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ZL2VAL > SETI 19.12.03 14:37l 79 Lines 3822 Bytes #999 (0) @ WW
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Subj: Arecibo Diary #6
Path: DB0FHN<DB0FOR<DB0SIF<DB0CWS<DB0ZDF<DB0LJ<DB0RES<ON0AR<VK6HGR<VK7HDM<
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Sent: 031219/1213Z @:ZL2BAU.#73.NZL.OC #:13937 [BleBy Seth Shostak
Senior Astronomer
posted: 07:00 am ET
18 December 2003
I was doing my best to stay awake while the Arecibo shuttle nosed its
way into the dark, bumpy hills south of the city. My driver was silent,
intent on dodging the homeless dogs and feral cats that line the road.
Eventually, the night sky was broken by the red lights of the telescope
towers, poking above the rump of a hill.
I stepped out of the van into a wall of humid air. Below me, barely
discernable amid the shadowy vegetation, hulked the telescope dish.
Here, 18 acres of aluminum mesh sprawl across the landscape, silently
collecting radio noise from the distant depths of the universe. This is
the big one, the alpha male of telescopes; the largest single antenna on
the planet.
Large, however, is a relative term. If Earth were squeezed and shrunk to
fit onto a football field, Arecibo?s mammoth reflector would be a
pinhead stuck onto its surface. And if the solar system were scaled so
that Pluto?s orbit was within that field, Earth itself would be less
than a pinhead.
Face it. As big as this telescope is, it only intercepts a minute
fraction of the radio waves that pound through the dark spaces of the
Galaxy. Fortunately, it?s got first-rate electronics. If as much as
0.00000000000000000001 watts of radio energy wafts onto the dish, our
receivers light up.
What does this mean for SETI? What sort of transmitting setup could this
instrument detect?
Imagine an alien civilization a thousand light-years away. Imagine
further that these cosmopolitan beings have constructed a clear-channel
radio station that broadcasts in all directions equally. Their signal
blankets the universe. Some of that signal could fall onto Arecibo?s
1,000-foot reflector. If so, it would be detectable only if the
transmitter power exceeds? 100 trillion watts!
That?s a lot of power. In fact, that?s ten times more power than the
total energy consumption of modern Homo sapiens. Ten times the energy
use of six billion gas-guzzling, kilowatt-consuming souls.
Of course, the aliens might just have that kind of power at their
disposal; it?s not inconceivable. However, Barney Oliver, one of the
brightest minds ever to consider the premises of SETI, was skeptical of
whether even sophisticated extraterrestrials could ever engineer such
high-powered radio sets. His concise pronouncement on this possibility
was to note that "waveguides melt." Maybe the aliens can muster the
energy, but don?t build such beefy transmitters because their hardware
can?t handle the juice.
Fortunately for both waveguide fabricators and SETI practitioners,
knowledge is power. Or rather, knowledge can be traded for power. Aliens
with good astronomy departments and a yen to get in touch willsmitters
would only need about 1 watt of power to be detectable by Arecibo.
That?s approximately the power of a flashlight.
It takes about 20 minutes to walk around the telescope?s perimeter,
sufficient time to be impressed with its dimensions. There?s a slight
drizzle in the air, wetting the path and coating my face. I stop to
squint at the perforated aluminum panels of the reflector and wonder if
right now, a pinging beacon from some distant society is falling unseen
on that broad metal expanse. A calling card sent our way in the hope
that this star may have an interesting world. The numbers, at least, are
favorable.
==============================
73 de Alan
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Points to ponder
~~~~~~~~~~~~~~~~
A conscience is what hurts when all of your other parts feel good.
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