CC5110 all earth climate change atmospheric science

Earth climate change atmospheric science

1. CC 5110: Earth’s Climate and Atmospheric Sciences (3)
N. Nakamura
(Artist)
Instructor:
Kaushik Nayak

2. 2
Course Content:
Solar System Physics- Evolution of Solar System (Kant-Laplace Nebular Theory), Planetary
Accretion and formation of planets, Stellar Physics, Structure of Sun, Comets and Asteroids,
Terrestrial planetary structure and atmosphere, Planetary Climates: Evolution of
atmosphere on Venus and Earth, Climate cycles on Venus and Earth, Earth System Science:
Gaia Hypothesis (Earth System Science), Faint Sun Paradox, Evolution of Earth’s
atmosphere and role of biosphere, Chronology of geological time, Emergence of Life, Solar
radiation budget on Earth, Climate Change on Earth: Causes of Climate change, Pleistocene
glaciation and Milankovitch cycle, Oceanic Sciences.
Reference Books:
[1] Environmental Geology: An Earth System Science Approach; by A Dewet, D Merritts,
and K Menking.
[2] Planet Earth: Cosmology, Geology, and the Evolution of Life and Environment by Cesare
Emiliani.
[3] The Earth System: Lee R. Kump, James F. Kasting and Robert G. Crane
[4] Earth's Climate Evolution by Colin P. Summerhayes.
[5] Atmosphere, Weather and Climate by Roger Barry and Richard Chorley
Course Structure and Syllabus (3 Credits)… [Y- Slot]

3. 3
Atmospheric Composition of Earth, Mars, and Venus
Ximena C. Abrevaya et
al., ASTROBIOLOGY
Volume 16, Number 8,
2016
Earth’s atmosphere has Oxygen (~21 % composition), which is
essential for our existence as mobile, thinking animals, but without
photosynthesis to create it, oxygen would be very rare trace gas.

4. 4
Planet Earth: A Self-regulating System or Super-Organism(?)
van Wyk de Vries et al.,
Global and Planetary
Change, 2017.
Geosphere: Solid Earth (the core,
mantle, crust and soil layers)
Hydrosphere: Water in oceans;
rivers, wetlands, lakes and; in the
atmosphere; and frozen in glaciers;
ground water in soil and rock to a
depth of ~2 km.
Atmosphere is a chemical mixture or
cocktail of highly reactive gases
(mostly nitrogen and oxygen) held to
earth by gravity and thins rapidly
with altitude.
Biosphere: Inhabited by biological
living organisms (Uppermost solid
earth, hydrosphere, and lower part
od atmosphere).
Cryosphere: Frozen water.
Extraterrestrial
outer space

5. Gaia (Gaa-Yaa) Hypothesis (James Lovelock: 1960-70)
Great Bear Rainforest (Canada): https://education.nationalgeographic.org/
Gaia Hypothesis: Biosphere
and it’s non-living
environment on Earth form
a self-regulating system
that maintains the Earth’s
climate and the composition
of the atmosphere in a
habitable state.

6. 6
Fig. 1 Fig. 2
Earth System Science (The obvious unity of the Planet)
Thompson and Turk, Physical Geology
Most of our planet Earth is made up of solid rock surrounded by hydrosphere,
biosphere, and atmosphere.
Internal and surface geological processes on Earth shape the entire Earth.
Internal processes are the driving forces for plate-tectonics, ocean floor spreading,
raising mountains, causing earth quakes and producing volcanic eruptions.
Surface processes sculpt Earth’s surface driven by water, wind, ice and gravity.

7. 7
Feedback loops in the Earth’s System and Climate
M. Ghil and V. Lucarini,
Rev. Modern Physics,
vol. 92, July-Sep 2020.
Earth’s climate system is
heterogeneous and complex.
It is forced, dissipative,
chaotic and out of
equilibrium.
Climate system’s complex
natural variability originates
from the interplay of positive
and negative feedbacks,
instabilities, and saturation
mechanisms.
The feedback processes span
a broad range of spatial and
temporal scales, includes
multiple chemical species and
physical phases.

8. 8
Globally Averaged Solar Energy Fluxes in the Earth System
Ximena C. Abrevaya et
al., ASTROBIOLOGY
Volume 16, Number 8,
2016
Macroscopic Level: Climate is driven by differences in the absorption of
solar radiation throughout the depth of the atmosphere, in a narrow
surface layer of the ocean and the soil, and convective motions in the
troposphere.
Fig. 1
Fig. 2

9. Atmospheric CO
2 Measurement: The Keeling Curve
https://keelingcurve.
ucsd.edu/
1958: Charles David Keeling,
began tracking CO
2 concentration
in the Earth's atmosphere at the
summit of the Mauna Loa volcano
in Hawaii.
The Keeling curve data shows
that humans have been
responsible for almost 40%
increase in atmospheric CO
2
concentration over the last two
centuries due to Fossil fuel
burning and deforestation.
Current
concern
about
Global
warming
424.35 ppm
of [CO
2]
(6
th
Aug 2024)

10. 10
Paradigm Shifters in understanding Earth System and Climate
Sciences
James Hutton (Scottish
Geologist): 1726-1797
Alfred Wegener(German
Geologist and
Atstronomer): 1880-1930
Charls Lyell (Scottish
Geologist): 1797-1875
James Lovelock(English
Scientist): 1919-2022
Lynn Margulis
(Amerian
Evolutionary
Biologist)
1938-2011
Carl Sagan: (American
Astronomer and
Planetary Scientist):
1936-1994.
Charles David
Keeling: 1928–2005

11. Thank you for your Attention..

12. Dr
.Kanchis
Nayak
CC5110
Lectures......
(2024)

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33. CC 5110 (Earth’s Climate and Atmospheric Sciences)
Lecture#1, 2 and 3 Summary

(1) The course will be taught in the perspective of Earth System and Planetary science to
understand the science of Earth's climate including its long-term natural and short-term
anthropogenic (Human activity) variations. The recent variation in the past few decades is
known as Global warming.

(2) In the past three lecture sessions, I have been discussing the key milestones in the past century,
which set the scientific study of the emerging field of Earth System and Climate sciences. Also,
I am trying to emphasize the motivation behind understanding Earth system's constituent parts
[5 parts/components: Atmosphere, Hydrosphere, Biosphere, Geosphere/Lithosphere, and
Cryosphere (frozen part of Hydrosphere] and the interactions between them. The most
important part among all, which makes our planet unique in the Solar system is the Biosphere
(all living organisms from microorganisms to complex lifeforms like us and plants etc).

(3) As the popular Hypothesis known as Gaia Hypothesis proposed by James Lovelock (in the
1960s) that "The Earth with its Biosphere and non-living environment form a self-regulating
system that maintains the Earth’s climate and the composition of the atmosphere in a
habitable state." The habitable state is for maintaining the sustainable living conditions for the
Biosphere on Earth by changing the atmospheric composition and regulating Earth's climate,
which have lasted for almost four billion years now. The Climate conditions are characterized
by important observables such as Earth’s surface temperature, atmospheric pressure, cloud
cover, precipitation, atmospheric gas chemical composition, Greenhouse gas concentration etc.

(4) The Earth system regulates the global climate involving all its parts. The part Biosphere has
been playing a very important role in the Climate regulation over past 3.8 billion years. The
inherent causal interactive pathways of energy and mass transport between the Earth system
components/parts have many feedback loops. The important feedback loops discovered in the
past six decades are the Ice-Albedo +ve feedback and Silicate rock weathering -ve feedback. The
above feedback loops were discovered while trying to fetch the answers behind the
puzzles/paradoxes such as the Faint Sun paradox, Ice ages, Snowball Earth glaciations, and
Withdrawal from glaciations etc.


(5) One of the major research directions in the Earth System Science is to identify and study the
inherent feedback loops involved in the global climate change and regulation.

34. (6) Anthropogenic cause of recent global warming: Since 1958 US scientist Dr. Charles David
Keeling, began tracking CO2 concentration in the Earth's atmosphere at the summit of the
Mauna Loa volcano in Hawaii. The famous Keeling curve data shows that humans have been
responsible for almost 40% increase in atmospheric CO2 concentration over the last two
centuries (from 280 ppm to current 424 ppm) due to Fossil fuel burning and deforestation.

35. CC 5110 (Earth’s Climate and Atmospheric Sciences)
Lecture#4 and 5 Summary
(1) Two important feedback loops in the Earth System are Ice-Albedo +ve feedback and
Silicate rock weathering -ve feedback. In fact, the big changes are caused by the
positive feedback loops, which cause the climate to jump to an unstable equilibrium
state for some time. Later, any stimulus or disturbance can cause the positive
feedback loop to work in reverse and shift the climate condition to a stable
equilibrium state, where the negative feedback loop tries to keep the state near stable
equilibrium by diminishing or damping any stimulus. The -ve feedback loops
maintain status quo by regulating the Climate so that the atmospheric gas chemical
composition and Earth's surface temperature are suitable for the Biosphere's
existence.
(2) The Ice-ages are an alternating series of glacial and interglacial periods on Earth. In
Earth’s geological history, the Earth has plunged into a frozen cold house (Ice-age)
five times. The fifth one is the recent ongoing Cenozoic Ice-age. We are currently in a
deglaciation phase of warming Earth. The ice-albedo +ve feedback is an important
feedback mechanism that takes the Earth’s climate to a low temperature Glaciation
state.
(3) The glaciation periods are typically observed to have ice-sheet/glaciation spread from
poles to low latitudes up to 50 -45
0
North/South latitudes. The Snowball earth is a
glacial period with ice-sheet covering entire earth from poles to equator making Earth
appear like a giant snow-ball from space. There have been two snowball earth events
in the Cryogenic Ice-age between 710 million years and 640 million years ago.
(4) Sometimes persistent disturbance (forcing) or sudden big disturbance can initiate the
+ve feedback loop to shift the climate state from stable to unstable equilibrium. One
such example of persistent disturbance is the great oxygenation event caused by
photosynthetic bacteria about 2.6 billion years ago. And one example of sudden big
disturbance is the K-T (cretaceous - Tertiary) boundary event of a 10 km diameter
impactor (An asteroid) hi&#1946186752;ing earth 65 million years back causing 5th mass extinction
including the dinosaurs.
(5) The stability criterion of the feedback loops is understood Mathematically by the
solution of coupled differential equations. The unstable equilibrium state of + ve
feedback loop is an unbounded exponential variation of change in either direction
(rise to infinity or fall to zero). There is no zero crossing.
(6) Whereas the stable equilibrium state solution for - ve feedback loop is a bounded
oscillatory solution like harmonic sinusoidal oscillations around the equilibrium
point. The later solution indicates maintenance of the status quo, i.e. regulation.
--------------------------------------------------------------------------------------------------------

36. CC 5110 (Earth’s Climate and Atmospheric Sciences)
Lecture#6 Summary
[1] The stability criterion of the feedback loops (+ve and -ve) were re-emphasized
using Physics and Mathematical reasoning. Please refer to points 5 and 6 of previous
lecture summary.
[2] As an example of sudden big disturbance (sudden forcing) to Earth’s Climate
system, the K-T (Cretaceous and Tertiary period) boundary event of a large 10
15
kg
mass and 10 km diameter Fe rich Asteroid impactor colliding Earth 65 million years
ago was discussed. (See annexed slides on next page). The K-T boundary or the
Chicxulub impactor event caused fifth mass extinction on Earth with the extinction of
non-avian Dinosaurs and other species (~ 75% species became extinct). The geological
& biological fossil evidences (Clay layer with Iridium anomaly and microfossils of
Forams in the limestone layers) behind the K-T boundary event was first discovered
and reported by Louis and Walter Alvarez in 1980.
[3] The effect of the above big impactors hi&#1946186752;ing Earth can cause large scale devastation
to Biosphere causing a large shift in the Earth’s stable equilibrium climate state to
unstable equilibrium state. The effects can lead to collapse of food-chain,
photosynthesis, mass-extinction and drop in Earth’s surface temperature (up to 7
0
C)
due to ejecta dust & aerosol particles covering entire Earth for decades.
[4] The above effects have been recently observed in the large volcanic eruptions (6 in
numbers) in the last 140 years from 1883: Krakatoa to 2022: Hunga Tonga eruptions.
In these recent huge volcanic eruptions, the ejecta dust and sulfate aerosols cover the
Earth like a blanket at stratospheric height leading to increase in Albedo and drop in
surface temperature up to 0.5
0
C for a year to five years. These scientific studies help
us reconstruct the aftermath of the K-T boundary impactor 65 million years ago.
[5] Finally we entered our Solar System Physics module with the historical
introduction to the scientific thought evolution about the models of our Cosmos and
Universe from Ancient hunter-gatherer cultures through the Greek civilization to
recent times. We are still in the Greek era in our lecture discussions and stopped with
Aristotle’s Earth-centric cosmos model in his seminal work “On the Heavens”, which
was the popular accepted model of the Cosmos/Universe with stationary Earth at the
centre of the Universe for almost 1900 years till Copernican revolution. This suggests
that we (humans) were in total ignorance for almost two millennia about the model
and structure of our cosmos. The scientific revolutions leading to recent
understanding of the structure of the Cosmos and Universe will be continued in the
next class.
(Dr. Kaushik Nayak)

37. Big Forcing: Iridium and K-T Boundary Event (65 M. A. before)
1980: Louis & Walter
Alvarez, discovered a
uiform layer of clay with
abnormally high conc. of
Iridium (~ 10 ppb by mass)
of extraterrestrial origin
dating back to 65 M Years
ago from the mountains
near Gubbio, Italy.
Iridium is a rare element (<
0.03 ppb) on Earth (in
crustal rocks, sediments
and Mantle) and anywhere
in the Solar system. Most
of the Iridium is found in
the Earth’s core alloyed
with Fe. It is very rare
element.
(The Clay
layer at the
K-T
boundary in
between
carbonate
rock
sediments)
G. Haxel et al., Rare
Earth Element
Resources (2002).

38. K-T Boundary Event Impactor: 10 km Size Asteroid
SCIENCE VOL 327 5 MARCH 2010
A rocky Asteroid of 10 km diameter and 10
15
kg
mass collided with Earth 65 M.A. ago at the
Chicxulub crater site (200 km in diameter) on the
Yucatan peninsula, Mexico.
The energy released by the impacting asteroid is
enormous ≥ 70 Million 1 Megaton H-bombs
triggering gigantic ejecta of debris, huge forest fires
and firestorms, extreme Earthquakes (~ 9 -9.9 on
Richter scale), and huge Tsunamis causing Mass-
extinction.
(https://massextinction.
princeton.edu/chicxulub/
2-impact-controversary.)

39. Chicxulub Asteroid Impact Effects
First hour (left) and after several days when dust has covered the globe and blocked the sun (right).
https://www.lpi.usra.edu/exploration/training/illustrations/chicxulub-effects/.

40. Chicxulub Asteroid Impact Effects…
https://www.lp
i.usra.edu/expl
oration/trainin
g/illustrations/
chicxulub-
effects/.
18
0
C –
37
0
C
≥ 7
0
C
drop

41. 1

CC 5110 (Earth’s Climate and Atmospheric Sciences)
Lecture#7 Summary (Date: 10-08-2024); Kaushik Nayak
[1] We started the lecture with the history of emergence of Scientific thought in
developing the models of our Cosmos/Universe since the ancient human cultures. Our
ancestors (~ 5000 yrs ago in the mid Neolithic age) conceived the image of the world
as made up of Earth (Below) and Sky (Above). Both are infinitely extent. They viewed
that the heavenly bodies (stars, Sun, and Moon etc) fly in the sky above us.
[2] The late Neolithic age the ancient cosmological models were based on religious
teachings and mythology. Some of the popular ancient cosmologies (more than 2000
yrs old) are developed in Indian, Egyptian, Nordic and Chinese late neolithic cultures.
[3] The Indian version of the mythological universe is hierarchical, where the heaven,
Sun, stars, moon, and Earth are all supported on the heads of four elephants. The
elephants also are supported by a Giant turtle resting on a divine cobra. The God
Brahma creates the universe (heaven, Sun, stars, moon, and Earth) from an cosmic
egg, and the created universe is preserved by God Vishnu and further it’s destruction
is carried out by God Shiva. The Universe follows a life cycle of creation and
destruction with age (Kalpa) of 4.32 billion years of existence. Concept of time was
relative.
[4] The other popular ancient cosmos model was proposed by Egyptians. Here, the
world is again made up of Sky, Earth and giant cosmic river/water body surrounding
both Sky and Earth. The celestial bodies, Sun, moon, and stars were treated as Gods.
The most prominent God was Sun god (Ra). The cosmos was understood through the
life of “Ra”. Ra emerges at Sunrise and sails through the sky in a boat called Manjet.
Other gods accompany “Ra” in this heavenly sail. Ra travels through twelve
provinces, each representing hours of the day. At Sunset in the western mountains,
“Ra” becomes a corpse to take rest and sails the cosmic river of darkness in a boat
called “Mesektet”. The night voyage ends again in the morning and “Ra” rises again
to sail though the Sky. The night sail is not smooth as the evil serpent God Apep
waited for Ra in a western mountain called Manu, where the sun set. The fight between
Apep and Ra accompanied by other Gods continues in the night and at the end Apep
is defeated.
[5] Apart from the above, the ancient Nordics had a world tree model and ancient
Chinese had Yin-Yang duality model of the cosmos. Like Indian mythological cosmos,
the Chinese believed that the universe emerged from a cosmic egg with the birth of a
sleeping giant called “Pangu”. The world (Sky, Earth and other celestial bodies) was

42. 2

created with growth of Pangu till he went into eternal sleep. Human beings and other
species are described as parasites living on Pangu’s body.
[6] After 2000 BCE, the image of Cosmos made a transition from mythology to facts
supported by evidence. Many believed that the mythological ideas and images leave
the door open for more speculations not backed by facts. Hence, man’s desire to know
the final answer about his origins, origins of what he observes, and the extent of
universe around him led to the development of Scientific Methods. The Scientific
methods are based on combinations of intellectual endeavours involving
observations, logic, scepticism, and open-mindedness.
[7] The Scientific methods were first practiced by Ancient Greeks with Anaximander
(~ 600 BCE) proposing that that the Sky is all around us and the Earth is a finite size
huge floating stone. The Sun, moon, and stars all carry out their cosmic dance in the
sky around Earth. Of course, the reasoning and knowledge behind the force that keeps
the earth floating in space was not there. During that time, the answers to such big
questions were placed within the realm of supernatural power of Gods and Divine
intervention.
[8] Later Greek natural philosophers Parmenides and Pythagoras (~ 500 BCE)
proposed that the floating earth is a giant sphere as it is the reasonable geometrical
shape to describe that the sky looks equal in all directions.
[9] Aristotle (~ 350 BCE), the disciple of Plato and teacher of Alexander the great,
added that the sky (or heaven) is also spherical in nature with the spherical earth at
the centre of dance of Sun, Moon, and stars. An image of heavenly sphere surrounding
the Earth appeared. This led Aristotle to develop the Geocentric model of the universe
and his model appeared in his great work “On the Heavens”. Aristotle’s geo- or earth-
centric model was further developed by Ptolemy (~ 200 BCE). This model of the
cosmos remained as the best described model of the universe until end of the Middle
Ages (~1500 AD). Most of the scientific minded intellectuals and natural philosophers,
who lived between (200 BC to 1500 AD) learned about the cosmos with the image of
geocentric model in mind.
[10] Apart from becoming the architectures of images of first scientific models of the
cosmos, Greeks also a&#1946186752;empted to make the measurement of size and distance of
heavenly bodies including Earth. Eratosthenes (~ 200 BCE) of Library of Alexandria
made the first successful measurement of size of Earth (Circumference) by observing
shadows casted by poles and wells due to incident Sunlight in Alexandria and Syene
in Egypt. Using trigonometry and angular measure, he estimated Earth’s
circumference to be 40,250 km. It is close to current measured value of 40,075 km.

43. 3

[11] Similarly, another Library of Alexandria natural philosopher Aristarchus (~ 280
BCE) a&#1946186752;empted first to measure the size of Sun and distance of Sun from Earth by
observing Moon’s 1
st
and 3
rd
quarter positions along it’s orbit around Earth. He used
angular measure and trigonometry to do this. Also, Aristarchus was the first to suggest
that Earth not stationary and it moves around Sun by observing the Parallax effect
associated with distant star 61 Cygni. But, he could not accurately do it due his wrong
estimate of the distance of 61 Cygni. This was the first step to revise the geocentric
model of Aristotle to heliocentric, but Aristarchus’s radical views were not accepted
by Ancient Greeks and public.
[12] Aristarchus’s views were supported and further improved by Nicholas
Copernicus (~1543 AD) resulting in the great scientific revolution with helio- or Sun-
centric model of the cosmos. The Copernican helio-centric model put Sun at the centre
of the cosmos with Earth moves around Sun like other planets and some stars in the
constellations. There are also far fixed starts on the spherical heaven surrounding the
Sun. Earth spins around its own axis and moon moves around Earth. This radical
cosmological model was developed towards the end of Middle Ages and start of
Renaissance or modernity in Europe. Of course, the modernity is no longer remained
restricted to Europe now and it has propagated everywhere on Earth via further
cultural exchanges, and connections through trade & commerce. The modernity is
being shaped by the recent scientific revolution and materials culture practiced
through industrialization.
[13] Of course Copernican model is not the true model of the universe as we
understand it in the grand scale now. In the past five centuries the cosmological
models were further improved, which led to the modern viewpoints of cosmology
based on Big-Bang cosmology (Universe was born with an explosion of ma&#1946186752;er, energy,
space and time from an infinitely dense state with extremely high temperature of ~
10
35
K from a point if singularity 13.77 Billion yrs ago) , expanding universe and large-
scale structure of the universe filled with la&#1946186752;ice, voids and filamentary structures
made up of super-cluster complexes of Galaxies in the length scale of 10s of billion
light yrs. The super-clusters contain Galactic clusters (~ 100 million Light yrs) in them.
The galactic clusters contain galaxy groups (~ 1 million Light yrs across), galaxy of
stars (like our Milky way with 100 billion stars with size ~ 10
5
Light yrs), inter-stellar
space (~ 10

- 10
4
Light yrs), Solar system (0.5 – 1 light yr), Earth (~ 12800 km) and
human observers (~ 1.5 – 2 m).
One light year is the distance light travels in a year, i.e. 9.46 ×10
12
km ~ 10 trillion km.
The observer human size in totally insignificant in comparison to the size and extent
of our current observable universe.

44. 4

[14] The lecture was put to a closure with the descriptions of two physical phenomena
encountered in astronomical observations, i.e. Aberration and Parallax. These two
observed effects led us to the conclusion that Earth is moving in space around Sun and
it spins around its own axis.
We will continue our journey in our next lecture session.

45. sics
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48. FromMythology
to
factsg
-
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5
Y
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of
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i
isa
*
around
En
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----
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Sky
a
great
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floating
stone.

50. Enuating
Suspended
Earth
is
asphere"
e
Parmenides(500BCE)
&
E
Pythagoras
(500
BCE)
E
-
BSky
·
isthe
most
O
shape
as7
reasonable
·
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*
T
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.
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Csymmetrics

51. Spherical
natureof
boththe
-
Earthandtheheavens(sky)
&
&
-
Aristotle(-350
BCE)&
-
E
v
g

52. Geocentric
Modelof
Solar
System&
gAristotle
Ptolemy
Ewal
theHave
# He
Image
*
*
Cosmos
-
&Middle
* Ages
(15)
·
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-
UNIVERSE"
-
*

53. Measurement
Sizeof
Earth
l
-
·
Eratosthenes
(200
BEE)
-
ClibraryofAlexandria)
(Source:
-www..
geo
,
hunter.
cury
.edu)

54. DistancestotheSunand
AttemptsDetermining Moon(first
--
-
·AristarchusSamos)Su
280BCE)
--d
Moon
-Used
Angular
measurequarter
Moon
D
-
atima
-
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-
&
d
z
AC
W
I
Earth
-
Determined
that
~
900
sumis20timesfurther
-
*
from
usthanMoon.
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O
-
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larger)
1stqua
on
more

55. Copernican
Heliocentric
Cosmos
m
-
-
-
NicolausCopernicus
(-1543)
-
AD
FPolish
Astronomer
&
Poly
math
-
-Earthisnot
creaticRevolutionatthe
Centre
the
cosmos
,
In
there
instead.!
Sun
I
around
Sun-CentricCosmos

56. (1931-7O
-
--BangTheory=
excepted
:-1964
12
-

57. Large-scale
structureof
theUniverse
(13)
-

58. -gescale
structureof
ourUniverse
G
Image
Source!-a stronomy
now
.com)

59. sics
CC5110LectureSession
n
of
Phy
Solar
-MaushikNayak3-
System
Macrocosmicstructureof
the
Universe
·
Emergence
of
scientificthought
!
is
--
-
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-
vity
m
(2)
-A±
#
F
-
--
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60. -
Ancientcosmologies
C
Base
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gy)&
-
-
Chinese
,
andNordic
(Indian,
etc...)
*
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C
m
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61. *
mos
throughthelife
ofa s
e
-
-
T
³
*
LIGHTJONEvening--
-
-
-
-
T
w
·
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T
--
---·
*-----
(Mesektet)
=>
-
--
/
-
-Utter BoatJourneyis
------
-
-
³

62. FromMythology
to
factsg
-
-
Man'sdesireto"KnowTheFINALANSWER"
5
Y
-&
·
Hisorigins
j
·ginsent
m
observes
&
round
H
-
&
Withhi scie
f
Understand
many
detailsof
our
6
universiticismWe

63. IntellectualEndeavors
of
Ancient
n
-
Greeks
-
-
F
-
--Sky
i
#
*
isa
around
----
us
.En-Y*
*Earthis
Sky
a
great
y
floating
stone.

64. Enuating
Suspended
Earth
is
asphere"
e
Parmenides(500BCE)
&
E
Pythagoras
(500
BCE)
E
-
BSky
·
isthe
7
most
O
reasonable
·
III
*
T
shape
as
*...Skyareequal
.
"¥
Csymmetrics

65. Spherical
natureof
boththe
-
Earthandtheheavens(sky)
&
&
-
Aristotle(-350
BCE)&
-
E
v
g

66. Geocentric
Modelof
Solar
System&
I
g
#
-
*
EARTH±
-
UNIVERSE"

67. Measurement
Sizeof
Earth
l
-
·
Eratosthenes
(200
BEE)
-
ClibraryofAlexandria)
(Source:
-www..
geo
,
hunter.
cury
.edu)

68. DistancestotheSunand
AttemptsDetermining Moon(first
--
-
·AristarchusSamos)Su
280BCE)
--d
Moon
-Used
Angular
measurequarter
Moon
D
-
atima
z
-
d
W
-
&
-
AC
Earth
I
-
Determined
that
~
900
sumis20timesfurther
-
*
from
usthanMoon.
390X
O
-
#Correctdatat
larger)
1stqua
on
more

69. Copernican
Heliocentric
Cosmos
m
-
-
-
NicolausCopernicus
(-1543)
-
AD
FPolish
Astronomer
&
Poly
math
-
-Earthisnot
creaticRevolutionatthe
Centre
the
cosmos
,
Sun
I
In
there!
instead.
Sun-CentricCosmos
around

70. (1931-7O
-
--BangTheory=
excepted
:-1964
12
-

71. Large-scale
structureof
theUniverse
(13)
-

72. -gescale
structureof
ourUniverse
G
Image
Source!-a stronomy
now
.com)

73. 1

CC 5110 (Earth’s Climate and Atmospheric Sciences)
Lecture#8 Summary (Date: 23-08-2024; C-LH2); Kaushik Nayak
[1] In this lecture, we progressed further from Copernicus’s heliocentric model (1543
AD) of the universe towards the modern viewpoint of the cosmos through few key
scientific milestones. The first milestone was set by Italian scientist Galileo Galilei in
early 17
th
century with astronomical observations using telescope to gather scientific
evidence to support the heliocentric model of Copernicus and abandon the first
Physical models of motion proposed by Aristotle.
[2] The pillar of Geocentric model rests on the key assumption that Earth is stationary
and at the centre of the spherical sky through which the other celestial bodies
including the Sun carry out their cosmic dance. Now, the stationary Earth viewpoint
was abandoned later with two key astronomical observations, i.e. (a) Aberration, and
(b) Parallax. Both these effects can allow the astronomers to check whether the Earth
moves in relation to the stellar background.
[3] The aberration effect was first observed by James Bradley in 1725 while observing
the star γ-Draconis. He could observe the change in direction of star-light for
continuous six months duration, which proved that Earth moves against the stellar
background.
[4] The parallax is the second observational method which proves that Earth moves.
A star observed from Earth separated by six months should show a very small change
of direction if Earth is moving. In fact, the effect is measured through a very small
angle (~ arcseconds = 1/3600 of degree) subtended at the target star by the Earth-Sun
distance (1 AU = 150 Million km), which is known as the parallax angle. Greek
philosopher and Mathematician Aristarchus failed to measure such ultra-small
angles.
First successful parallax effect was measured by Friedrich Bessel in 1838 with star 61-
Cygni.
[5] The above two effects observation proved that Earth is non-stationary and it moves
in space around Sun due to the force of Gravitation. The Earth’s motion in space was
suggested earlier post-Copernican era by Danish astronomer Tycho Brahe, his
German assistant Kepler (three laws on Planetary motion: K1, K2 and K3) and Italian
astronomer Galileo around end of 16
th
century and early 17
th
century. Galileo started
the modern astronomy with painstaking Telescope observations of planets, Sun, Moon
and stars. Galileo used refracting type telescope, which suffered from an optical defect
known as Chromatic Aberration.

74. 2

[6] Later English natural philosopher and mathematician Isaac Newton (1687:
Philosophiae Naturalis Principia Mathematica—Mathematical Principles of Natural
Philosophy) provided the first logical framework using Mathematics to explain the
motions of planets and Earth around Sun using his theory of gravitation and celestial
mechanics. Newton built his inverse square law of Gravitational force by
mathematizing Kepler’s third law of planetary motion (Law of orbital period) and also
discovered one of the fundamental constants of nature related to gravity, i.e. &#2959829876;=
6.673×10
−11
&#2959829890;.&#2959829940;
2
/&#2959829936;&#2959829936;
2
hidden in Kepler’s third law.
[7] The Galileo’s refractive telescopes were improved by Sco&#1946186752;ish mathematician James
Gregory by replacing the objective refracting lens with a reflecting concave mirror,
which led to the development of Reflecting telescope. The reflecting telescope was
devoid of any chromatic aberration defect and it got further improved by Isaac
Newton in 1668. The Newton’s version of the reflecting telescope is still being used by
Modern Astronomy.
[8] The next big step in the widening of our knowledge horizon about the cosmos came
with the discovery of our home galaxy “Milky Way” in 1785 by German astronomers
William and John Herschels (Father and Sun duo). Sun is in fact an average star and
member of our home galaxy, which is home to some 100 -200 billion stars. This made
further revision to the Heliocentric universe model that Sun and its planetary system
is not at the centre of this vast universe, where a very large no of stellar congregations
(galaxies) exists ~ 2 trillion in numbers. Galaxies can be irregular, elliptical and spiral
in shape. See the presentation slides on Milky Way galaxy copied next page.
[9] Further the Herschel and his sister Caroline Herschel discovered interstellar clouds
of gas and dust within Milky way, known as Nebulae. We will see soon that stars are
born and also end their life in these nebulae within Galaxies.
[10] We also discussed about the small angle formula used in Astronomy based on
Angular measures of size and distance of celestial objects. The size of distant planets,
celestial bodies and stars using modern telescopes can inferred both in terms of angles
(α in degrees, arcminutes and arcseconds) and linear size (D). Small-angle formula:
&#2959829974;=
&#2959829868;&#2959829868;
&#2959829920;&#2959829920;&#2959829920;,&#2959829920;&#2959829920;&#2959829920;
; where D =linear size, α= angular size, and d = distance.
[11] We introduced two large distance measures used in Astronomy and cosmology,
i.e. light years (Ly) and parsec (pc) - parallax second.
1 light year (Ly) is the distance travelled by light in 1 year, i.e. &#2959829934;.&#2959829924;&#2959829920; ×&#2959829918;&#2959829920;
&#2959829918;&#2959829920;
&#2959829784;&#2959829784; (~ 9.5
trillion km).
1 pc = 3.26 Ly = 206265 AU. We also use kpc (1000 pc), Mpc (Mega pc), and Gpc (Giga
pc). A distant object 1 pc away will correspond to a parallax angle of 1 arcsecond. 1
AU = 1 Astronomical Unit = Average Earth-Sun distance (~150 million km).
----------------------------------------------------------------------------------------------------------------

75. Our Home Galaxy (Milky Way)
Web Reference: https://earthsky.org/earthsky-community-photos/
(Western Desert, Egypt) (Rocky Mountain National Park,
Colorado)
The starry band
across the dark
night sky is our
home galaxy
“Milky Way”.
It is a barred
spiral galaxy.
It is composed of
~ 100 - 200
billions of stars,
one of which is
our Sun.
Size: 100,000 L
yrs across
(950,000 trillion
km).
Age: Older than
12.7 billion years.

76. The Milky Way Galaxy
Composed of hundreds of billions
of stars, clouds of gas and dust,
pockets of dark matter.
 Two major spiral arms: Scutum-
Centaurus and Perseus.-  Young
and Ancient stars.
Two minor arms: Sagittarius and
Norma.  Nebulae and Young stars.
Our Sun burns in the much
smaller Orion Arm, located
between the Sagittarius and
Perseus arms.
Solar system is located about
26,000 L yrs from the Galactic
center.

Reference: NASA/JPL-Caltech/R. Hurt (SSC/Caltech))

77. Milky Way’s Central Black
Hole (Sagittarius A)
 Saittarius A (Galactic Nuclei): ~
26000 L Y from Earth (9.5 Trillion km);
 Mass ( Sgr A*) : 4.6 Million ×&#2959829992;
&#2959830004;&#2959830004;&#2959830004;
 Size (Event Horizon): R = 12 Million km
~ 17.14 times radius of Sun….It would
within the size of planet Mercury’s orbit.