Interstellar Communications William H. Waller Ph.D. Waller William H. Ph.D. Deneen Michael Ph.D. 9 6 2013


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It took less than two billion years for our Milky Way Galaxy to emerge from the chaos of the Hot Big Bang some 13.8 billion years ago. Another 7 billion years would elapse before our Sun and Solar System took form. During this time, the thermonuclear processing of matter in the cores of stars and during the violent deaths of massive stars collectively forged the heavy elements that characterize our rocky home planet.

On Earth’s moist surface, microbial life took hold less than a billion years after the Sun turned on. Yet another three billion years would have to pass, before multi-cellular life forms began to leave fossil records in the accumulating sediments of sand, mud, and limestone. The remaining 500 million years up to the present day have witnessed the successive flourishing of primitive sea animals, land animals, flowering plants, dinosaurs, mammals, and – in the last two million years – humans.

Timeline of Earth’s history, including the origin of microbial life 3.8 billion years ago and the evolution of multi-cellular life forms to the present day. Courtesy of Andree Valley (see ).

Homo sapiens began creating their distinctive and enduring stone tools, middens, and burials about 100,000 years ago. Only in the last century (1/1000 the history of modern humans and 1/ 50-million the history of Earth) have we begun to telecommunicate beyond Earth. Using radio and television transmitters, we have become inadvertent players on the galactic stage. Already, our broadcasts have faintly traveled past thousands of stars and their associated planetary systems.

The Allen Array of radio telescopes is scanning the sky for artificial signals from extraterrestrial intelligences. Image courtesy of the SETI iInstitute.

We have also begun the search for distinctive electromagnetic signals from technologically communicative life forms beyond Earth. What those species may be and what sort of signals that they may be sending out remain highly challenging questions. Once the exclusive province of science fiction authors, the topic of Interstellar Communications has come into its own as a scientific and technological field worthy of deliberate investigation.

The following journals currently host peer-reviewed technical articles on the Search for Extraterrestrial Intelligence (SETI) and the even more provocative topic of Communications with Extraterrestrial Intelligence (CETI).

Acta Astronautica (Amsterdam: Elsevier Publications)

... See

Astrobiology (New Rochelle, NY: Mary Ann Liebert Inc., Publications)

... See

International Journal of Astrobiology (Cambridge, UK: Cambridge University Press)

... See



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Appendix 1


10 11 2016

RE: SETI My opinion on spending time and money searching for intelligent life on other planets has evolved through my life. In my younger years, the movie ET definitely introduced me to the idea of aliens outside of our planet Earth. The thought of an alien coming to Earth always fascinated me, and I always believed that if another intelligent life form was in space, they would eventually bump into us. It never occurred to me that we would have to do the searching to find these aliens. Now as a young adult, with more understanding of the complexities and costs of exploring outer space for new life, I feel as though I can’t support the expense. The explanation for me is simple enough. We are living on a dying planet that is infected with a plague known as human development. I can’t understand spending millions if not billions of dollars searching for some intelligent life that may or may not exist. Our money needs to be spent on fixing what we already have, not trying to find a new version of what we have. Either we are alone in this galaxy, or there is life that isn’t advanced enough or cares enough to hear our current signals. Like the article mentioned, our television and radio transmitters are already sending signals out into space. It appears that no other life forms are interested in exploring what these signals could possibly be coming from, perhaps an issue of intelligence or technology. With the possible cost and time associated with SETI, I’m content waiting for ET to show up on our planet. I understand the fascination with seeking out extraterrestrial intelligence, but the fact is I can’t justify it yet. If we were to improve our own living conditions and our planet first, however, I would definitely be interested in committing more resources to SETI. I'm a local highschool student at RHS and a Physics II student

5 10 2016

Your thoughts on alternative substances making up organismal life open up many possibilities. Several of these are explored in the well-researched Wikipedia entry on hypothetical types of biochemistry. Meanwhile, NASA's directive to "follow the water" in their search for extraterrestrial life continues to drive much of its robotic missions to Mars, Europa, and Enceladus. Titan remains the outlying attraction, with its seas of methane and ethane. It will be during your adult life that these 4 worlds will be explored in sufficient detail to assay their respective prospects for hosting life! Which world would you pick to explore first?

16 9 2016

Ok. I thoroughly enjoyed this introductory article, including its timeline of life on Earth and the importance of water. However, I still believe that other organisms could potentially survive on substances other than water. Even though organisms on Earth primarily evolved off of water, other organisms on different planets could survive due to another primary substance on their planet other than water. For example, take a planet where there is little to no sunlight. There will be little to no reactions to produce energy for organisms on the planet (e.g. via the Calvin cycle and the Krebs Cycle). Thus, organisms must utilize different materials and produce energy in different forms other than the two light and water dependent cycles mentioned above to essentially survive. Therefore, organisms other than the ones occupying the evolutionary niches on the Earth are created. However, one could argue that the evidence leading to the conclusion of organisms needing water is spurious (as Stephen Grier said about SETI) because we, as humans, try to convince ourselves that the easiest and quickest solution to any problem is said by a person and universally accepted by the rest of us without any objection. Googling the presence of water in our universe results in little information shown (okay, maybe 9 million results is not considered little) which actually makes me wonder whether scientists have actually research the full variety of substances that could lead to organismal survival (life!).

2 9 2015

Dr. Waller, disregarding the science behind the existence or nonexistence of life, what role do you believe emotion plays in the search for extraterrestrial life? So far, searching of life in the universe has been futile. Furthermore, there is minimal evidence to suggest the actual existence of life in the past, present, or future of this universe (excluding earth, of course). And yet, regardless of these major obstacles, the search for extraterrestrial life continues. Do you believe this is because the facts truly do imply the possible existence of alien life? Or do you think that this search for life is simply an inherent loneliness of the human race? Now this comment is not, by any means, coming from a sceptic on alien life, who believes that this search is silly. I truly do believe, or want to believe, that alien life exists; but maybe the thought of being truly alone in this vast universe is a bit scary. I guess the real question is 'is this search for life based on fact or fear?'.

2 9 2015

Just as the comment before me I've always believed that there are civilizations in the Universe we haven't discovered yet. It is quite possible that these civilizations know much more about us than we know about them. These aliens could be much more advanced and more wise than we are. On the other hand we could run into some very primitive creatures, whether they're a smart species or one relations more to a animal other than humans. There are millions of possibilities and there is likely a variety. To not explore space and not try to find these civilizations would be stupid. Earth as a whole needs to explore space. Not only would an exploration benefit our knowledge but it would likely stop wars. The joint effort to explore space would be a common goal and if every interested country worked together space exploration would likely be much more successful. Exploring space would open up hundreds of new opportunities. We could learn more about physics, chemistry, and biology. We could also map outer space and make explorations more accessible. This would also better technology on Earth advancing our cultures. Space exploration should not be set aside, it is important research that could advance our planet in many different ways.

19 11 2013

As one who has accumulated in excess of some 25,000 hours of SETI participating GPU processing power on a series of Linux based home machines for the last ten years, this topic has fascinated me ever since I was presented with the Drake Equation by the world renowned and now deceased Astrophysicist and Educator , Dr. Carl Sagan. Probability Mathematics assures us that the likelihood of other sentient life prevailing in the universe is reasonably great and with a modicum of extrapolation, no doubt to an advanced state. The question now arises . If that is the case, then given our current state of affairs with all the criterion of what constitutes an advanced state of civilization, how would we as terra based earth beings measure up? The answers to that question encompass an entire panacea of disciplines which if honestly evaluated from a cultural, scientific, philosophic and ultimately an existential perspective , then perhaps our current state of consciousness would be looked upon by other galactic civilizations with a measure of curiosity but coupled with a tempered and worrisome, if not pitied trepidation. For starters, our unleashing the power of scientific technologies for industrial mass consumption and fluid and interactive communication constructs has indeed provided us with what we term a convenient life style. It has concomitantly also induced the possibility of genocidal annihilation either by waging thermonuclear war and or defaulting to entire systemic and sustainability breakdown encompassing the very biological , financial and life sustaining systems of the planet. Homo Sapiens of today cannot rest upon their laurels characterized by a shallow and narcissistic belief that they represent the crowning and pinnacle epoch of human achievement when we gaze upon the state of humanity, both from a posterity driven and resource depleting schema. Technology has proven to be a double - edged sword and when in the hands of those who are intent on unrestrained growth , hubristic avarice and the concentration of power for less than humanistic concerns for the species as a whole, THEN , we might ask, “ If THEY are out there, they perhaps are just watching and hoping.” I am reminded often by this quote, “Our scientific power has outrun our spiritual power. We have guided missiles and misguided men.” Martin Luther King , Jr. In conclusion , it is not beyond the realm of possibility that perhaps other civilizations are waiting for us to mature to a more enlightened and humanistic condition where greed, corruption and a lemming like propensity to fuel the fires of our own extinction are overcome. If they are betting on the issue, then what are the odds ? It is for each of us to answer that ultimate question.