Life in the Universe
ASTR 1420
Tu/Th 12:30-1:45, Room 221
by Inseok Song
Lecture #1
I am an exo-planet hunter!
1st Imaged Exo-palnetary system !
… trying to understand the origin of planetary systems
• In Pleiades, a collision between
two planets!
First Day of the Class
• Syllabus
• contact info.
• Office Telephone Number: 706-542-7518
• E-Mail Address: song@uga.edu
Inseok Song
Physics Building, Room 240
• Office Hours: Tue/Thu after the class or by an
email appointment
Course Webpage: Check the course webpage frequently!
http://cosmos.physast.uga.edu/iSong/ASTR1420
or
http://www.physast.uga.edu  “course websites”  ASTR1420
First Day of the Class
• Syllabus
• contact info.
• course goals
• Course Goals: This course is not the one to
simply memorize gory details.
1. Understanding the meaning of life in the
Universe
2. Scientifically understand the possibility of alien
life forms in the Universe and put us in the
grand context
3. Appreciating the precious nature of human
beings are the most important goal
Generally, 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. Or
later)
• Additional Reading: Occasional reading
material (not in the textbook) will be posted
in the course webpage.
• Prerequisite: None
Final Score
= best two in-class exams (80%) +
lowest exam score (20%) + bonus
credits (up to 10%)
• Exam: Three in-class exams, two best ones
(40% + 40%) and the lowest one (20%).
Occasional optional homework for bonus
credit (up to 10%). Questions will be a
mixture of “multiple choices, “short
answers”, and “essay”.
First Day of the Class
• Syllabus
• contact info.
• course goals
• textbook + exam
• grading
• extra credits
• make-up exam
• Grading: Final score will be scientifically
rounded (i.e., 89.9  90 and 89.4  89).
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.
• Make-up of missing exam: With a legitimate
excuse, student may submit an essay paper
(about 10 pages) on a subject from the list of
term paper topics.
Term paper:
• Single-spaced
• ~5 pages
First Day of the Class
• Syllabus
• contact info.
• course goals
• textbook + exam
• grading
• extra credits
• make-up exam
• course goals
• instruction method
• withdrawal policy
• Method of Instruction: During class periods,
lectures will be given mostly via powerpoint
presentation and all lecture notes will be
accessible from the course webpage.
• Withdrawal Policy: Know the rules
concerning withdrawals and incompletes,
published in the UGA Undergraduate
Bulletin. Note that I will NOT withdraw you
from the course for excessive absences.
Note also that after the midpoint of the
semester, a withdrawal is assigned a grade of
WF, except in those cases in which the
student is doing satisfactory work and a
withdrawal is recommended by the Office of
Student Affairs (because of emergency or
health reasons).
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 a nearly identical planet to Earth, then could a similar biological process
happened on Earth take place on this planet?
o Vast Universe!
One step at a time: We can make a significant advance in the 1st part of the
question (“if we find identical planets”) already!
We should be able to find such planet(s) in near future.
Vast Universe
Hubble Ultra Deep Field: in a very small region of the sky (similar to the
angular extent of a penny placed at the end of a football field), ~10,000
galaxies were found.
Vast Universe : Hubble Ultra Deep Field
In the Universe, there are about 100 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)
Currently, it does not include all kinds 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?
Astrobiology
•Astrobiology is …
• More than a 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!
Search for Life as a science
What is Science ?
Characteristics of Science
1. Seek explanations for observations
2. Create/test models to explain observations
3. Testable predictions
scientific observations  should be verifiable by a 3rd person.
counter-example: UFO sightings
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” = a true explanation of a given phenomenon should make as
few assumptions as possible.
All science models should be in the simplest form!
Pseudo-Science (“false” science)
Pseudo-science : handling the nature appearing as a true science, but it involves a nonscientific 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.
Pseudo-Science
Astrology : a relationship between astronomical phenomena and events in the
human world.
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.
It’s quite natural for you to wonder…
?Why should the price be so low?
?Does the car run?
?Has it been wrecked and poorly rebuilt?
$3,000
Ask your friend
Take a test drive
Get examined by a mechanic you trust
Or all of the above
being scientific : skeptical and looking for
greater confidence in drawing a conclusion.
Being “Scientific” is relative!
• 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 and
there is no way to confirm it or
deny.
Then, the claim by Ernst Chladni
received a spectacular
confirmation by a prominent
meteor 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!
Astrobiolgy
Astrobiology is the scientific study of life in the
Universe!
The origin, evolution, distribution, and future of life in the Universe
Verifiable!!
In summary…
Important Concepts
Important Terms
• Universality of Natural Laws
• Astrobiology
• Astrobiology as science
• Occum’s razor
• Scientific or non-scientific?
• Pseudo-science
Chapter/sections covered in this lecture : sections 1.1, 1.2, 1.4, 2.1, 2.3