It's estimated that there are 50-200 BILLION planets like Earth just within our Milky Way galaxy.
The motto of ATS is "Deny Ignorance". In that spirit I thought It might be a good idea to post an ignorance-killing post surrounding a subject which
often is brought up but often misunderstood: The Search for Extraterrestrial Intelligence aka SETI.
Most people are familiar with SETI from various TV shows and movies. Usually what is portrayed is that of a specific branch of SETI: Radio SETI
This is for good reason, Radio SETI is the oldest and until fairly recently, most widespread form of SETI. The first SETI experiments were conducted
back in the 1960s, most notably Project Ozma a 1960 SETI experiment
astronomer Frank Drake who examined the nearby Sunlike stars Tau Ceti and Epsilon Eridani for artificial radio signals.
These experiments were not very sensitive (they would not have even detected our most powerful military radars beyond a few light years) nor did they
cover much in terms of frequency space (they were kind of like listening to one channel on a radio at a time), nor did they cover the entire sky.
Nevertheless they were important experiments because they helped define challenges (such as eliminating false positives in the form of terrestrial and
orbital radio frequency interference). And early experience gave way to more sophisticated ones which lead to the development of more sensitive
equipment, receivers which first covered thousands, then millions then billions of channels simultaneously, and both targeted searches (such as the
first experiment Frank Drake conducted) as well as all-sky searches (such as the one at the now defunct "Big Ear" radio telescope which detected the
"Wow!" signal and the current SETI experiment at the Arecibo radio telescope which feeds SETI@Home).
Radio SETI turns 55 as of this year and like astronomer and "grandfather of SETI", Frank Drake (pictured above), is a well seasoned,
Mainstream media often reports that SETI has been searching the skies for over 50 years without detecting anything in the way of radio signals from
extraterrestrial civilizations. Unfortunately such stories usually fail to mention the enormity of the task and just how little of the sky and
frequency space has been covered:
As you can see from the above chart of various SETI experiments, Radio SETI over the last 55 years has not covered much in the way of frequency space
nor has it examined the entire sky at high sensitivity.
So Radio SETI has a long way to go before anyone could say it's a waste of time in terms of covering every frequency and every part of sky at high
It should also be noted that most of the experiments on the chart above were short in duration, lasting weeks, months or a few years. It is not as
though Radio SETI has been looking for signals around the clock 24/7 year after year. There were huge month and year-long gaps between observing
Additionally we've only just begun doing SETI at the lower frequencies similar to what we use for radio and TV. Until now most SETI experiments
operated in the microwave (above 1 Ghz) range. While most of our own radio leakage operates at lower frequencies.
massive, muilti-country, long frequency radio telescope array in Europe:
The Low Frequency Array feeds data to UC Berkeley's SETI@Home
Jocelyn Bell - Discoverer of the first 4 known pulsars (two of which were briefly labelled LGM-1 &LGM-2 for "Little Green Men") with one of
the elements of the LOFAR array which conducts SETI
experiments at frequencies similar to what we use for radio and TV. LOFAR is a precursor to the Square Kilometer Array
"But it's still radio duh....."
A more common criticism of Radio SETI has to do with the use of the word "radio". Most people hear radio and think of the thing in their car or the
thing their parents used to listen to before the ubiquity of MP3 players, Pandora, and other streaming services.
It seems almost antiquated and counterintuitive in this day and age we'd be looking for advanced alien civilizations with something as old-fashioned
as radio. After all, our own use of radio is vastly different today than it was in 1960s.
Unfortunately most people do not know that plenty of our technology today STILL uses radio, not just for communication either. Many of the same people
also assume Radio SETI is looking for some form of communication when in reality all Radio SETI is looking to detect initially is a narrowband signal
less than 1Hz wide. Such signals are not produced by nature but plenty of our technology produces them.
In fact Earth's most powerful radio signals are not for communication at all. They're not beaming entertainment and information in audio or video form
(in the case of Broadcast TV).
Nope, our most powerful radio transmitter is the Arecibo Planetary Radar in Puerto Rico which is used to take radar images of near earth asteroids,
especially ones which make close approaches.
Radar delay-Doppler images of asteroid 2014 HQ124 taken with the Arecibo planetary radar. The Arecibo Planetary Radar transmits up to 1
MegaWatt (1 MW) of power with an antenna gain of about 73.3 dB at 12.6 cm wavelength, resulting in an equivalent isotropically radiated power (EIRP)
of roughly 20 TeraWatts (20,000,000,000,000 watts or 20,000,000 MW). Most commercial TV and radio stations have EIRPs far less (100,000-1,000,000
watts or 0.1-1.0 MW)
An extraterrestrial version of Arecibo with the same sensitivity as modern SETI receivers could detect Arecibo's planetary radar at a distance of
5,000 light years (ly).
An extraterrestrial version of our Square Kilometer Array (SKA), which is due to see first light in 2024 would be able to detect Arecibo's planetary
radar at a distance of 40,000 ly
- almost half the diameter of our Milky Way
galaxy. The SKA in it's first building phase would also be able to detect an alien
equivalent of our airport radars at a distance of 60 ly.
Radar is just one use of radio an advanced civilization might still use because of its ease and usefulness in detecting and imaging objects in the
cold darkness of space. Other uses might include beaming power to space colonies using microwaves from off world solar power collectors or even using
such collectors to propel a starship (See: Starwisp).
As you can see, far from being a "Silly Effort To Investigate" as one UFO proponent often proclaims it, Radio SETI could still be valid in terms of
detecting advanced civilizations who long ago stopped using it for communication.
"Enough about radio, what about other wavelengths?"
I thought you'd never ask....
edit on 14-4-2015 by JadeStar because: (no reason given)