2. A being should have…
• An interaction to the environment
• To take in nutrients and energy from the
environment
• The ability to reproduce
• The ability to evolve to keep its competitive
edge
3. Life in Earth
• The building blocks (amino acids) are
cosmically common. The “miracle” of Nuclei
acids (DNA and RNA) with the right message
evidently occurred on Earth almost
“immediately”
• Although intelligence offers some evolutionary
advantage, there has NOT been any steady
march towards bigger brains. Humans may be
a lucky evolutionary accident.
8. STELLAR
EVOLUTION
Stars get brighter as they
age along the main
sequence. This results in an
outward migration of the
“habitable zone”. The
continuously habitable
zone--the region where
liquid water is always
stable—probably only
includes 1 planet.
10. The rate of star formation: 10 stars per
year (dividing population of Milky Way
by its present age) Fraction of stars
having planetary systems: Most
planetary systems like our own have not
been detected yet, but we would expect
to be able to detect those using current
methods such as Kepler Telescope.
11. PLANETARY
Some stars have
planetary systems
revolving around them.
One example is our
very own, Solar
System. If earth, one
of the planets revolving
the sun could host life,
who knows what the
other stars have in
them.
12. CHEMICAL
There are 92 chemical
elements allowed by
the laws of physics in
this Universe. There is
only one which is
capable of making
complex molecules –
carbon.
13. Life is Carbon-based.
• We see no way that any conceivable life
could be based on any other chemistry
than carbon.
• Finding life elsewhere means finding
environments where carbon can
assemble complex molecules – organic
molecules.
• Life as we know it, carbon-based
molecules originated in liquid water. That
is why scientists are eager to find flowing
water on nearby planets, the best
example: MARS.
• These molecules occur naturally
throughout interstellar space. The
organic molecules needed for life to
originate were probably brought to the
young Earth by comets or meteorites.
14. Possible life in Mars and Europa
• Besides Earth, only two worlds in our solar system—the
planet Mars and Jupiter’s satellite Europa—may have had the
right conditions for the origin of life. Mars once had liquid
water on its surface, though it has none today. Life may have
originated on Mars during the liquid water era.
• Europa appears to have extensive liquid water beneath its icy
surface. Future missions may search for the presence of life
there.
• Recently, we have discovered that life without the sun is
possible. Instead of photosynthesis, organisms have been
discovered living in a variety of places via chemosynthesis -
the use of chemical energy.
16. CULTURAL
As life adapts to its
environment, it
changes its own
features. This comes
the Lamarckian
Evolution and
Darwin’s Theory of
Evolution.
17. Maybe Our Earth is More Rare
and Special Than we Thought
• One astronomer calculates that if Jupiter
weren’t there, we’d have ~10,000 times higher
rate of comet impacts to the Earth.
• Moon needed to stabilize rotation axis and
therefore climate. We’re the only inner planet
with a real moon, and it took an extraordinary
collision to make it.
18. THE DRAKE
EQUATION
N=R* fp n fL fI fc L
• R* = rate of formation of
suitable stars
• fp = fraction of these with solar
systems
• n = number of life-suitable
planets per solar system
• fL = fraction of these planets
with life
• fI = fraction of living planets
with intelligent life
• fc = fraction of intelligent living
planets which choose to
communicate across the stars
• L = average lifetime of a
communicating civilization
Can be used to
estimate the total
number of intelligent
civilizations in our
Galaxy, although a
number of its factors
are extremely
uncertain.
19. WHAT CAN THEY DO TO
CONTACT US?
• EM waves such as radio are “easy” for
the persistent (Arecibo can now
communicate with a copy of itself on
other side of the Milky Way Galaxy!)
• Water hole - is a good place both to
broadcast and to seek messages.
20. But are we sure we want to be contacted? Are
you SURE that all advanced ETs are really “nice”
and enlightened?
Galactic Species could be:
• Uninterested
• Maybe they’re too far away to have received the
RECENT ‘news’ of our development of technology
• They’re already here, but incompetent or “messing with
us”?
• No–UFO’s internally inconsistent
• They are STRICTLY QUARANTINING us
21. BUT…
Until proven otherwise, this may be the only
place in the entire Universe where
consciousness has developed. We certainly
can’t count on a bunch of super/enlightened
beings to swoop down and ‘save’ us just at the
brink of some calamity, cures cancer, etc—even
if ‘they’ are watching, WE’RE ON OUR OWN.
