Are We Alone in the Universe?

Acta Astronautica, 2012

Speculations about the existence of life beyond Earth are probably as old as mankind itself, but still there is no evidence-neither for its presence nor for its absence. Moreover, we neither know the necessary nor the sufficient conditions for life to emerge, sustain or evolve. The Drake equation famously quantifies our ignorance by writing the number of detectable civilizations as product of factors that get increasingly uncertain the further one goes to the right. As a result, the predictive power is poor, and it ultimately depends on the most uncertain factor. However, if we were able to derive a reasonable estimate, we would not need SETI experiments to tell us whether we are alone or not. What has changed substantially over human history is our ability to explore the Universe. Most significantly, radio transmission technology gives us the opportunity to communicate over interstellar distances, and we are now able to not only determine the population statistics of planets within the Milky Way, but even in principle to find biosignatures in their atmospheres. By finding life beyond Earth, we will learn how frequently it emerges. By finding signals from intelligent extra-terrestrial civilizations, we will get unprecedented insight into our biological, technological, and societal evolution. The Drake equation is not such a useful means for assessing the chances of success of SETI, but instead it provides the framework for using observational data in advancing towards understanding the origins of our existence and our role in the cosmos, and maybe to get a glimpse of our future.

Proceedings of the International Astronomical Union, 2006

In his book Plurality of Worlds, Steven J. Dick (1984) has chronicled the millennia of discourse about other inhabited worlds, based upon deeply held religious or philosophical belief systems. The popularity of the idea of extraterrestrial life has waxed and waned and, at its nadir, put proponents at mortal risk. The several generations of scientists now attending this General Assembly of the International Astronomical Union at the beginning of the 21st century have a marvelous opportunity to shed light on this old question of habitable worlds through observation, experimentation, and interpretation, without recourse to belief systems and without risking their lives (though some may experience rather bumpy career paths). The newly-named and funded, multi-disciplinary field of astrobiology is extremely broad in its scope and is encouraging IAU members to learn and speak the languages of previously disparate disciplines in an attempt to answer the big picture questions: ‘Where did we ...

2016

Each recent report of liquid water existing elsewhere in the solar system has reverberated through the international press and excited the imagination of humankind. We have come to realize that where there is liquid water on Earth, virtually no matter what the physical conditions, there is life. Dr. Lynn Rothschild, an evolutionary biologist known for her work on life in extreme environments and a founder of the field of astrobiology, tells us about intriguing new data. The prevalence of potential abodes for life in our solar system and beyond, the survival of microbes in the space environment, modeling of the potential for transfer of life between celestial bodies, and advances in synthetic biology suggest that life could be more common than previously thought. Are we truly "alone"?

2016

We are not completely able to determine if there are, indeed, life-forms outside our planet, yet we may not neglect the fact that there could be extraterrestrial life things considering how big the universe is. There are countless planets, starts and galaxies, so there is enough room for us to believe that life outside earth is possible. Hence, taking into account that life in other planets is possible, we may agree that since there are numberless galaxies there might be planets with suitable conditions for life and that certain living beings can live in and adapt to different and/or extreme conditions in specific areas on Earth and outside it.

Astronomers' Universe, 2016

Physics Today, 2008

Proceedings of the IEEE, 2000

The systematic search for extraterrestrial intelligence (SETI) has been ongoing for slightly more than half the century that this journal has been in print, and the topic has been of human interest through recorded history. Are we any closer to detecting cosmic company or knowing whether it should be there? This paper takes a look at what has been done,

Physics Today, 2008

2023

The lack of any radio signals or other astronomical evidence supportive of the existence of intelligent extraterrestrial life possessed of technology of sufficient sophistication to bring itself to our attention here on Earth is not, per se, evidence of an absence of life, or even intelligent life, in the cosmos itself, but it does indicate that any such advanced societies, if they have come into existence at all, may be extremely rare and comparatively short-lived, destroyed by the very technology that might have brought them to our notice. This, it will be suggested, is the solution to Fermi's famous 'paradox', and the reason no SETI signals have been detected. The lessons we should learn are that life like that on our planet is very rare and precious, and we must not risk destroying it.

Zygon®, 1997

From antiquity to the present, humans have debated whether intelligent life exists elsewhere in the universe. This presentation will survey this debate, examining the roles played in it by science, religion, philosophy, and other areas of human learning. One thesis that will be developed is that whether or not extraterrestrials exist, ideas about them have strongly influenced Western thought.