Greek Philosopher Metrodorus once said that "To consider Earth as the only populated world is as absurd as to assert that in an entire field sown with millet only one grain will grow" (qtd in Arvey 12). Since the dawn of time, humans have looked up at the stars in the sky, wondering whether they were alone in this vast Universe. Many have believed that there must be at least a small spark of life somewhere out there, while many others have scoffed at the idea. It is now the year 2001, and the same question is still asked. Despite several leaps in technology and science, accompanied by massive amounts of research and analysis, there is still no hard evidence that proves, without a doubt, that intelligent life does or does not exist outside of Earth.
One skeptic, Michael H. Hart of the National Center for Atmospheric Research in Colorado, believes that if there are other civilizations containing intelligent life somewhere out there, we should have ran into them by now. According to him, they should be capable of interstellar flight and have the ability to colonize space. Since we have not run into any of these civilizations yet, then they must not exist (Arvey 21).
However, many disagree with him. Author and scientist, Isaac Asimov, in his book Extraterrestrial Civilizations states that "we have not been visited by them [other civilizations], very likely because the interstellar distances are too great to be penetrated" (qtd. in Arvey 22). Carl Sagan supported Asimov's viewpoint in his book Cosmos when he wrote "If there are millions of civilizations distributed more or less randomly through the galaxy, the distance to the nearest is about two hundred light-years [12,000 trillion miles] away. Evan at the speed of light [light travels 186,000 miles a second; six trillion miles a year] it would take two centuries for a radio message to get from there to here" (qtd. in Arvey 22).
But how can anyone really know if humans have had contact with an alien civilization? Maybe we have, but haven't realized it yet. Duncan Lunan, a young Scottish "spaceflight enthusiast," once claimed that he had evidence of an alien probe circling Earth. His evidence was based on his own personal interpretations of a few mysterious long-delayed echoes of short-wave radio signals that had been first heard in the 1920s (Sheaffer 129). Lunan claimed he found a way to take the echoes and plot them on a map to create a map of the stars in the constellation Bootes (Sheaffer 129). In an excerpt from his book, Interstellar Contact, Duncan said "...If the data points are plotted with delay time on the y-axis (normal scientific practice, followed by all the 1920s experimenter' s who presented their results graphically), nothing significant appears. With delay time on the x-axis, however, the graph looks more like an intelligent signal. There is a vertical "barrier" at 8 seconds dividing the diagram into two parts of an equal area; on the left there is a single dot, at three seconds, which was unique in being an exact repeat of the transmitted signal, three dots, the other echoes being 2 second long dashes.
On the right of the barrier the main figure has a striking but incomplete resemblance to the constellation Bootes, the Herdsman. If the 3 second dot is transplanted across the barrier to a corresponding position on the right, it occupies the position of the star Epsilon Bootis and so completes the constellation figure. ..." (qtd. in Pawsey).
However, many seriously doubt that Lunan had made some kind of major discovery. First of all, this map only resembles the constellation; it is not an exact replica of Bootes. Two stars, Epsilon Bootis Alpha Bootis are out of place on his map. Lunan explains that Alpha Bootis appears out of place because it's position appears to change much more rapidly to earthlings than the positions of any of the other stars. His only explanation for Epsilon Bootis is that if the point representing the star is "moved to the right to be equidistant from the vertical line on the other side of it," picture of the constellation Bootes is then completed. One thing that he has failed to explain is how the 'Booteans' had learned of the "arbitrary constellation boundaries" created by earthlings (Sheaffer 129-132).
Another man, Nikola Tesla, also came across unusual radio signals. "Late one night...as he was working at his powerful and sensitive radio receiver...the inventor became aware of strange rhythmic sounds on the receiver. He could think of no possible explanation for such a regular pattern, unless it were an effort being made to communicate with Earth by living creatures on another planet...no one at that time had ever heard of such phenomena as regular sounds from space" (qtd. in "Artificial Lighting, Radio Experiments"). Tesla was unable to think of any other phenomenon that produced similar radio signal patterns. "Such a clear suggestion of number and order" gave him reason to believe that he may have stumbled upon a message sent to Earth by an intelligent civilization (Arvey 23).
There is also another mystery that has yet to be solved. On August 15, 1977, Ohio State University picked up a signal that has only been heard once. It is called the Wow! signal, getting it's name from the note written in the margin of the computer printout by Dr. Jerry Ehman ("Wow! Signal Page"). "I came across the strangest signal I had ever seen, and immediately scribbled 'Wow!' next to it," Ehman explained. "At first, I thought it was an earth signal reflected from space debris, but after I studied it further, I found that couldn't be the case" (qtd. in Shuch).
The symbols 6EQUJ5 represent the number of "standard deviations" by which the received signal exceeds the average background noise, on a scale of 0 to 35." For example, "0" means that the signal is not any stronger than background noise, "9" means that it is nine sigma above the background level, and "U" (the strongest point of the Wow! signal) is "30 standard deviations above the mean background level" ("Wow! Signal Page"). U is the 21st letter in the alphabet, therefore a "U" means 9+21.
Analyzing the Wow! signal shows that its source was moving with the background stars. From its "Doppler shift signature," terrestrial interference (such as interference from radios and telecommunications equipment), aircraft, and spacecraft can all be ruled out as the possible origin of the signal. It was indicated by the antenna coordinates that the signal was not coming from any known nearby stars ("Wow! Signal Page").
Although several other radio observatories performed over one hundred follow-on studies of the same region of sky where the Wow! Signal originated, it was never picked up again (Shuch). The fact that the signal has only been received once casts some doubts on whether it was sent by another civilization. Ehman himself has said that "Even if it were intelligent beings sending a signal, they'd do it far more than once" and "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" (qtd. in Kawa). However, since the Ohio State Big Ear radio telescope views just one part in a million of the sky at any given time, that lessens the chance of a repeat signal being picked up ("Wow! Signal Page").
Even if the signals were from alien civilizations, there are still a few obstacles in the way. Ian Ridpath, author of Message from the Stars, says that "if the basic science theories are true, the nearest possible alien civilization must be about 2,000 light-years away" (qtd in Arvey 27). That means it would take about 2,000 years for a message from them travelling at the speed of light to get here, then another 2,000 years before they could receive a reply from us. After the 4,000 year round-trip, we could all be gone. In addition to that problem, Gerrit Verschuur says that "no two civilizations are likely at the same stage of development." What he meant was we may be unable to decipher a message sent by an alien civilization (Arvey 27). This would be like a human trying to speak with a primate. Chances are a chimpanzee would have no idea what I was talking about if I went up to it and told it my life story.
If humans are receiving messages from distant civilizations, how many are out there trying to contact us? Is there just one in some far off corner of the universe, or is the Milky Way teeming with life waiting to be discovered? No one knows for sure how many advanced civilizations exist in the universe, if any, but one man has attempted to estimate this number.
Frank Drake once asked "What do we need to know about to discover life in space?" Well, answering his own question, Drake came up with several important factors and used them to create The Drake Equation, which looks like this:
Nc = N* × fp × ne × fl × fi × fc × L
He created this equation to "estimate the number of technological civilizations that might exist among the stars" (qtd. in "Drake Equation Background"). "N* represents the number of stars in the Milky Way Galaxy. . .fp is the fraction of stars that have planets around them. . .ne is the number of planets per star that are capable of sustaining life. . .fl is the fraction of planets of ne where life evolves. . .fi is the fraction of fl where intelligent life evolves. . .fc is the fraction of fi that communicates. . .fL is fraction of the planet's life during which the communicating civilizations may survive. . .and Nc is "the number of communicating civilizations in the galaxy."
Right now, it is estimated that there are 200 to 400 billion stars in the Milky Way Galaxy ("The Drake Equation"). 20% to 50% of these stars are estimated to have planetary systems. For each of these stars, it is estimated that there may be 1 to 5 planets (or moons) capable of supporting life. Out of those, you could use the argument that "Where life can evolve it will" and say that life will evolve on 100% of the planets. Out of those planets, it is estimated that 50% will evolve intelligent life, and 10% to 20% of the intelligent life are estimated to have the "means and desire" to communicate. fL is probably the most difficult number to estimate. If we use Earth as our model, the expected lifetime of the planet is about 10 billion years. Communication by radio has been around for under 100 years. How long will our civilization last? If the human race were to die today, the estimated fraction of a planet's life that a civilization will survive would be 1/100,000,000th. If I were to be conservative and use 200 billion for N*, 50% for fp, 1% for ne, 50% for fl, 20% for fi, 20% for fc, and 100,000,000 for fL, Nc would turn out to be 20.
This is just a very rough estimate. All of the numbers are estimates, and a few changes could dramatically effect the outcome. Even with all the variables and no definite solution to The Drake Equation, it is still a "generally accepted tool used by the scientific community" ("The Drake Equation").
Before we go on, let's not forget that these estimates are only the numbers for the Milky Way galaxy. There are billions of other galaxies out there for life to develop in, each with billions of more stars within them. That is an overwhelming number of places for life to exist.
Let's say my first estimate was actually correct, and there are 20 civilizations in the Milky Way Galaxy capable of communicating. Where are they? Well, they could be anywhere, but chances are they probably aren't in the Solar System. However, there is a chance that there may have been some form of life, not necessarily an advanced civilization, on somewhere else in the Solar System.
Although Jupiter's moon Europa probably doesn't have an advanced civilization on it, it is one of the more promising places in our solar system for the existence of life. "High-resolution images of the surface taken by the Galileo spacecraft have revealed a world with a complex surface covered in groves, icy domes, and features remarkably similar to the ice rafts found in the oceans of the Earth." The smoothness and lack of craters on Europa's surface suggests that below the frozen layer of ice there may exist liquid water, one of the major requirements for life. Below several km of ice and possibly an ocean of water, Europa is nothing but rock (Urquhart). There is a huge gap between finding water and finding life, "but it certainly makes it a more intriguing possibility," (qtd. in "Life on Europa?") says space physics scientist Margaret G. Kivelson.
The contact between the water and rock could provide the "ingredients essential to life, especially if the rocky portion of the moon is volcanically active, as it would have been early in the history of the solar system" (Urquhart). Also, "Europa could possibly produce sources of energy for basic chemical reactions needed for life, thanks to billions of charged particles that constantly rain down from Jupiter," says Stanford University professor Christopher Chyba (qtd. in "Jupiter Radiation"). The copious amounts of water on Europa and likelihood of past volcanic activity has caused some scientists to believe that there is an even better chance of life on Jupiter's moon than there is on Mars (Urquhart).
But there are many that still feel Mars is a strong candidate as a place where life had once existed. Despite the extreme cold and dryness of the surface of Mars today, it is very likely that in the distant past, the climate of Mars may have been a much more hospitable for life. "Billions of years ago, water flowed on the surface of Mars, indicating Mars had a wetter, and probably warmer, climate". Even with the "seemingly inhospitable surface," the discovery of life in some of the most extreme environments on the Earth suggests that life could also be living somewhere deep underground on Mars today. The martian subsurface most likely holds a large amount of ice, maybe even some liquid water. "The presence of volcanos on Mars, which can melt ground ice and circulate water in the subsurface, would provide an excellent environment for microorganisms." In the past Mars has "at the very least" had all of the requirements for life: liquid water, a source of energy, and the "chemical building blocks of life" (Urquhart).
There is evidence that Mars may have once been capable of harboring life, but is there any evidence of the life itself? In August of 1996, NASA announced that it had found evidence on a 3.6 billion-year-old rock hailing from the Red Planet. Three months later, researchers at London's Open University and London's Natural History Museum say residues and chemicals were found that only living organisms could have formed in another meteorite that crashed into Earth 600,000 years ago ("British Present Evidence"). Kathie Thomas-Keprta and her team at the Johnson Space Center believed that some of the microscopic magnetite crystals found inside of the carbonate granules found inside the meteorite had unusual "elongated hexa-octahedral" forms that were so uniform in size that it was almost impossible for something inorganic to have created it. (Moomaw). "This is a smoking gun for life on Mars," said chemist Ian Wright, one of the three scientists that participated in the study (qtd "British Present Evidence"). "I believe I can say life existed-and may still-exist on Mars" ("Researchers Confirm").
Another interesting occurence relating to life and water on Mars has been the appearance of dark spots near the tops of dunes located nears the poles. Scientist A. Horvath came up with a bold theory concerning these spots. He thinks they may be "large films of living Martian algae taking advantage of water frost melting on the dunes in spring to rapidly grow and reproduce before retreating back into dormant spore form after the liquid film of water disappears." His theory is based on the fact that the spots tend to form long streaks running down the surfaces of dunes, indicating that they may be following water flowing down the surface of the dunes (Moomaw).
E.F. Albin also has a theory that deals with water running down the surface of Mars. However, he thinks the dark spots may be caused by the water sweeping away some material that lie on the Martian surface, exposing darker materials underneath it (Moomaw).
There is still not enough information to determine whether or not Mars contains life, but organizations around the world are still collecting more data. Several trips to the Red Planet are planned for the next 10 years. Agencies such as NASA and the European Space Agency are hoping to collect more data on Mars' climate, geology, etc. (DiChristina).
"To think we are the only place uniquely selected for life would be incredible" said Colin Pillinger (qtd. British Present Evidence"). As much I personally agree with Mr. Pillinger, that is only an opinion. Humans have often contemplated the existence of life outside of Earth, and have come quite a long way since the days of our early ancestors. We've built radios and received 'messages from space' on them, we've sent man-made objects into the far reaches of the solar-system, and we've seen incredible things on other worlds that really aren't too far away from our home. However, the most important thing is that we still have not found any conclusive evidence proving, without a doubt, that intelligent life exist outside of Earth. Will the mystery every be solved? Is there an advanced civilization lurking in the depths of a galaxy far, far away? The answer is still unknown, but one thing is for sure: the truth is out there.
