Space, the Final Frontier: In the Scientiﬁc Pursuit of Extraterrestrial Life Away from Earth

or decades we have been searching for an answer to the knotty question, ”do aliens exist?”. Other questions in line are: ”where are they?”, ”are they like us, sophisticated intelligent beings?” or ”do they exist in the form of simpler lifeforms?”, ”Have they ever visited us?”, ”Why haven’t we encountered them yet?”, ”or have we?” To satiate this curiosity, astrophysicists and astronomers have come up with innumerable theories and ideas, engaged in building facilities and institutes and come up with a planet-wide eﬀort for the search of extraterrestrial intelligence - SETI@home. This article will take a ride through time, from the ﬁrst documented idea to look for extraterrestrial beings to the current exploration of this ﬁeld.


I. INTRODUCTION
The well-known intro from the Star Trek franchise, Space: the final frontier. These are the voyages of the starship Enterprise. Its continuing mission: to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no one has gone before, has been deeply imprinted in our hearts since the beginning of the 60s. We will always be mesmerized by the imagination of its creators and never stop wondering whether, indeed, a time comes when we will be advanced enough to engage in interstellar and intergalactic exploration and meet new life forms, with possibly equally advanced intellect and technology and whether we will ever receive a message from them, if indeed they are somewhere out there.
The first written account reflecting the thought process related to the presence of ex-traterrestrial life dates to 400 BC. In his book 'On Natura', Metrodorus of Chios doubted the likelihood of the existence of one living world only in the infinite universe. 1 Later, in 50 BC, the Roman philosopher Lucretius in his book 'On the nature of things' reflected on the possibility of the existence of many Earths with many worlds, conceivably different from us. 2 Giordano Bruno noted in the 15th century, "there must be an infinite number of suns with planets with life around them", a notion for which he was prosecuted. 3 Later in 1690, physicist Christian Huygens wrote in his book 'Cosmotheoros, "that life can exist on any other planets". 4 Hence, for centuries our intellect has driven us to question the presence of extraterrestrial life out there, somewhere, maybe on an Earthlike planet in the Milky way or other galaxies. This question has led to a zealous search for extraterrestrial life for decades now. Physicists, astrobiologists and engineers alike have developed many theories and are in a constant strive to prove their validity. Scientists have even developed tools and machines to send out signals to look for life far away from Earth.
In this exploration for extraterrestrial life, mankind has developed a peculiar interest towards finding its own counterpart, an intelligent lifeform in outer space. One such ini- Through this article, we will embark on an expedition in the quest for extraterrestrial life and intelligence. The opening section will unfold the events that materialized over the years, from the beginning of the 19th century up till now, in the search for living beings away from Earth. We will then, through the latter sections, take a closer look at the landmark events and theories that opened new horizons to this pursuit. Such will include the already mentioned famous Drake equation, the Fermi paradox, including explanations to the Fermi paradox by way of a paper written by Michael Hart and the great Filter hypothesis. We will then take a brief walk through the biggest SETI experiment of all time, SETI@Home ("SETI at home"). We will conclude this article with a glimpse at the future of the search for extraterrestrial life. 3

II. CHRONOLOGICAL ACCOUNT
The idea of the existence of aliens has evidently perplexed and mystified the human mind for centuries. However, the first scientific thought to communicate with extraterrestrial intelligence was made circa 1830 by the famous German astronomer and mathematician, Carl Friedrich Gauss. He proposed that using the Pythagoras Theorem, we could create a strong visual message for the aliens who might be observing us through their strong telescopes. Gauss suggested erecting a large right triangle in the Siberian forests. As per his vision, the triangle was to be constructed of large pine trees on the outside borders while having wheat piled on in on the inside. This colossal right triangle was supposed to be bordered by squares of giant wheat fields 6 , thus forming the shape as depicted in Figure   1. Gauss' intention was to convey to those aliens out there the message that our Earth is inhabited by intelligent beings familiar with the Pythagoras Theorem. One of his other ideas to communicate with our intelligent counterparts was to reflect sunlight towards our neighboring planets 7 using his invention, the Heliotrope.
At the end of the 19th century, Nicola Tesla claimed that he had received alien radio signals. 8 According to him, while experimenting in his laboratory in Colorado Springs with high-frequency electricity and wireless energy transfer, he received cosmic radio waves on one of his instruments. After analyzing and searching for the origin of the received signals, he declared that the signals were sent by intelligent Martians from the planet Mars in an attempt to contact us. 9 The scientific community dismissed those claims. Nevertheless, Tesla's idea of communicating with extraterrestrial intelligent beings had already spread amongst scientific communities. It was only after five decades, in the mid-20th century, that Tesla's idea was accepted by the scientific community and further embraced in the form of a search for extraterrestrial intelligence (SETI).
In 1959, two physicists, Cocconi and Morisson at Cornell University, published an article in Nature titled "Searching for Interstellar Communications", arguing that radio telescopes had then become sensitive enough to receive radio transmissions broadcasted from other star systems. 10 They also stated that those messages might be transmitted at a wavelength of 21 cm (1420 MHz), corresponding with a wavelength at which neutral hydrogen emits radio signals. They argued that as Hydrogen is the most abundant element in the universe, intelligent extraterrestrial beings might consider it a feasible wavelength at which to send To experimentally test this theory, Frank Drake did the first SETI survey, known as Project Ozma, using 25 meters radio dish, utilized to monitor two nearby sun-like stars, Epsilon Eridani and Tau Ceti, at the National Radio Astronomy Observatory in Green Bank, West Virginia. The dish was enabled to monitor at frequencies close to 21 cm (1420 MHz) for six hours a day, between April and July 1960. These attempts to receive radio transmissions from extraterrestrials were unsuccessful. 11 In 1961, Frank Drake organized the first official meeting for SETI at Green Bank Facility.
It was to be a promising meeting, as Drake was fresh out of Project Ozma. But the problem was, in the words of Nadia Drake, Drake's daughter, "the meeting's scientific agenda was in disarray. Drake, who was 31, had been busy acting as a one-man organizing and hospitality committee and had been distracted by meeting logistics". 12   This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings. We are attempting to survive our time so we may live into yours.
Along with this was added the inspirational Latin phrase, Ad astra per aspera (through hardships to the stars), encoded in Morse code. 27 Currently, both Voyager probes are sailing adrift away from our solar system, in the interstellar space. Voyager 1 has become the first human-made object to go that far in space. 28 We must keep in mind, however, that Pioneer and Voyager missions are far from agile messenger services for messaging between the stars: even with the most optimistic estimates, it will take hundreds of thousands of years, maybe even millions of years, for the spacecrafts to pass near some star, and who knows what remains of them by then. If by some miracle, a space faring extraterrestrial species encounters these vessels, and this might take who knows how long, the message conveyed will be pretty straightforward: the spacecraft's origin, the time it has left Earth, and how the creatures, and their technology, that sent it, looked like.
Additionally this group made a significant contribution to this field during that time by initiating radio communication attempts all around the world and keeping logs of those attempts.
Early 80s saw a significant development and stirring of this field in terms of scientific credibility. In its report for the allocation of resources for Astronomy and Astrophysics Not only do they have to scan the sky methodically and systematically over a long period of time, they also need to tune in to the exact frequency at which the message is broadcast: it is not enough to observe that very part of the sky from where the message is sent at just the right time; we also must tune in to the appropriate frequency. If not, the message will be lost. Moreover, interference from television or radio broadcasts on earth does not make it easy for scientists to differentiate a historical message sent by another culture from the TV series "Friends".     Some of the unspoken assumptions made by Drake, while writing the equation, are: • That intelligent, technologically advanced civilization will not colonize other worlds.
We need to keep an open mind to the fact that a technologically advanced civilization has a chance of spreading or colonizing other planets. Thus, scientists must consider this parameter as well while making estimates and modifications to the Drake equation.
• And that broadcasting-and-listening-for radio signals are the methods by which an intelligent species would choose to communicate across interstellar space. We need to be flexible to the possibility that these civilizations might develop alternative communicative technology along with the radio communication or not rely on it entirely.
Their technology might be way advanced in comparison to ours. There is also a possibility that they might be trying to communicate with us using entirely different media and technology and that their efforts might have gone futile just like ours.

B. Where is the Drake equation leading us?
According to some scientists and mathematicians, the Drake equation is broken for it does not account for evolutionary effects, nor considers the history of the galaxy. 48 The equation was written before the Big Bang theory was validated. Therefore Where, N is the number of planets with detectable signs of life, N * the number of stars observed, f Q the fraction of quiet stars (M class dwarf stars which are dimmer and cooler).
Those are the most common stars in our galaxy. It is easier to look for planets transiting those stars because they are less noisy in terms of brightness. f HZ is the fraction of stars with rocky planets in the habitable zone, f O the fraction of those planets that can be observed, f L the fraction that have life, and f S the fraction on which life produces a detectable signature gas. Gedye's plan was to unfold thus: a software would mine the data from the Arecibo radio telescope, convert it into processable bits, send it to the user desktop, command it to be processed upon to hunt for alien signals while the computer is idle and send the results back to Berkeley home base. That would thus work as distributed computing, virtually acting like a supercomputer due to the immense collective computing power provided by the volunteer computers. By the fall of 1995, the proposal was ready. Anderson would work in his company during daytime and code the software during the evenings.
By May 17, 1999, they were up and running. Gedye and team thought more or less a thousand people might join the project. As a result, they set up only one desktop for lending out data and receiving back the results. But apparently the idea of lending out your computer for a search for aliens was so alluring that at the launch over a million people signed up for SETI@home. The lone data-serving desktop suffered immense load.
Sun microsystems then donated computers to act as a collective server end. The project got back up and since then, more than 4 million people have used SETI@home. An early analysis in the year 2000 showed that a million volunteer computers had processed the amount of 22 data that would otherwise take a single desktop a thousand years to process. Currently, the collective computing power of those volunteer computers exceed 2008's premier computer.
As of now, there is an enormous amount of data from Arecibo that has been sent over from volunteer computers to UC Berkeley home server, data that has been examined over 21 years of operation and still needs to be analyzed. As such, the researchers at UC Berkeley have decided to halt the public-facet of the SETI@home project by discontinuing to send more work to the volunteer computers and, according to Dr. Eric Korpela, director of SETI@home, the project, while not dead, is going into hibernation. Situated before the team , comprising of a 4 full-time researchers, is a huge amount of 2 decades worth of collected data that needs to be analyzed . 62 Once the data analysis is over, SETI@home might be relaunched sending the data from other telescopes such as MeerKAT array in South Africa or FAST telescope from China. SETI@home might be over but the search for extraterrestrial intelligence continues. For all we know, our galactic neighbors did leave us a message; let us wait and see what is unveiled once the data analysis is over.

VII. EPILOGUE
What the estimates shown above clearly indicate is that there is most likely an alien civilization somewhere out there capable of communicating with us. However, the vast size of the galaxy, let alone the universe, strongly nullify the alluring possibility of alien past or near future visits. Compared with the immensity of the universe, the search for extraterrestrial intelligence, even after 60 years of operations, is still in its infancy due to its technological limitations. Not only that, but it is anyone's guess when this research will come to fruition in actuality.
Finally, if we put it as captain Picard's log entries, "Captain's log, supplemental. To gain knowledge of the existence of other life forms on other planets in the Milky Way galaxy has been one of the prime incentives of humanity's space quest. We are taking necessary measures to keep each step forward in this quest for life. Maybe someday in the near future, we will learn that there are complex organisms somewhere out there. Maybe, a time will come when we will make the first contact with a highly advanced, intellectual beings or maybe we will be visited by them. Or maybe they are there, observing us, waiting for us to make an evolutionary breakthrough so that they can contact us, and we can exchange knowledge with them which would forever change the course of humanity. We must, however, keep in mind that the universe and the galaxy are vast and gigantic, beyond anything we humans can perceive. Hence, it might take millions of years to make such a galactic journey.
For that we must keep moving forward with hope and optimism, taking strong educated steps towards technological advancement. We have a long way to go, there is still so much to do. However, slowly but surely, we will get there."