
any knowledge of the empirical world;
all knowledge of reality starts from
experiment and ends in it... Galileo
saw this, and particularly because he
drummed it into the scientific world,
he is the father of modern physics indeed,
of
modern
science
altogether”… .
- Albert Einstein
Thank You for Patient Listening