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Advanced technology that lets us see previously unseen parts of the solar system, combined with the frequent discovery of “Earth-like” planets, has strengthened our longstanding cultural belief that aliens could exist (not to mention the fact that extraterrestrials continue to capture our imagination at the box office). And now, there’s even more to the idea that there is life beyond our planet.
Some of the latest scientific theories supporting the existence of alien life are collected in an anthology of essays called “Aliens,” edited by theoretical physicist Jim Al-Khalili. He and a couple of contributors weigh in on why scientists are more optimistic than ever before that we’re not alone in the universe.
- Jim Al-Khalili Theoretical physicist; editor, "Aliens: The World's Leading Scientists On The Search For Extraterrestrial Life"
- Adam Rutherford Geneticist; host, "Inside Science" on BBC Radio 4
- Nathalie Cabrol Senior research scientist at the SETI Institute and director of the Carl Sagan Center
Excerpts From The Anthology, "Aliens"
From “Where Is Everybody?” by Jim Al-Khalili:
“Of course, an alien planet being suitable for life is one thing, but the really big unknown is this: given the right conditions, how likely is it that life could evolve elsewhere? To answer is that we need to understand how life began on Earth. If we are indeed alone in the vastness of the cosmos, then we need to understand why we are so special. Why would the Universe be apparently so finely tuned for life to exist, yet harbour it in just one isolated corner?
One way of thinking about this is to ask yourself how come you exist? What were the chances that your parents would meet and produce you? Indeed, what were the chances of their parents meeting, and so on all the way back? We are each of us the culmination of a long and highly unlikely chain of events leading back to the origin of life itself. Break any one of the links in that chain and you would not be here to ask the question in the first place. Maybe our existence is really no more remarkable than the lottery winner contemplating his or her good fortune: had that sequence of numbers not come up, then someone else would have won and they would also reflect on the improbable odds of their win.
What life on Earth can tell us about alien existence elsewhere in the Galaxy is limited by the fact that we have a statistical sample of just one. Our own example tells us nothing about the likelihood of life elsewhere, or what it would look like if it did exist. Could there be advanced alien civilisations out there or would they only be in the form of simple, single-celled microbes? If we can’t begin to address that issue, how will we even know where to look?
Most profound of all of course is what it would mean for us if we did find them?”
From “What Are We Looking For?” by Nathalie Cabrol:
“At the crossroads of scientific disciplines, astrobiology uses advances in all fields to answer these questions: How does life begin and develop? Does life exist elsewhere in the Universe? What is life’s future on Earth and beyond?
These questions represent a puzzle of cosmic proportions, to which we are missing several key pieces. We do not have a clear definition of what life is. Could it have been seeded on Earth through panspermia (in which comets and asteroids transfer material between other bodies in the solar system on impact) and planetary exchange (the idea, for example, that there was some exchange of material between Mars and Earth at the time they were forming)? Or was it created on our planet through abiogenesis, a process by which life arises naturally from simple organic compounds and chemical processes? We also do not have a record of when – or in which environment – the transition from prebiotic chemistry to life took place. We don’t know whether life is a common universal occurrence or a fluke. But if we are to solve the puzzle, it makes sense to start with us.
The terrestrial biosphere we inhabit – even if it hasn’t provided the answers to the questions above – is a record of life’s evolution and adaptation driven by environmental and cosmic bottlenecks, extending over billions of years. Further away, we can see the solar system we belong to as a lab where, over eons, nature has created a diversity of environments surpassing in complexity anything we could develop in an experiment. Beyond the solar system, our most sophisticated instruments provide windows in space and time where we can catch a glimpse of how galaxies, stars and planets are formed. Last, but not least, the human mind can model, theorise, and generate limitless thought experiments.
With this in hand, we have started to build an understanding of what, where and how to search for life beyond our planet. By necessity, our vision is still anthropocentric: we are searching for life as we know it, and this approach is a logical one because it is always easier to start with what you know, when what we know of life is still so limited. As our knowledge broadens, hypotheses and models grow more complex, and the technology to test them becomes more sophisticated, which allows more discoveries to be made, and fundamental hypotheses and models to be refined. This is an iterative process. In that regard, the past few decades of exploration of the Earth’s most extreme environments, the solar system, and deep space have revolutionised our definition of habitability and life potential.”
From “It Came From Beyond The Silver Screen!” by Adam Rutherford:
They mostly get it wrong. Mostly. Film-makers have been infusing culture with their visions of aliens for more than a century, and almost all of them have been a lot like us. The Moon natives in the first cinematic trip into space, Georges Méliès’s La Voyage dans la Lune (1902), were Selenites, named after Selene, the Greek goddess of the Moon. They’re a bit like arthropods with bulbous heads and lobster claws, but mostly human – upright and bipedal. The next trip was when the 1919 adaptation of H. G. Wells’s The First Men in the Moon landed, which also had Selenites as the endogenous lunar men. Alas, all prints of the film are lost. In the few remaining stills from the shoot, the Selenites are also somewhat insectoid, but look disturbingly like the blue, globoid-headed, oval-bodied Igglepiggle from the bewildering otherworldly toddlers’ programme In the Night Garden. And so the tone was set for a century of aliens – humanoid, insect or insect-like humans are the mainstay of cinematic extraterrestrials. We turn to human-like forms either because of budgetary constraints or for reasons of anthropocentrism.
We lazily assume aliens will be a bit like us, because we do like thinking about ourselves. Star Trek and dozens of imitators have got away with simply gluing bits of lump onto human faces or painting them green to indicate their non-human status. The Star Wars Universe offers little but variations on humans. Budget didn’t seem to be much of a problem in James Cameron’s Avatar (2009), just a tiresome lack of imagination. ‘Let’s make them taller than us, and a bit cat-like, but sexy, and give them tails. They need to be primitive but wise. Oh, and make them blue too.’
We have a pretty good grasp of evolution these days, and our bounteous fossil record, now coupled with genetics, gives us a picture of how life evolved on Earth. There are plenty of mysteries remaining, but we know much about our nearest ancestors: the emergence of bipedalism and all the many factors by which we came to be who we are. To assume that on other worlds, evolution would deliver a species identical in physical stature is plain silly. We don’t really know why we became two-legged when almost all terrestrial animals are not, but we can hypothesise that it is an adaptation to a range of complex environmental conditions, primarily to equip a species for a life on the savanna rather than swinging in the trees, and an increased efficiency of movement. If the Earth ever got a reboot, and the story ran again from the beginning, with just a few variables altered we would not have come out like this. Even a seemingly unconnected matter like the tilt of the Earth’s axis has played a crucial role. That 23° tilt, which gives us our seasons, was caused by a rock the size of Mars colliding with the neonate Earth, and knocking off a block that would form the Moon. Imagine if the rock had missed; no tilt, no seasons, no Moon, no tides. This would have meant a different weather system, different climate changes over time, and an entirely different set of evolutionary ancestors. Imagine if that sixmile-wide asteroid hadn’t tumbled out of the Cretaceous sky into what is now the Gulf of Mexico and caused an extinction level event that wiped out the dinosaurs and so many other species, yet allowed our small mammal ancestors to thrive. Imagine that rock being half the size, and only half of the dinosaurs had been wiped out. Would we be as we are? The answer is almost certainly no. Our form is not inevitable – it’s mere cosmic happenstance.”
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