Tag Archives: aliens

Cosmos 12: Encyclopaedia Galactica

by Shane L. Larson

Back in the Olden Days (and by that, I mean the 1980’s and 1990’s) information and knowledge were truly commodities. The sum of all human knowledge was not instantly available with the swipe of a finger from every backwater Irish pub or aisle at Walmart.  Never-the-less, information was systematically collected (much to the regret of middle school teachers the world over) in encyclopedias.

I had a set of encyclopedias I had commandeered from the family, and kept on the bookshelf at the head of my bed, spending long hours (often late at night, with a flashlight) pouring over the pages, drinking it all in.  It was a seminal time in my life, with volumes of information literally at my fingertips, spending every moment I had attempting to assimilate as much as I could.

How I remember my room as a kid in elementary and middle school. I had a lot of space stuff around, my stuffed animal (a snake named Shorty, who I still have), and my headboard bookshelf full of the family encyclopedia set.

How I remember my room as a kid in elementary and middle school. I had a lot of space stuff around, my stuffed animal (a snake named Shorty, who I still have), and my headboard bookshelf full of the family encyclopedia set.

This was the beginning of a long trajectory for me, one example of how the Universe stirs atoms together in such a way that they can think about the world around them. It is remarkable, really.  A rock is also a collection of atoms that the Universe has stirred together, but if a rock contemplates the Cosmos, I have no strong notion of what its rocky thoughts might be.  A platypus can think more than a rock, but I don’t know what a puddle of platypuses talk about over drinks on a Friday night.  Humans, on the other hand, have a possibly unique habit of thought: we ask questions, and then we figure out the answers.  

Of particular interest are questions about life and our own existence.  What is the origin of life?  Is there life elsewhere?  Is there intelligent life (on this planet or others)? Could we talk with extraterrestrial intelligences?  These are BIG THOUGHTS — heady questions that for the most part have no answers yet, no entry in our encyclopedias of knowledge.

I often imagine what it would be like to live in a galaxy brimming with life.  Suppose we knew we weren’t the only intelligent beings in a vast and lonely Cosmos.  How would we communicate with each other? The distances between the stars are vast, too far to be traversed in a single human lifetime (who knows about alien lifetimes!). Fortunately, there is another way to communicate — we call it “radio astronomy.”  We can beam messages from Earth, out into the depths of space, and wait for a reply.

A few of the radio telescopes that make up the Very Large Array (VLA) near Socorro, New Mexico. The VLA is one of the premiere radio astronomy observatories on planet Earth. [Image by S. Larson]

A few of the radio telescopes that make up the Very Large Array (VLA) near Socorro, New Mexico. The VLA is one of the premiere radio astronomy observatories on planet Earth. [Image by S. Larson]

In my reverie, I often wonder what can we send to our civilized alien friends?  What can we, the human race, contribute to the Encyclopaedia Galactica, the composited knowledge of a million intelligent species in the Milky Way?  One could imagine beaming the entire contents of Wikipedia into the vast darkness, a merging of one of our encyclopaedias with the common knowledge of the galaxy. All things being equal, that would probably be a waste of time because English is not the Universal Langauge (nor is any other language on Earth).  greenPopsicleFurthermore few, if any, of our aliens will understand the nuance and meaning of much of the cultural content in our encyclopaedias.  What is a Centaurian going to do with an article about popsicles?

But as it turns out there is a language that, for reasons that are subtle and not well understood, describes everything.  That language is called mathematics, and the Universal vocabulary built from it is called science. One of the prejudices we have about the nature of intelligent life is that to become technologically advanced, they will have to discover and understand the basic laws of Nature, just as the human race has.  In order to understand and interpret the laws of Nature, particularly in the application to technology, will necessarily require an intimate appreciation of mathematics.

If we imagine using mathematics then, we can use a very few basic principles to construct a message that could be sent to the stars, and understood. One of the first concepts to make good on this idea is often attributed to the mathematician, Karl Friedrich Gauss. The proposed idea was to plant vast lines of trees in the shape and form of geometric elements that illustrated our understanding of the Pythagorean Theorem (a relationship between the lengths of the sides of a right triangle). In 1840, Joseph von Littrow suggested we dig enormous trenches in the Sahara desert, fill them with kerosene and set them on fire at night.  The trenches would be large enough to be visible from nearby worlds like the Moon or Mars.  People who think of these things are my heroes!

There are all kinds of ways to imagine talking to aliens. [Calvin & Hobbes, by Bill Watterson]

There are all kinds of ways to imagine talking to aliens. [Calvin & Hobbes, by Bill Watterson]

A modern approach to using mathematics for communication with extraterrestrial civilizations was worked out by American astronomer, Frank Drake.  Drake was interested in “communication without preamble,” and presumed that if one constructs a message with underlying mathematical principles, no preamble would be necessary to begin decoding a received message. A great debate had started after Drake’s 1962 Project Ozma, a radio observing project to detect radio signals from extraterrestrials. If aliens were beaming their encyclopaedia entries at us, and if we detected them, people doubted we would even be able to decode them.  More to the point, if we were beaming our encyclopaedia entries into space, would an extraterrestrial intelligence be able to decode the message?

Drake's original pictorial message, to test communication without preamble. [Image from D. Vakoch, in Mercury (March, 1999)]

Drake’s original pictorial message, to test communication without preamble. [Image from D. Vakoch, in Mercury (March, 1999)]

This question interested Drake, so he constructed an anonymous challenge. He mailed to several scientists around the world a piece of paper that had only a string of 1’s and 0’s on it, in an unmarked envelope.  No explanation, no requests, no instructions: just the number string.  Every single person who received the number string extracted a message that Drake had encoded into it!

Drake’s premise in constructing his message is that there are certain fundamental concepts that exist in mathematics, of which any civilization technical enough to receive radio information should be capable of understanding.  One such concept is the relationship of the area of a circle to the square of the radius (they are related by the number, pi = 3.141592654…).  Another such concept, and the one Drake employed in his experiment, is the idea of prime numbers.  Every number can be factored into a unique set of non-factorable numbers, which are called its prime factors.  Factors are the numbers you have to multiply together to get another number.  For instance, it has been 106 years since the Chicago Cubs have won a World Series (the last time being in 1908, against the Detroit Tigers); two “factors” of 106 are 2 and 53:  106 = 2 x 53.  You use factors everyday.  You’re preparing for the Cosmos: A Spacetime Odyssey premiere, and want pizza for 4 friends.  Each person will eat 4 slices of pizza, so you need 16 slices. There are 8 slices per pizza, so you buy 2 pizzas:  16 = 2 x 8.  A prime number is a number with only two factors: itself and the number 1. An excellent example is 5.  There is no way to multiply two whole numbers together to get 5 other than 5 x 1.

So what was the message? It was a string of 1’s and 0’s. On the paper, it was written as 1’s and 0’s, and the astute reader should object to this — “Alien’s won’t read our alphabet! How will they know what is a 1 or a 0?”  In the context of communicating with extraterrestrials, we’ll be sending radio signals.  A series of written 1’s and 0’s can be sent as a series of signals are that are ON or OFF, LOUD or QUIET, UP or DOWN. All that matters is that however they aliens are reading out the radio signals, they see two distinct states.

A pulsing radio signal, showing how a message consisting of 1's (signal on) and 0's (signal off) can be encoded without writing the characters "1" or "0."  [Image by S. Larson]

A pulsing radio signal, showing how a message consisting of 1’s (signal on) and 0’s (signal off) can be encoded without writing the characters “1” or “0.” [Image by S. Larson]

The remarkable result of Drake’s experiment was that every person the puzzle was sent to was able to decode it.  At first glance, a string of 1’s and 0’s might appear as some type of binary numbering or lettering system, akin to that used in modern digital computers, but that would not be information that aliens could readily decipher, since it is highly unlikely that they have a written alphabet similar to ours. The key to Drake’s idea, is that the numbers represent the pixels in a picture.

Drake’s experiment proved the idea that communication without preamble was a viable idea, and was the basis for a signal which the planet Earth sent out into the galaxy (towards the globular cluster M13 in Hercules, some 24,000 light years away) from the Arecibo Radio Telescope, in Puerto Rico, in 1974.

(L) The 300 m Arecibo Radio Telescope, built into the landscape of Puerto Rico. (R) The globular cluster in Hercules, M13, located 24,000 lightyears from Earth.

(L) The 300 m Arecibo Radio Telescope, built into the landscape of Puerto Rico. (R) The globular cluster in Hercules, M13, located 24,000 lightyears from Earth.

So how was the message formulated?  What bit of the Encyclopaedia of the human race did it contain?  Drake imagined a message formulated as a grid of pixels that when properly displayed would make an image.  By carefully choosing the grid size of his message, he created a quantity of characters for which there were precisely two prime factors.  The Arecibo Message of 1974 was a string of 1’s and 0’s, 1679 in all, that was beamed toward the globular cluster M13 in Hercules.  There are only two prime factors for this number of digits: 1679 = 23 x 73.  This is the only way to multiply two numbers together and get 1679!

Here is the full content of the original Arecibo Message:

0000001010101000000000000101000001010000000100100010001000
1001011001010101010101010100100100000000000000000000000000
0000000000011000000000000000000011010000000000000000000110
1000000000000000000101010000000000000000001111100000000000
0000000000000000000001100001110001100001100010000000000000
1100100001101000110001100001101011111011111011111011111000
0000000000000000000000010000000000000000010000000000000000
0000000000001000000000000000001111110000000000000111110000
0000000000000000000110000110000111000110001000000010000000
0010000110100001100011100110101111101111101111101111100000
0000000000000000000001000000110000000001000000000001100000
0000000000100000110000000000111111000001100000011111000000
0000110000000000000100000000100000000100000100000011000000
0100000001100001100000010000000000110001000011000000000000
0001100110000000000000110001000011000000000110000110000001
0000000100000010000000010000010000000110000000010001000000
0011000000001000100000000010000000100000100000001000000010
0000001000000000000110000000001100000000110000000001000111
0101100000000000100000001000000000000001000001111100000000
0000100001011101001011011000000100111001001111111011100001
1100000110111000000000101000001110110010000001010000011111
1001000000101000001100000010000011011000000000000000000000
0000000000000011100000100000000000000111010100010101010101
0011100000000010101010000000000000000101000000000000001111
1000000000000000011111111100000000000011100000001110000000
0011000000000001100000001101000000000101100000110011000000
0110011000010001010000010100010000100010010001001000100000
0001000101000100000000000010000100001000000000000100000000
0100000000000000100101000000000001111001111101001111000

By arranging the number string in a grid of characters, the length of each side being one of the prime factors, an image can be formed (color in squares with 1’s and leave 0’s blank, or vice versa).  There are two ways to organize the entire string of digits: I can make a picture which is either 23 digits tall and 73 digits wide, or a picture which is 73 digits tall and 23 digits wide.  Both cases are shown below, where the 1’s have been shaded in as black squares and the 0’s have been left as open squares. There is a remarkable difference between the two! for 23 rows and 73 columns, the image looks like a random collection of dots, without an obvious organization to them.

(L) The Arecibo message string arranged horizontally into 23 rows, 73 columns wide. (R) The same message, shown as shaded squares; there is not much that seems obviously organized in the message.

(L) The Arecibo message string arranged horizontally into 23 rows, 73 columns wide. (R) The same message, shown as shaded squares; there is not much that seems obviously organized in the message.

But if you make 73 rows and 23 columns, it becomes far more clear that there is some kind of organization to the string of digits.  Even in the printed numbers, your eye will pick up patterns, which are much easier to see when converted into a shaded grid.

(L) The Arecibo Message string, arranged in 73 rows and 23 columns. Even in text, your eye can see patterns emerging. (C) The same message shown as a shaded grid, making the patterns more clear. (R) The same image colorized for discussion. [Images by S. Larson; R image from Wikimedia Commons]

(L) The Arecibo Message string, arranged in 73 rows and 23 columns. Even in text, your eye can see patterns emerging. (C) The same message shown as a shaded grid, making the patterns more clear. (R) The same image colorized for discussion. [Images by S. Larson; R image from Wikimedia Commons]

What does it all mean? Here is the information we encoded in the message, starting at the top (referring to the colorized version, for ease):

  • Numbers from 1 to 10 (white pixels): this shows how numbers are represented throughout the rest of the message. In all places where a number is shown, the pixels are colored white
  • Atoms (purple pixels): the atomic numbers (the number of protons, which uniquely identify each kind of atom) of hydrogen, carbon, nitrogen, oxygen, and phosphorus. These are the basic atoms needed for the biochemical description of life
  • Sugars and bases (green pixels): the chemical formulae, using the atoms described above, that are the sugars and bases that make up the nucleotides, the building blocks of DNA.
  • Double Helix (blue pixels): the DNA double helix; the number it winds around is the number of nucleotides in a strand of human DNA
  • Human Figure (red pixels): the DNA terminates on the organism it represents, the human figure. On the left is a bar and number representing the average height of a human, and on the right is the total population of humans on Earth
  • Solar System Map (yellow pixels): a map of the solar system from where the message came; the third planet is offset toward the figure, indicating this is the organism that sent the message
  • Arecibo Telescope (purple pixels): a graphic of the telescope that sent the message, with a line and number underneath it telling how large it is

There is, of course, some debate as to whether or not even this message would be understandable by an alien intelligence.  Maybe they decode the message upside down, and instead of a human balancing on two feet under a strand of DNA, they see a 4 tentacled alien swirling uncontrollably down into a cosmic maelstrom (maybe a black hole?).  Perhaps extraterrestrials are intelligent and technologically advanced, but don’t have a sensory facility similar to vision.  Will they even understand the concept of images?  Perhaps, perhaps not; but they will understand prime numbers and hopefully realize there is something intelligent in the long string of radio pulses.

What is most important about the Arecibo Message, is that we are thinking about how to communicate with the rest of the Cosmos. Someday, if there is life elsewhere, we may become aware of each other, and when we do, we’ll want to think about how we can co-author a true Encyclopaedia Galactica.  How can we exchange information, to know more about the Cosmos and our place within it?

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This post is part of an ongoing series, celebrating the forthcoming science series, Cosmos: A Spacetime Odyssey by revisiting the themes of Carl Sagan’s classic series, Cosmos: A Personal Voyage.  The introductory post of the series, with links to all other posts may be found here:  http://wp.me/p19G0g-dE

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Cosmos 2: One Voice in the Cosmic Fugue

by Shane L. Larson

imaginationHumanity is simultaneously blessed and cursed with one of the most ingenious creations of Nature: our imaginations.  Our brains have developed not just to run our bodies, and not just to absorb sensory data from the world. They store all the vast myriad of experiences we have and then, at a later time, recall that data for the express purpose of inventing ideas that may or may not have anything to do with reality.

An excellent example of how your brain works can be found in a simple game my daughter and I play at restaurants while we’re waiting for our food.  We call it “The Napkin Game.”  One person draws a simple line doodle, without lifting the pen, then the other person takes that doodle, looks at it from all angles, then adds more lines to turn it into a picture. When you draw a doodle for your partner, you don’t a priori know what it will be turned into.  That’s the magic of brains! Any random doodle could be Batman’s cowl, or a Wonka Bar, or a turtle. Your brain takes a little bit of visual input, maps it onto one of the trillions of neural connections in your mind, and makes something new!

An example of the Napkin Game. One person draws a simple line doodle, and the other person adds to it to make a picture.

An example of the Napkin Game. One person draws a simple line doodle, and the other person adds to it to make a picture.

One of the most important things your imagination does, is it extrapolates into the future.  Sometimes it makes up extrapolations out of whole cloth that likely have little bearing on reality (though they may be perfectly entertaining, if not desirable, daydreams).  I count among such extrapolations imagined futures where zombies have taken over the world, Apple Slice has made a comeback, or I am close personal friends with Queen Elsa of Arendelle.  But very often, the extrapolations are really simulations — attempts to divine a realistic future. This is the origin of wonder, of anticipation and excitement, and also of fear (particularly fear of the unknown). Imagination uses both of these extrapolations in the game we call science.

The most remarkable thing about imagination is that it knows no boundaries. T-rex flying a fighter jet? No problem. I’m really Walter Mitty, a member of MI:6 who cleans up after Bond?  Duh. Every kind of particle we have ever seen maybe has an undetected and completely made up “super-symmetric” partner particle?  Sure, that sounds cool to think about! 

Examples of imagination, possibly run amok. (L) Dinosaurs flying fighter jets [Lego model; dino added by S. Larson]. (C) The Standard model of particle physics. (R) The "SuperSymmetric" addition to particle physics, imagined by some physicists.

Examples of imagination, possibly run amok. (L) Dinosaurs flying fighter jets [Lego model; dino added by S. Larson]. (C) The Standard model of particle physics. (R) The “SuperSymmetric” addition to particle physics, imagined by some physicists.

Unfettered by physical limitations or abstract societal rules, our imaginations can stray from the possible to the impossible, from the real to the unreal, and from the mundane to the extreme. The most powerful aspect of this ability is that it allows us to ask questions about things of which we currently are completely ignorant.

Consider the question of life in the Cosmos.  Is there life elsewhere? Are we a singular instance of life, or is there a vast froth of life-filled worlds filling the deep, deep dark of the Universe?

One dish in the Very Large Array (VLA) near Socorro, NM. [image by S. Larson]

One lonely dish in the Very Large Array (VLA) near Socorro, NM, staring out into the Cosmos. [image by S. Larson]

It is a deep and through provoking question that has profound implications for our philosophical and cultural identities. We can ponder such questions precisely because our brains can take the question and push it to the extreme boundaries, which are:

(1) The Earth is unique. We are a singular instance of the music we call life, a lone voice shouting vainly into the vast, dark cathedral of the stars.

(2) The Cosmos is teeming with life, a vast ecosystem of atoms that have organized into patterns capable of replicating and contemplating their own existence.

Arthur C ClarkArthur C. Clarke once famously summarized these extremes, saying “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”  The amount we are terrified by this thought is the fault of our imaginations.  We are inherently social creatures — we thrive on contact, discussion, and shared common experience. All of us have, at some point in our lives, experienced profound loneliness — being lost, being trapped, being left out by our peers. When we imagine being alone in the Cosmos, our brain magnifies that sense of loneliness a trillion-fold.  What gets simulated is not the Earth all alone, but ourselves all alone — what if I were alone in the Cosmos, lost in the vast dark? We anthropomorphize the entire human race, mapping our own personal feelings onto 7 billion other souls.

In the opposite case, our imagination proposes a Cosmos completely contrary to the normal hubris that humanity wields.  Despite our proclaimed belief in the fundamental tenets of Copernican astronomy, where the Earth is not the Center of All That Is, we certainly don’t lead our lives that way. Humanity, as a rule, does not pretend to be anything other than the Center of Everything!  But it could be that we inhabit a Cosmos with other intelligences, some perhaps vastly greater than our own, some perhaps implacable and as unaware of us as we might be of ants or bacteria.  Such musings are disquieting because they challenge the central tenet of our perceived existence as the premiere lifeform, on planet Earth or anywhere else.

The question of whether the Cosmos harbors life elsewhere is a compelling one from the perspective of our psychology, but also because there is an apparent conflict between two eminently reasonably scientific viewpoints.  The first of these viewpoints is the so called “Principle of Mediocrity.”  This is the no-holds barred manifestation of the Copernican Principle — there is nothing special about the Earth.  The Cosmos seems to be filled with planets (the latest count, as of today, 9 Dec 2013 is 1051 known planets (visit the Exoplanet Encyclopedia Catalog), with some 3000 candidates from the Kepler mission.  Our deepest probes of the Cosmos (the Hubble Extreme Deep Field) suggests there could be as many as 600 billion galaxies. If each galaxy has 300 billion stars, and every star has at least 1 planet (probably more) then there are a staggering number of possible worlds on which life could have arose. There is nothing special about Earth, so if life arose here, there should be no impediment to life arising on any of the trillions and trillions of other worlds that fill the Cosmos.

The Hubble Extreme Deep Field (XDF). [Credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team]

The Hubble Extreme Deep Field (XDF). [Credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team]

Enrico FermiThe opposing viewpoint is something called “The Fermi Paradox.”  It was originally proposed by Enrico Fermi, and can succinctly be summarized as, “Where are they?”  What Fermi wondered was why has the Earth, or any world in the solar system, not been visited by self-replicating robotic explorers of some distant alien race?  His point was that if we really want to explore the galaxy, the most efficient way to do that would be to send a robotic probe out to the nearest star.  It won’t get there in a human lifetime, but it will get there in a time substantially shorter than the age of the galaxy.  When the robot gets to a star system, it pokes around a bit, then builds 10 copies of itself using the natural resources it can find, and sends those copies out to the next 10 closest stars.  If every robot successfully makes 10 copies of itself, it only takes 11 replication cycles before there is 1 robot for every star in the galaxy.  But really, why would they stop there? They would just keep replicating until there are a whole lot of robots in the galaxy.  But we haven’t seen one yet!  Why not? One’s immediate gut reaction might be to think, “Well humans are just the first species to have such a crazy idea. The galaxy is not full of self-replicating robots because we haven’t built them yet!”  But if we apply the Copernican Principle to Earth and humanity in particular, there is no reason to believe we are the first instantiation of intelligent life; some civilization should have preceeded us, and built the fleet of galaxy filling robots.  But there are no robots, and the chance that we are the first civilization in the entire galaxy is vanishingly small.  The fact that there are no robots means that we are alone in the Cosmos. 

Why has our solar system not been visited by alien robots, sailing through to see what the galaxy is full of? This is the central tenet of the Fermi Paradox. [Model by S. Larson]

Why has our solar system not been visited by alien robots, sailing through to see what the galaxy is full of? This is the central tenet of the Fermi Paradox. [Model by S. Larson]

The space in between these two possibilities is a matter of intense debate among aficionados of the search for extraterrestrial life, as well as professional scientists who spend their careers thinking about this. There are as many facets of the debate as there are persons engaged in the discussion!  In the absence of true, reliable knowledge, our imaginations have free reign. We imagine every idea we can, then argue about whether the idea is plausible or even possible.  One of the most intriguing ideas in this space is that perhaps no civilization ever survives to build a self-replicating army of robots to explore the galaxy. Maybe the Cosmic fugue of life never grows beyond the initial swelling notes of the song.

The dinosaurs haven't (didn't?) go exploring the galaxy. [Image from Captain Raptor and the Moon Mystery, by O'Malley and O'Brien]

The dinosaurs haven’t gone (didn’t go?) exploring the galaxy. [Image from Captain Raptor and the Moon Mystery, by O’Malley and O’Brien]

This is not an unreasonable idea. Even if we confine our considerations to the history of life on Earth, we’ve seen “civilizations” that persist for long periods of time. The dinosaurs existed on Earth for 160 Million years, and never developed a single bit of technology (so far as we know), let alone build a self-replicating robot to proclaim their existence to the Cosmos. In the end, the dinosaurs were completely obliterated, wiped off the face of the Earth by an asteroid. Today, their closest living descendants are the birds, but no chicken has reached out to explore the Cosmos either. 

But we don’t even have to think about lifeforms long gone. Even among our own species, entire civilizations have utterly vanished from the world.  Five thousand years ago, the Indus Valley Civilization (IVC) was comprised of 5 million persons, fully 10% of the entire world population at that time. It stretched all along the Indus River valley, in what is today the borderlands between modern India, Afghanistan and Pakistan. The preeminent civilization of the era, the IVC developed the first system of weights and measures; quantitative measure is the foundation of all technology and science.  But they did not colonize the galaxy. The civilization survived for almost two millennia, until the cities were mysteriously abandoned and the civilization collapsed, never having once cast their voice out into the Cosmos. Before they had the ability to build a robot, drought and shifting economics with other, nearby civilizations destroyed the greatest civilization the world had known to that time.

If I were to take these two examples at face value, and use my imagination to extrapolate to other worlds, I might imagine that life is common throughout the Universe, but perhaps it is far too fragile a form of matter to survive. Perhaps it is always obliterated, by the abusive hand of the Cosmos or through ignorance and self-destruction. Obliterated before it can send its seed, robotic messengers, out into the Cosmos.  That would be a depressing thought, with terrifying implications for our future on this world. But it is not inconceivable (even knowing what that word means); even in my lifetime, the spectre of the destruction of our world has constantly loomed, though it has been an evolving chorus of spectres, each sharing the lead.  As a child growing up in the 1980s, the possibility of nuclear annihilation was real and forefront in our minds, even as children. The threat is perhaps no less real today, but the end of the Cold War has reduced the threat in people’s imaginations. Today, the fragility of our climate and environment plays a more prominent role in considerations of what our future may be. Now, as in The Cold War, the conversation is driven by ideology and arguments built around emotional viewpoints rather than scientific considerations. It is not clear we will survive to build a robot army that will explore the galaxy. 

The Earth as seen from Saturn.  Can you tell there might be life there from this picture?

The Earth as seen from Saturn. Can you tell there might be life there from this picture?

Another possibility is that maybe it is just too hard to find other life.  Maybe it is out there, but detecting it is far more difficult than finding the proverbial needle in a haystack.  We are not even sure if there is life elsewhere in the solar system, and we live here! What would an alien robot sailing into the solar system find?  There are almost 100 known worlds in the solar system that are at least large enough to be round (say larger than 200km; list at Wikipedia). Would a robot explore all of them, or simply gaze from afar?  Consider what the Earth looks like from beyond Saturn.  Can you tell there is life here?  Look at the Earth from the Moon.  Can you tell there is life here, especially compared to a picture of Titan from roughly the same distance?  What if the probe never came in this close, landing on the first world it encountered, say Neptune’s enigmatic moon Nereid? 

The Earth (L) and Titan (R), each viewed by a spacecraft from roughly the same distance.  Can you tell if either harbors life?

The Earth (L) and Titan (R), each viewed by a spacecraft from roughly the same distance. Can you tell if either harbors life?

Despite all the difficulties, real and imagined, of searching for life elsewhere, we continue to do it, both by sifting the surfaces of worlds near Earth, as well as plumbing the depths of interstellar space looking for messages from other beings.  The idea of there being life elsewhere is one that is hard to let go of, because the alternative is far too depressing — that we truly are alone. It is a staggering thought, which we are constantly reminded of.

There is a very famous picture of Earth, taken by Michael Collins during the Apollo 11 flight.  As the ascent stage of the Lunar Module Eagle returned to dock with Collins aboard the Columbia in lunar orbit, he snapped a picture showing the Eagle (containing Aldrin and Amrstrong) hanging in front of the magnificent desolation of the Moon, with the partially illuminated Earth in the background.  Collins later remarked,  “I remember most vividly the picture of the lunar horizon and then the LEM ascent stage in the foreground with these two guys in it, and then the Earth popping up at that instant… You’ve got 3 billion people over there, two people here and that’s it.” 

A picture from Apollo 11 of every human being, alive or dead, except for Michael Collins (the photographer).  [NASA Image AS11-44-6642]

A picture from Apollo 11 of every human being, alive or dead, except for Michael Collins (the photographer). [NASA Image AS11-44-6642]

It is perhaps one of the most poignant images of the lonely Cosmos ever taken — every member of the human race, alive or dead, except the photographer. If indeed we are alone in the Cosmos, then that was everything, captured in a single frame, at a single moment in time.  Every voice in the Cosmic fugue, the chorus of life.

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This post is part of an ongoing series, celebrating the forthcoming science series, Cosmos: A Spacetime Odyssey by revisiting the themes of Carl Sagan’s classic series, Cosmos: A Personal Voyage.  The introductory post of the series, with links to all other posts may be found here:  http://wp.me/p19G0g-dE