Signatures of Life: Science Searches the Universeby Edward Ashpole
An intriguing overview of the ways in which science could find evidence for extraterrestrial life
Are we alone in the universe, or is life a universal phenomenon? For fifty years, astronomers in SETI (Search for Extraterrestrial Intelligence) have scanned the universe for intelligent signals, but/i>/b>
An intriguing overview of the ways in which science could find evidence for extraterrestrial life
Are we alone in the universe, or is life a universal phenomenon? For fifty years, astronomers in SETI (Search for Extraterrestrial Intelligence) have scanned the universe for intelligent signals, but with no success. In this intriguing book, Edward Ashpole explains the probable reasons for this and discusses other avenues of investigation more in line with the nature of science and technology.
The author examines the problems inherent in scanning the universe for radio or optical signals from an alien intelligence. These include the difficulty of trying to communicate with another species possessing a completely unknown form of technology and the vast distances that alien communications would have to travel to reach us.
This leads Ashpole to other ways of finding evidence for extraterrestrial life, given that advanced civilizations would probably use artificial intelligence for interstellar travel. Our scientists now know how to detect the presence of life on a planet by observing its spectral lines, so more advanced alien researchers would have had ample time (about two billion years) to investigate these “signatures of life” coming from Earth. Hence, the author argues, alien space probes could exist within our own solar system; there might be evidence on the erosion-free Moon or on another moon or planet. In fact, a few scientists have scanned NASA's best photography, looking for evidence of such “alien archaeology.”
In a final chapter, the author urges an open-minded attitude on the part of scientists to all credible sources of information, along with the use of the scientific method to test various hypotheses and weed out the fantasy factor, which so often interferes with serious attempts to find hard evidence of extraterrestrial intelligence.
Informative and fascinating, Signatures of Life delves into a topic that often provokes wild speculation in a thought-provoking yet scientifically responsible way.
“Advising reliance on scientific methods over fantastical thinking, Ashpole urges us to continue ‘trying to discover the status of our lives and our world in the immensity of the universe.’”
“A very enjoyable book.... Ashpole is noticeably good at getting complex ideas across in clear, simple prose.”
-Open Letters Monthly
- Prometheus Books
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Read an Excerpt
SIGNATURES OF LIFE
SCIENCE SEARCHES THE UNIVERSE
By Edward Ashpole
Prometheus BooksCopyright © 2013 Edward Ashpole
All rights reserved.
LOOKING FOR UNIVERSAL LIFE
So what is the status of life in the universe? This book examines this question and looks at what science is telling us about how we might discover the different signatures of life and confirm the major hypothesis in human history: that life and intelligence are universal phenomena. I like to call this the Grand Hypothesis because they don't come any grander.
Life is the greatest mystery in the universe. The chemical systems and molecular structures that keep every living thing alive are almost beyond comprehension in their complexity, yet they work perfectly. So we have to ask how it is that the universal physics and chemistry has not only created the galaxies, stars, and planets of the physical universe but also formed the basic molecular units that evolution has been able to put together to create complex life. Why, at a molecular level, should everything fit together and work? It's not the outward forms of life that most perplex us, though these are amazing in their infinite variety. It is what continually goes on within every living organism. Each one of us is composed of many billions of cells, and each cell is a factory of marvelous complexity, producing everything needed for life—from proteins to energy. So we have to ask ourselves if all this is the same or similar on other worlds—or substantially different. The range of possibilities must be limited by the universal physics and chemistry and what the process of evolution can do with this. But there's the rub. We don't know what evolution may be able to do. Only the detection of alien life may begin to answer our questions.
Astronomers tell us that the oldest sunlike stars are twice the age of the sun, which means that Earthlike planets orbiting such stars could have supported life a few billion years before its origin on our planet. However, as we know, life can be highly successful without intelligence, and many intelligent species can exist without one having the ability to create technologies. Here we stand alone in this respect, but what about all those other planetary systems? Judging from what has happened here and from the ages of the oldest sunlike stars, technologically intelligent creatures, our counterparts, could sometimes have evolved—and at any time from a few billion years ago. That's an immense period of time during which world civilizations could have developed advanced space programs and explored other planetary systems—at least by robotically controlled craft. So evidence of alien technology could be within the solar system. It seems more likely that intelligent signals are being broadcast from other planetary systems, signals that could be received in our time with our current level of technology. However, evidence of alien broadcasts or alien technology within the solar system would be clear signatures of life and intelligence in the universe.
The fact is that no one knows what the situation is out there or what we might be looking for, but we do have mainstream science to guide us, plus the scientific method to follow. That should be enough for the scientific investigation of ideas and possible relevant data. That is the position taken in this book: that ideas and data must lead to testable hypotheses. Otherwise we are not engaged in science. Testable hypotheses have to be based on what seems possible and on what we already know. A good example of this is the hypothesis that started the scientific discipline of SETI (search for extraterrestrial intelligence). It was published in the science journal Nature in September 1959, and its authors, Philip Morrison and Giuseppe Cocconi, two physics professors, suggested that the frequency of neutral hydrogen at 1420 MHz would be chosen by aliens who wanted to communicate with their neighbors. This speculation was based on the fact that hydrogen is more abundant than all other elements put together, and that it radiates this frequency from most of the celestial objects studied by our radio astronomers. Therefore, astronomers everywhere, in whatever life-form, might spot any artificial signals the frequency carried. It was such a persuasive hypothesis that, for the past fifty years, multimillion-dollar programs of radio astronomy have searched for signs of intelligence on that frequency and others near it. A little later, laser technology was developed to a stage where it was suggested that the aliens might prefer to communicate by very brief but intense flashes from lasers rather than by old-fashioned radio. This brought optical astronomers into SETI—and still does.
So both groups of astronomers are looking for evidence on the assumption that, given suitable physical and chemical conditions, life will form on planets and their moons, and that sometimes the equivalent of astronomers will evolve who wish to contact their cosmic neighbors. This might happen in only a tiny proportion of planetary systems, but with a few billion stars like the sun in our galaxy, there could be plenty of planets for the evolution of our fellow travelers in space and time.
However, the searches for radio or laser signals from these other worlds now seem unlikely to succeed for two reasons—and not because our counterparts have never existed. The probable reasons for the failure to find signals to confirm the universal nature of life are the vast expanses of time involved in the history of life on any suitable planet or moon before high intelligence can evolve, and also the speed with which technology develops once such high intelligence exists. These are obstacles to avoid in testing the Grand Hypothesis. And we will see later in this book how this can be done—and is being done. In assessing the justification for "testing," we must keep in mind that world civilizations that might be detectable would be far older than ours and supported by technologies beyond our power to imagine—because we are not yet familiar with the science that would support them. Also, we know from the fossil record and geology that watchful aliens might have detected the Earth as an inhabited planet from its spectral lines at any time during the past 350 million years, and probably for a much longer period. We know that those lines would have been radiating from the Earth during this immense period of time—and they still do—making our planet a target of interest. Consequently, the arrival of evidence such as probes from other worlds during the past 350 million years is not impossible. In fact, it looks a considerably better bet than the arrival of detectable alien broadcasts in our time. Many planetary civilizations could have evolved and become extinct during that period.
Nevertheless, we owe a lot to the scientists in astronomical SETI who still scan the galaxy for signals. They may not have found any aliens during the past fifty years, but they have made us think hard about the status of life in the universe and about the possibilities that other world civilizations exist or have existed in the past. Yet we still don't know if we are a one-off miracle or just a tiny sample of a spontaneous phenomenon that flourishes throughout the universe. And although we can never know if we are a one-off miracle, we can use science and technology to check if life and intelligence are inevitable products of the way our universe works.
But the territory to be explored is different from anything science has tackled before. Consequently the approaches to it are different—and more diverse. In the history of science there can have been few subjects open to attack from so many different angles, though you wouldn't think so from what is being published in the science journals. A few of these angles may seem too acute for comfort, but when the objective is to answer the most important question about life, we have to consider everything that might be relevant. Everyone is on the fringe in this line of research, supported more by speculation about what the relevant science may indicate than hard data. So it's essential to distinguish the "rational fringe" from the "lunatic fringe" and to stick closely to the tried and tested ways of science. It's the results from testing hypotheses that matter. Nothing else. We have to form hypotheses, where that is possible, and test them with the aim of getting repeatable results. But while we're waiting for someone to shout "Eureka," you can review the relevant science and the different projects being run by good scientists to test the Grand Hypothesis.
Excerpted from SIGNATURES OF LIFE by Edward Ashpole. Copyright © 2013 by Edward Ashpole. Excerpted by permission of Prometheus Books.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Meet the Author
Edward Ashpole (UK) is a science writer who has covered the life sciences for numerous publications in Britain and abroad. He is the author of The UFO Phenomena: A Scientific Look at the Evidence for Extraterrestrial Contacts and Where Is Everybody?
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