by Robby Berman
Taking into account what we do know, and mixing in
some assumptions about life on Earth, a team of
scientists have made predictions about alien life.
Even if aliens are relatively close by, they and we
would have to be around for over 6,000 years just to
Our current technology will likely not allow us to
communicate with anyone or thing.
communicating with us...
"The Ultimate Answer
to Life, The Universe and Everything is... 42!"
supercomputer Deep Thought in Douglas Adams'
Hitchhiker's Guide to the Galaxy"
Thus began a grand
experiment involving humans and pan-dimensional, hyper-intelligent
mice designed to figure out more exactly what the question was
As if in tribute to
Douglas Adams, a group of
astronomers this week announced their answer to a Great Question,
and it is 36...
This time, though, we at
least know what the question is:
How many contactable
alien civilizations are there in our galaxy?
"I think it is
extremely important and exciting because for the first time
we really have an estimate for this number of active
intelligent, communicating civilizations that we potentially
could contact and find out there is other life in the
universe - something that has been a question for thousands
of years and is still not answered."
So says astrophysicist
Christopher Conselice of
University of Nottingham.
He's co-author of a
Astrobiological Copernican Weak and Strong Limits for Intelligent
Life) published in the Astrophysical Journal, and
Nottingham and his colleagues are dead serious about the 36 likely
Communicating Extra-Terrestrial Intelligent (CETI: pronounced
Image source: Google
The scientists' calculations are a response to the
In 1961 astronomer
Frank Drake proposed that having knowledge of seven factors
would allow scientists to reasonably estimate the number of
intelligent alien civilizations out there.
The Drake equation is so
named because it's a mathematical formula, shown above.
The seven factors are:
N = number of
civilizations with which humans could communicate
= mean rate of star formation
f = fraction of stars that have planets
ne = mean number of planets that could support life per star
fl = fraction of life-supporting planets that develop life
fi = fraction of planets with life where life develops
fc = fraction of intelligent civilizations that develop
L = mean length of time that civilizations can communicate
Even today, a lot of
these blanks remain unfillable with our current knowledge.
estimates have ranged from zero to a few billion [civilizations]
- it is more like a tool for thinking about questions rather
than something that has actually been solved."
So Conselice and his
colleagues set out to refine the equation based on what we do know,
the one environment we're certain supports life as we know it:
Astrobiological Copernican Principle
The Astrobiological Copernican Principle is based on the
notion that what worked here could work elsewhere.
"Basically, we made
the assumption that intelligent life would form on other
[Earth-like] planets like it has on Earth," Conselice tells
The Guardian, "so within a few
billion years life would automatically form as a natural part of
On the other hand, the
report concludes these planets would be more likely to be orbiting
M dwarf stars than strong stars
like our Sun, and these dwarves are less likely to be
life-supporting over an extended period.
life] in a scientific way, not just a random way or just a very
unique way, then you would expect at least this many
civilizations within our galaxy."
Such alien life might be
more like off-planet "Star Trek" guest stars than, say, squid.
"We wouldn't be
super-shocked by seeing them."
Of course, begins the
"One of the oldest
questions that humans have asked is whether our existence - as
an advanced intelligent species - is unique."
Getting to 36
The study authors operated on the assumption that a planet's life
would have to take form between 4.5 billion and 5.5 billion years
after the creation of its system's star, as it did here.
We've only been producing
radio waves to send out there for 100 years, so that's assumed to be
about the minimum time a civilization would have to be in existence
and broadcasting for us to detect them, but really much longer -
it's not as if we crawled out from the primordial ooze with radios.
More realistically, the authors expect that a CETI population would
have to exist for an average of 3,060 years to be detectable, which
means that if life formed in both places at the same time, we'd both
need to be in existence for 6,120 years (beyond that minimal 100
years) for a single,
"Hi, we're from
Earth," "Hi, we're not" exchange to occur.
The report is, understandably, mostly being met with a shrug,
at least according to three experts who checked in with The
"[The new estimate]
is an interesting result, but one which it will be impossible to
test using current techniques," says Andrew Coates of the
Mullard Space Science Laboratory at University College London,
though he agrees that the report's assumptions were reasonable.
Sanchez-Baracaldo of University of Bristol notes just how many
things have to go right for life to happen as it has here,
suggesting that this additional what-if that makes accurate
estimates even more difficult.
Oliver Shorttle of
the University of Cambridge cited the significant unanswered
questions we would need to know the answers to in order to really
hazard an irrefutably plausible estimate of CETI civilizations.
But we do have one answer, at least:
Sorry, two. Let's not
Update, or What
Smart People Do for Fun:
Steven Wooding of
U.K.'s Institute of Physics sent us the link to an
online alien civilization calculator
that he and his friend, molecular physicist Dominik Czernia,
It works with both of
the models mentioned in this article to deduce the likely number
of contactable civilizations given a set of variables. Enjoy!