Life in the Universe
ASTR 1420
Tu/Th 12:30-1:45PM
Room 221
by Inseok Song (“iSong”)
Lecture #1
Are we alone in the Universe?
Ancient folks were wondering also…
• Epicurus (341-270 B.C.) : atomists
There are infinite worlds both like and unlike this world of ours. … we must believe
that in all worlds there are living creature and plants and other things we see in
this world.
• Aristotle (384-322 B.C.) : aristotelians
The world must be unique... There cannot be several worlds
• St. Thomas Aquinas (1225-1274):
o integrated Aristotle’s philosophy into Christian theology.
I am an exo-planet hunter!
Co-Principal Investigator
of Gemini Planet Imager
Campaign Science team
• Awarded 890hrs of 8m telescope
time in Chile
• 50 PhDs throughout the world.
• 40+ million dollars project
• starting late 2012 – 2015
• Will image dozens of Jupiters
orbiting other stars
The 1st Imaged Exo-palnetary system !
… trying to understand the origin of planetary systems
• In Pleiades, collision between two planets!
First Day of the Class
• Syllabus
• contact info.
• Professor: Inseok Song
• Office Number: Physics Building, Room 240
• Office Telephone Number: 706-542-7518
• E-Mail Address: song@uga.edu
• No Facebook…
• Course Webpage:
http://www.physast.uga.edu/iSong/ASTR1420
• Office Hours: 1hr after the class or by
appointments (email preferred)
Check the course webpage frequently!
http://www.physast.uga.edu  “course schedule”  ASTR1420
First Day of the Class
• Syllabus
• contact info.
• course goals
• Course Goals: This course is not the one to
memorize gory-details of “facts”.
1. Understanding the meaning of life in the
Universe
2. Logics behind various searches for life
3. Scientifically understand the possibility of alien
life forms in the Universe and put us in the
grand context
4. Appreciating the precious nature of human
beings is the most important goal
Class attendance will not be tracked.
But, there will be significant(?) benefit
for attending classes. ;-)
First Day of the Class
• Syllabus
• contact info.
• course goals
• textbook + exam
• Textbook: Life in the Universe, AddisonWesley, by Bennett & Shostak (2nd Ed.)
optional
• Additional Reading: Lecture notes..
• Prerequisite: None
Final Score
= best two in-class exams (80%) +
worst exam (20%) + term paper (5%) +
bonus credits (5-10%)
• Exam: Three in-class exams, two best scores
will be counted 40% each, and the worst
score is to be counted 20%. Optional term
paper for 5% credit.
• Test questions will be a mixture of “multiple
choices, “short answers”, and “essay”.
First Day of the Class
• Grading: Final score will be rounded (i.e.,
89.9  90 and 89.4  89).
• Syllabus
• contact info.
• course goals
• textbook + exam
• grading
• extra credits
• make-up exam
Term paper:
• Single-spaced
• a separate title page.
• no more than 5 pages
90 ≤ A
87 ≤ B+ < 90
83 ≤ B < 87
80 ≤ B– < 83
77 ≤ C+ < 80
73 ≤ C < 77
70 ≤ C– < 73
60 ≤ D < 70
F < 60
• Extra credits: Occasional extra credit works
• Term paper: A term paper counted as bonus
points (up to 5%) toward the final score.
Need to tell me about your incoming
submission by March 1.
• Make-up of missing exam: Need to send a
notice to me before the exam. Or, with a
legitimate excuse, you can tell me afterward.
Then, I will arrange a make-up test.
First Day of the Class
• Syllabus
• contact info.
• course goals
• textbook + exam
• grading
• extra credits
• make-up exam
• course goals
• instruction method
• withdrawal policy
• Academic honesty
• Code of conducts
• Academic honesty: If you are using someone
else’s work in your report, you need to
clearly provide the reference (even if it is a
simple URL). Otherwise, your work will be
regarded as plagiarism and a serious case will
be reported to the University.
• Classroom code of Conducts: Follow general
rules and use your common sense.
Synopsis of the Course
ASTROBIOLOGY
SCIENCE VS. NON-SCIENCE
sections 1.1, 1.2, 1.4, 2.1, 2.3
Is it reasonable to imagine life beyond Earth?
• Universality of Physics and Chemistry
Observed data show that same laws of nature govern our Earth, Solar System,
Galaxy as well as galaxies far far away. Similarly, distant stars/galaxies are made
from the same chemical elements as ours.
• Can biology also be universal?
If we find nearly identical planets to Earth, then, could similar biological processes
of Earth have happened on those planets?
o Vast Universe!
At least to the 1st part of the question (“if we find identical planets”), yes we started
finding such planet(s) already (Kepler 22b).
Vast Universe!
Vast Universe
Hubble Ultra Deep Field: in a very small region of the sky (similar to the
angular extent of a penny at the end of a football field), ~10,000 galaxies
were found.
Vast Universe : Hubble Ultra Deep Field
In the Universe, there are about 10 billions galaxies!
And, each galaxy has about the same number of stars as in the Milky Way
 So, there have to be Earth-like planets somewhere out there…
Astrobiology
• What is astrobiology?
scientific study of life in the Universe : (= bioastronomy = exobiology)
; any kind of conceivable life forms!
It spans biology, chemistry, geology, physics, paleontology, planetary science,
religion, philosophy, and astronomy.
• Three major areas of astrobiology
o Astronomy : provide context to the search. “If something happened here on
Earth, the same thing might have happened somewhere else.”
o Planetary science : understand planets; frequency, formation & evolution. 
Habitability of planets!
o Biology : universality of biology? Life on Earth arose quite early in Earth’s history!
Astrobiology
•Astrobiology is …
• More than simple search for extraterrestrial
life or intelligence.
Connection between life and environment
Therefore, even the “null result” of the
search for life is significant as finding life!
Astrobiology as a science (not pseudo-science)
What is Science ?
Characteristics of Science
1. Seek explanations for observations
2. Create/test models to explain observations
3. Testable predictions
observations  verifiable by a 3rd person.
models  should be as simple as possible.  Occum’s razor
Occum’s Razor
lex parsimoniae = Law of Parsimony = Law of Succinctness
14th century English Franciscan Theologian, William Ockahm
“entities must not be multiplied beyond necessity”
“Occum’s razor” = true explanation of a given phenomenon should make as
few assumptions as possible.
All science models should be in the simplest form!
Pseudo-Science
Pseudo-science : handling the nature appearing as a true science, but it involves a
non-scientific handling of evidence or method.
(Ex) Biorythm: every human being has three distinct cycles (physical: 23 days,
emotional: 28 days, intellectual: 33 days) which determine the fate of an
individual.
Scientific…
You are being scientific in
your daily life…
Say that you are looking for a used car, and you
are offered a lovely, 1-year old Porsche for
just $3,000.
?Why should the price so low?
?Does the car run?
?Has it been wrecked and poorly rebuilt?
Ask your friend
Take a test drive
Get examined by a mechanic you trust
being scientific : skeptical and looking for
greater confidence in a drawing conclusion.
Tentativeness : Being “Scientific” is not absolute!
• 200 years ago, French Academy of
Science declared that the notion of
stones falling from the sky (e.g.,
meteorites) by Chladni is not
scientific; a complete nonsense.
why? Scientific evidence for this
hypothesis (claim) is lacking…
Then, the claim by Ernst Chladni
received a spectacular
confirmation by a prominent
metro shower near L’Aigle, France
in 1803.
Scientific or not?
? UGA has the best college football team in the nation.
? Several miles below its surface, Europa (one of Galilean moons) has an
ocean of liquid water.
? Terrestrial bacteria can survive on Mars.
? A huge fleet of alien ships will land on Earth and introduce an era of peace
and prosperity on January 1, 2020.
? There is no liquid water on the surface of Venus today.
? My house is haunted by ghosts, who makes the creaking noises I hear each
night.
? God created the Universe with all Laws of Nature (e.g., Law of Motion,
evolution, etc)
Logic and clarity are the most important!
Does not matter if it is right or wrong!
In summary…
Important Concepts
Important Terms
• Universality of Natural Laws
• Astrobiology
• Astrobiology as science
• Occum’s razor
• Scientific or non-scientific?
• Pseudo-science, false science
Chapter/sections covered in this lecture : sections 1.1, 1.2, 1.4, 2.1, 2.3