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Tag Archives: arecibo-signal

August 15, 1977. Jerry Ehman is analyzing computer printouts from the Big Ear radio telescope at Ohio State University. He is not being paid for his work because he is a volunteer but he believes strongly that the work is important and he dutifully pours over each transcript. He taps his pencil against the table, sips his coffee and adjusts his glasses as he flips through each page. Masking the mechanical hum of the instruments in the lab a small transistor radio picks up the Cleveland Indians game against Oakland; the Indians are up 7-1 in the top of the 5th. Outside his window a grounds keeper is mowing the commons and the smell of warm, freshly cut grass filters in through the air conditioning unit.

No runs score in the fifth. The radio plays an ad for the Star Wars movie. Jerry separates each page into two piles – one for further investigation and another, much larger pile for trash. Most of the signals are just background noise, the signals of distant stars and interference printed off as 1’s and 2’s in vertical columns. The more interesting signals usually turn out to be pulsars, dying stars emitting massive amounts of electromagnetic radiation like a lighthouse with a lamp that can rotate as quickly as once every 33 milliseconds and be seen halfway across the universe. Sometimes the telescope picks up terrestrial noise or a weather satellite as it passes overhead. To an untrained eye this could seem like an extra-terrestrial signal but Jerry has analyzed thousands of signals and is not easily fooled.

The Indians leave the bottom of the 6th inning still up 7-1. A couple of research scientists outside his office door wave at Jerry as they pass by. He thinks about getting lunch soon, maybe grab a beer too. Then near then bottom of the stack amidst all the 1’s and 2’s he spots a 6 and circles it with his pencil. Further down is another 6 followed by the vertical series “AEQUJ5″ with a 6 and 7 off to the right. On the radio Oakland scores a run at the top of the 7th but Jerry is no longer listening to the game. He checks the printout again. He’s stopped tapping his pencil against the desk and has forgotten about that beer. He quickly looks up to see if the scientists are still outside his door but he’s alone and even the grounds keeper is just a distant shadow at the far end of the commons. Without thinking he writes the word “Wow!” in the margin.


Hard copy of the 'Wow!' signal

30 years later this signal has never been heard again. Was it a fluke, a glitch, a terrestrial signal being bounced off space debris or was it contact? Dr. Jerry Ehman did state the possibility of the signal coming from Earth “We should have seen it again when we looked for it 50 times. Something (?) suggests it was an Earth-bound signal that simply got reflected off a piece of space debris.” Countering his own skepticism he has stated that since the signal was transmitted at the protected frequency of 1420MHz and due to the unlikely nature of such a signal being bounced off of debris at that declination he still can’t rule out the nature of the signal being extra-terrestrial in nature. “It was the most significant thing we had seen.” he has been quoted as saying.


The Arecibo message

In 1974 we humans sent our own signal to the stars. Using the powerful Arecibo Radio Telescope the message “was sent only once, over a period of about three minutes, on a narrow beam directed toward a group of about 300,000 stars called the Great Cluster in Hercules, Messier 13. The globular cluster is 25,000 light-years away in our galaxy, the Milky Way. So far, moving at the speed of light, the message has traveled only one thousandth of the distance, or about 147 trillion miles. There are stars closer to our solar system than that, but none of them is in the path of the message.” The chances of an alien civilization “tuning” into this broadcast are pretty slim since the globular cluster it was aimed at will have moved out of the way by the time the signal reaches it.

This signal was created by Frank Drake who is also famous for the Drake Equation. The Drake equation states that : (from Wikipedia)


The Drake Equation


N is the number of civilizations in our galaxy with which we might expect to be able to communicate at any given time


R* is the rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is average number of planets that can potentially support life per star that has planets
fl is the fraction of the above that actually go on to develop life
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of the above that are willing and able to communicate
L is the expected lifetime of such a civilization for the period that it can communicate across interstellar space.

In other words it predicts that there is an excellent chance that intelligent life exists elsewhere in the universe.

Recently the “fp” in the equation has undergone serious scientific study based on observations made by a new generation of ground based techniques. When the Aricebo Signal was sent back in 1974 there was no evidence that there were planets orbiting around stars other than our sun and astronomers could only theorize their existence based, in part, on the Drake equation. Yet in 1995 Michel Mayor and Didier Queloz of the University of Geneva discovered a planet orbiting the main sequence star 51 Pegasi. They used a method called high-resolution spectroscopy and this technique opened the floodgates for other researches to discover 202 extrasolar planets in 172 planetary systems (as of March 10, 2007). The technique works by detecting subtle gravitational shifts in the host star. As a planet makes an orbit it’s gravity “tugs” on the star and scientists can detect the small, regular movements.


Pioneer image


Other methods have been employed to contact our possible neighbors. The spacecraft Pioneer 10 and Pioneer 11 both carried a plaque which is expected to outlive both the Earth and the Sun. The later Voyager probes contained even more information, this time on a golden record. Since the earlier Pioneer plaque had what some considered “smut” on it (a naked man and naked pregnant woman) these drawings were included only as silhouette. Hopefully if these time capsules are ever found our social mores will have advanced somewhat.

The best chance we have of detecting our neighbors is by just listening to the sky. This is what Jerry Ehman was doing back in 1977 when he detected his now famous “Wow! signal”. Jerry was working for SETI whose main mission is to “explore, understand and explain the origin, nature and prevalence of life in the universe.

SETI is what you could call a “faith-based initiative”. Faith not in the sense of God or religion, but faith in the true sense of hoping for something to be true. The work SETI does is serious but rarely is it perceived as serious by the general public or even by other scientists. Spending money on scanning the heavens for a distant signal from alien civilizations seems like a waste of resources to the cynical eye. All that money could be spent on finding a cure for HIV or housing the homeless or rebuilding bridges and interstates but SETI is an endeavor that fulfills an equally important aspect of our lives.

Just as public schools cut funding for the arts because the government mandates that children meet a minimum educational criteria that same attitude has spread into the world of academia. Many scientists focus on the “here and now” problems that face our species but dare not to dream about the greater discoveries for fear of being ostracized by their peers. Imagine if Ferdinand Magellan had not attempted to circumnavigate the globe or Sir Edmund Hillary had not ascended Mt. Everest. What sort of world would we be living in? Should our lives be spent only focusing on the negative aspects of our species or is it acceptable to dream?

Ask a child if it is good to daydream and they will gladly say it is but ask that child’s guidance counselor and they will disagree. Good science maintains that childlike view of the world and always asks “why?”. Humans need to understand the world around us because we thrive when we benefit from new discoveries. Too be sure we also thrive when science is applied to concrete and practical issues such as medicine and many good scientists have devoted their careers to these fields. Yet science is so much more than just problem solving. Science dares to go inside a black hole or to the very edge of the universe not because it may offer a practical benefit to our lives this coming fiscal quarter but because it gives our lives meaning.

Franz Schubert did not compose Death and the Maiden because it would feed the poor but because the music was inside him and since he knew he was dying he needed to get it out. Imagine a world without this piece of music and now imagine a world where all things deemed “impractical” are discarded. Failing to dream kills the human spirit and does not give us much reason to live.

So why is the search for life off the earth important? Because it fulfills within us a basic need all humans have and that is to know that we are not alone in the universe.