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Tue Dec 3, 02019, 12:00AM UTC

Avi Loeb

Searching For Life In Deep Space

Searching For Life In Deep Space

A Long Now Boston Community Conversation with Kirk Bosma, P.E. Woods Hole Group and Paul Kirshen, Ph.D., UMass Boston on the deep uncertainty and dynamic adaptation facing the Boston coastline.

Life Among the Stars

Avi Loeb is confident in the existence of extraterrestrial civilizations, and optimistic that confirmation, when achieved, will fundamentally transform the human perspective, just as the Copernican revolution, based on increasingly detailed astronomical observations, did a half-millenium ago.  With the rapid increase in relevant data from more advanced observations and increasingly sophisticated space missions, that confirmation may come soon.

“Our civilization will mature only by leaving home to the cosmic street and meeting others.”  Avi Loeb

Abraham (Avi) Loeb is the Frank B. Baird, Jr. Professor of Science at Harvard University. He has published 4 books and over 700 papers on a wide range of topics, including black holes, the first stars, the search for extraterrestrial life and the future of the universe. He serves as chair of Harvard’s Department of Astronomy, founding director of Harvard’s Black Hole Initiative and director of the Institute for Theory and Computation within the Harvard-Smithsonian Center for Astrophysics. He is a Faculty Member of Harvard’s Origins of Life Initiative. He also chairs the advisory committee for the Breakthrough Starshot Advisory Committee, serves as the science theory director for all initiatives of the Breakthrough Prize Foundation, as well as chair of the Board on Physics and Astronomy of the National Academies. He is an elected fellow of the American Academy of Arts & Sciences, the American Physical Society, and the International Academy of Astronautics.

Avi Loeb
Avi Loeb


Cosmic Modesty

It is naturally human to be curious, and one of the compelling questions that we continue to ponder is “are we alone?”.  There was a time when we thought the earth was the center of the universe.  That perspective helped perpetuate an anthropocentric arrogance: The belief that only this place, and the humans living here, really mattered.  The Copernican revolution, brought about by increasingly detailed astronomical observations, profoundly changed that perspective to a more humble one.  Our planet is not the center.  And, as we continued to explore, we learned that our sun was not the center either.  In fact, our planet and our sun, even our galaxy, are all rather unremarkable.  The latest observations confirm that there are untold billions of suns, many just like ours, and that almost all of them have planets.

But, perhaps, ours is the only planet with life, and we are the preeminent form of life.  Many people continue to believe that this is the case, and the fact that we have yet to discover extraterrestrial life is confirmation of this belief.  Such a narrow perspective is unwarranted.  Of the uncountable number of planets in the known universe, many are similar enough to support life as we know it.   The opportunities for life in the universe are more numerous than the grains of sand on all the beaches on our world.

According to Avi, a more reasonable working hypothesis is that we are not alone in the universe, just as we are not at the center of the universe.  There should be life out there in both primitive and intelligent forms. We just have to find it.  Avi characterizes this conclusion as a form of “cosmic modesty” and suggests that, since life is likely to exist elsewhere, we should search for it in all of its possible forms.

The Search

Observations in the search for interstellar life come in a variety of forms.  The earth itself serves as a detector, as meteors and meteorites provide opportunities for direct observation.  On January 8, 2014, a meteor over the northeast coast of Papua New Guinea was detected.   Its calculated speed and trajectory implied that it originated outside the solar system.  These events are frequent enough to provide useful observations, and many are large enough to have landed.  By studying the composition of meteorites we already know about, we can learn a lot – and potentially could find a piece of non-terrestrial, artificial equipment.

The moon is also an interstellar fishing net.  It has no atmosphere, water or life, so the objects that have landed on the surface are all there for the picking.  Potentially we may find the remains of objects like the mysterious Oumuamua that was observed passing through our solar system in October, coming within 15M miles of Earth.  Oumuamua was quite a surprise but was detected too late and moved too fast to provide a lot of data.  We do know it was a small, shiny, spinning object that behaved as if propelled (perhaps by solar wind).  In spite of its close pass to the sun, there appeared to be no outgassing or tail (as there is for comets).  While conventional consensus has downplayed these anomalies, Avi suggests that it could be a light sail of artificial original.  We should remain curious and humble about such anomalies, and perhaps next time we can get a better look.

Jupiter and the Sun also act as a fishing net for interstellar objects passing within ten Jupiter radii.  There may be 6,000 or more trapped Oumuamua-sized objects at any time, which could potentially be observed by flyby photography or landings.  Objects with interstellar origin can be identified from spectroscopy or outgassing near the Sun, or from high inclination of orbits (suggesting capture from interstellar space).  There are four highly inclined objects in existing catalogs.  There is also a calculated probability that such objects collide with Earth every 100,000 years or so.  Such collisions could even be a source of panspermia, the seeding of life on Earth from interstellar objects.

Beyond the solar system, interstellar object detection becomes more difficult, but we have been getting much better, very fast.  In 2016, a planet was identified orbiting the habitable zone of the red dwarf Proxima Centauri, the star closest to our solar system.  Called Proxima b, this is the closest known exoplanet, at a distance of about 4.2 light-years (25T miles).  Even if habitable, the real estate value would be limited as the planet is tidally locked, with one side always facing the sun.  The sunny side will be hot, and the dark side quite cold – but the terminator, with its perpetual sunset, might be nice!

It will take some time, though, and some new technology, to get there.  Exploring space is a long-term proposition.  Even with advanced, powerful laser propulsion capable of boosting tiny payloads to 0.2 times the speed of light, the trip to Proxima Centauri b would take a couple decades – and another 4 years to get any data back (assuming we solve that challenge).  But there are great minds working on these problems under the STARSHOT Project, one of the BREAKTHROUGH Initiatives.  The goal for the first decade is proof of concept.  In the second decade, they intend to construct a prototype.    Construction of the full system will take place in the third decade.

We will leave the Earth

Avi challenges us to take the very long-term view that Earth is our home, but only for a while.  In about 5 billion years, our sun will evolve to a red giant star and consume the Earth.  But we may be looking for extraterrestrial habitat far sooner.  Not only do we face the internal threats of climate change or nuclear, biological or chemical wars that may make Earth uninhabitable, we also have to consider potential external threats:  asteroid impacts, solar flares, or exploding stars.  Any of these could make the search for new habitat a necessity for survival, not just a matter of human curiosity and passion.

Moving to the stars will take time and technology far beyond the scope of the STARSHOT project.  It is true that if you could generate constant acceleration at 1 gravity, you could cross the universe in 25 years (notwithstanding the relativistic effects).  But that is a technical and energy problem of insoluble proportions given the weight of even nuclear fuels.  More realistic is the concept of light sails.   STARSHOT may be a pre-curser to applications for space travelers to ply the solar winds with sails, in the same way pre-industrial mariners sailed with the winds across the seas.  But still, the time spans and rigors of space travel would likely be prohibitive for biological beings — perhaps space sailing will be work for robots.


The Fermi Paradox asks a simple question.  Life happened on the planet Earth, and we know there are many other planets, a very large many as it turns out, that have satisfactory conditions for life.  But we have yet to find any evidence of extraterrestrial life of any kind, much less sentient life capable of building an industrial, space-faring civilization.  “Where are they?”

Perhaps they have all died off.  Perhaps they have advanced beyond the point where we can perceive them.  Perhaps they are hiding — we want to be cautious about what we broadcast to space, so perhaps they are too.  Perhaps the problem is simply a matter of time, and we have barely started the search with still rudimentary tools.

Avi is confident that the search will be successful.  He suspects we will find answers in technological artifacts, bio-fingerprints, reflective edges and spectroscopy.  The answer may demonstrate the existence of many dead civilizations extinguished by  climate catastrophes or by wars.  Will our human civilization be inspired by such discoveries to work together to avoid a similar fate?  Neutron star mergers have seeded the universe with uranium (raw material for nuclear power), gold (raw material for economics) and molybdenum (raw material for life).   These can be wasted, or utilized in productive ways, by civilizations throughout the universe.  His hope is that ours will be one to succeed.


The conversation with Avi continued for an extended period after his presentation.  One of the themes that emerged is that humans, including scientists, have a tendency to unquestioning acceptance of the prevailing consensus.  We learn from those around us, and we accept their ideas.  This can create a powerful negative environment for the introduction of new, creative ideas.  The article that he co-authored suggesting that Oumuamua could be a light sail was strongly opposed by a consensus view unwilling to entertain such a different explanation of the object’s anomalous features.

Avi appeals for all of us to remain humble in our beliefs, including our beliefs about scientific theories.  All scientific truths are hypotheses that may later be refined our rejected.  Anomalies should become objects of curiosity and speculation.  They may provide clues to new information and new perspectives that can enrich and expand our understanding.

What we all need is greater curiosity and humility.  New ideas and knowledge are never motivated by fear, envy or greed.

Event Summary

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