106 DECEMBER 2019|COMPUTER SHOPPER|ISSUE 382
THE ARGUMENTSTHE ARGUMENTS
Churchill’s conclusionto that age old
question soundsaconvincing
argument. “With hundredsof
thousandsof nebulae,each containing
thousandsof millionsof suns, the odds
are enormous that there must be
immense numbers which possess
planets whose circumstances would
not render lifeimpossible,” he said, a
sentiment that has beenoft repeated.
However,making such an
assumption raises another question.
In 1950, physicist EnricoFermi asked a
group of other eminent scientists,
“Don’t youever wonder where
everybody is?”.The question, now
generally referred to as the Fermi
Paradox, can be expressed like this.
If the numbers suggest the galaxy
ought to be teeming with intelligent
lifeand, even at the speedof our
present-dayspace vehicles, it would
take only five millionto 500 million
years forany one of them to colonise
the galaxy–ashort period in
cosmological time frames–why is
there noevidence fortheir existence?
The somewhat qualitative
assertion–that with so many
potentially habitable planets, there
must by countless extraterrestrial
civilisations–was brought under
more mathematical scrutinyby
Frank Drake,just 11 years after
Fermi raised his thought-
provoking question. The
equation that bears his name
is the one shown above.
Drake’s aim was profound: to
provideamethod by which the
numberof intelligent civilisations in
the galaxy could be calculated. What’s
more,hes ucceeded. It’s not hardto see
that the equation is surely correct; after
all, it seemsto be common sense.
If only things were that simple.For
while the equation is undoubtedly
correct, give or take the odd slight
amendment here and there,assigning
values to its variables is considerably
trickier.For example,estimatesforthe
fractionof habitable planets on which
lifecomes intobeing havevaried from
virtually zero–which would imply that
the Earth is about the only planet
where it’sever happened–too ne,
suggesting it’sacertainty.His results
would have beenvastly more diverse
had he thought that this fraction
could be anything other than one,
but by plugging in his best guessesto
the othervariables, Drake concluded
that the galaxy contains anywhere
between 1,000 and 100 million
communicative civilisations.
We’re really no closerto coming up
with adefinitive figuretoday, and two
recent studies bring this intosharp
focus. Astudy by Anders Sandberg,
Eric Drexler andToby Ord of the Future
of Humanity InstituteatO xford
University has takenafresh look at the
Drake equation. Theyconsider that the
difficulty in drawing any meaningful
conclusions is dueto the uncertainties
in somevariables that span multiple
orders of magnitude.When theyuse
realistic distributionsof uncertaintyfor
the variables, theyconclude that
there’s asubstantial probability that
there’s no other intelligent lifeino ur
observable universe.
AstrophysicistAdam Frank at the
Universityof Rochester has also looked
at the Drake equation, but takes a
different view.Using data on the recent
discoveryof exoplanets–planets
orbiting other stars–hec oncludes
that, “As long as the probability that a
habitable zone planet develops a
technological species is larger
than about 10−24,humanity is not
the only timetechnological
intelligence hasevolved.”
Effectively,therefore,he’s
saying that if the chanceof
intelligent lifeappearing on a
habitable planet is greater than
the probabilityof you being hit
by lightning twice inayear,
then intelligent lifewill have
materialised elsewhere.
However,Frank has also been
thinking about the ‘L’term in the
⬆The Drake
equation has
allowed scientists
to calculate
the number
of intelligent,
communicative
civilisations in
our galaxy
⬇Given thevast
numberof stars in
the galaxy,many
experts maintain
that it’s barely
conceivable that
we could be alone
Illustration: Danielle
Futselaar,courtesy SETI Institute
Image: NASA and
STScI
