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Extra-Terrestrial Intelligence

Frank Drake In order to communicate with the other worlds, it requires that both sides should be highly evolved to an advanced technological stage. In 1961, Frank Drake (Figure 09-19a), now President of the SETI (Search for Extra-Terrestrial Intelligence) Institute, proposed a formula for estimating the existence of communicating Intelligent Life elsewhere in our galaxy. This is known as The Drake Equation, which states that

N = R x Fp x Ne x Fl x Fi x Fc x L


Figure 09-19a Frank Drake
[view large image]

N = The number of communicating civilizations in the Milky Way
R = The rate of star formation in the Milky Way ~ 6x5/year = 30/year, taking account for higher rate 5 billion years ago.
      2010 Update : The new number is about 10 including some M stars and excluding higher rate of formation.
Fp = Fraction of such stars with planets ~ 0.1, according to the latest search for extraterrestrial planets.
      2010 Update : Recent observations infer that about 90% of all stars have plants.
Ne = Number of habitable planets ~ 0.2, estimated from warm dust around stars.
      2010 Update : It is at least 4 with the new evidence of water on Mars, Europa, and Enceladus.
Fl = Fraction of hospitable planets that have life ~ 3/8, including Earth, Mars, and Jupiter (Europa) among the eight planets.
      2010 Update : The original number of 1 (by Drake in 1961) has been solidified in the intervening years.
Fi = Fraction of arisen life where intelligence develops ~ 1/3, as intelligence life only exists on Earth among these 3 planets.
      2010 Update : The original number of 1 (by Drake in 1961) is preserved by recent investigation.
Fc = Faction of intelligent life that develops communications technology ~ 1.0, by observing our own technology development.
      2010 Update : Drake and others now favor 1 instead of 0.1 estimated previously.
L = The 'lifetime' of such intelligent life ~ 100 years, as we have been broadcasting for around a century.
      2010 Update : This number is the most uncertain term in the Drake Equation. No new estimate is given.

By substituting these numbers into the Drake equation, we obtain a value of N 8 ( 400 according to updated data) civilizations within the
ET Drake Parameters Drake Diagram Milky Way that are currently broadcasting detectable signals. These chosen numbers are the lower limits and worse case scenarios. For example, a techno-logical civilization could last for 1000 years or more, dramatically increasing the value of N. Figure 09-19b depicts the parameters of the Drake equation in a pictorial form. The diagram in Figure 09-19c illustrates the stringent requirements in limiting the number of communicating civilization into a small fraction of the number of stars in the Milky Way.

Figure 09-19b Drake Parameters
[view large image]

Figure 09-19c Drake Diagram [large image]

The 2010 updates yield N 3600. Such number actually involves a lot of uncertainty. But as someone points out: "The Drake Equation's biggest contribution is in framing the discussion rather than providing an absolute answer"

Since the dawn of history, sentient beings have been pondering if there is anybody out there (Figure 09-19f). The search has become more sophisticated by the 21th century. SETI currently uses the multichannel spectral analyzer to scan the sky for radio signal from the "advanced civilization". It also runs a project, which uses programs executing as screensavers on millions of personal computers worldwide to sift through signals picked up by the Arecibo radio telescope. The search is now supplemented by the Allen Telescope Array in Northern California. The array will eventually consist of 350 dishes (by 2011), each 6 meters in diameter, which can be used to listen for signals from several stars in many different radio bands simultaneously. Meanwhile, a privately funded (by the Planetary Society) 180 cm telescope has been installed at the Oak Ridge Observatory to look for flashes of laser beacons from alien civilizations. The instrument will record flashes briefer than a nanosecond because no known natural process would produce such flashes.

Allen Telescope Array The Allen telescope array (Figure 09-19d) began operations in 2007 with just 42 antennas (out of the proposed 350 dishes). It fell victim to the budget cut in 2008. The project managed to limp along for a few years until 22 April 2011 when the SETI Institute and the University of California (at Berkeley) were forced to terminate funding of the $2.5 million annual operating costs. In spite of public misunderstanding about the usefulness of searching for ET, smaller and cheaper SETI searches are still running around the world. Some are seeking alien radio beacons, others are looking for the flicker of interstellar communication lasers.

Figure 09-19d Allen Telescope Array [view large image]

There are projects looking at specific stars that seem likely to host Earth-like planets; others are doing a less sensitive but broader scan of the entire sky in the hope of catching signals of a type not yet conceived.
Figure 09-19e shows the various small scale SETI projects with annual operating cost and Funding agent.

Small Scale SETI Projects Thanks to the 2300 individual donations (including contribution from Jodie Foster of the 1997 movie Contact) for a total of $206,000 in early August 2011, the Allen Telescope Array may be able to hang on to its dear life if the USAF accepts the offer of using the facility to track space debris around the Earth. This is just one facet to reveal a once great power in decline. Other scientific projects such as the JWST (replacement for the HST) are also in danger of cancellation. The "debt ceiling" debacle threatens more cuts in funding things of science.

Figure 09-19e Small Scale SETI Projects

ET Search In the summer of 2004, a flurry of reports in the media indicate that radio signals (at 1420 megahertz = the hyperfine transition frequency of the hydrogen atom) have been detected three times from a point between the constellations Pisces and Aries. The transmission is very weak and shifting rapidly in frequency. It is pointed out that such drifting of frequency is too rapid to be produced by the rotation of planet and three occasions of detection is not statistically significant. The signals could be generated by a previously unknown astronomical phenomenon, or it could be something much more mundane, maybe an artefact of the telescope itself.

Figure 09-19f Search for ET
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    Followings are some suggestions related to the puzzle of "where are they?"

  1. It could be that primitive life may be common in the universe, but intelligent life is exceeding rare. We may be the very few that have advanced to a state where travelling in space is a possibility.
  2. Another theory suggests that many plantets harbouring technologically advanced extraterrestrials exist, but space travel has fundamental limitations or inhereent dangers that we have not yet experienced. In this case, everybody is staying near home.
  3. An alternate explanation about advanced extraterrestrials claims that they don't want to interfere with our development or they just don't have interest in us.
  4. The absence of radio contact may be related to the fact that artificial signals are inherently weak. It is very difficult to detect. If we have ever received anomalous signal from outer space, we still have to uncover the nature of its origin.
Strange Signal There are ten strange signals detected from 2001 to 2014 by the Parkes radio telescope in Australia as reported in a "2015 New Scientist article". The signals are in the form of short duration radio wave lasting for a few milliseconds but with a rather large bandwidth. Components with different wavelength in these radio bursts are spatially separated as they travel through the interstellar medium. The dispersion in wavelength is found to be in an integer multiplication of 187.5 for all the ten measurements (see Figure 09-23a). This is the opposite of ET signaling criterion as shown in Figure 09-20. Nevertheless, these curious signals have generated considerable interests. The short time duration implies that the source cannot be larger then hundreds of kilometers; and the energy output could be enormous depending on the distance of the source from Earth. It could be a new kind of astronomical object, or may involve a new kind of physics, or originated from an unknown human technology. Failing with such kind of explanations, the source could ultimately be

Figure 09-23a Strange Signals [view large image]

attributed to Extra-Terrestrial Intelligence. According to the Optical Dispersion formula, these data points are the manifestions of either the spread of wavelength or variation of optical path length in integer steps.
BTW, The numerals associated with the data points in Figure 09-23a are in the format yymmdd.

News in May 09, 2015 reports that the strange signals were actually originated from a microwave oven in the facility's break room. This is bad news for people who are longing for contact with "Extra-Terrestrial Intelligence". The good news is that integrity is preserved in modern day scientists.

Tau Ceti 2 In all the great oceans of emptiness, stars of type G are the best candidates to look for life - these are stars like the sun. They are of moderate, but comfortable brightness and remain stable for about 10 billion years - sufficient time for complex life forms to evolve. Tau Ceti is such a G-type, sunlike star, devoid of stellar companions and close enough for detailed studies. It was the first object searched for ET radio signals. Though Tau Ceti has about half the sun's luminosity, its habitable zone still comprises about one third AU - this is wide enough that a terran planet may have formed there. But we know from other stars that giant gas planets are common, and they are often very close to their parent star. So if Tau Ceti happens to have a system of planets, a gas giant may orbit within the habitable zone, leaving no space for an additional terrestrial planet. But this giant planet may have moons, possibly of Earth's size, where life may get a start. Climate on

Figure 09-23b Tau Ceti [view large image]

such a large moon of Tau Ceti's giant planet would not be substantially different from our own.
Depending on the parent planet's orbital radius, this world might see the whole range of conditions from the greenhouse of the Mesozoic to the great ice ages of the Pleistocene. Advanced forms of life, even sentient beings, are not excluded. Figure 09-23b is an artist's rendering of a hypothetical moon in Tau Ceti.

Pioneers Plaque
    The Pioneers-10 space probe was launched on March 1972. In an attempt to contact "advanced civilizations", a plaque bearing engraving such as shown in Figure 09-24 was attached inside. The plaque depicts:
  • an "average" man and an "average" woman standing before an outline of the spacecraft.
  • a diagram showing the hyperfine transition of neutral hydrogen (spin flip of the electrons).
  • a map locating the position of the Sun relative to 14 pulsars and the center of the Galaxy.
  • some symbols representing the binary equivalent of decimal 8.
  • all the planets in the Solar System with distance to the Sun in binary digits.
The probe is now about 10 billion km from Earth and is flying toward the red star Aldebaran in the constellation Taurus. It will reach the destination in

Figure 09-24 Pioneers-10 Plaque [view large image]

2 million years. So far no "alien" or "advanced civilization" has yet seen the plaque. The last signal was received on January 22, 2003.

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