| Are
we Alone in the Universe? --- SETI and Drake’s Equation
Yun
Hwang
Ever recalled watching ET: The Extra-Terrestrial? I certainly
do. At that point of time, I walked away with two thoughts
– one: the girl I was sitting next to in the movie did
not really like me, and two: I really wanted a friend
like ET. Although the thought of a friend with mystical
powers is nice, it was the idea of living on a giant spaceship
and sailing among the stars that captivated me. As I turn
my eyes toward the night sky, I can not help but wonder
if there is really someone out there cruising through
the galaxies.
Many
people have claimed to see Unidentified Flying Objects
(UFOs) soar the skies, but who know whether its a photographic
trick or whether if there is really something out there.
With the developments
of science and our interest in space, the thought of not
being alone is growing in our consciousness. Like any
controversial issue, the existence of life beyond Earth
is supported by many believers and disapproved by many
unbelievers. “Are we alone in the Universe?” The answer
to this fundamental question will inevitably impact human
existence. The existence of an extraterrestrial culture
more advanced than ours, whether benign or hostile, would
confront our curiosity and pose difficult challenges.
Even if the answer to the question is ‘yes, we are alone,’
that will indicate how precious life, sentience and intelligence
are, and that there will be a desperate need to foster,
develop, protect and preserve the unique environment of
the Earth.
Currently,
it is not known whether ETs are out there and the issue
revolving around the existence of ETs cannot be resolved
by argument alone. Thus in the 1950s’, a long-term multinational
project called ‘Search for Extra-Terrestrial Intelligence’
(SETI) began. SETI started its quest by directing a radiotelescope
toward the sky and listening for any signals that could
have been emitted by another intelligent culture. This
search was based on a number of key assumptions: that
ETs are close enough for their emissions to be detected
on our radiotelescopes and that their emissions would
be along the same frequency as ours.
Until now,
except for an unidentified signal that was heard once
and only once, there have been no other detections that
might be emissions by ETs. Skeptics of the program exploited
the opportunity to claim this lack of evidence as proof
that ETs do not exist. Others who are more optimistic
have suggested that the ETs in our neighbourhood of the
universe are just a very quiet bunch. Researchers have
found that these optimists may not be far from the truth.
Over the last 50 years, the level of radio emission escaping
the Earth’s atmosphere has decreased significantly as
the efficiency of telecommunications, radar, and the like
increase; likewise this could be an indication that the
ETs may very well have reduced their radiowave emissions.
While there
is no concrete argument for the existence of ET, and postulations
are based on zero evidence, scientists are at their wits’
end when it comes to formulas and equations. In 1961,
Dr Frank Drake formulated an equation (that is presently
named in his honour – Drake’s Equation) to limit the maximum
number of technological civilizations in our galaxy. Believe
it or not, even the skeptics accept the equation as a
valid method of estimating the number of ET civilizations
that are potentially out there.
So, what exactly
is this equation that has brought all the dissenting opinions
together? It is presented as:
N
= R* • fp • ne • fl • fi • fc • L
Where each
variable represents an estimate based on the best available
scientific knowledge, as follows:
N
= The number of civilizations in The Milky Way
Galaxy whose electromagnetic
emissions are detectable. So if there are any ETs, we
may be able to get in touch.
R*
= The rate of formation of stars suitable for
the development of intelligent life.
fp
= The fraction of those stars with planetary
systems.
ne
= The number of planets, per solar system, with
an environment suitable for life.
fl
= The fraction of suitable planets on which life
actually appears.
fi
= The fraction of life bearing planets on which
intelligent life emerges.
fc
= The fraction of civilizations that had developed
a technology that releases detectable signs of their existence
into space.
L
= The length of time such civilizations release
detectable signals into space.
Although this
equation has been the means of bringing people on both
sides of the divide together, it has initiated hotly contested
arguments on the values of each variable in the equation.
For instance, some people argue that the values of fl,
fi and fc are whatever it takes to make N = 1, then that
will make humans the only intelligent life releasing detectable
signs of our existence into space. With respect to the
other values, they are difficult to estimate, considering
that scientists do not yet have an appropriate model of
our vast universe and its planets to carry out experiments
and investigations on. As a result, the values are merely
speculations, hence accounting for the wide range in estimates
of each value.
To refer to
this as an issue that will not be resolved easily is an
understatement. The Milky Way Galaxy is vast, and Drake’s
Equation only illuminates key factors that are involved.
The answer to the fundamental questions will remain unanswered
until the aliens come knocking on our doors, or until
humans develop their technology to scan in a thorough
way a fairly large fraction of the Milky Way Galaxy and
beyond. The latter is unexpected in the near future, and
the former is seemingly not probable at all. So for now,
we will continue to ponder … to wait … to listen in silence,
looking for any potentially meaningful noise that penetrates
our surroundings.
Then again,
who knows? ET might arrive on our doorstep tomorrow and
give us the answer.
Further
Reading:
www.seti.org
http://www.setileague.org/
http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html
http://en.wikipedia.org/wiki/Drake_equation
http://www.homoexcelsior.com/omega.db/datum/extraterrestrial_life/
drake's_equation/8525
http://www.jb.man.ac.uk/research/seti/drake.html
http://www.the-ba.net/the-ba/ResourcesforLearning/BACRESTAwards/ProjectIdeas/Space/
IsAnybodyOutThere/Drakesequation.htm
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