Black Holes 5: Inklings & Obsessions

by Shane L. Larson

There are many exotic phenomena in astrophysics — some pervade the public consciousness, and others do not. Most folks have heard of the “Big Bang” and probably about “dark matter.” Fewer people have heard of the “Cosmic Microwave Background” or “neutron stars.” Perhaps even fewer have heard of “cosmic strings” or “radio jets.” But of all the strange and wonderful things astronomers and physicists have contemplated, the most universally known and recognized are probably “black holes.” Just about everyone has heard of black holes, and just about everyone has some cool science factoid they know about black holes and keep in their pocket — they pull the factoid out anytime the subject of black holes come up because the factoids typically MELT YOUR BRAIN.

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist’s illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. New studies with data from Chandra and several other telescopes have determined the black hole’s spin, mass, and distance with unprecedented accuracy.

I find black hole factoids to be a curious mix of some things that are true, some things that are speculative but possibly true, and some things are are outright fiction. Where do all of the exotic facts about black holes come from, how do we all learn them, and why are some right and some wrong? Wondering about this led me to contemplate when I first heard about black holes.

Black holes have long been a passion of mine — my mom will tell you I was always kind of obsessed with them. But when did I first hear about and learn about them? I certainly can’t answer that question definitively, but I do know some things about my early exposure, so I can try to understand what strange and awesome ideas first attracted my attention.

The earliest encounter of which I am certain is during the 1979/1980 timeframe. This was the time that many people saw Disney’s epic space opera The Black Hole, replete with adorable robots, killer robots, really awful bad dialog, and archetypical mad scientists. It has often been derided for its scientific inaccuracies (most notably by Neil deGrasse Tyson [link]). I definitely saw The Black Hole. Multiple times. And I still watch it sometimes. Neil’s right, there is a lot of inaccurate science about black holes in The Black Hole, but there is a lot that I think was okay too (more on that later). There are definitely modern movies that get the science more uniformly correct (Interstellar), but I don’t mind The Black Hole — certainly not as much as Neil. The point here is this is a known anchor point in my love affair with black holes.

So what could a movie like The Black Hole teach me about real black holes? If you ask almost anyone, they know the correct fundamental thing: a black hole is an object whose gravity is so strong, not even light can escape — even The Black Hole got that right. Since nothing can travel faster than light, nothing can escape. If you fall into a black hole, your fate is sealed. It is this idea of being trapped forever, without recourse or hope of rescue, that lies at the heart of our fascination with black holes. They are strange; indubitably. But to be inescapable suggests a kind of absolute and infinite supremacy. 

Me in elementary school. I’m not sure what I’m doing, but I’m pretty sure I’m not getting into trouble! [Image: Pat Larson]

In 1979/1980 I was in fifth grade, and I was gobbling this stuff up left and right. I was a well known fixture in both my school library (Hygiene Elementary School, in Colorado), and in the Longmont Public Library, where my mom had gotten special dispensation for me to have an “adult” library card so I could prowl through all the science books in the grown-up section. My parents also exposed me to a steady diet of books at home, and while they were all nominally “family books,” some of them made it to the bookcase by my bed and never went through anyone else’s hands. In 1980 one such book was Roy Gallant’s lavishly illustrated Our Universe, published by the National Geographic Society.  I was certainly enraptured with outer space by then, steadily fed by the ongoing exploits of Viking and Voyager as they played out on the pages of National Geographic. But this book — this book. Blew. My. Mind.

It is a book filled with great pictures from an exquisite generation of space probes, and from the best telescopes the world knew in the pre-Hubble era. But the art and scientific illustrations are what sucked me in. Paintings of the surface of Venus. Speculations of what weird alien lifeforms evolution could have created. Stupendous cutaways of planetary interiors and atmospheres. All of it was linked together with Gallant’s trademark lucid storytelling.  This ode to the Universe captured my mind and imagination and never let go. That first copy my parents gave me was read cover-to-cover, and carried for miles and years everywhere I went, pulled out of my backpack in moments of wonder and curious indulgence.

Examples of the art and technical imagery in Roy Gallant’s “Our Universe.”

Near the end of the book, Gallant talks about black holes in just 4 short paragraphs, but accompanies the text with a lavish, full-page artist’s idealization of a black hole in space, tugging on a nearby star, bending the shape of spacetime, and absorbing a beam of light that was inexorably caught in its pull.

He asks in the caption of the picture, “Can you imagine a star so massive that its gravitation eventually crushes it out of existence, leaving only a black hole in the sky?” This is classic Gallant, imploring the reader to immerse themselves in the mystery, throw caution to the wind, and employ their imagination — take what little knowledge you have and simply speculate. That is where good ideas come from, and it is the basis for all science.

The artist’s representation of a black hole in “Our Universe.” [Image: Helmut K. Wimmer]

In many ways, the reason you and I are having this little blog conversation is precisely because astronomers know that black holes exist in Nature and are the central players in many astrophysical phenomena. But reading Gallant’s text it is clear that when he wrote Our Universe, the existence of black holes was still a subject of much debate among scientists. Today there are many ways that we have measured the properties of black holes and confirmed their existence, not the least of which are the many that have been detected via gravitational waves. But still, pictures of black holes remain elusive. The best we have so far is the Event Horizon Telescope picture, a silhouette of a black hole against the backdrop of stuff around it.

The picture in Gallant’s book is an attempt to show a black hole as a three dimensional object in real space, but how do you do that?  It was a noble attempt, and it is certainly not what a black hole looks like, but it served its purpose — it got my attention, it fueled my imagination, and it made me ask questions then go see if the answers were known. To this day I keep copies of Our Universe nearby — one in my office and one in my study at home. It is never far from my mind nor my fingertips, and I often pull it down and lose myself in the epic stories it tells.

The other thing I know happened to me in the fall of 1980 was my first exposure to Carl Sagan’s Cosmos. Starting in late September, every Sunday night, I sat rapt on my parents’ living room floor in front of the television, whisked away to worlds and places in the Cosmos I had only previously imagined, transported by the magic of film, the lilting and elegant soundtrack of classical music, and Sagan’s poetic and sonorous narrative. One of the most widely known episodes is Episode 9, “The Lives of the Stars” which famously begins with Sagan declaring, “If you wish to make an apple pie from scratch, you must first invent the Universe.”

Sagan uses his famous declaration about pies to introduce the concept of the chemical elements — the atoms from which all the beautiful and complex structures of Nature are built. Beyond the simplest elements — hydrogen and helium — very little was created when the Cosmos was born. Almost everything on the periodic table is created by stars during their lifetime, and a great deal of it (the heaviest elements) during the catastrophic death throes we call supernovae and gamma ray bursts. In telling us about the death of stars, Sagan uttered the magic words I had heard before — black hole. In his trademark penchant for poetic description, he called it “a star in which light itself has been imprisoned.”

Sagan’s Cosmos was the first place I was introduced to the ideas of black holes in the context of general relativity, beginning with masses curving space and affecting the motion of other masses, and also a discussion of the principles of black holes as tunnels [Images from Ep 9: “The Lives of the Stars”]

He had led us to the existence of the super-strong gravity of black holes through an imagined tea party with Alice and her friends in Wonderland, but then he hung on it all the modern picture of curved spacetime. It was, as far as I know, my first exposure to Einstein’s brilliant realization, and it has ever since dominated my destiny. Today, I have a doctorate in theoretical physics, earned for studying the magical mysteries of that self-same curved spacetime.

Me and J. Craig Wheeler. He’s one of the reasons you’re reading this blog right now!

For many of us, our interest in black holes might be piqued by these kinds of exposures, and then we go back to our lives as dental hygienists or soybean farmers or city managers. But this was all still swirling in my mind when I entered college, and in the true traditions of higher education, my exposures took those latent passions and exploded them into what would become my life. I was an undergrad at Oregon State University and at that time there was a stupendous class on campus called “Rocks & Stars,” run by the indomitable Julius Dasch. This was one of the most popular classes on campus, and had a regular stream of guest speakers who visited and talked to us about cool stuff.  I have strong memories of one visit from J. Craig Wheeler, a supernova expert from the University of Texas at Austin.

Supernovae are one of the pathways for making black holes in the Universe, and Wheeler gave us a spectacular talk that culminated with him reading to us from a science fiction book he wrote, called “The Krone Experiment.” I won’t give it away (go read it!) but what I remember from the talk was Wheeler talking us through what would happen if you were standing on a sidewalk and a micro-black hole came booming up out of the ground next to you. What would you see and experience? It’s the sort of question that just captures your brain and won’t let go. To be honest, it was the perfect question to ask a young scientist in the throes of deciding to commit their career to studying these enigmatic objects.

I think every one of these stories illustrates a key fact in my mind: it didn’t matter what I heard about black holes in my youth, only that I did hear about black holes. Exposure did what it should: it filled my head with all kinds of possibilities, all of them totally brain-melting, and made me pay attention and ask questions later.

This last point is the most important point here: we want people to ask questions. Either because they are confused, or because they are idly curious, or because they want to learn more. To that end, having mind bending movies like The Black Hole is stupendously important, and I don’t care if they get the science perfectly right! I have colleagues who often grouse about bad science in movies, complaining vociferously that the producers should have taken a basic science class, or gotten a good science advisor. They proclaim, “Is it really that hard to get the science right? The right science is just as cool!” 

But people aren’t watching The Black Hole to learn science (I certainly wasn’t) — they are being entertained, itching a part of their brain that wants to be asked “is that even possible or real?” And that serves its purpose, because eventually every one of them ends up in an audience somewhere at a public lecture and raises their hand and asks someone like me “is what happened in the movie real?”  THAT is where we get the science right. The movie’s job was to put a question in someone’s mind, to make them care enough to know what the right answer might be, and then in some other part of their lives have some discussions about science, what is known, what is not known, and what the other mysteries of the Cosmos might be.

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This post is the last in a series about black holes.

Black Holes 01: Imaging the Shadow of Darkness

Black Holes 02: What are black holes made of?

Black Holes 03: Making black holes from ordinary stuff

Black Holes 04: Singularities, Tunnels, and Other Spacetime Weirdness

Black Holes 05: Inklings & Obsessions (this post)

Feeling Small in a Big Cosmos 01: Vastness

by Shane L. Larson

One of the great pleasures in my life is that I am both a professional as well as an amateur astronomer. I spend my days, like many of us do, behind a computer keyboard, staring at a computer screen. I get to think about things that are cool, like black holes and the death spiral of binary stars, and whether or not we can hear the faint whispers of gravity washing over us from some unimaginably distant cosmic shore.

There is nothing quite like standing out in the dark and seeing the Cosmos with your own eyes. [Grand Tetons, by Royce Bair; http://NightScapePhotos.com/ ]

But when I go home, I like to spend long hours of the night out under the stars, in deep personal communion with the Cosmos. Stand out in your backyard, or in a dark mountain meadow, and look up. The sky is deep and vast, studded by thousands of stars, tantalizing bright and inviting, but inexorably far away. If you’re lucky, you can see the Milky Way striking up from the horizon, soaring overhead into the velvet darkness, holding the sky up over your head. I find it deeply comforting to lose myself in that view, to let the Cosmos envelop me in its embrace; some part of me knows “this is home.”

The deep connectedness we often feel with the Cosmos is tempered by another realization: that we are small in the face of the vastness of the Universe. It is an ephemeral and unsettling feeling that is hard to explain and vocalize, but in the opening scene of Cosmos, Carl Sagan captured it perfectly, writing

“The size and age of the Cosmos are beyond ordinary human
understanding. Lost somewhere between immensity and eternity
is our tiny, planetary home, the Earth.”

Beyond ordinary human understanding. We can quantify the scale and age and makeup of the Cosmos, but most of the numbers we are forced to use are big — crazy big! Well outside the boundaries of our everyday experience. Numbers so far outside our everyday experience that to simply state them is almost meaningless, because when we hear them said aloud, our brains fail to process what we are really saying (or hearing). Saying and hearing the numbers fails to adequately capture what we instinctively know, but can lyrically convey one person to another with words that are poetic, but somehow deeply meaningful: somewhere between immensity and eternity.

Our understanding of the vastness of the Cosmos starts not by looking outward, but rather by looking inward. This photograph is one of the most iconic images of the Space Age, known as “The Blue Marble.” There have been many versions, updated every few years as new and better images become available. It looks, for all the world like a child’s blue, glass marble.

The Blue Marble, 2012. [NASA]

There are very few people who, when presented with this photograph, don’t recognize it as the Earth. But here is something to consider: to actually see the entire Earth at once, as it is presented in this picture, you have to be tens of thousands of kilometers away. In all the history of our species, there have only ever been 24 people who have seen the world this way: the Apollo astronauts who made the voyage to the Moon and back.  The rest of us have only become familiar with this image of our small, fragile world though their words, their memories, their pictures. Since that time, now approaching 50 years in the past, the picture has been updated and refined, not by human eyes, but through the lenses and electronics of robotic emissaries, cast out into the night to make voyages that we humans seldom seriously pursue.

The most common and fastest modes of transportation most of us will ever encounter.

This small, blue world is the starting point for all our voyages into the Cosmos, whether they be on ships adapted to the abyss of space, or on wings of thought, unfettered by physical separations in time and space. One way to think about the size of the Cosmos is to imagine making a voyage of exploration. In the stack of notebooks on my desk is one non-descript composition notebook marked “Destinations.” It contains within its leaves lists and notes of destinations on Earth that, given time and freedom, I would love to visit. Kind of my own personal Atlas Obscura.  Many of those destinations can be reached using an automobile, the transport du juor for most of the modern world. Most of us have been in an automobile, and have traveled regularly at a speed of say 100 kilometers per hour (about 60 miles per hour).  By contrast, many of the other destinations can only be reached using the air travel network that girdles our world, travelling by jet aircraft at about 900 kilometers per hour (about 550 miles per hour). Few of us have had the opportunity to travel faster, in a military jet or by rocket.

British astronomer, Fred Hoyle, once remarked “Space isn’t remote at all. It’s only an hour’s drive away… if your car could go straight upwards!” He’s right — the boundary of the Earth’s life-sustaining atmosphere is not that far over our heads. If our cars could drive straight up, we would be off on an epic, Cosmic road trip unlike any other before. Let’s consider a few interesting mileposts, and what their entries might look like in my Destinations notebook. My roadtrip car of choice: a Yugo.

Consider Earth orbit — the first stop on the way to anywhere beyond the Earth. For your spaceworthy Yugo, the journey up will be a few hours, and only 23 minutes at the speeds of a passenger jet. By contrast, it took the space shuttle just under 10 minutes to reach orbit.

The Moon was 4 days away if you travelled on Apollo; to drive your car would take 5.4 months of non-stop driving, and just over 17 days by jet. Here, we begin to get the inkling of why exploring the Cosmos is hard — at the speeds of everyday life, even the closest destinations are far away.

Spacecraft take 6-12 months to reach Mars by rocket. Driving in your car would take more than 106 years — longer than a human lifetime. If you left for Mars in a jet when you entered first grade, you’d make it just in time to have your high school graduation on the Red Planet.

Pluto has long been the outermost sentinel of the small neighborhood we call home. The New Horizons spacecraft has taken 9 years to fly there, and as of the time of this writing is less than 2 weeks away from its flyby encounter. If the ancient Egyptians had left for Pluto in a spacefaring Yugo, they still would not have arrived— the voyage by car takes almost 7000 years to complete; the voyage by jet takes 740 years.

Beyond the boundaries of the solar system, voyages by ordinary means can be computed, but they become utterly meaningless in terms of timescales. The center of the Milky Way is 26,000 lightyears away, which would take 31 billion years to reach at the speeds of a passenger jet — more than twice the age of the known Universe. The Andromeda Galaxy, the nearest spiral galaxy to the Milky Way, is 2.5 million lightyears away, but it would take us 3 trillion years to reach via jet.

We can compute these times, we can say these words, but our eyes glaze over and we let the words for the immensity of the Cosmos slip by us with little regard for what they really mean. The size of the Cosmos is beyond ordinary human understanding.

The Hubble Space Telescope. Arguably the most capable and successful telescope ever built by humankind.

Despite the fact that we can’t voyage across the Cosmos, we can look. The most capable and accomplished telescope the human race has ever built is the Hubble Space Telescope. In its 25 year lifetime, it has seen farther than any telescope before, with tens of thousands of scientific papers published using its data. One of the most remarkable tasks we set before it was the creation of “deep fields.”

Consider the evening skies, shortly after 9pm in January. The constellation of Orion, the Hunter, lies just to the east of the meridian (an imaginary line, running from due north to due south in the sky). Striking out from his western knee is the long and sinuous constellation of Eridanus, the Great Sky River, that winds and wends its way around a non-descript constellation known as Fornax, the Furnace.

Location of the Hubble Extreme Deep Field, between Eridanus and Fornax.

Between Fornax and one of the bends of Eridanus there is a small, blank patch of sky. Like many patches of the sky, there is nothing there visible to the naked eye. Even far from the city lights, if you stare into the void there, you will see little. To make a Deep Field, we take Hubble, the most storied telescope in history, and stare at one empty spot in the sky. For many days on end. In the case of this lonely spot on the banks of Eridanus, Hubble stared for 23 days.  The result is one of the most startling and revelatory pictures taken in human history.  It is called the Hubble Extreme Deep Field (XDF; NASA page here).

The Hubble Extreme Deep Field (XDF).

As you can see, the blank patch of sky is not so blank after all. Every fleck of light, every smear of something in this picture is a distant galaxy, a remote shoal of stars and planets and gas and dust, and just maybe, other intelligent beings staring up at the sky.  All told, in this single image, there are about 5500 individual galaxies. The faintest are 10 billion times too faint to be seen with the naked eye; it took Hubble, the most powerful telescope we’ve ever built, 23 days to see them.

And what have we learned from this picture of the Cosmos? All told, there may be as many as 500 billion galaxies in the entire known Universe. We know that the Universe is 13.7 billion years old, but the oldest galaxies we’ve seen formed soon after the birth of the Cosmos, about 13.2 billion years ago. Big numbers, huge numbers. Numbers beyond ordinary human understanding.

The Cosmos is ginormous (that’s a technical term). It is easy to be overwhelmed when faced with the enormity of it all. But you should also take heart. One of the most remarkable things about the Cosmos, one of the most remarkable things about our species, is that we can figure it out. Despite the size and vastness we have managed to see and understand remarkable and astonishing things about our home, and are capable of pondering the implications of our existence in the Universe. Next time, we’ll explore some of those discoveries and ponderings.

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This post is the first in a series of three that capture the discussion in a talk I had the great pleasure of giving for Illinois Humanities as part of their Elective Studies series, a program that seeks to mix artists with people far outside their normal community, to stimulate discussion and new ideas for everyone.

Part 1: Vastness (5 July 2015)

Part 2: Discovery (11 July 2015)

Part 3: Proverbs (20 July 2015)

Illinois Humanities taped this talk and you can watch it online;  many thanks to David Thomas for doing the videography!

Cosmos 14: A Personal Voyage

by Shane L. Larson

As I write this, I’m heading home from the PhD defense of a new young mind in Physics, where we argued about how Nature might have created time from gravity. I’m typing this on an iPad, a glossy piece of imagination made of glass and aluminum that instantly connects me to all the collected knowledge of the human race.  I’m sipping a cup of coffee, water infused with flavor and essences of a plant, extracted with one of the oldest human discoveries, fire.  Most impressively, I’m sitting in an airplane as I write this, blazing along at 520 mph.  To quote the comedian, Louis C.K., I’m sitting in a chair in the sky! I’m like a Greek myth right now.

The CRJ700 I flew today; one small bit of a modern Greek myth.

All these things are a result of the human proclivity to know the world around them. Each one is an evocative realization of imagination and creativity. Someone once imagined that we could do what birds do, and fly through the sky — an ancient dream told in the myth of Icarus, unrequited in the notebooks and imaginings of Leonardo da Vinci, realized at last barely more than a century ago. Someone imagined that I should be able to more or less instantly find out when the Slinky was invented, or hear Johann Sebastian Bach’s Brandenburg Concerti  on demand (No. 2 in F major is included on the Voyager Golden Record). Someone imagined that we could understand how Nature created time itself, and suggested ways that we could test those ideas. And perhaps most importantly, someone imagined that you should throw an innocuous bean into the fire, pull it out before it is completely destroyed, mash it up, mix it with boiling water and drink it — a stunning tour de force of imagination, perseverance and creativity!

iPad and coffee — two important and remarkable outcomes of science!

These are the kinds of things I think about every day — the trappings of every day life, which we often take for granted.  We overlook how truly remarkable every one of them is. Everything around you in your life we discovered by studying the world and figuring out how it works. That game of curiosity, exploration, discovery and application is what we mean when we say SCIENCE, and it is one of the most important things humans have figured out how to do.  Not just important because we know how to make smartphones and pharmaceuticals and band saws and rubber duckies, but important because in all the vastness of the Cosmos, we are the only form of life that we know of (with certainty) that has figured out how to do science. The methods of science are a natural and inevitable consequence of applying our curiosity to the world, and with it we can improve our lives.  This was one of the central themes of Cosmos.

The frontpiece to my Ph.D. thesis.

For the past two and a half months, I’ve revisted Cosmos each week, once again walking along the shores of the Cosmic Ocean, turning over interesting shells and poking at bits of cosmic flotsam and jetsam that have washed up on our shores.  I’ve listened to the tales of adventure and discovery; I sailed along side our robotic emissaries once again as they made the first grand voyages to the other planets in our solar system; and I once again learned a little bit of the history of how we came to start thinking about the wonder and mystery of the Cosmos.  And woven throughout it all, I once again soaked in the unshakable belief in our ability to learn, adapt, and make a better tomorrow.

I’ve enjoyed revisiting Cosmos one more time; I’m sure I will do it again, many times in the future.  On this particular visit, I did something I hadn’t done before — I tried to add to the stories, as many of you reading along know (my series started here).  All told, this game produced 31,000 words posted to the blog (not including this post).  I learned some new things along the way, and enjoyed myself immensely. For now, this is the last bit that I’ll write about Cosmos directly, though I’m sure we’ll return to it now and again in the future.

For the moment then, my Personal Voyage has come to a resting point.  In a few short hours, we will all return once again to a broken cliff on the shores of the Pacific Ocean, a place where more than thirty years ago we set off on a journey with Carl Sagan to explore the Cosmos.  Tonight, we’ll start the journey anew, with a new guide.  Like that first personal voyage, this one promises to be full of wonder, mystery, introspection, and discovery.  It’s time to get going again.

Carl Sagan, on the Pacific Coast, where the Cosmos journey began.

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This post is the last in a 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

Cosmos 13: Who Speaks for Earth?

by Shane L. Larson

Let me tell you a story about me that many people don’t know. When I was in junior high school, I was a small, exceptionally nerdy child who loved Star Trek, science, games of all sorts (provided they didn’t involve “teams” or “athletics”), and learning. My very best friend of the day was a similarly minded young gentleman, who introduced me to computer gaming (“Colossal Cave”, which we played on the mainframe at Ball Aerospace, where his father worked), World War II aircraft, and car mechanicing. He also had epilepsy. It was frightening when he would have seizures, because he would go blank and suddenly it was like he didn’t know me or anything about the world around him. I don’t recall how long these episodes would last, but what I do remember is his father would swoop in, and sit with him for time, and eventually my friend would be back, and we’d be off to explore the world again.

A scar on the orbit of my left eye; stitches in my 7th grade year. The scar has faded slowly over the years, but is still obviously there if you know to look for it.

Now, as was often the case in the cruel world of middle-school aged children, we were the target of bullies. My locker neighbors reveled in shutting my locker each time I opened it, or knocking all my books on the ground so I was tardy to next period. Once they took my prized possession of the day, the Collected Novels of H.G. Wells; when I decided that day to fight back, I was bodily thrown across the room into a metal chair, gouging myself on the orbit of my left eye, requiring 7 stitches and leaving a scar I still have today. My best friend was a similar target, with more serious consequences because the physical bullying would often trigger a seizure. The school administration took an all too common viewpoint on these matters: no one saw it, so it is your word against theirs. An odd viewpoint in light of the amount of blood streaming down my face (I don’t know what the bully had told them, but to be fair I had bit him when he had me in a headlock).

Me and my family, in my high school years. My mom and dad instilled in all three of us boys a robust sense of justice.

Now my parents are the most moral, upstanding people I know, and taught me a deep personal philosophy about justice. Now, in the wisdom of my adulthood, I like to hang quotes from Gahndi on it, like “It is better to be violent, if there is violence in our hearts, than to put on the cloak of nonviolence to cover impotence.”  But really, what I remember are words from my Pa: “Bullies are really just cowards, so knock them down. And make sure the bastards don’t get back up.”  The matter all came to a head on a late winter day during my 7th grade year. My best friend had his head bashed against a locker, which triggered a bad seizure. No teacher saw it happen, but I resolved it was going to stop.  At the end of lunch period that day, I bought an extra milk, and opened the carton on both sides. I remember one of my other nerdy-friends standing next to me saying, “Aw, how are you going to drink that now?” I didn’t answer; I was standing behind the locker-basher, who was sitting at a table. I upended the carton of milk over his head, and beat the tar out of him. The event instigated one of the largest food fights the junior high school had ever seen, and I was awarded a 2-week suspension, which I took without argument.

One of the most often reproduced Apollo images; Jim Irwin on the plain at Hadley, in front of the Lunar Module Falcon and Lunar Rover. [NASA Image AS15-88-11866]

The aftermath was the most important. My friend and I were never the target of these particular bullies again; nor were we the target of a somewhat wider group of bullies who had always circled on the fringes of our lives. This kind of mayhem was far outside the boundaries of what was expected from me. The event somehow incited some people to ask what really happened, and to pay attention. After a long discussion with the faculty advisor about the event and the reasons behind it, my National Junior Honor Society membership was maintained. My suspension was lifted a week early, so my friend and I both could attend a school assembly featuring Apollo 15 astronaut Jim Irwin, whom we met and talked with! But most importantly, my science teacher docked my term project about the anatomy and life cycles of frogs from a 100% to an 80%, dropping me a letter grade in the class. It blemished an otherwise admirable middle-school academic record. She never said a word, and just kept right on treating me like the scientist she seemed to know I was going to become. She reinforced a lesson my parents had already touted — there are always consequences, even when you are doing the right thing, but it shouldn’t stop you from doing the right thing.

Now, in my adulthood, I still carry that same overbearing, black and white opinion about justice, and an unfailing opinion that people who can stand up should stand up for those who can’t. It is something that I often think about as I push my way blindly forward in my career.  What do I do everyday, when I’m not writing this blog for you to read?  I’m a scientist; an astronomer. What does that have to do with bullies and childhood scraps? Everything in the modern world.

A white dwarf is the skeleton of a star like the Sun, long after it has died. It has about the mass of the Sun, but is the size of the Earth. [Image by STScI]

In my everyday life as a professional scientist, I spend my time thinking about astrophysics, exploring our understanding of how gravity influences the evolution and life of white dwarf stars, the ancient cooling skeletons of stars that lived their lives like the Sun. Some days, I teach intro science classes to young women and men bound for careers in business, medicine, law and management; people who may never take another science class in their lives, nor think all that much about science ever again. Every now and then, one of them asks me, “What is understanding white dwarfs good for?” There are a whole host of reasons related to how stars act as astrophysical laboratories, simulating conditions that are difficult and expensive to replicate on Earth, and how the knowledge has applications to technology, energy, and medicine.  But the real reasons, the important reasons are these:

(1) Astronomy, unlike bench science in a laboratory, in an exercise in looking, thinking, and understanding Nature from afar. The practice of astronomy teaches us how to think deeply about the Cosmos, how to unravel the secrets of Nature, and not fool ourselves into thinking something false. More than any other science, astronomy teaches us to be harshly critical of our reasoning, to be brutally honest about what we know and don’t know, and to be quite certain of our conclusions when we say them out loud.

(2) Every person has a deep seated sense of wonder, waiting to be ignited and tapped. We cannot know who or what will inspire those who see the future for us, but we know it will happen, just as it has happened in the past to people named Steve Jobs, Temple Grandin, Dean Kamen, Rachel Carson, and a thousand others. We explore, learn, and teach the wonder of the Cosmos with the certainty that it can and will inspire someone someday to consider a life in science and technology, a life in service to our species and our planet. The consequences of not teaching people about the wonders of astronomy are almost too awful to contemplate. What if the next Newton never discovers science? What if the cure to cancer is hidden inside someone who is never inspired to continue their education?

(3) Lastly, in a world increasingly dependent on science and technology, science has become a weapon.  Not a a tangible device of destruction (though there are certainly plenty of examples of those), but a psychological bludgeon used to prey on those who have weakness or uncertainty in the realms of science and evidence based reasoning. The Earth faces an uncertain future in terms of its long term evolution, and the survivability and impact of our species on this planet. Special interests, driven by economics, politics, or ideology, have become the bullies of the modern world. Their tactic of choice is the subversion of knowledge and evidence-based wisdom, using modern media to sow uncertainty and discontent, holding the world hostage in a constant state of confusion and embittered debate. The weapon against those with shallow vision and self-serving interests is critical thinking, and common cause.  For the first time in all the history of the Earth, we have both. The practice of science is the human species’ profound realization of the process of critical thinking; it’s only goal, is to seek the truth with unflinching respect for the evidence and facts. Technology has given us the ability to communicate, directly and personally, with every person on the planet.

In a 1990 essay for the Committee for Skeptical Inquiry Carl Sagan wrote, “We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology.”  This is a trend that has not changed in the two decades since; if anything, it has become exacerbated as technology and mobile technology has interlinked our world and become enmeshed with our daily lives.

Smartphones and carburetors, two of the great mysteries of the modern world. Making sure everyone can explain their inner workings is not the goal of science literacy.

The danger is not that people don’t understand the workings of a smartphone touchscreen or the purpose of a carburetor.  No, the true danger lies with people being told what they should think about a complex and interconnected world, instead of being able to think critically about how trustworthy the information being passed to them is. The best way for the citizenry of the Earth to protect themselves from charlatans is to know how science works. The second best way is for scientists to put some more skin in the game.

Science cannot be limited to those who practice it; it cannot be an esoteric playground of wonder and imagination for the privilege of a few.  What scientists know must be explained and popularized for the citizens of the world; people must understand that the purpose of science is to improve their lives, and it has.  Modern medicine has erased crippling diseases, satellites girdle the world providing a never-ending stream of data about the weather and evolving state of the planet, and telecommunications technology has deprovincialized knowledge to build a global community. The world-spanning internet has made communications instantaneous and egalitarian, exposing a vast fraction of the world to the wisdom and art of our species, but also connecting all of us instantaneously to the abject horrors our race is capable of, and showing the implacable forces of Nature casually destroying human constructs. Science is all around us.  It is not perfect, but it has repeatedly demonstrated an unfailing ability to change the world.

There are plenty of vocal scientists and active science communicators.  Phil Plait (twitter: @BadAstronomer) is a robust opponent (among many other things) of the anti-vaccination lobby. James Hansen and Michael Mann (twitter: @MichaelEMann) are prominent faces in the battle against climate denialism. Jennifer Ouellette (twitter: @JenLucPiquant) writes and blogs tirelessly about science and mathematics.  But there need to be more — many more. It is estimated that only 5% of the labor force in the United States are practicing scientists or engineers. That is an extraordinarily tiny fraction, so there is a challenge for everyone.

Richard Feynman

On the part of the scientists, the challenge is to talk with your neighbors, talk with your friends, talk with anyone who will listen. There has been a slow and steady decline in the public percpetion of the value of scientists and academics in general.  This has been widely discussed recently in light of an excellent OpEd by Nicholas Kristof. Many academics have taken great affront to this article, but as I tell my 7-year old: how you act is up to you, but how people think you act is up to them. If you want people to change how they think of you, then you have to change how you act (especially when they are watching). In this case, many many decades of unremitting dedication to the urbane life of an academic, steeped in our own traditions and mindsets, have burned bridges that should never have been severed. Scientists are particularly bad at this, and we see the results — charlatans are slowly eroding public confidence in science to the point where despite overwhelming evidence, people don’t know what to think about the future of our planet or species. Richard Feynman always said, “Science is what we do to keep from lying to ourselves.”  Our job is to help people understand that.

George Bernard Shaw.

On the part of everyone else, the challenge is learn to think critically, just as you do with everything else in your lives — you are the ones who are going to decide the future of our civilization, with your money, your actions, and your votes. Talk with your neighbors, talk with your friends, talk with your children.  Honor the wisdom of George Bernard Shaw, who admonished us to “Beware of false knowledge; it is more dangerous than ignorance.” We are being bullied, scarred for life, and we don’t even know it.  Forces within our society think they can play on our fears, for their own benefit, by encouraging us to doubt and deny our hard-fought ability to reason.  It’s time to fight back against these nebulous and callous forces, with the most powerful weapon we have: science. Denial of science is a denial of our birthright, an abandonment of a legacy of 40,000 generations of human beings who have walked before us.

With all the long future days of our planet and our race in front of us, there is but one task before us: preserving the lives of the citizens of the Earth, be they human or not, and ensuring the future habitability of this planet, the only place in the Cosmos we know, with certainty, where any form of life can and does survive.

We speak for Earth, you and I.  Our loyalties are to the species, and the planet. We speak for Earth. Our obligation to survive and fluorish is owed not just to us, but to the Cosmos, ancient and vast, from which we spring.

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Final Note: This closing quote, is the closing quote from Cosmos as well. Thank you, Carl, for a journey that defines much of what I think, say, and do every day of my life. From the stars we came, and to the stars we shall return, now and for all eternity.

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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

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.

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]

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).  Furthermore 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]

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)]

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]

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.

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.

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]

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

Cosmos 11: The Persistence of Memory

by Shane L. Larson

One of my all time favorite books is the 1952 novel “City” by Clifford D. Simak. It is a yarn spun of a distant future where humans have utterly vanished from the planet, and the Earth is inhabited by an intelligent society descended from our domesticated canine friends.  The dogs regale their young pups with tales of the websters (humans) who once inhabited the world.  After the telling of the tales, the pups are always full of questions: “What is Man? What is a city? What is a war?”  As their elders calmly tell them, “There is no positive answer to any of these questions.”

It is a curious thought, to look at our civilization, and ask what some future generation might ask of us if they had nothing but our cities to look at.  It is a question we often ask ourselves when encountering the constructions of civilizations that have utterly vanished from the annals of history.  Staring at the crumbling remains of ancient buildings, massive temples and pyramids, and monolithic stones, we ask ourselves questions: “Why are these here? What was this for? Who were these people?”

Imagining a distant future without us has become a cottage industry, with striking images by excellent, modern artists, imagined against the backdrop of our greatest cities, such as Chicago (L) or New York (R).

As scientists, when we look at the crumbling remains of lost civilizations, we try to let our minds imagine how it happened.  When I stare into the ruins of a society long since vanished from the Earth, such as the Anasazi of the American Southwest, the Tiwanaku of western Bolivia, or even the ancient Romans, I often wonder what happened near the end?  Did they know their civilization was crumbling, that it would soon be subsumed by the slow and steady march of time?  What did the people think and do as their society was collapsing around them?

(L) The Cliff Palace at Mesa Verde, one example of an abandoned Anasazi city [National Park Service image] (R) The Kalasasaya and lower temples at Tiwanaku. At equinoxes, the sun shines into the Ponce Monolith, aligned in the main door. [Image from Wikimedia Commons]

One of the difficulties we have when considering the fate of these long lost ancestors of ours, is there are few, if any, records of their civilization that survive to the current common era. No great papers of statesmanship, no news clippings; no children’s textbooks, no essays from great scholars; no grocery lists, no lusty romance novels.  A few works survive, to be sure, but nothing in great numbers; nothing to give our anthropologists and historians the raw material to understand what was going on in the minds of the people in those far away civilizations.  Virtually everything they were, everything they thought, is now lost. They speak to us only through shattered and incomplete artifacts, remnants of everyday life buried under centuries of accumulated soil and detritus, and through what few remaining architectural constructions still stand in the shadow of our civilization.

A typical household bookshelf (this is one of mine) contains a wide variety of books — the collected knowledge, wisdom, and imagining of our civilization, gathered and preserved on paper and capable of surviving into the far future.

But today, unlike 2000 years ago, books and paper and writing abound. In addition to those who diligently secure the knowledge of the human species in scholarly works, there are tremendous amounts of other information being captured by a species that has become enamoured with the written word.  Bookstores abound, and books are produced and sold in massive numbers. Journalling and daily writing are a common and well regarded activity.  People collect, hoard, and use notebooks and fountain pens. Families, libraries, and city councils make and bury time-capsules full of books, newspapers, messages, and artifacts for future generations. I would love to slip into hibernation, and emerge several centuries in the future, to see what survives, and what our descendants think of us after sifting through the surviving scraps. 

A family time capsule my wife and I made in 2000. We picked the 2017 opening date, guessing that any potential children we might have would be in elementary school, and interested in artifacts of the past. Our daughter will be 10 years old when we open this time capsule. The suspense is killing her!  🙂

Imagining how to store information, so our memory persists and is understandable in the future brings three immediate questions to mind: What would we want the future to know about us? What will the future think about us? And how do we get a message (that can be understood) from us to them?

It is a fascinating mental puzzle to me, to try and imagine how best to speak to someone far removed from you in time, if not also in space and culture. Consider this blog.  The post you are reading lives now, in this moment.  Will WordPress and web-browsers and Unicode-8 exist 400 years from now? Probably not. All this will be lost, faded back into the ethereal fabric of the Cosmos.  For the moment, these words are organized into well-ordered bits of data, stored and represented as a few fleeting photons of light that leap from the surface of your tablet to the retina of your eye, where they are transformed into electrical impulses deep in the furrows and cores of your brain. But eventually it will be gone; the memory circuits will be loose silicon atoms in a landfill, perhaps. When I’m 107, I may remember writing this, but when I return to star-stuff, those memories will become unorganized electrical and thermal energy once again, lost forever. Maybe, on a forgotten and dusty shelf, someone will find my hardback copy of Carl Sagan’s Cosmos, the pages somewhat yellowed with age,and obviously well-thumbed, but still readable. They will scan the words, and wonder what it was like to live today, in the age where we were first exploring the Cosmos beyond Earth. But this blog, this personal exploration of Carl Sagan’s Cosmos, will be lost forever.

Do you think the loss of information in today’s age is unlikely?  Try finding something on Geocities — it is estimated that 38 million webpages vanished when it shut down in 2009. Where are the 97 lost episodes of Dr. Who? Information can and does disappear, even in our digital age.  How often do you back up your hard drive? Do you have a copy of every email you’ve sent and received (Stephen Wolfram has his)?  Can you still read the report on life in Rhodesia (now Zimbabwe) you wrote in high school using WordStar? 

The lack of WordStar, the computer it can run on, and a floppy disk drive that can read a 5-1/4” floppy disk means all that you wrote in that report is virtually gone, lost forever.  Technology creates the ability to collect, store, and distribute information; but when the technology becomes obsolete the information becomes endangered.  I’m pretty sure in our family time capsule, there is a VHS tape.  I haven’t owned a VHS player since around 2006, a scant 6 years after I closed up the time capsule!  How am I going to play that tape back???

But the truth is, no matter how carefully we preserve our technology, and strive to make it readable by some distant future generation, it will all be lost eventually.  Because someday, all stars die.  When they do, they destroy the planets around them, and all record of the life and civilizations that may have existed there.  Someday, around 5 billion years in our future, the last day of the Earth will dawn.  The Sun, having exhausted its supply of hydrogen deep in its core, will be on its way to the grave. It will have swollen to enormous size, swelling until it swallows the entire inner solar system during its “red giant phase.”  When that happens, the Earth will be no more.  It has happened to billions of stars before the Sun, and it will happen to us.  When those stars that came before the Sun died, did the galaxy lose some impossibly ancient civilizations?  Does there perhaps exist some persistent memory of them, drifting among the stars?  And if there is, can we possibly hope to understand how those memories are encoded?

I often daydream about a distant future, thousands if not hundreds of thousands of years in the future, where our distant descendants sail the stars. Still not far from us in evolutionary terms, our imagined future descendants will be far separated from us in time, farther than we are from our ancestors who walked the Nile Delta or the Indus River Valley a few thousand years ago. It is improbable, but not impossible, that they may stumble across a ancient hulk drifting among the stars — a device of intelligent design, cast out among the stars by some ancient, long lost civilization.

Taking it amidships, they will quarantine it.  Like us, our descendants will be good at figuring things out — science and engineering are tools that will have allowed them to overcome many challenges, and led them to the stars.  The intriguing device will be scanned, examined, and prodded from afar. Once they are convinced it is safe, they’ll approach it up close, touch its surface, and see how it is constructed. It is only then they will discover a great wonder — bolted to the side, obviously meant for intelligent eyes, is a message. It is not written in any language that they will recognize, but it is clear it is meant to be decoded — a message from the builders.

What will a message found drifting on a lost hulk in space look like? If we stumble on a message, will we be able to decode it?

Science and engineering teams will be brought in, together with linguists, technologists, and mathematicians. They will uncover a code, a simple cipher built around fundamental numbers related to hydrogen, the most common substance in the Cosmos. Following the simple, encoded instructions, they will find sounds and images, and a great mystery. The languages are foreign to their ears, the messages meaningless; but there is music — stunning music; and images, probably of the builders and their far-away world, cloudy and water shrouded.  But the builders are us.  The device is one that you and I are intimately familiar with. We call it Voyager 1, and the message is known as the Voyager Interstellar Record.  But to our distant star-faring progeny, it will be a long forgotten artifact, unknown in the fragmented historical records they have from their past.

It is not impossible that our descendants will have forgotten us, and possibly forgotten the world they even came from.  Consider our own distant past. Some of the oldest known artifacts from our ancestors are pieces of jewelry, made from mollusk shells between 90,000 and 100,000 years ago. We know nothing about the people who made those artifacts, only that they were deliberately made; all other knowledge of them is gone, lost forever.

Someday the knowledge of us could similarly be lost forever, but some small and incomplete memory of us will persist.  Buffetted by the quiet tradewinds of the galaxy, the two Pioneer and two Voyager spacecraft will spend the next billion years sailing the interstellar voids, far outliving their creators, bearing only the merest scrap of memory about who and what we are.

As of this moment, the Pioneer and Voyager spacecraft are the only artifacts of our civilization, the only memory of us, that will definitely persist beyond the death of the Sun.

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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

Cosmos 10: The Edge of Forever

by Shane L. Larson

My parents are both natural scientists — my mother is a forester, and my father is a plant ecologist. As kids, we would spend long weeks in the summer camping doing “field research” in the wild backwoods of the Rockies.  Tents were optional, and at night I would often lie in my sleeping bag staring up into the blackest night you can imagine.  

The Milky Way, rising over a campsite near Crater Lake, Oregon. [Image by Shane Black, Website]

From the dark valleys and meadows of the Rockies, the sky is a seemingly endless tapestry of black velvet, studded with a sparkling horde of stars converging on the vast gossamer seam of the Milky Way.  It is impossible to scan that deep darkness, as you slowly drift into that fuzzy netherworld between wakefulness and sleep, and not feel like you are falling into an infinitely deep sea that goes on forever.

And for all we know, it does go on forever! The vastness of the Cosmos, especially compared to the typical scales of our everyday lives, is mind-bogglingly large. It is a fact that we have always been cognizant of — our stories, our legends, even our everyday experiences place the sky very far away, beyond the simple reach of human hands. The glitter of distant stars provide an ideal tapestry upon which we can paint our wonderings about the Universe and our place within it. Where did the stars come from? Where did the Earth come from? Where did we come from?  These are the oldest questions we know of, uttered around campfires and over late night dinners and in scholarly classrooms for countless generations.  The answers to these questions are part of an exquisitely interlinked puzzle that starts with the birth of the Universe, and leads ultimately to me and you.  The study of that puzzle is called cosmology.

Cosmology is a branch of science that is a bit like history — we are reconstructing the past history of the Cosmos as a way to understand what we see around us today, and to predict what the ultimate future and fate of Everything might be.  We reconstruct that past history by looking deep into the Cosmos, and with the Laws of Nature in hand, attempt to explain what we see.  As we have talked about before, looking out into the Cosmos is a kind of Wayback Machine — looking across space is looking back in time.  Today, we can see farther across the Universe than at any other time in human history; we have discovered and know more than all the 40,000 generations of humans who have come before us.  And we’ve discovered something remarkable; we’ve discovered that in the beginning, something happened.  Cosmologists call that something, “The Big Bang,” the origin of Everything that Is.

When studying cosmology, you will often read a sentence about the Big Bang and the Origin of the Universe.  The Origin Statement goes something like this: everything in the Universe began in an infinitely dense point smaller than the period at the end of this sentence.  What does that mean?  The answer is the basis for our current understanding of all of the Cosmos.  Let’s parse that question into several smaller questions.

The first obvious question is what do we mean by Universe?  Here, we will take the fundamental definition of Universe to be “everything that exists.”  But there is an unspoken subtlety in the Origin Statement as we wrote it here — in this case, the use of the word “Universe” actually means “Observable Universe.”  What’s the difference between “The Universe” and “The Observable Universe?”

My favorite lunch dive, in Logan, UT.

Consider an example from your everyday life — lunchtime.  Imagine one sunny day you decide to forego the sack lunch you brought with you and instead decide to go out to lunch with some of your friends.  You only have 1.5 hours before you have to be back, and you are walking on foot.  You can only walk so fast, so where are you going to go?  Perhaps Guy Fieri has pointed you toward an excellent BBQ joint on a late night episode of “Diners, Drive-Ins and Dives,” but that would require either a plane flight or a very long road trip, both of which will take far longer than the 1.5 hours you have. Instead, you confine your attention to restaurants within a certain distance — reachable if you walk as fast as you can for a limited amount of time.

The Universe is kind of the same way — there is a maximum speed that anything can attain, namely the speed of light. Thus, in the age of the Universe, there is a maximum distance over which any information can come to the shores of Earth — the distance that light can travel in the age of the Universe!  The “Observable Universe” is that part of the Universe from which we could have received some light that started travelling at the moment the Universe was born, and is just now reaching Earth today (analogous to how far you can walk during your lunch hour).  It is a small part of the “Entire Universe,” most of which we know nothing about because the light from there has not had the chance to reach us (analogous to the entire vast world full of restaurants, which you cannot reach during your lunch hour!).

The Observable Universe is just a small part of the Entire Universe. It is bounded by the farthest distance light could have travelled in the age of the Cosmos. If Earth is at the center of this boundary, then light from outside the blue boundary (such as from the yellow galaxy on the right) hasn’t had time to reach us yet. [Illustration by S. Larson]

In the beginning, the Entire Universe was just a vast (possibly infinite) collection of the ultra-dense points mentioned in the Origin Statement.  The Big Bang was not really an explosion, not in the sense of an exploding stick of dynamite; the Big Bang was the apparently spontaneous and rapid expansion of every single point in the Entire Universe.  What is expanding?  The fabric that makes up the Universe itself is expanding, carrying everything that would become stars, galaxies, trees, kangaroos and people along with it.  Cosmologists call that fabric spacetime.  The very stuff that the Universe is made of — spacetime — is stretching.

Now if that doesn’t immediately make sense, don’t worry! It is a disconcerting and unfamiliar idea. The contemplation of big ideas is always a bit uncomfortable, because we’re stretching our brains in ways that it is not used to; that’s the way science works.  One way to help settle your mind around unfamiliar concepts and to build intuition is to appeal to analogies.  Analogies and metaphors are not perfect, but they help connect the ideas that need to be connected.  One of the classic analogies to understand the Big Bang is to imagine other things that stretch and expand.

Consider a large piece of spandex, with a checkerboard on it, as in the figure shown here.  The checkerboard pattern is not necessary, but it provides a quick and easy way for us to see and talk about distances. This checkered fabric is an analogy, a metaphor that we use to think about the Universe, and in this picture imagine it stretches far beyond the boundaries of the page of your computer screen.  For the moment, I have made the checkers large enough to see, but you could easily imagine them being smaller than what is drawn here, even much smaller (perhaps as small as the proverbial period at the end of the Origin Statement).

Imagine I have two ants sitting on the spandex, one named Xeno (the black ant) and one named Scarlett (the red ant).  They have both staked out a square they like, and are staying put, watching closely that the other ant does not move off their chosen territory.  This is the case shown in the first figure.

(L) Consider two ants, Xeno and Scarlett, on a stretchy sheet representeding the spacetime fabric of the Cosmos. (R) When the Cosmos expands in every direction and at every point, the two ants get farther apart. [Illustration by S. Larson]

Now, unbeknownst to our ants, the very fabric of the Universe is expanding around them, as shown in the second figure. It expands uniformly, in every direction. The result of that, in the context of my spandex checkers, is that every square gets larger (though our ants remain the same size, comfortably bound together by the biological goop and intermolecular forces that give their bodies form).  What are the observational consequence for our ants, keeping their beady little ant eyes on each other?  Much to their surprise, they find themselves slowly getting farther apart!  Scarlett looks around, and clearly she is not moving — she has not moved at all since our little experiment began. Never-the-less, it is quite clear that Xeno is receding from her. Meanwhile, Xeno is thinking the same thing. He has not shifted nor moved at all, but Scarlett is inexorably getting farther away.  The explanation? The very space between them, the stuff that the Universe is made of, is expanding.

What is interesting is that every square in the fabric of our Universe is expanding — the squares are getting larger, and everything is getting farther apart.  No matter how tiny every square started, if we wait long enough, it gets bigger.  The consequence is that from the perspective of anyone anywhere in the Universe, every other point is flying away from them.  Consider a few more ants: Xeno, Scarlett, Kermit (the green ant) and Indigo (the blue ant). If each one of them measures the distance to every other ant, they find that if they wait a while, the distance to every other ant increases.  From  the perspective of any ant, firmly rooted to their little territory in the Cosmos, every other point in the Universe is slowly getting farther and farther away, no matter what direction they look.

Imagine an army of ants (clockwise from the top: Kermit, Scarlett, Indigo, and Xeno). If they all watch each other as the Universe expands, they think ALL other ants are moving away from them, no matter what direction they are. [Illustration by S. Larson]

This is how we think about the Big Bang.  Everything that you can see (the Observable Universe) was once contained in a dot smaller than the period at the end of this sentence; it was like a teeny, tiny square on our spandex.  Then the Big Bang happened, and every point in the Entire Universe — every point on the spandex — started to expand.  The part of the Universe you can see is only one small part of the vast fabric that is everything, but it all started long ago in a very tiny spot.  Everything you can see in the Universe began in an infinitely dense point smaller than the period at the end of this sentence!

On the surface, this story sounds fantastical, almost beyond belief. We can always make up fantastical ideas about the nature of the Cosmos, but for those ideas to move beyond mere speculation and into the realm of science, we must be able to test those ideas.  There must be something we can look for, something that we can observe. In the case of cosmology, there is.

One of the things that physicists know about the world is that if you compress things they get hot. This is the principle behind pressure cookers, this is why it is hot in the core of the Earth, and this is why the Sun burns hydrogen in its core. When the pressure goes up, things get hot!  If the Universe is expanding today, we can imagine running the movie backward in time, watching everything run backward toward the Big Bang.  Because we see everything flying apart now, when we run the movie backward what we see is the entire Observable Universe being compressed down into a small point. The pressure in that point would have been enormous, which means it would have been tremendously hot.  If that were true, there should be some thermal signature of that early, hot, dense state of the Cosmos.

There is such a signature. Arriving on Earth from every direction on the sky, is a faint fog of microwave radiation, known as the Cosmic Microwave Background. It is the light that was released from the birth of all the atoms in the Cosmos, 400,000 years after the Big Bang.  Before this time, the Universe was so hot and dense that atoms could not hold together; they would constantly crash together and break apart into the fluff from which they are made, melting back into the primordial soup of light and sub-atomic particles. But as the Universe expands, it cools slowly until atoms could hold together. The moment that happened, the soup immediately thinned and the light flew free, carrying the message of the birth of the atoms.

The Planck map of the Cosmic Microwave Background. [ESA/Planck Collaboration]

This picture of the Cosmic Microwave Background is the most accurate map every made of the microwave sky; it is the youngest picture of the Cosmos we have ever taken, and the strongest piece of evidence we have that the Big Bang unfolded in the way we have just discussed. This picture, an image of the Cosmos very shortly after its birth, is one of the greatest legacies of our race. It captures, in an exquisite map of subtle patterns and colors, the ability of our species to reduce our ignorance, to become more enlightened about the Cosmos and our place in 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

Cosmos 9: The Lives of the Stars

by Shane L. Larson

A distant memory is anchored in my mind of a warm fall afternoon shortly after I started college. I was sitting in a musty old university classroom, in a battered wood and steel desk chair from around World War II. The gentle breezes that wafted in the window carried the promise of frisbees and afternoon picnics in the shade, but not until my art appreciation professor was finished droning on.

At one point in the lecture, my professor’s voice pierced my reverie and longing for the end of class.  “Art is a way for people to know themselves. If you let it, art is a window into your feelings, your past, your future, your aspirations, your dreams.”  This is, more or less, the classic explanation of why we appreciate art and need art as part of our society.  By contrast, science is often portrayed as the opposing activity — while science is a way to know something, it is not yourself, but rather the world around you.  Science is a window into the inner workings of the Cosmos.

But I don’t think there is a difference between art and science, not really. Both are a way for humans, the stuff of the Cosmos made animate, to try and discover what everything is really about.  To explore that idea, let’s consider the stars.  Most of us are aware of the stars, though maybe we haven’t looked at them much.  When asked, we might describe them as small, cold white points of light in the sky.  But to someone who has really looked at the stars, they have depth and character that most of us have scarcely imagined!

Several paintings featuring the stars, by Vincent Van Gogh. (L) The Starry Night, (C) Country Road in Provence by Night, (R) Starry Night over the Rhone.

Perhaps the most famous representation of stars ever created is Vincent Van Gogh’s De sterrennacht (“The Starry Night”) painted in the summer of 1889 while he was committed to the sanitarium in Saint-Rémy-de-Provence (he had painted many other starscapes, including another the previous fall, known as “Starry Night Over the Rhone”). One may consider the stellar presentations in Van Gogh’s paintings to be fanciful and abstract in the extreme, but it is clear that Van Gogh had discovered the wonder and diversity of the stars.  In a letter to his sister, Willemina, in September of 1888, he wrote:

“The night is even more richly coloured than the day… If only one pays attention to it, one sees that certain stars are citron yellow, while others have a pink glow or a green, blue and forget-me-not brilliance. And without my expiating on this theme, it should be clear that putting little white dots on a blue-black surface is not enough.”

Van Gogh’s observation is not that far from the truth. Even to the naked eye, many stars show distinct colors — Sirius blazes bluish-white, while Antares glows a baleful red, and Mira fades to be invisible then reappears as its cool yellow-orangish self over the course of 11 months. Through the telescope, even more stars show color — the twins stars in Albireo are blue and gold, and Herschel’s garnet star is definitely red.

A gallery of stars. Left to right: (1) Sirius, the brightest star in the night sky. (2) Antares, embedded in the cloud known as the Rho Ophiuchi complex, near the globular cluster M4. (3) Mira, a dramatic variable in the constellation Cetus. (4) Albireo, a blue and yellow double in Cygnus. (5) Herschel’s Garnet Star, mu Cephei.

Annie Jump Cannon.

What do the colors of the stars mean? The understanding of stellar color is a story intimately tied to how we came to understand the lives of the stars. There have been many players over the years, but the story really begins with an astronomer named Annie Jump Cannon. In 1896, Cannon went to work at Harvard College Observatory to work on the completion of the Henry Draper Catalogue, an ambitious project to identify and map every star in the sky down to a brightness about 10 times fainter than the eye can see (photographic magnitude ~9); all told, the catalogue had 225,300 stars. Working on the Draper Catalogue, Cannon simplified two disparate systems for classifying stars based on their spectra.

The spectrum of the star Vega, clearly showing strong hydrogen absorption lines.

What was Cannon looking at? If you dump the light of a star through a prism, the light is split into a familiar rainbow, known to astronomers as a spectrum. If you look closely at the spectrum, you will see that some colors are missing, like they have been deleted, appearing as a black line. These lines are called “spectral lines” or “absorption lines”.  They come in sets that when looked at together form a unique fingerprint that identifies each kind of atom that the star is made of. Cannon was looking at the strength of lines that identified hydrogen, and developed the system that is still used today known as the “Harvard Classification System.”  What she discovered was that there was a natural way to order all the stars based on their color.  She took the old classification systems that had been established before she started working on the project, simplified them, and rearranged the order into a sequence that is familiar to astronomers: “OBAFGKM.”  Every star has a letter that describes its color, known as the “spectral class.”

Cecilia Payne Gaposchkin

The meaning of the classification system was not well understood until 1925, when theoretical astronomer Cecilia Payne-Gaposchkin demonstrated in her PhD thesis that the stars were, primarily, composed of hydrogen and helium, and that the spectral class and behaviour that Cannon observed were related to temperature — the Harvard Classification System was a sequencing of stars from hottest to coolest. Otto Struve, soon to become the director of the Yerkes Observatory, said it was “undoubtedly the most brilliant Ph.D. thesis ever written in astronomy.”

(L) Typical spectra for stars of different spectral type. Note how the central color shifts with type. (R) The Harvard Classification System for spectral type.

The Harvard Classification System has the letters out of order because it was derived from older systems that didn’t understand that temperatures were affecting the spectra. Once that connection was understood, it became clear that the reason “OBAFGKM” was the correct order was because it is the correct temperature sequence.  But you have to remember that silly order of letters!  To help, mnemonics have been developed over the years to help you get the order right, including a few by me and my students… 🙂

Some helpful mnemonics for remembering the correct order of spectral types! The first on the left is the classic many of us learn when we first take astronomy. The others are suggested alternatives.

Understanding the color and temperature of the stars leads directly to an understanding of how stars are born, live, and ultimately perish. The final fate of any star, like the fate of any human, is governed by how they live their lives.  Stars that burn hot and fast in their youth, die young. Stars that take it slow and easy, live to old age.  For stars in the prime of their lives (what astronomers call “on the main sequence”) temperature is a measure of how fast they are burning their bodies up, consuming their fuel in nuclear fires that burn down in their core.

At this point, you may be scratching your head.  How do we know how stars live their lives? Humans live to around 100 years of age, but even the youngest stars live to be tens of millions of years old; the oldest stars live to be billions. No human ever has, nor ever will, live to watch a star live through its entire life cycle.  But we don’t have to, because there are millions of stars to watch, all at different stages of their evolution.  Consider the pictures of people below.  Do you think you can sort them into age order?  Most of you probably can.  How?  You can’t even see the faces of some of them!  But you have encountered people in your life at all stages of a human lifetime, and have learned what to look for to identify age: youngsters play with toys and are smaller than old people; older folks have grey hair, and or wrinkles.  And so on.  Using very quick, visual cues, you can get the age pretty quick. 

Can your sort these people (none of whom you know) by age?

For stars, the cues that tell us something about their status in life are the brightness, and the color.  In the prime of their lives, the brightness and color are directly related, a fact that results from the physical laws that govern the nuclear fusion that burns in the stellar hearts.

But what happens when stars get older? Like many of us, the onset of their elder days causes stars to swell up in size.  A star like the Sun sits well within the orbit of Mercury today, but when it reaches old age it will swell up and expand to roughly the size of Earth’s orbit, consuming all the worlds of the inner solar system. This swelling spreads the energy of the nuclear fires more thinly across the surface of the star, so the temperature goes down.  We know from our spectral classification scheme that cooler stars appear redder — the Sun will expand into a “red giant star.”

Antares is in its red giant phase, and is larger than the orbit of Mars! [Image from Wikimedia Commons]

Stars will live their short elder years as red giants stars.  What is their ultimate fate? Once again, it depends on the genetics of their youth: their fate is strictly dependent on how massive they are.  Midsize stars like the Sun, shrug off their outer atmosphere to form one of the great spectacles of the Cosmos, a planetary nebula. After this, what is left of the star slowly shrinks down to a dying ember, about the size of the Earth, called a white dwarf.  Big stars try to keep burning hard, but eventually their nuclear fuel completely runs out; when this happens, the outer layers of the star spontaneously collapse in on the star, crushing the core in a titanic explosion known as a supernova. The explosion blasts almost all the material that was the star out into space, synthesizing all the “stuff” that you and I are made of.  All that is left behind is a skeleton of its former self: a dark, compact remnant smaller than a city.  Slightly large stars leave a skeleton known as a neutron star, and the biggest stars leave a skeleton known as a black hole.

(L) The Helix Nebula, a planetary nebula. (R) The Cygnus Loop, an 8000 year old supernova remnant.

Cradle to grave, the story of the lives of the stars is as complex and compelling as the story of any life on Earth.  To be sure, I have cast this story in language that is a reflection of our understading of biological life, but it is still a wondrous tale. It astounds me still that not a single person now or in the long history of our species has ever visited a star (not even the Sun), but we have still managed to figure the story out.  It has taken the tale more than a century to unfold, through the diligent work and pioneering efforts of astronomers like Cannon and Payne-Gaposchkin.  But in the end, we begin to understand that the stars are more than just little white points of light in the sky.  Every time I stand out in the backyard, staring up at the stars, I’m always reminded of van Gogh.

A little reminder from Van Gogh, at the eyepiece of my telescope.

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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

Cosmos 8: Journeys in Space and Time

by Shane L. Larson

When I was a kid, I wanted to be one of four things when I grew up: an astronaut, Captain Kirk, Carl Sagan, or Indiana Jones. Now that I am (almost) grown up, it seems my chances of being an astronaut are limited by the slow pace of progress in space tourism, and as far as I know the Enterprise is not being constructed as we speak in some remote cornfield in Iowa. I’m still working on learning to communicate like Carl Sagan. What about Indiana Jones? Well, let’s see: Bullwhip? No (sigh).  Cool hat? Cool enough hat.  Professor?  Check!  Archaeologist, adventure fraught life?  Yep!

Wait, what? I’m an astronomer, not an archaeologist! Archaeology is the study of human activity in the past. In a very similar way, astronomy is the study of the Cosmic past, not entirely limited to the human perspective. (So basically, astronomy and archaeology are the same; that is to say, me and Indiana Jones, we’re the same!)

My childhood ambitions, left to right: (1) astronaut [this is Heidemarie Steefanyshyn-Piper on STS115], (2) Captain Kirk, (3) Carl Sagan, (4) Indiana Jones

Archaeology is often described primarily as being conducted through the study of artifacts. Astronomy also sometimes relies on artifacts (such as meteorites), but more often than not astronomy is about images captured by telescopes. But herein lies a fundamental difference between archaeology and astronomy: archaeology is about the interpretation of artifacts in an attempt to understand the past, whereas astronomy is a direct observation of the past. The light we see from the Cosmos beyond the shores of the Earth takes time to make the journey across the deeps of space.  At the moment we detect the light from some remote shoal of stars, the image we see is a snapshot taken millions of years before, when the light left its point of origin.

Consider this supernova (known as SN 2014g), detected only one week ago on 14 January 2014, in the galaxy NGC 3448, located just under the bowl of the Big Dipper.  Astronomers call this particular type of supernova explosion a “Type II Supernova” — an explosion from a massive star imploding on its core, then bouncing back from the enormous pressure in an explosion that, for a time, will outshine all the other stars in the parent galaxy.  When did this occur?  NGC 3448 is 157.9 million lightyears away, so this explosion occurred 157.9 million years ago!  When this star exploded and the light started travelling toward Earth, there were still dinosaurs on our planet (it was the Jurassic Period!); but we just heard the news of the supernova this week.

(L) NGC 3448 as seen by GALEX and Spitzer [Image, JPL/NASA], (R) Supernova SN2014g.

Even stuff “close” to us is far away.  During the month of January, if you go out shortly after it gets dark, you will see the constellation Orion.  The belt stars point down and to the east toward a brilliant blue-white star called Sirius, the brightest naked eye star in the sky.  Sirius is 8.611 lightyears away.  When the light you see tonight left Sirius, it was June 2005 (assuming you are reading this in January 2014).  What was going on then?  The San Antonio Spurs had beaten the Detroit Pistons 4 games to 3 in the 59th NBA Championship; Batman Begins had just been released; Watergate informer “Deep Throat” was revealed to be former Associate Director of the FBI, Mark Felt; and NASA was less than a month away from Discovery’s STS-114 flight, the first flight of the space shuttle since the loss of Columbia in 2003.

Some of the happenings 8 years ago, in June 2005. Left to Right: (1) Robert Horry’s game winning 3-point jumper during overtime in Game 5 of the NBA Finals; (2) Batman Begins was dominating the box office; (3) former FBI Associate Director Mark Felt was revealed to be the Watergate informant “Deep Throat“; (4) Discovery returned the Space Shuttles to flight, just over 2 years after the Columbia disaster.

Looking across space is looking back in time. The farther away from the Earth you look, the farther back in time you look.  This connection between distance and time may seem a bit esoteric and weird at first sight, but in fact we are used to conflating space and time; you do it every day and don’t even realize it! Just go around the house and ask different members of the family how far it is to the grocery store across town. Some of them will say 10 minutes, and some of them will say 3 miles. There is no difference in the amount of space between you and the store — these are just two different ways of saying the same thing, and you understand them both!

Even Google Maps knows you can understand travelling either in terms of space, or in terms of time, telling you both!

But travelling into space is not the same thing as travelling to the supermarket. The distances are far vaster, so the travel times are far longer. It took Apollo astronauts about 4 days to fly across the gulf of space to the Moon; that’s about the same time it takes to drive from New York to Los Angeles (assuming you aren’t doing some kind of Cannonball Run thing).  It has taken Voyager 36 years to reach the boundary of our solar system, where the interstellar winds from all the stars in the galaxy dominate over the faint, fading stream of wind of our own Sun; light takes 35 hours to make the round trip out to Voyager and back.  Voyager is the fastest object ever built by humans; if we could travel with Voyager, it would take an entire human lifetime to travel to the edge of the solar system and back.  The stars are vastly farther away; travelling by the means we know today would seem to preclude us ever travelling to the far corners of the Cosmos.

Despite the fact that we often conflate time and space, we perceive them to be very different, as evidenced by the tools I use to measure them — we use rulers to measure space, and we use wristwatches (if you’re old enough; otherwise you use a cell phone!) to measure time.  We see space and time as different because we only travel through space when decide to get up and go somewhere, but we are always travelling through time — there seems to be no way to avoid getting to next Tuesday.

Different ways we have devised to measure space or time.

At the start of the 20th Centruy, a young Albert Einstein had a startling realization: time and space are really manifestations of a single, unified fabric that underlies the entire Cosmos, called spacetime. That space and time are inextricably intertwined is hard to see in our slow, everyday lives, but what Einstein realized is the intertwining becomes far more important and obvious when you start travelling fast, at speeds approaching the speed of light. The laws of Nature that describe how we experience and measure the world at high speeds are called “special relativity.”  The laws of special relativity are a generalization of the usual Newtonian laws of mechanics that govern cricket games, the flights of unladen swallows, and car crashes; at the low speeds of these everyday events, special relativity gives exactly the same predictions and results as Newtonian physics.

But suppose you had a fast car, and you could stomp on the accelerator, increasing your speed without difficulty. As you approach the speed of light you would notice that your observations of the world change compared to your friends who are standing still (or driving Yugos). Special relativity accurately predicts the consequences of travelling at high speeds, and foremost among these predictions is an effect known as time dilation — clocks that move at high speeds (mechanical, electronic, or biological — it matters not) tick more slowly than clocks that move slowly or remain at rest.

Free neutrons die, on average, after 881.5 seconds, decaying into a proton, an electron, and an anti-neutrino.

Changing how fast you move through space changes how you move through time. It is an altogether astonishing result, completely counter-intuitive to our everyday experiences here on Earth.  But science is a game where the proof is in the pudding — extraordinary claims require extraordinary evidence, and special relativity has been put through the wringer. The most prominent way in which special relativity has been tested is in particle accelerators.  Many species of atoms and sub-atomic particles have limited lifetimes and eventually die by breaking apart (“decaying”) into smaller, more stable pieces. The time that these particles live is called the “half-life” and it is easy to measure in the laboratory — you plunk a particle down on your bench and you watch it until it dies!  The classic example of this is the neutron, one of the fundamental particles that makes up all the atoms in your body.  If you set a neutron on your workbench, it will live for about 881.5 seconds, just over 14 minutes and 41 seconds. Special relativity tells us that all clocks moving at high speeds run slow; this includes the clock the neutron carries with it that determines when it is going to decay. If we accelerate the neutron to speeds approaching the speed of light, we find that it lives longer than the predicted 881.5 seconds, confirming that its internal clock is running slow.  Special relativity has been tested in this way billions and billions of times in particle accelerators around the world, and never once has it failed to correctly describe the outcome of an experiment.  

While special relativity explains a great many physical phenomena that can be observed in the Cosmos, there is an important realization to be had: special relativity provides a way for us to journey to the stars. If we can construct a rocketship that could travel close to the speed of light (a not implausible idea, even with today’s technology), special relativity tells us that as passengers, our biological clocks will tick slowly enough that we will live to see the journey’s end.

Nuclear powered starship concepts that, in principle, are not outside the boundaries of our technology. (L) Starship Orion; (C) Project Daedalus; (R) Bussard Ramjet. [Images from Cosmos: A Personal Voyage] For many detailed starship concepts, see the book The Starflight Handbook by Eugene Mallove.

What kind of travels could we imagine? Consider a rocket where we hold down the accelerator and never let up. We accelerate just enough that it feels like we have Earth normal gravity (“one gee”) on the ship, allowing us to pass time on our journey in comfort, pursuing ordinary everyday activities like ping-pong and shuffleboard. Our rocketship would increase its speed rapidly, ticking off the decimal places ever closer to, but never reaching, the speed of light.  The table below shows what different trips would look like.  For destinations close to Earth, like the Voyager spacecraft, our rocket travels fast enough to make the trip no more onerous than an extended vacation, but not so fast as to see the relativistic slowing of time.  But over Cosmic distances, time slows dramatically aboard the ship.  Travelling to the center of the Milky Way,to explore the wilderness near the monstrous black hole that lurks there, would take only 10.6 years, less than 22 year around trip.  But on Earth, 52,000 years will have passed, changing our planet and civilizations in unimaginable ways. We don’t even know what human life was like 52,000 years ago, because our written histories only extend back a tenth that long — who knows what 52,000 years in the future will look like!  To those of us on the voyage, scant decades will seem to have passed, but our species will have moved on without us.

Distance an measured times on relativistic rocket trips at acceleration of 1 g.

For most of these journeys, those of us who make the trip will behold firsthand the wonders of the Cosmos, but there will be none of our friends and family to hear the tales when we return home.  I often think  about these journeys, and wonder whether I would do it, given the chance.  Would I leave the Earth behind, never to walk her green meadows again?  I would never be able to Sail the Aegean Sea, or hike down Olduvai Gorge, or howl with coyotes on cool fall evenings in the Sonoran Desert.  But in return I would see the galaxy from the inside out, watch as the Milky Way black hole tears a star apart, and surf along the tendrils of molecular gas and dust that will one day become a new generation of stars.  It may be, perhaps, a fair trade — one set of Nature’s wonders for another.

The black hole at the center of the Milky Way, surrounded by a swarm of stars and the strained tendrils of gas clouds and stars that have been eaten by the black hole. [Image from European Southern Observatory]

But for now, it is only a lovely daydream, enabled and provoked by our growing understanding of the Cosmos, and how it is put together.

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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

Cosmos 7: The Backbone of Night

by Shane L. Larson

Science is a powerful method to know the world. Without science, the Cosmos would be an impenetrable mystery to us; we would live our lives without the benefit of knowing how to make fire, how to cross the water or fly in the sky, or how to combat fevers and illness. Early in our education, we are often instructed in The Scientific Method.  I remember long hours as a student, filling up lab notebooks with precisely organized and formatted records of investigations into the mysteries of Nature, followed by my professors mercilessly docking me points for not completely writing out an equipment list or forgetting to record a step of the procedure in my notebook — points lost for not following explicitly the formal steps listed in The Scientific Method. I’m sure those days of bleeding red ink on my lab notebook taught me to be more careful in my scientific records, but they did little to inspire me about the way to do science.

One of my lab notebooks, from my undergraduate days.

Now, many years into my career as a professional scientist, I still think I practice The Scientific Method, but in reality I find the process of science is more organic, moving forward on leaps of inspiration, mixed together with careful planning, fraught with confusion and difficulties, and punctuated with debate and argument. Science is a very human endeavour, and as such has all the elements of every story ever told: ignorance, curiosity, hubris, depression, discovery, elation, and ultimately wisdom.  One such story, spanning more than 400 years, is about how we have come to understand our own galaxy.

The Milky Way rising over Mt. Hood and Lost Lake, Oregon.
[Image by Ben Canales, http://www.thestartrail.com]

From remote dark skies, far from the bustling life of modern cities, you can see the Milky Way, arching overhead. Nebulous and shimmering, it has evoked wonder and questions for many thousands of human generations. While today the nature of the Milky Way has passed from our scientists into the collective knowledge base of our species, there was a time when the Milky Way was a tremendous mystery upon which we hung stories, myths and legends. The peoples of the Indian sub-continent called the Milky Way Akash Ganga, the Ganges of the heavens. Life along the Ganges is intimately tied to the river, and it is sacred to the Hindu people; perhaps staring at the vast gossamer river in the sky touched some deep chord in their minds, igniting the idea that we here on the Earth are connected to the sky.  The !Kung bushmen tribes of the Kalihari desert call the Milky Way The Backbone of Night, because it looks like a ghostly arch, soaring overhead and holding up the sky.

Galileo Galilei.

Our knowledge of the Cosmos is like an archway — it is built up stone by stone, and supported by keystones, essential pieces of knowledge that define how we think about Nature. The Milky Way has come to be a keystone, a focal point of attention that has guided us in our long journey to understanding the Cosmos. In our understanding of the galaxy, that journey began 400 years ago with a 45 year old professor from Padua, Italy, who turned a spyglass to the heavens — Galileo Galilei.  His telescope was a simple device, of poor imaging quality compared to the cheapest pair of binoculars you might find at a discount store today. But it could show more than just the eye alone.  Peering through his telescope at the diaphanous mist of the Milky Way, Galileo was presented with a staggering wonder — the galaxy was comprised of innumerable stars, packed so closely together that the eye could not resolve them, instead seeing only a nebulous fog. The Universe had suddenly gotten much larger.

There is a bit of folklore that in those early days, Galileo doubted what the telescope was showing him. How could he be certain that what he saw when he looked to the skies was real, and not some phantasm born of his mind’s inability to interact with his new-fangled optical device? To answer this question, he dutifully did what Galileo is known so well for — he conducted an experiment. Setting up a coin across a courtyard, he viewed and sketched the coin through his telescope, noting every detail he could see.  Then, leaving his telescope behind, he walked right up to the coin and sketched it again viewing it from a distance of only a few inches. After much examination, he convinced himself the telescope was not lying to him, and all the wonders he had seen were real.

A Venician silver scudo, from around the same era when Galileo was learning to use his telescope.

He published his first telescopic observations of the heavens in 1610, in a book called Sidereus Nuncius — “The Starry Messenger.”  Despite having convinced himself of the truth, he had less luck convincing others of the utility of the telescope.  He complained in a letter to Kepler, 

“…I think, my Kepler, we will laugh at the extraordinary stupidity of the multitude.  What do you say to the leading philosophers of the faculty here, to whom I have offered a thousand times of my own accord to show my studies, but who with the lazy obstinacy of a serpent who has eaten his fill have never consented to look at planets, nor moon, nor telescope?  Verily, just as serpents close their ears, so do these men close their eyes to the light of truth.  These are great matters; yet they do not occasion any surprise.”

Even in Galileo’s day, communicating science was hard.  But the Age of Enlightenment was soon upon the world; modern astronomy was born in this time, a direct descendant of Galileo’s stargazing.  Telescopes began to proliferate. Larger telescopes were built, new designs were invented, observatories were constructed, and astronomers were appointed.  We began to plumb the heavens, trying to see all that we could see.

As we looked deeper into the sky, we came to understand that there was far more to the Milky Way than even Galileo knew. The first person to map the Milky Way was William Herschel.  In 1784, Herschel used his telescope to count stars in every direction on the sky.  From those studies, he produced a map, eerily accurate to what we know today, concluding that the Earth and the Sun are near the center of a flat disk of stars (you can read a detailed description of Herschel’s method in this paper).  But as telescopes scanned back and forth across the sky, observers would occasionally see things that were not stars — new, dim fuzzy objects.  Some were round, some were oblong, some were completely irregular. The looked for all the world like the Milky Way looked before Galileo’s telescope — thin, white, diaphanous fogs among the stars. They were generically named nebulae, Latin for “clouds.”  Herschel himself catalogued more than 2400 of these in an epic survey of the sky conducted with telescopes he built.

(L) William Herschel, (R) Herschel’s first map of the Milky Way.

This first reconnaissance of the sky brought to the forefront of our minds questions we had asked before: how big is the Cosmos? where did it come from? what is our purpose in it? At this time, most astronomers had decided that the entire Universe was the Milky Way. They had no reason to believe (nor ability to measure) that distances in excess of thousands of lightyears were reasonable.  Thus all the nebulae, since they were parts of the Universe, must reside within the Milky Way itself.  One prominent view of the day was the “nebular hypothesis,” which supposed that stars and planets formed from gravity acting to collapse vast clouds of gas. The detection of nebulae among the stars of the Milky Way could explain where all the stars in the galaxy came from.

Today we now accept that the nebular hypothesis is correct, but in the 19th Century there were those who certainly did not. Among those who disliked the notion was William Parsons, the Third Earl of Rosse. He believed that like the Milky Way, the nebulae should resolve themselves into innumerable faint stars, if you could just look with a powerful telescope.  So in 1845 he built one of the largest telescopes the world had ever seen.  More than six feet in diameter, the structure of the telescope had to be held up by a castle wall, and was colloquially known as “The Leviathan of Parsonstown.”

(L) Lord Rosse, (R) The Leviathan of Parsontown (next to its support wall at Birr Castle).

One of the great truths of telescopes is that bigger telescopes can see more, because they collect more light.  By all accounts, the Leviathan could see more than any telescope of the time — it revealed details in the nebulae that had never been seen before.  In 1845, shortly after it was built, Lord Rosse pointed the Leviathan toward a distant nebula, just under the handle of the Big Dipper, known as Messier 51 (“M51”). In a moment that must have been utterly breathtaking, Lord Rosse realized that he could see spiral structure in the nebular cloud. He promptly declared that M51 was an “island universe,” another galaxy like the Milky Way.

(L) Lord Rosse’s first sketch of M51 in 1835, showing the spiral structure seen through the Leviathan. (R) A modern HST image of M51 [NASA/ESA].

This ignited “The Great Debate” in astronomy, which persisted for more than 80 years before it was resolved.  Arrayed against each other were the scientists who believed the Milky Way was the entire Universe, versus those who contended that the Milky Way was but one of a vast number of other galaxies.  Both sides had good arguments that supported their position, but there was no way to decide that one group was more right than the other — the observations simply weren’t good enough.  To resolve this debate we had to know two things: the size of the Milky Way itself, and the distance to the spiral nebulae.  Astronomers noodled this over in vain for decades to no avail.

Henrietta Swan Leavitt at her desk [Harvard College Observatory].

In the end, the solution to the problem was discovered in 1912 at the Harvard College Observatory by astronomer Henrietta Swan Leavitt.  She had discovered a type of star now known as a Cepheid variable that changes its brightness in a regular way over time (a variable star). Leavitt demonstrated that for Cepheid variables, if you could accurately measure the time it takes the star to get dim then bright again, you could use the change in brightness to determine the distance to the star.  This was the first, robust method for using telescopic observations of stellar brightness to determine distances through the galaxy; Leavitt’s discovery transformed astronomy.  Sadly, Leavitt died of cancer at the age of 53 in 1921, before The Great Debate was resolved.

Hubble at the eyepiece of the 100″ Hooker Telescope on Mount Wilson [Time & Life Pictures/Getty Images].

Knowing that bigger telescopes see more, the Mount Wilson Observatory built a 100” telescope overlooking Los Angeles in 1917; it would be the largest telescope in the world for more than 30 years.  In 1924, Edwin Hubble announced that he had used the 100” telescope to detect Cepheid variables in several spiral nebulae. Using Leavitt’s discovery, he was able to determine the distance to the spiral nebulae, discovering that they were vastly farther away than astronomers had imagined.  The Universe was suddenly a very big place!

How big? The Milky Way galaxy is about 100,000 lightyears across — it takes light 100,000 years to travel from one side to the other. The disk, which we see edge on as the faint river of light in the night sky, is on average only about 10,000 lightyears thick.  By contrast, Hubble was observing the Andromeda Nebula, which is 2.5 million lightyears away!  It would take 25 Milky Way galaxies laid edge to edge to span the gulf of space to our closest neighbor, and there are  galaxies further still.  While these vast distances startled astronomers, The Great Debate was, for all practical purposes, resolved instantly. The data was clear and unambiguous. Leavitt’s great breakthrough in the discovery of the Cepheid variables was a singular event — it resolved an argument that had plagued and befuddled us for almost a century.  Astronomers shook hands, dusted off their chaps, and moved on to new, equally difficult mysteries, suddenly revealed by uncountable galaxies far, far away.

Our current best understanding of the structure of the Milky Way, if it could be seen from above the galaxy. [Image by European Southern Observatory].

How do we study those galaxies that are so far, far away? We build bigger telescopes. We look at the Milky Way up close, and assume galaxies far away are similar. We spend time being confused. We argue. We make inspirational breakthroughs, and eventually, we understand.  This is the nature of science.

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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