110 DECEMBER 2019|COMPUTER SHOPPER|ISSUE 382
tasks at lightning speed
with the potentialfor
massive parallelism.
ALTERNATIVEALTERNATIVE
APPROACHESAPPROACHES
Here we’ve concentrated on
listeningforradio signals.
While this approach might
accountfor90% of the
effort being put intoSETI,
though, it’s not the only
wayoft rying to find little
green beings.
One other method is
referred to as optical SETI,
and it takes, as its
assumption, that
extraterrestrials might
chooseto use laser beams
insteadof radio signals in
their attemptto attract
the attentionof other
civilisations in the galaxy.
Now,ofc ourse,we’re
intothe realmof image
processing. But perhaps the
method that has most been
in the news recently is one
of lookingforalien art efacts.
One such approach,forexample,
assumes that advanced civilisations
might solve their energy problemsby
building huge solar arrays in orbit
around their closest star.This would
manifest itself in theform of unnatural
changes in the brightnessof that star.
If some conspiracy theorists are
correct, we don’t haveto go looking
forartefacts because they’ve already
come to us and are under lock and key
at Area 51, but that’s another story.
Our emphasis here has been the
technologyof SETI. However,we’ll give
the final wordto Dr Shostak, whotold
us about someof the most common
questions he’s asked. There are no
answers, but at least these questions
might give you somefood forthought.
Promptedby the conspiracy theories,
‘What happens if the signal is picked
up?’ is oneoft-asked question. ‘Would
the publiceven learn about it or would
the government keep it quiet?’ is
another popular one.
Needlessto say, alot of the
questions come closerto home,as
Shostak illustrated with the next
question. ‘How is it goingto affect
me? I’m selling fish here inSwindon,
is it goingto affect my lifeina ny
significant way?’
But the last one he mentioned is
perhaps the most profound. ‘If we
pick upasignal, should we respond
by saying, “Heywe’re the Earthlings,
we’d love youto buy our used cars”,
or is thatabad idea?’
THE WATER HOLE
Although the SETI Institutelooks at huge
numbersof channels in its searchfor
extraterrestrial intelligence,traditionally,
SETI researchers havetended to concentrate
theirefforts onavery specific bandof
frequenciesforawell-argued reason.
First of all, agraphof absorption against
frequency across the electromagnetic
spectrum shows two main windows through
which radiation could reach the Earth. All other
frequencies are blocked dueto arange of
natural phenomena. Oneof these windows
correspondsto the visible spectrum, and the
other is in the microwave region, otherwise known as partsof the
UHF and SHF radio spectrum. Therefore,these are the two regions
used in optical and radio astronomical observations respectively,
and theyare also the only sensible contendersforSETI.
Although the microwave region isawindow of transparency
through the atmosphere,itc ontainsacouple of signals that would
cause interferenceto observations. These are causedby natural
effects involving the hydrogen atom at about 1.4204GHz and the
hydroxyl radical at 1.66GHz.
It has been argued that any advanced civilisations attempting
to make contact with other worlds would be awareof the signals
at these two frequencies, and that theywould also recognise
them as being causedby the disassociation productsof water ,the
substance that’s essentialto lifeasweknow it. It is speculated,
therefore,that extraterrestrial civilisations would be drawnto
transmitting in the ‘water hole’, the clear frequencies between
those two natural signals, in their attemptto communicatewith
their neighbours in the galaxy.
⬆Byu sing esoteric
custom hardware,
data from the Allen
Telescope Array
can be processed
in real time using
anetworkof
standard PCs
Photo: Seth Shostak/SETI Institute
⬆Most of the electromagnetic spectrum is shielded from the Earth, but the so-called water hole is
where extraterrestrials might tryto contact their galactic neighbours
