Who’s Out There—Revisiting the Drake Equation5 min read

Frank Drake wrote his famous equation in 1961 while planning an early
SETI meeting. He came up with a list of probabilities to predict the
chance of finding extraterrestrial life advanced sufficiently to be
using radio signals. The result (N) is the number of civilizations in
our Milky Way galaxy capable of communication by radio, N = R* . fp .
ne .fl . fi . fc . L, described below.


The value of N has risen due to the Kepler findings of so many planets
orbiting so many stars in our galaxy. Kepler’s data includes 4175
“planet candidates,” about 800 of them the size of Earth, probably at
least 13 in zones capable of retaining liquid water, orbiting suns old
enough to have given life a chance to start.

However, several other parameters in the equation have estimates that
cover the full range from 0 to 1. Others are simply guesses, based on
various assumptions. That’s why the usefulness of the Drake Equation is
its role in keeping our speculation realistic. It’s a tool for thinking
about just who we are and how precious the living Earth is within this
huge universe.

Proposals have been made to include in the Drake Equation parameters for
the effects of cross-planet colonization, the reappearance of advanced
civilizations or new life on individual planets, and a measure of alien
paranoia. Would these ideas impact N? Not much. The number of
radio-users in the galaxy might get a boost, but nothing like the boost
it would get if current missions were to find evidence of life in
planetary atmospheres or geysers from sub ice oceans.

Two recent findings also boost hopes for life, parameter N. 1) Bacteria
in clouds above Earth gobble up carbohydrates there to make protective
polysaccharide coatings and 2) M dwarf stars, the most common types in
our galaxy, have narrow habitable zones, but recent findings suggest
that “heat in a planet’s atmosphere may prevent tidal locking,” giving
life a better chance. See Science News Frb.7, 2015.

Wikipedia lists the latest values of the Drake parameters for our
R*, the average rate of star formation in out galaxy is about seven per
fp, the fraction of those stars that have planets, is close or equals
one now, since we have recently found one or more planets orbiting the
most life-friendly red dwarf or sun-like stars. Based on Kepler data,
there could be 40 billion Earth-sized planets in habitable zones out
there somewhere in this galaxy.

The parameter ne, the average number of those planets that could
support life, is reduced to near zero when considering the Rare Earth
Hypothesis. A habitable planet needs the existence of heavy elements but
some distance from supernovae. They also eed an orbit the right distance
from a long-lived star. By including the possibility of habitats near a
larger variety of stars and on the moons of gas giants, fpne could be
raised .

The good news for astrobiology is that fl ,the fraction of habitable
planets that actually develop life, may be about 1, given our sample of
one. Doubt is raised by the current difficulty of re-creating wet
artificial life here on Earth. If life were found elsewhere in our solar
system, we would at least have a sample of 2, including Earth.

Estimates of fi, the fraction of life becoming intelligent enough to
invent radios, range from 0 to 1, depending on one’s viewpoint. The Rare
Earth theory would have us lower the parameter, given the idea that
larger or complex life forms need more time and help from geology,
biology, astronomy and pure luck to escape extinction long enough to
invent radios.

The fraction of those intelligent civilizations that create detectable
radio (or other) signals (fc) is 100%( fc = 1), since “near-future
Earth-level technology” reveals itself. Deliberate communication is not

Carl Sagan believed that L, the expected lifetime of a
technology-savvy civilization, was the most limiting parameter in the
Drake equation, given our capacity for self-destruction. A low value is
also suggested by the fact that only one species out of billions on
Earth have achieved radio technology. On the other hand, if one believes
that complexity eventually results in species that can do radio
technology, then L would have a large value.

Is it surprising that SETI has not heard from anyone in its 50+ years of
searching, even with advancing technology? Claims that life would fill
all available territory are vastly overstated, as are claims that “a
civilization lasting tens of millions of years would have plenty of time
to travel anywhere in the galaxy.” At least we know that there are not
many civilizations nearby “continuously broadcasting near the 21 cm
hydrogen frequency.” (Quotes are from Wikipedia “Drake equation”)

Time and distance play a role in the drama entitled “Are We Alone or
Not, and Why Does It Matter?”. It took life 4.5 billion years for
humans to evolve and develop the radio, so our total life span before
the sun ages into it Red Giant phase will be about 600 to 800 million
years. Given our current technology, it would take 70,000 years to go to
the nearest star, 4.2 AU from Earth. Therefore, it would take more or
less 70,000 years to go anywhere else from there, since ‘anywhere elses’
are on average 5 AU apart.

To “travel anywhere in the galaxy” means visiting any of 100 billion
stars in a disk of thickness of 1000 light years and a diameter of
100,000 light years. That would be one visit in 100 billion possible
visits, as we hopped from one star to another, perusing stars with
habitable planets. It would take 7 x 1014 years to visit them all. More
realistically, it would take 7 x 109 years just to cross the galaxy. But
the entire projected lifetime of Earthlings is probably less that 7 x
108 years.

We humans have trouble realizing just how huge those numbers are. In
reality we are truly alone, for all practical purposes, so we had better
take care of Mother Earth. Philosophically, however, the Drake Equation
asks questions that challenge the deepest levels of our identity and
sense of meaningful existence.

Author of The Archives of Varok
The View Beyond Earth (Book 1. Rewrite of A Place Beyond Man 1975)
The Webs of Varok (Book 2.)
Nautilus silver award 2013 YA
ForeWord finalist 2012 adult SF
The Alien Effect (Book 3.)
An Alien’s Quest–Reconciliation and Hope (Book 4. coming in 2015)
Excerpts, Synopses, Reviews, On Writing, Characters and More-
Other Book Reviews- www.goodreads.com/Cary_Neeper
How the Hen House Turns- www.ladailypost.com
Complexity, Bio, Bibliography and Links- caryneeper.com
Astrobiology- astronaut.wpengine.com search:Who’s Out There[/vc_column_text][/vc_column][/vc_row]


Cary Neeper is an avid student of complexity theory, sustainability, steady-state economics, and the impact of cosmology on issues of science and religion. She grew up in the foothills of Hayward, California, where she helped rack dried fruit on her father’s 40-acre apricot ranch. After studying zoology/chemistry and religion at Pomona College and medical microbiology at the University of Wisconsin, she moved with her husband to northern New Mexico, where they raised their family. The Neepers still live in the Southwest with a friendly menagerie of dogs, fish, chickens, geese, ducks and a turkey called Little Bear. Cary plays string bass with local folk, symphony and jazz groups and tennis with local retired physicists. She paints landscapes in acrylics, including the cover art for her first Penscript title, The Webs of Varok. Cary's first novel and Webs of Varok prequel A Place Beyond Man was originally published in 1975 by Charles Scribner’s Sons, Dell, and Millington, London. Cary re-released A Place Beyond Man as an Author’s Guild Backinprint edition, now available from online booksellers. Its themes of sustainability and interspecies cooperation have now grown into new adventures for its human, elll and varok family as they travel the alternate 21st century Solar System in the five-volume Archives of Varok, coming from Penscript Publishing House in 2012–2014. Cary’s other works include two musical science fiction comedies “U.F.F.D.A.!” and “Petra and the Jay,” as well as newspaper and magazine articles, essays, short stories, and book reviews for The Christian Science Monitor.

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