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New Astronomy at the New Year (GW170104)

by Shane L. Larson

Newton’s portrait.

January 4 holds a special place in the hearts of scientists — it is Isaac Newton’s birthday (*). Newton stood at the crossroads that led to modern science, and astronomy in particular. He was the first person to build a workable reflecting telescope, a design that now bears his name and for the past 4 centuries has been the dominant type of telescope used by amateurs and professionals alike. Newtonian telescopes have revealed much about the Cosmos to our wondering minds. Newton was also responsible for the first formulation of a physical law that describes the working of gravity, called the Universal Law of Gravitation. Today we use the Universal Law to launch satellites, send astronauts into orbit, convert the force of your feet on the bathroom scale into your “weight“, and a thousand other applications.  There is much to celebrate every January 4.

(L) Aerial view of LIGO-Hanford Observatory [top] and in Google Maps [Bottom]. (R) Aerial view of LIGO-Livingston Observatory [top] and in Google Maps [Bottom].

But on January 4, 2017 the Cosmos celebrated with us, singing in the faint whispers of gravity itself. On January 4, the signal of two black holes catastrophically merging to form a new bigger black hole washed quietly across the shores of Earth, carried on undulating vibrations of space and time. You were very likely unaware of this cosmic event — it happened at 4:11:58.6 am in Chicago. It was a Wednesday morning, and I imagine most people were blissfully asleep. But two of the grandest pieces of experimental apparatus ever built by humans were paying attention – the twin LIGO detectors in the United States.  For only the third time in history, a gravitational wave signal from the deep Cosmos was detected here on Earth.

The signal was the signature of two black holes (a “black hole binary,” in the lingo of the astrophysicists) merging to form a new, bigger black hole. The black holes, by definition, emit no light themselves. However, astronomers know that black holes can often be surrounded by swaths of interstellar gas. The intense gravity and motion of the black holes can stir the gas into a violent froth that can emit light. At the time of the event, the LIGO team sent out alerts to astronomers around the world, who turned their telescopes skyward looking for a tell-tale signature of light bursting from the energized gas. Our best estimate of the location of the event was canvased by 30 groups, in many different kinds of light ranging from radio waves, to optical light, to gamma rays. No tell-tale emissions of light were seen. The only way we were aware of this event is from the LIGO detectors themselves.

An artist’s impression of two black holes insprialling, near merger. [Image by Aurore Simonnet, SSU E/PO]

The Gravitational Wave Signal. We call the event GW170104, named for the date it was detected. The signal from the black holes registered first in the LIGO detector outside Hanford, Washington, and 3 milliseconds later registered at the LIGO detector outside Livingston, Louisiana. All told, it only lasted about 0.3 seconds. The signal exhibited the characteristic chirp shape expected of compact binaries that spiral together and merge — a long sequences of wave peaks that slowly grow in strength and get closer and closer together as the black holes spiral together.

Comparison of the chirp waveforms from the first 3 detected gravitational wave events. LVT151012 was a very quiet event that was not strong enough for LIGO scientists to be confident it was a pair of black holes. [Image: LIGO Collaboration]

During the early inspiral phase of GW170104, where the black holes are independent and distinct, the heavier black hole of the pair was 31 times the mass of the Sun, and the smaller black hole was 19 times the mass of the Sun. Ultimately, they reached a minimum stable distance (in astrophysics lingo: the “innermost stable circular orbit“) and plunged together to form a new bigger black hole. When that plunge happened, the gravitational wave signal peaked in strength, and then rang down and faded to nothing as the black hole pulled itself into the stable shape of single, isolated black hole. For GW170104, this final black hole was 49 times the mass of the Sun.

All of this happened 3 billion lightyears away, twice as far as the most distant LIGO detection to date. Perhaps these numbers impress you (they should) — they tell the story  of events that happened billions of years ago and in a place in the Cosmos that neither you, nor I, nor our descendants will ever visit. We add them today to a very short list of astronomical knowledge: the Gravitational Wave Event Catalogue, the complete list of gravitational wave signals ever detected by human beings. There are only three.

The current Gravitational Wave Catalogue, of all known events [click to make larger].

Take a close look at the list. There are interesting similarities and interesting differences between the three events. They are all black hole binaries. They are all at least a billion light years away from Earth. Some of the black holes are heavier than 20 times the mass of the Sun, and some are lighter than 20 times the mass of the Sun. Astronomers use those comparisons to understand what the Universe does to make black holes and how often.

This is the most important thing about GW170104 — it is a small but significant expansion to this very new, and currently, very limited body of knowledge we have about the Cosmos. These three events are completely changing the way we think about black holes in the Cosmos, forcing us to rethink long held prejudices we have about their masses and origins. We shouldn’t feel bad about that — evolving our knowledge is the purpose of science. LIGO is helping us do exactly what we wanted it to do: it is helping us learn.

What do we know? There are many things we are trying to learn from the meager data contained in these three signals. The new signal from GW170104 in particular has tantalizing evidence for the spin of the black holes, and some neat assessments of how close these astrophysical black holes are to what is predicted by general relativity. But I think the most important thing about the event from the perspective of astronomy is this: the black holes are, once again, heavy. GW170104 is the second most massive stellar mass binary black hole ever observed (GW150904 was the heaviest).

The masses of known black holes. The purple entries are observed by x-ray telescopes, and represent what we knew about the size of black holes before LIGO started making detections. [Image: LIGO Collaboration]

With the first two events we had one pair of heavy black holes (GW150914), and one pair of lighter black holes (GW151226). There is a great mystery hiding there: where do the heavy black holes come from, and how many are there in the Cosmos? Perhaps they are just a fluke, a random creation of Nature that is possibly unique in the Cosmos. But the detection of GW170104 suggests that this is not the case; we’ve once again detected heavy black holes. The race is on to decide how the Cosmos makes them. The answers to those questions are encoded in the properties of the black holes themselves. How many are there? Are they spinning or not? Are they spinning the same direction as one another? How do their masses compare to one another? GW170104 is another piece of the puzzle, and future detections will help solidify what we know.

How can you help? If you’d like to help the LIGO project out, let me direct your attention to one of our Citizen Science projects: GravitySpy. Your brain is capable of doing remarkable things that are difficult to teach a computer. One of those things is recognizing patterns in images. The LIGO detectors are among the most sensitive scientific instruments ever built; they are making measurements at the limit of our capabilities, and there are all kinds of random signals that show up in one detector or the other — we call them glitches.  It is very hard to teach a computer to tell the difference between glitches and interesting astrophysical events, so we have citizens just like you look at glitches and identify them, then we use that information to train the computer. So far citizens like you have helped LIGO classify more than two million glitches, and they put more on the pile every day.

If you’d like to help out too, head over to http://gravityspy.org/ and try it out; you can do it in your web-browser, or on your phone while you’re sitting on the train to work. We have citizens from kids to retirees helping us out. If gravitational waves aren’t your thing, there are more than 50 other projects in science, arts, history and more at http://zooniverse.org/ you can try out!

A representation of the GW170104 signal, from the scientific paper. These are the kinds of images citizens can classify easily, whereas computers sometimes have trouble. [Image: LIGO Collaboration]

PS: For all of you super-nerds out there, let me point something out if you haven’t already noticed. Suppose you were to parse the name of the signal in the following way: 1701 04. Look familiar? The 4th incarnation of 1701; for the cognoscenti, this event shares the designation of the Enterprise-D. 🙂  Until next time, my friends. Live long, and prosper.

(*) When Newton was born, England had not yet switched to the new Gregorian Calendar, which we use today. They were still using the older Julian Calendar, by which Newton was born on December 25; when converted Newton’s birthday falls on January 4 on the Gregorian Calendar.

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You can read about the previous LIGO detections in my previous posts here:

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Many of my colleagues in the LIGO Virgo Collaboration have also written excellent blog posts about the GW170104 event, and the work we do to make gravitational wave astronomy a reality. You should visit their blogs!

Vampires, Mummies, and Ghost Fears

by Shane L. Larson

By the time I went to college, I had mastered my fear of vampires enough to not have to sleep with my neck covered. Kept my kid sheets, mastered my kid fears.

When I was a kid, I was completely terrified of the dark. I would sleep at night with the blankets bunched up around my neck (to protect me from vampires) and with a bright light on all night long so if I happened to wake up, I’d see anything sneaking up on me.

Don’t get me wrong — I’m still terrified of the dark. I don’t do stupid things like walk into dark rooms without turning the light on, or watch horror movies (in case you’re wondering — 25 years is too short of a gap between viewings of The Exorcist). But as I got older, my fears evolved.

I grew up during the Cold War, and I was terrified of a nuclear holocaust — my nightmares of vampires were replaced by mushroom clouds and warheads unexpectedly raining down on Saturday morning breakfast. There was a lot of general malaise about this, but a particularly strong memory I associate with my burgeoning fear was seeing a 1985 Twilight Zone episode called “A Little Peace and Quiet“. The closing shot of that episode planted enough disturbing imagery in my head to fuel dark dreams for years to come.

The final terrifying scene in the Twilight Zone episode, “A Little Peace and Quiet.” The image of a warhead hanging over a town terrified me.

Today, I still worry about nuclear conflict (moreso lately, given the instability in the United States’ executive leadership). But other nightmares, possibly far more likely, have found purchase in the soil of my psyche. I worry about the resurgence of diseases like measles and whooping cough, the result of peoples’ resistance to vaccinations. I worry a lot about the steady and constant damage we are inflicting on Earth and its biosphere. I worry about the collapse of bee colonies and the massive bleachings of coral reefs. I worry that we see unprecedented changes in climatic patterns, atmospheric chemistry, and arctic ice that herald an uncertain terrifying future not just for humans, but for every lifeform on the planet.

There are lots of problems facing the world. (L) Rampant impact of human civilization on the environment. [Wikimedia Commons] (C) Coral bleaching, one indicator of planetary wide changes due to climate change [NOAA] (R) Viruses once held in check by herd immunity gaining footholds once again amid people disavowing vaccinations [Wikimedia Commons].

But none of this produces the same inconsolable dread in me as vampires. One of my friends was befuddled by this fact. She insisted that climate change and resurgent killer diseases were real threats that should terrify us, whereas vampires and ghosts are figments of our imagination. How could it be that I’m terrified by a figment of our imagination?

A peek inside my (irrational) nightmares.

She’s right — vampires and ghosts are a figment of our imagination, but as such there are no fixed rules about how to deal with them. There are as many ways of conquering and facing the supernatural as there are fiction authors.

But virulent diseases, arms control, and climate change? There are well established ways of finding out what’s at the heart of those threats and figuring out how to combat them. You and I call that science.

Where does my faith in science come from? A long and storied history, written by you and me and 40,000 generations of people before us. Humans, more than any other lifeform we are aware of, look at the world with a critical eye and ask “what do we see happening? what does it mean? what can we learn from this?” The result of that process, pursued relentlessly in the face of superstition and the over-active darkness of our imaginations, are all the wonders of the modern world we see around us — wi-fi and pacemakers and insulated coffee mugs and teflon pans land ballpoint pens and flying drones and digital cameras.

Technology is one of the most obvious manifestations of science in our everyday lives. Simple examples include insulated coffee mugs that exploit a deep understanding of thermodynamics (L), modern pens that utilize fluid dynamics and mechanical interfaces (C), and teflon coated non-stick pans are the product of chemistry and materials science (R).

But the process of science has also resulted in knowledge and discoveries that are as poetic and stunning as the finest piece of porcelain, the most beautiful rhythm of poetry, the most exquisite painting or the most stirring symphony. Consider the lives you and I lead — we live in a world where baseballs and rosebushes abound, we walk around at the pace our feet carry us, and the most extraordinary event most of us ever experience is a thunderstorm or a kiss on a first date.

Some of the everyday extreme events experienced by ordinary humans.

But that same world is a world where people like you and me have left footprints on the Moon. We’ve sent robots to sift the sands of Mars and photograph the far side of a remote icy world called Pluto. We’ve discovered that stars burn at millions of degrees in their hearts and when they die they explode, creating every atom in every cell of you and me. We’ve taken those atoms and broken them apart to discover they are made of smaller particles called protons, neutrons and electrons. We’ve even broken protons and neutrons apart to find they are made of even smaller particles, called quarks.

Well before science turns into ways to improve your golf game or make your life in the kitchen easier, it is simply pushing the limits of what we think is possible. [L] Buzz Aldrin’s bootprint on the Moon; the Moon is the farthest any human has ever been from Earth [NASA]. (C) The New Horizons spacecraft, after a 10 year journey, sent home the most exquisite images of Pluto ever taken. Pluto is the most distant object ever visited by spacecraft from Earth. [NASA] (R) We have the technology to manipulate and image individual atoms, a million times too small to be seen with your naked eye. [NIST]

We’ve got no business knowing any of that, because it has nothing to do with foraging for food, or making babies. It has nothing to do with sheltering from hail storms, or staying warm. It has very little to do with making clothes or making farm implements from rocks and sticks.

So why do we know about the Moon and Mars and Pluto? Why do we care about atomic nuclei and quarks? Because we let our imaginations get the better of us. Unfettered, we let ourselves ask any question we want to ask, and we set out to find the answers. Every time a curious question presented itself, we rolled up our sleeves and we figured out the answer. But discovery and understanding are only the beginning. Once we have the knowledge in hand, then our innovators and engineers can figure out how to bring it into our homes and lives.

That’s how science works.

In the end, science is the most powerful tool we have to solve problems, and we can use it to solve any problem in front of us. We should be convinced of that by the fact that we can visit planets that no human has ever been to, and that we manipulate and image the very atomic building blocks that make up the world even though we cannot see them. We have the ability to use these tools for our own good. We have the choice to use these tools to overcome those dark corners of our imaginations and create a future our children will look back on and remember for all the good that we did to save ourselves from ourselves.

The Saturn Moment

by Shane L. Larson

I just returned from the 33rd annual Winter Star Party, hosted by Miami’s venerable Southern Cross Astronomical Society. Every February, for a week during the new moon, 400 amateur astronomers and their families descend on Camp Wesumkee in the Florida Keys.  During the idyllic days, we sit in lawn chairs, enjoy the gentle sea breezes, watch sandpipers running along the tideline, or beachcomb on the key front looking for pretty shells or little fishies trapped in tidepools.

Sunset over Scout Key, Florida, the site of the Winter Star Party. [Image: S. Larson]

But the real reason we are there becomes apparent as the Sun sinks over the western sea, and the black velvet of night emerges, studded by brilliant diamonds of light. The vast majority of us live our lives under the glaring lights of modern cities, and all too often we forget that the Cosmos is there, hiding behind our artificial fluorescent glow, waiting for us to remember. At the first sunset of the Winter Star Party, it all comes roaring back and you remember what you’ve been missing.

The Milky Way rises over Scout Key around 3am in February. You can watch a timelapse movie of the whole night, including the rising of the Milky Way, on YouTube. [Image: S. Larson]

People often ask me, “are you religious?” My answer is that I am not in the sense of modern churches and institutions, but I do know that we are part of something larger — a Cosmos infinitely vast and wonderful and intricate beyond anything we can imagine or will ever know. The cathedral of night is my church.

In his poem “When I Heard the Learn’d Astronomer,” Walt Whitman espoused the idea that you don’t need sages to know a deep connection to the sky, only the solitude of the night.

When I Heard the Learn’d Astronomer 
by Walt Whitman 

When I heard the learn’d astronomer, 
When the proofs, the figures, were ranged in columns
     before me, 
When I was shown the charts and diagrams, to add,
     divide, and measure them, 
When I sitting heard the astronomer where he lectured
     with much applause in the lecture-room, 
How soon unaccountable I became tired and sick, 
Till rising and gliding out I wander’d off by myself, 
In the mystical moist night-air, and from time to time, 
Look’d up in perfect silence at the stars. 

(http://www.poetryfoundation.org/poem/174747)

But in today’s fast paced world, driven by small screens, instant communication, and more information than has ever been gathered by a civilization before, it is hard to slow down enough to realize those moments of solitude. Living beneath the glare of our cities, there are generations of people who have never truly seen a starry sky and thus never built a deep personal connection to the night.

My telescope (named EQUINOX), on the observing field at Scout Key. [Image: S. Larson]

While the Winter Star Party is dominated by amateur astronomers who, like me, do this as often as we can, there are also a lot of people who are experiencing the dark night sky and the Milky Way for the first time. They walk among the telescopes at night, peering at a nebula here or a star cluster there, all the while being regaled with tales and facts of all that we have learned from 400 years of telescopic study of the sky.

This year, at around 4 in the morning, the Milky Way climbed up above the horizon, it’s center studded by a pale yellow “star.”  A young couple, at their very first star party, had stopped by my telescope for some quiet conversation and some views of the sky.

“Do you want to see something cool?” I swung my telescope over to the pale yellow “star” and let them peer through the eyepiece. The view elicited startled gasps, and loud exclamations of joy.

View of Saturn through the telescope, taken with an iPhone [Image by Andrew Symes; visit his blog here]

There is no way that is real!”  The pale yellow “star” was in fact not a star at all — it was the planet Saturn, a cream colored orb bejeweled by its famous ring, the ring itself narrowly divided by a thin black gap known as the “Cassini Division.”

Delivering a personal experience with the night sky is part of the promise of amateur astronomy. We show people the Moon, stars, clusters, perhaps an occasional galaxy. But nothing moves people like their first view of Saturn through a telescope. Most people who take the time to look walk away remembering that moment for the rest of their lives.

We call this “the Saturn Moment.”

More than any other far away object in the sky, Saturn looks like what people expect. They often respond to their view with incredulity, joking that it looks almost painted, or like a picture that has been taped over the end of the telescope.

The Moon often engenders similar responses, but people expect the Moon to look that way. They can see it with their eyes, and imagine craters and mountains, so they aren’t necessarily surprised by the telescopic view.

By contrast, most people have never seen Saturn, except through the eyes of space probes. The telescope somehow takes the NASA pictures we see on our computer screens, and makes it real and visceral.

At the Adler Planetarium in Chicago, you can see a “20 foot Refractor” similar to the kind used in Huygens time (left). We have it set up so you can look through it, and see the same kind of fuzzy image of Saturn he may have seen (right). [Images: S. Larson]

The first person to have a Saturn Moment was Galileo, who turned his telescope on the skies in 1609. His views of Saturn were not the greatest, as his sketches published a year later in Sidereus Nuncius show. It was clear Saturn wasn’t normal because he could make out blobs on either side. He wrote in a letter to his student Benedetto Castelli that Saturn had “ears.” It wasn’t until 1655 that Dutch astronomer Chrstiaan Huygens, using a much better telescope (though still fuzzy) was able to discern that Saturn was surrounded by a thin, flat ring.

A 57 mm diameter lens, all that remains of the telescope Huygens used to observe Saturn. Around the edge is carved a verse from the Roman poet Ovid: “Admovere Oculis Distantia Sidera Nostris” (They brought the distant stars closer to our eyes). It is an anagram, establishing the details of Huygens’ discovery of Saturn’s moon, Titan. When translated, it reads “A moon revolves around Saturn in 16 days and 4 hours.”[Image: Utrecht Univ. Museum, from APOD]

Today, ordinary people like you and me can own telescopes that would have made Galileo and Huygens swoon with envy. Technology is better, and available to everyone.

My Saturn Moment happened long ago, at a sidewalk astronomy event. An amateur astronomer invited me over to look through her “telescope” — it wasn’t an ordinary telescope, it was a spotting scope for birding that she had pointed at the sky. But what I saw blew my socks off. I was seeing Saturn, with my own eyes, and I could see the rings! Though I don’t remember it, I’m sure the rusty dot of Titan, Saturn’s largest moon, was also lurking nearby.

The ultimate result of that encounter is that today my wife and I are both amateur astronomers ourselves, and we guide people through their own Saturn Moments every year. Each moment is unique, exhilarating, and moving in their own way. Among the most memorable was several years ago, my wife had guided a young boy to our telescope to have a peek at Saturn. The view elicited a loud gasp, and the exclamation, “It looks just like a Chevy symbol!” Yep, it kind of does!

If you’ve never seen Saturn before, go to your local planetarium or astronomy club. They would love to show you Saturn for the first time. And when you’re done, tell everyone what you’ve seen, and encourage them to have their own, first #SaturnMoment, a moment of perfect beauty between us and the Cosmos.

Looking Back 108 Years…

by Shane L. Larson

Today would have been Carl Sagan’s 82th birthday. It is an auspicious year, because after a 108 year drought, the Chicago Cubs have won a World Series title. The Cubs win reminded me of Sagan because his son, Nick, had told a story once of introducing his dad to computer baseball based on statistics, whereby you could pit famous teams in history against one another. Sagan apparently said to Nick, “Never show me this again; I like it too much.”

Today, Carl Sagan would have been 82 years old.

Today, Carl Sagan would have been 82 years old.

It is an instantly recognizable feeling to those of us who do science — a nearly uncontrollable urge to ask, “What if…” and then construct an experiment to answer that question. When faced with the prospect of being able to pit two great teams from baseball history against each other, the little science muse in the back of your mind begins to ask, who would win? What if I changed up the pitchers? Does the batting order matter? What if they played at home instead of away?

This incessant wondering is the genesis of all the knowledge that our species has accumulated and labeled “science.”  And so, to commemorate Sagan’s birthday, and the Cubs win this season, I’d like to look back at what we knew of the world the last time the Cubs won the World Series, 108 years ago, a time well within the possible span of a human life.  The year is 1908…

The title page of Einstein's PhD Thesis.

The title page of Einstein’s PhD Thesis.

In 1908, a young physicist named Albert Einstein, 3 years out from his college degree and after a multi-year stint working as a clerk in the Swiss Patent Office, got his first job as a professor, at the University of Bern. This era was a time in the history of physics where scientists were trying to understand the fundamental structure of matter. Einstein’s PhD thesis was titled, “A New Determination of Molecular Dimensions.” Despite the fact that he could not find a job as a faculty member in the years after he graduated, Einstein worked dutifully at the Patent Office, and did physics “in his spare time.” During 1905, he wrote a handful of transformative papers that would change physics forever. Like his PhD work, some of those were about the invisible structure of matter on the tiniest scales. One explained an interaction between light and matter known as the “photoelectric effect,” which would be the work for which he would win the Nobel Prize in 1921. Physicists had for sometime known that some materials, when you shone a light on them, generated electric current. Einstein was the first person to be able to explain the effect by treating light as if it were little baseballs (Go, Cubs! Go!) that were colliding with electrons and knocking them off of the material. Today we use that technology for devices like infrared remote controls to turn your TV on and off!  By the time Einstein became a professor, he was thinking about new and different things that had caught his attention, sorting out some new ideas about gravity that would, after an additional seven years of work become known as General Relativity.

(Top) Marie Curie in her laboratory. (Bottom) Curie's business card from the Sorbonne. [Image: Musee Curie]

(Top) Marie Curie in her laboratory. (Bottom) Curie’s business card from the Sorbonne. [Image: Musee Curie]

Other physicists were hard at work exploring other aspects of the properties of matter. In 1908, already having earned her first Nobel Prize (in 1903), Marie Curie became the first female professor ever at the Sorbonne in Paris. Her 1903 Nobel Prize in physics was for her work in the characterization of radioactive materials. She and her collaborators were not only trying to understand the nature of radiation and the properties of radioactive materials, but were discovering many of them for the first time. Today, we look at a periodic table of the elements and there are no gaps, but in 1908 there were. Curie and her colleagues discovered radium and polonium. They also discovered that some previously known elements, like thorium, were radioactive and we hadn’t known it. Before this pioneering work, the world knew nothing of radioactivity. At this time, the dangers of radiation were unknown. Curie for years exposed herself to radiation from samples in her laboratory; today, many of her notebooks are still too radioactive to be handled safely without protective equipment. In 1934, Curie died of aplastic anemia, a blood disease brought on by radiation exposure whereby your body cannot make mature blood cells.

We think a great deal of Curie’s exposure to radiation came not just from carrying radioactive samples around in her pockets (something that today we know is a bad idea), but also exposure from a new technology that she was a proponent of: medical x-rays. During World War I she developed, built, and fielded mobile x-ray units to be used by medical professionals in field hospitals. These units became known as petites Curies (“Little Curies”).

Orville Wright (R) and Lt. Thomas Selfridge (L) in the Wright Flyer, just before take off at Fort Myer. [Image: Wright Brothers Aeroplane Co]

Orville Wright (R) and Lt. Thomas Selfridge (L) in the Wright Flyer, just before take off at Fort Myer. [Image: Wright Brothers Aeroplane Co]

There were other technological advances being introduced to the world in 1908.  That year, the world was still becoming acquainted with the notion of flying machines. The Wright Brothers had successfully demonstrated a powered flying machine at Kitty Hawk in 1903, but in May of 1908, for the first time ever, a passenger was carried aloft when Charlie Furnas flew with Wilbur Wright over the Kill Devil Hills in North Carolina. Just as with Curie, the Wrights were in unexplored territory, learning about the art and science of flying for the first time. Dangers and unexpected events abounded — the Wright Flyer experienced a crash late in 1908 after a propellor broke during a demonstration for the military at Fort Myer. Orville Wright was seriously injured, but his passenger, Lieutenant Thomas Selfridge, sustained a serious skull injury and died 3 hours after the crash: the first person to perish in the crash of a self-powered aircraft.

(L) The 60-inch Telescope at Mount Wilson. (R) A young Harlow Shapley. [Images: Mt. Wilson Observatory]

(L) The 60-inch Telescope at Mount Wilson. (R) A young Harlow Shapley. [Images: Mt. Wilson Observatory]

On the opposite coast of the United States, also in 1908, the largest telescope in the world was completed on Mount Wilson, outside of Los Angeles: the 60-inch Reflector, built by George Ellery Hale. The 60-inch was built in an era when astronomers had discovered that building bigger and bigger telescopes enabled them to see deeper into the Cosmos in an effort to understand the size and shape of the Universe and our place within it. One of the biggest discoveries made with the 60-inch was still ten years away — astronomer Harlow Shapley would use the great machine to measure the distances to globular clusters near the Milky Way and discover that the Sun did not lie at the center of the galaxy(see Shapley’s paper here); today we know the Sun orbits the Milky Way some 25,000 light yeas away from the center.

The nature of the Milky Way was still, at that time, a matter of intense debate among astronomers. Some thought the Milky Way was the entire Universe. Others argued that some of the fuzzy nebulae that could be seen with telescopes were in fact “island universes” — distant galaxies not unlike the Milky Way itself.  The problem was there was no good way to measure distances. But 1908 saw a breakthrough that would give astronomers the ability to measure vast distances across the Cosmos when astronomer Henrietta Swan Leavitt published her observation that there was a pattern in how some stars changed their brightness. These were the first Cepheid variables, and by 1912 Leavitt had shown how to measure the distance to them by simply observing how bright they appeared in a telescope. A decade and a half later, in 1924, Edwin Hubble would use Leavitt’s discovery to measure the distance to the Andromeda Nebula (M31), clearly demonstrating that the Universe was far larger than astronomers had ever imagined and that the Milky Way was not, in fact, the only galaxy in the Cosmos. By the end of the 1920’s, Hubble and Milton Humason would use Leavitt’s discovery to demonstrate the expansion of the Universe, the first hint of what is today known as Big Bang Cosmology.

(L) Leavitt at her desk in the Harvard College Observatory. (R) The Magellanic Clouds, which Leavitt's initial work was based on, framed between telescopes at the Parnal Observatory in Chile. [Images: Wikimedia Commons]

(L) Leavitt at her desk in the Harvard College Observatory. (R) The Magellanic Clouds, which Leavitt’s initial work was based on, framed between telescopes at the Parnal Observatory in Chile. [Images: Wikimedia Commons]

Today, it is 108 years later. When I reflect on these items of historical note, I am struck by two things. First, it is almost stupefying how quickly our understanding of the workings of the world has evolved. It really wasn’t that long ago — barely more than the common span of a human life — that we didn’t know how to fly and we didn’t know that the Cosmos was ginormous beyond imagining. The pace of discovery continues to this day, dizzying and almost impossible to keep up with. The second thing that is amazing to me is how quickly we disperse and integrate new discoveries into the collective memory of our society. Flying is no longer a novelty; it is almost as common and going out and getting in a car. Large reflecting telescopes capable of making scientific measurements are in the hands of ordinary citizens like you and me, gathering starlight every night in backyards around the world. Most people know that the Milky Way is not the only galaxy in the Cosmos, and that radioactive materials should not be carried around in your pocket.

It is a testament to our ability to collect and disperse knowledge to all the far flung corners of our planet and civilization. In a world faced by daunting challenges, in a society in a tumultuous struggle to rise above its own darker tendencies, it is a great encouragement to me that the fruits of our knowledge and intellect are so readily shared and accessible. When the challenges facing the world seem to me too daunting to overcome, I often retreat to listen to Carl’s sonorous and poetic view of our history and destiny (perhaps most remarkably captured in his musings on the Pale Blue Dot). He was well aware of the problems we faced, but always seems to me to promote a never ending optimism that we have the power to save ourselves– through the gentle and courageous application of intellect tempered with compassion.  It seems today to be a good message.

Happy Birthday, Carl.

And Go Cubs, Go.

cubswinwrigley

#AdlerWall 06: #XPLORESTEM

by Shane L. Larson

All too often, we think of STEM as some kind of activity related to education — it is, after all, an acronym formed from “possible fields of study” in school: Science, Technology, Education, Mathematics.

But this is a great failure of imagination on our part. STEM is bigger than simply education, or careers. STEM is bigger than K-12 kids or young adults navigating college.

xplorestem

This week’s #AdlerWall segment is a hashtag that reads simply: #XPLORESTEM. While your high school guidance counselor may have used this notion to encourage you to think about certain majors in college, I’m going to use it as an aperture to an elegant truth: you do #XPLORESTEM every day, you just might not recognize it.

STEM, quite simply, is a way of life. One that we are all immersed in everyday, and one that we all appreciate and enjoy whether we realize it or not. But more importantly, STEM is something we practice every day without realizing it. It is something we were all once fantastic at (and very likely still are), but we’ve forgotten. We’ve listened to all those people who watch us through our lives say “you don’t think very clearly”, “you’re not good at math”, “science isn’t for you.” We’ve melded those soundbites with the seeds of doubt that talk to us in the quiet alone hours before the day dawns; we’ve sown and watered those seeds with inferiority gleaned from watching people around us who are seemingly unbaffled by IRS tax codes, computer operating systems, or the irrational math required to order pizza for teenagers.

I’m here to tell you it is time to burn that field of weeds you have sown.

I’m a theoretical physicist. I spend my days being baffled by really frickin’ hard stuff in astrophysics. I spend a lot of time teaching students and people just like you. I like to think I know what I’m talking about when I talk about STEM. So trust me when I say this:

We are all explorers. We are all scientists. We are all problem solvers. We are all critical thinkers. We just don’t know it.

You may think you are bad at math, you may think you are bad at science, you may think that scientific thinking is baffling, but that’s just the weeds talking. You think like a scientist every day; you practice the art of critical thinking (“scientific reasoning”) every day. You’ve just been trained to believe a lie that says you haven’t. Let’s take a walk, you and I, through some everyday things you encounter and think about in your life.

Like many of you, I’m related to a quilter. Which means I have a LOT of quilted stuff around my house. Here are some awesome examples.

Some excellent examples of quilt patterns. Quilts by Peggy Beauvais.

Some excellent examples of quilt patterns. Quilts by Peggy Beauvais.

Quilting is an artistic and crafty endeavour, to be sure, but there are well defined mathematical principles at work here, related to a topic we call “tiling” (which not surprisingly is similar to another household activity called “tiling” that is related to shower stalls and backsplashes in your kitchen). Tiling is the process of covering a space completely, without gaps. When the space is covered by the same shape over and over again, we call that “periodic tiling” or “regular tiling.”  Good examples include the gridded tread on your shoes, or a regular grid of floor tiles.

Zentangles are a a modern meditative artform that is built around completely filling a space with irregular tiles. [Zentangles by Shane L. Larson]

Zentangles are a a modern meditative artform that is built around completely filling a space with irregular tiles. [Zentangles by Shane L. Larson]

Tiling has given way to spectacular art. Part of the current trend toward meditative art has people engaged in coloring large patterns such as mandalas that symmetrically tile large spaces, or drawing Zentangles that cover a small space with a number of different patterns. Famous artists have made spectacular works of tiling, such as the colored tiling work of Marlow Moss and Piet Mondrian. MC Escher was especially well known for his talent with tessellations.

Tiling also appears in Nature — you can see it in the structure of the cells on a leaf, and in the “granulation” caused by convection on the surface of the Sun, and in the hexagonal lattice in the honeycomb of a beehive.

Two examples of tiling in Nature. (L) Granulation on the surface of the Sun [Image by NASA] (R) Honeycomb by bees [Image from Wikimedia Commons]

Two examples of tiling in Nature. (L) Granulation on the surface of the Sun [Image by NASA] (R) Honeycomb by bees [Image from Wikimedia Commons]

As I wander around my house I encounter another activity that my father taught me when I was young: woodworking. My dad mostly makes furniture (I have several pieces that I quite like that came from him and my childhood), but the form this most often takes for me is in building telescopes. At its most basic level, a lot of woodworking is about taking two pieces of wood and putting them together to make something, like a piece of art or a telescope or a piece of furniture. However, once you name a woodworking piece “chair” or “footstool” then there are some deeper requirements, namely “it should not collapse if I stand on top of it and do an arabesque!”

(L) My daughter doing ballet on a footstool my father made. There is a great deal of engineering that has to go into the woodworking of the footstool to make this possible. (R) One of my daughter’s creations from when she was perhaps 4 years old, and I was first teaching her about woodworking. There is no engineering requirement here beyond “it must stay together.” (Neither she nor I remember what this was supposed to be; it says "volcano" on it.) [Images by Shane L. Larson]

(L) My daughter doing ballet on a footstool my father made. There is a great deal of engineering that has to go into the woodworking of the footstool to make this possible. (R) One of my daughter’s creations from when she was perhaps 4 years old, and I was first teaching her about woodworking. There is no engineering requirement here beyond “it must stay together.” (Neither she nor I remember what this was supposed to be; it says “volcano” on it.) [Images by Shane L. Larson]

The Willis Tower in Chicago was enabled by a new thought in structural engineering -- tubular construction. [Image by Shane L. Larson]

The Willis Tower in Chicago was enabled by a new thought in structural engineering — tubular construction. [Image by Shane L. Larson]

This is the heart of structural engineering. I don’t do any serious design and planning when I make a footstool; I do it more or less by trial and error and appellation to past experience (“I better put a brace here, or it will be wobbly.”). The fundamental principles, however, are the same ones that go into bridge design, or keep the Willis Tower upright. Engineers and architects, to be sure, plan their buildings ahead of time. They do calculations and build models to make sure the beams are the right sizes and the braces are in the right places. But the beginning of any building or bridge or train tunnel is the same place every footstool or backyard tree fort starts — a sketch on the back of a Five Guys napkin with a little guesswork and a bit of previous experience.

I would be remiss, if I closed this oeuvre to life and STEM without mentioning the most obvious example of science hiding in your life: cooking.  Cooking is a bunch of thermodynamics and a helluva lot of chemistry.  We could spend weeks — months! — writing every day about the chemistry that goes into cooking. So let’s just focus on one small bit of culinary wonder: crisping and browning.

Imagine something simple, a little comfort food from childhood: grilled cheese sandwiches. Mmmmm. It starts with some simple bread, a few slices of cheddar nestled between, and a searing griddle. As soon as the bread hits the griddle, it sizzles and sings as heat seeps into the sandwich, beginning the slow melt of the cheese. The process of melting is a bit of thermodynamics, which describes how energy can change the state, the physical properties of matter. The outside of the bread (and probably some bits of cheese that have oozed out on the griddle) are browning under the heat. This is the beginning of pyrolysis, the conversion of organic material into charred material (like “charcoal”). But before the complete conversion of your sandwich into an inedible charcoal briquette, it attains a crispy golden brown state, crunchy and delicious. What happened there? The browning process and flavor change of food during the early stages of cooking (before burning) is called the Maillard process. It is a chemical process where amino acids (the building blocks of organic molecules in living things) and sugars (long chain molecules that are broken up by organisms to make energy) work together and combine into something new. The idea of the browning process was first described by French physician Louis-Camille Maillard in 1912, but the chemical reactions were not worked out until 1953 by John Edward Hodge, an African-American chemist working for the Department of Agriculture in Illinois.

The secret of my lasagne, is the sauce. [Image by Shane L. Larson]

The secret of my lasagne is the sauce. [Image by Shane L. Larson]

Of course, cooking is often as much an art as science. The exact blending of flavors to make something new from common ingredients is unique to every chef. My lasagne is probably quite different than your lasagne. We might both enjoy each other’s lasagne, trade some secrets and ideas, and then experiment to see if we want to tweak our individual recipes. Sometimes we decide the experiment was a success, and sometimes not.  It all depends if the result of the experiment tastes good or not!

Here’s a bit of cooking chemistry from my childhood. Do you know what doesn’t taste good? Tang mixed with hot chocolate. I know it sounds like it should be okay, but trust me. Barf.

Of course, it isn’t all over with the cooking. You and I can cook with guidance from a cookbook — that’s chemistry in the kitchen. But once you eat what we cooked, your body takes over. Without any input from your brain, your body fires up a process called “anerobic glycolosis” — how to take food molecules and quickly make energy out of them. YOU are a walking chemistry experiment, every hour of every day.

So what’s the point in #XPLORESTEM? While on the one hand the impetus is often to encourage the young generation of students to think about careers in STEM fields, because we largely associate such fields with the success of the economy, with progress and brighter tomorrows, and general competitiveness on the world stage, I think about it the way we’ve been talking about it here: the ideas and use of STEM are not just careers and equations and laboratories. The ideas and use of STEM are fundamental principles that we often use unconsciously and in our everyday lives and hobbies. I can’t go build a building bigger than the Willis Tower because I can make footstools. I can’t predict solar storms because I can make a pretty kitchen tile pattern. I can’t make a new durable metal alloy for joint replacements because I know how to mix up a great vinaigrette.

But I can understand and use the same basic ideas as the scientists and engineers who do those bigger things. I can appreciate that what we know about the Cosmos is not an unfathomable mystery, because it is rooted in action and activity you and I do every day.

Your kid may decide they really want to be a marine biologist or a mathematician or a computer engineer. You may decide to go back to school (now that your kids are out of college) and study astronomy, or physical chemistry, or geology.

When any of those things happen, don’t throw up your hands! Don’t make a face like you’ve eaten a bug and declare “I hated science!” I’m sure you did, but that’s because we didn’t tell you the truth — you’re a scientist every day, and you #XPLORESTEM every day. I know you do, because I do it too.

See you out in the world! I’ll be the guy at the chili competition, quite certain that my newest experiment is totally going to win the cook-off. 🙂

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This post is part of an ongoing series about the #AdlerWall. I encourage you to follow along with the activities, and post your adventures, questions and discoveries on social media using the hashtag #AdlerWall.  Links to the entire series are here at the first post of the #AdlerWall Series.

#AdlerWall 05: Share Interesting Observations, Ask Questions

by Shane L. Larson

Apparently this creature eats quarters.

Apparently this creature eats quarters.

My wife and I just bought a new couch and when we flipped the old one over to carry it downstairs, a quarter fell out. When I was in high school, arcades were the rage and a quarter was a ticket to a nice half-hour playing Xenophobe or Blasteroids. These days, it goes in my pocket and gets spent on parking. Despite the sad evolution of my life into adulthood, the appearance of the quarter sparked an interesting thought: I don’t remember dropping a quarter in my couch, and probably no one else would either, so that must mean almost everyone’s couch likely has a loose quarter in it! That observation, sparked an interesting question: how much money in quarters is hidden in couches?

(L) How I used to spend quarters. (R) How I spend quarters now. If the place on the left still existed, I could feed the the thing on the right with my phone and put those quarters to good use! :-)

(L) How I used to spend quarters. (R) How I spend quarters now. If the place on the left still existed, I could feed the the thing on the right with my phone and put those quarters to good use! 🙂

Because you and I live in the future, information is at our fingertips. I pulled my phone out of my pocket and was quickly at the US Census site, which told me there are approximately 116,000,000 households in the United States (this page is where I landed). So if they all have a couch, and each couch has a quarter in it, that amounts to:

$0.25 * 116,000,000 = $29,000,000

There are 29 MILLION dollars in quarters hiding in couches! This observation has sparked some interesting discussions with friends that are wide ranging and varied: is there really only 1 quarter per couch? How much money disappears from circulation every year? Is there some way we could collect all that money? What could we do with $29 million?

This little exercise is something known as a “Fermi Problem,” — taking something you know (my couch has a quarter in it) and figuring out the implications based on other things you know (the number of households in the United States). Scientists use the method all the time to understand what the Universe is all about, particularly in astronomy where we don’t know much. But the interesting bit about the quarter question is not the number, it is the discussions that ensue afterward.

Just a few observations I have made and shared with friends, found on my smartphone. You most likely have a similar set!

Just a few observations I have made and shared with friends, found on my smartphone. You most likely have a similar set!

You make observations of the world around you all the time, and share those observations on social media or over coffee with friends. I know you do, because I see jillions of people everyday taking pictures of flower bushes and posting them to social media, asking friends over coffee if they noticed they way the clouds were streaked over the city that day, speculating on why the traffic was heavy or light today, or simply enjoying the spectacle of the brilliant turquoise color of the lake on a sunny day. You see the world around you and record it and talk about it, every single day.

adlerwall_questionsobservations

Given our social connectedness in modern life, this week’s exhortations from the #AdlerWall are ones that might not seem totally incongruous: “Share Interesting Observations” and “Ask Questions.” We are all good at this to some varying degree, but kids are masters. Children ask incessant questions of their parents:

“How do airplanes fly?”

“Where do frogs go in the winter?”

“Why do we say ‘bark’ to mean the sound dogs make and the skin of a tree?” 

They also share interesting observations:

“Look how you can make a loud sound by squishing your hand in your armpit!”

“If I hit my spoon right here, it flips oatmeal WAY over there!”

“The shadows from this tree look like an octopus!”

But sadly, somewhere along the pathway to adulthood, many of us lose that unbridled enthusiasm we had as children for exploring the world around us, and declaring our discoveries to the world. Sure, I’ve wondered how many gummy bears I can fit in my mouth and figured out the answer (37) — who hasn’t? It’s not that we don’t know how to ask questions and share our observations.  It has just become the societal norm to squelch the unbridled enthusiasm.

Yes, that’s right: squelch, not kill. Because in the quiet moments, we all give into the most basic impulse to ask a question, to look at the world around us and see what is going on. You might not always post a picture of the weather radar during a torrential thunderstorm, but you still made a screen capture. You have stayed up too late at night because you went to Wikipedia to find out about The Great Platte River Archway and two hours later found yourself still on your tablet, having randomly navigated through clicks until you were reading about the Toledo War. You’ve almost certainly been hanging out with your friends, when someone has asked some esoteric question about the difference between fountain pens and calligraphy pens, igniting a debate that was only resolved by asking Google or Wikipedia.

img_7696For most of us, making interesting observations and asking questions of our friends and the internet are diversions to everyday life, something we do for the sheer enjoyment of learning. But lurking just below the surface of those questions and observations is always a myriad of important ideas and applications, some of which we understand and some of which we may not. Irrespective, it points a simple and inescapable fact: we are all close to being scientists, simply by doing what we do — asking questions and making observations.

Let me illustrate with a curious observation I just made the other day. I have a vertical glass shower door; the glass is maybe 10 mm thick. If you put your eye right up against the edge of the door, and look into the glass (not through the glass), you a mesmerizing collection of reflections inside the glass door!

The view inside a glass door, looking edge on into the glass.

The view inside a glass door, looking edge on into the glass.

I’m sure I could work out the physics of the all the reflections as to why it happens (and could probably subject some future students to the analysis of that problem), but instead I’ll just share that observation with you. The next time you walk through a glass door, take a moment and peer in through the edge, looking longways into the glass — you’ll be treated to the same awesome spectacle I discovered. Maybe you’ll show it to a friend, or you’ll sketch it in your pocket notebook, or you’ll create a new glass sculpture inspired by the sight.  Irrespective, I’ve shared my observation with you, and hopefully shown you something you haven’t see before!  You should share what you see too.

So what does that have to do with anything? Peering into the glass of your shower door produces a spectacle that is fun and pleasing to behold, like a piece of symmetric art or a kaleidoscope. But the basic physics, called internal reflection, led to many, many modern applications, not the least of which are fiber optics, and the heart of most high-speed communications networks that are likely streaming internet and movies into your home right now. Binoculars have a pair of prisms that use internal reflection to gather the images of distant objects and route them through the binoculars to make a correct, right-side up image at your eye. Internal reflection of light in a raindrop takes the light from the Sun behind you, and directs it back at you to make a rainbow. And perhaps last, but not least, internal reflection is the basic physical principle behind infinity mirrors (IMHO, one of the coolest pieces of home decor you can have — your spouse may or may not disagree…).

Everyday examples of internal reflection. (Top L) Binoculars. (Top R) Rainbow creation by raindrops. (Bottom) Light propagating through a fiber. [All images from Wikimedia Commons]

Everyday examples of internal reflection. (Top L) Binoculars. (Top R) Rainbow creation by raindrops. (Bottom) Light propagating through a fiber. [All images from Wikimedia Commons]

All of this is connected, in a simple way, to the little pane of glass on my shower door. The world is a strange and wondrous place, full of moments of giddy discovery if you take the time to notice. 🙂

So I’ll see you out in the world — I’m the guy blocking the entrance to the coffee shop as I try to snap a picture looking longways into their glass door. 🙂

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This post is part of an ongoing series about the #AdlerWall. I encourage you to follow along with the activities, and post your adventures, questions and discoveries on social media using the hashtag #AdlerWall.  Links to the entire series are here at the first post of the #AdlerWall Series.

The Cosmic Classroom on Boxing Day

by Shane L. Larson

The seas of the Cosmos are vast and deep. From our vantage point here on the shores of Earth, we have seen much that is beautiful, awe-inspiring, frightening, humbling, confusing, and enigmatic. The simple truth of astronomy is that it is a spectator sport. The only thing we can do, is watch the skies and wait for the next Big Thing to happen. We collect events, like bottle-caps or flowers, and add them to our collection. Each new addition is a mystery, a new piece of a puzzle that takes shape ever-so-slowly over time.

On 14 September 2015, the LIGO-Virgo collaboration announced that they had detected the first gravitational waves ever, and that those waves had been created by a pair of merging black holes far across the Cosmos.

Today, we have some more news: LIGO has detected the second gravitational wave event ever, and those waves were also created by a pair of merging black holes far across the Cosmos. But as is often the case with astronomy, we know what we’ve observed, but we still don’t know what it means.

The name of the event is GW151226 (the date of the event), but within the collaboration, we call it “The Boxing Day Event.” On 26 December 2015 (Boxing Day in Europe), the two LIGO detectors responded to the faint ripple of gravitational energy washing across the Earth, the signature of two black holes merging to form a new larger black hole.

LIGO detected the black holes merging at 3:53 UTC in the morning on Boxing Day (it was late in the evening on Christmas Day in the United States, 9:53pm Central Standard Time). The event happened 440 Megaparsecs away — almost 1.4 billion lightyears! As with GW150914 before it, this titanic merger of black holes happened long, long ago, in a galaxy far, far away. It happened before multi-cellular life had ever arisen on Earth, and for a billion years that information has been sailing through the void, until it washed across our shores.

Learning to do astronomy: We can’t do experiments in astronomy, not the way we all learned to do them in middle schoolExperiment. Observe. Fail. Learn. Repeat.

The timeline of LIGO's first Observing run (called O1). The first detection (GW150914) and the second detection (GW151226) are marked. There was also a candidate that looked like a gravitational wave, but was not strong enough for astronomers to confidently say a detection was made.

The timeline of LIGO’s first Observing run (called O1). The first detection (GW150914) and the second detection (GW151226) are marked. There was also a candidate that looked like a gravitational wave, but was not strong enough for astronomers to confidently say a detection was made. [Image: LIGO Collaboration]

In astronomy, all we can do is observe, and hope that when we see something interesting happen, it happens again. Or something similar happens again, so we can start trying to make connections. Since the first LIGO detection, we have been patiently waiting for more detections. It could have been anything: merging neutron stars, a gamma-ray burst with an associated gravitational wave signal, a supernova explosion in the Milky Way, or perhaps other pair of black holes similar to GW150914.  As it turns out, it was the merger of black holes, but somewhat different than the one we observed before. Excellent! A chance to learn something new about the Cosmos!

When you look at the pile of gravitational wave events we’ve seen before (it’s a very small pile — there is only one event there, GW150914), we do the most obvious thing you can imagine: we start to compare them.

sll_blackHoleSummary

Strictly in terms numbers, you see that the Boxing Day black holes are less massive than the GW150914 black holes, by a substantial amount. This tells astronomers something very important: black holes can and do come in a variety of masses. That certainly did not have to be the case; there are many instances in the Cosmos where almost every example of an object is similar to every other object. People are all roughly the same height; grains of sand are almost all roughly the same size; yellow-green stars like the Sun (“Type G2” in astronomer speak) are all roughly the same mass. Though we did not expect it to be true, it could have been the case that all black holes were about the same mass; LIGO is happy to report that black holes come in many different masses.

But this, in and of itself, inspires new questions and new mysteries. The question for astronomers now is where do black holes of different sizes come from? The Boxing Day black holes are “normal size” — we think we understand how black holes in this mass range are made in supernovae explosions. The GW150914 black holes are a much grander mystery — they are larger (by a factor of 2 or 3) than any black holes that we expect to form from stars today. We have some interesting ideas about where they may come from, but those ideas can only be tested with more gravitational wave observations.

Comparison of the size of black holes observed by LIGO, as well as other candidates detected with conventional telescopes. (L) The physical size of the black holes overlaid on a map of the eastern United States. (R) The same image showing the masses on the vertical axis, and the black holes that combined to make larger black holes. [Image: LIGO Collaboration]

Comparison of the size of black holes observed by LIGO, as well as other candidates detected with conventional telescopes. (L) The physical size of the black holes overlaid on a map of the eastern United States. (R) The same image showing the masses on the vertical axis, and the black holes that combined to make larger black holes. [Image: LIGO Collaboration]

Gravitational wave astronomy: Every observation is different, because every source is different. Every set of waves is a unique fingerprint that encodes the physical properties of the objects that made the waves: their masses, how fast they are spinning, what kind of object they are,  how physically big they are, the distance to them, and so on. It’s like looking at the pictures in your high school yearbook — every picture is the same size, and is what we all call a “picture,” but each one uniquely identifies you or your friends. It encodes the color of your hair and eyes, whether you were smiling and wearing braces, the sweater you wore on picture day, and so on.

A typical visualization of a black hole binary. They emit no light, so there are no pictures! [Image: SXS Collaboration]

A typical visualization of a black hole binary. They emit no light, so there are no pictures! [Image: SXS Collaboration]

When we look at our data, we don’t usually show pictures. LIGO is not a telescope, so it does not generate images like we are used to seeing from the Hubble Space Telescope. Most “pictures” you see are simulations or realizations of the data. Instead, we show our data as graphs and plots that represent our data in ways that tell astronomers what LIGO is measuring and how that relates to quantities in physics we understand, like orbit size or energy.

A stereo equalizer display.

A stereo equalizer display.

One common picture we use is something called a “spectragram” — you may have encountered something like a spectragram on a stereo. The equalizers on your stereo tell you how loud the music in terms of whether it is more treble sounding or bass sounding.  In LIGO, we look at our data by looking a spectragram and how it changes over time.  The fact that the Boxing Day black holes and GW150914 are different is immediately obvious when comparing their spectragrams — the fine details of the shape and duration is different in the two cases, but they have the same basic swoopy shape to them. Think about your high school yearbook: the pictures are all kind of the same, but different in the details.

The comparison of spectragrams from GW150914 (top) and the Boxing Day event (bottom). The blue swoop is the gravitational wave signal as it evolves in time (early in the event on the left, and the final merger in the tall swoop on the right). [Images: LIGO Collaboration]

The comparison of spectragrams from GW150914 (top) and the Boxing Day event (bottom). The blue swoop is the gravitational wave signal as it evolves in time (early in the event on the left, and the final merger in the tall swoop on the right). [Images: LIGO Collaboration]

The difference in the gravitational waves LIGO detected is even more obvious if you look at the waveforms themselves. Imagine you are standing on the beach watching waves roll in and crash on the sand. In between waves, the water is calm and relatively low, but at the moment the wave is washing ashore, the height of the water increases subtantially; if you happen to be standing in the wave as it washes by, you might not be able to stand up because the energy carried by the wave is enough to knock you over. In a very similar way, the waveforms illustrate the strength of the gravitational waves as they wash past the Earth. The size of the “up and down” in the waveforms we plot tells us how strong the waves are.  If you compare the Boxing Day black hole waveforms with the GW150914 waveforms, you see they both have a lot of up and down (a measure of strength — they were strong enough for LIGO to detect!), but their overall shape and duration is different.

Comparison of the "waveforms" for GW150914 (top) and the Boxing Day black holes (bottom). The signals are considerably different, and longer in the case of the Boxing Day event. [Images: LIGO Collaboration]

Comparison of the “waveforms” for GW150914 (top) and the Boxing Day black holes (bottom). The signals are considerably different, and longer in the case of the Boxing Day event. [Images: LIGO Collaboration]

Gravitational wave astronomers at LIGO are most excited about the long chain of up-and-downs in the Boxing Day waveforms. This is a part of the black hole evolution we call the insprial — the long, slow time where the orbit is shrinking, the black holes drawing inexorably closer, creeping toward their ultimate fate: the coalesence into a new, single, spinning black hole. The longer the inspiral is visible to LIGO, the longer we can study the black holes with gravitational waves. Once they merge to form a new black hole, they very quickly become quiet, much like a bell fading into silence after being struck by a hammer. The inspiral, and the merger, are the only chance we have to take the measure of these tremendous astrophysical entities.

What now? LIGO has now made two detections of gravitational waves, both during our first observing run (what we call “O1”). In mid-January 2016, we turned LIGO off and have spent the ensuing months combing over the machine and addressing all the problems and difficulties we encountered in O1. In late summer 2016, we’ll start up for “O2.” We’ll turn up the lasers a little bit, and LIGO will be able to see a bit farther into the Cosmos. If our first stint as gravitational wave astronomers is any indication, we will likely see something new; we don’t know, all we can do is observe.  After a few months, we’ll shut down again, tune things up, think hard about how we are working with the machine, and in 2017 expect to come back online with everything at full design specifications.  We are like toddlers, learning to walk. We’ve taken our first few steps, and have discovered there is a tremendous world just waiting to be explored. We’re learning to keep our balance and do things right, but in the not too distant future will be confident and excited in our new found ability to observe and discover a Cosmos that up to now, has been completely hidden from us.  Carpe infinitum!


Many of my colleagues in the LIGO Virgo Collaboration have also written excellent blog posts about the Boxing Day event, and the work we do to make gravitational wave astronomy a reality. You should visit their blogs!