The 2018 Nobel Prize in Physics

I woke up a little late this morning. I wanted to be up at 4:30am. It was 4:40 when I realized the alarm I had set the night before was going off, and I pulled myself out of bed. Jodi was already up, working on her class prep for the week. I grabbed a cup of coffee and headed upstairs to my office to connect to and listen to the announcement of the 2018 Nobel Prize in Physics (“… no earlier that 11:45am” European Central Time, as their website always says). 

“I think the internet is down again,” Jodi said as she sat at the writing desk in my office. I sat down at my computer desk, and verified it – our internet connection to the outside world was out, as it had been on Sunday when I returned from a conference in Sweden. We tried a few things with the cable modem, but nothing worked. So, I fired up the LTE connection on my iPad and connected to the live stream of the announcement a few minutes late.

They were still in the part in Swedish, but a minute or so after we connected, they switched to the English version: the prize for physics was awarded…

…for groundbreaking inventions in the field of laser physics” with one half to Arthur Ashkin “for the optical tweezers and their application to biological systems”, the other half jointly to Gérard Mourou and Donna Strickland “for their method of generating high-intensity, ultra-short optical pulses.”

When I first saw a demonstration of optical tweezers in 1998, it was in the summer at a CERN colloquium by then new Nobel Laureate, Steve Chu. Optical tweezers were thre basis of his own prize, and so it was fitting the the optical tweezer breakthrough itself would one day be highlighted by the Swedish Academy of Science and the Nobel Prize. LASIK surgery, among many other applications, were enabled by the other half of the prize. The ability to generate ultra-short, highly intense pulses of laser light have made a great deal of modern technology possible. The seeds of all that were planted by the 1985 paper on chirped pulse amplification by Strickland and Mourou. This was the subject of Strickland’s Ph.D. research, and by the time she earned her Ph.D. in 1989 she and Mourou had also demonstrated the first tabletop Terawatt laser prototype. Not bad for a Ph.D.!

As I put together my slides for the beginning of my introductory physics class today, other interesting things came to my attention. Ashkin was drafted to serve in WWII but put into the enlisted reserve to work on the technology for radar at the Columbia Radiation Laboratory. Mourou has a very thin paper trail on the web, making learning more about his career more difficult then the other two. Strickland has been the President of the Optical Society but is only an Associate Professor at her university (which makes me wonder about promotion standards at her university, and then fear for them at my own). 

You learn a lot from a Nobel Prize… and not always what you expect.

The Summer of 2018 – By The Numbers

The sun sets over Green Bay in Wisconsin. As this summer draws to a close, some reflections on the events of this period… by the numbers.

The summer of 2018 was both predictable and unexpected. As I began reflecting on this past summer, now that teaching is nearly upon me again, I came to find numbers that represented its many aspects. I want to share some of those numbers with you, and the meaning behind them.

Let me begin by clarifying something: for a research professor, summer begins the day after spring graduation and it continues until August 1, which marks the tolling of the last bell at midnight. August first is the beginning of the new day, the month that heralds the bright and blinding sunlight of teaching at month’s end. The research activities have ended, and the teaching preparation begins. It’s crucial to steal time for vacation during this period as well, or you’ll go mad.

Author’s Note: I originally wrote this several weeks ago, before the start of classes. As is typical, the end of summer and the beginning of teaching hits like a freight train you never see coming. And though I did see it coming, I somehow still never saw it coming.

72 [Days of Summer]

That’s the number of days from the first day after Spring Commencement to August 1. I would define that as “academic summer.” Those are the number of days in which to pack as much research as you humanly can, while also putting your life back onto something resembling the “regular schedule of research.” For me, that means interweaving home life (such as it is in the summer for two roving research professors) with personal time (exercise, etc.) and work (time with research students, time in meetings, etc.). For 72 days I can largely avoid class prep… or, at least, serious thoughts of class prep. But after that, I can avoid no longer.

It’s not that I don’t love teaching. It’s that I understand and respect that if allowed to take all the space it wants it will get all the space I have. Research is a precious and fragile thing that much be protected at all costs. Without research, there would be nothing new to teach. You cannot have one without the other, but one of these tries at all times to steal away all the time from the other. Like a helicopter parent, I must hover over my research time, protect it from outsiders, and shield it against the endless demands of teaching. If it dies, my reason for teaching (and thus my love of teaching) also dies.

59 [Days Apart from Jodi]

Those were the number of days apart from Jodi this summer. In point of fact, once Jodi moved to Santa Barbara in March to begin her time as a resident expert for the cold dark matter workshop at the Kavli Institute of Theoretical Physics (KITP), we were apart for all but a few weeks between mid-March and August 1. But since I’m just counting summer (as defined above), I’ll spare the more sob version of this story.

Jodi and I sit in a room at KITP during a weekend visit to see her in early May. KITP was her home for about 3 months in the spring and early summer.

Our geographic separation was really for all the right professional reasons. I had two classes to teach at SMU this past spring; Jodi had a semester off teaching (made up for by teaching two classes in the Fall) so that she could fully participate in the KITP workshop. In addition to getting to work with the brightest minds in her fields, discussing new ideas for experiments, evidence for and against theoretical notions, and a host of other matters, this also looped her back into being interviewed for public radio’s “Science Friday” program

By the time Jodi landed back in Dallas to return to our “normal life,” I was was gone to see my parents in Connecticut before a 3 week visit to CERN. I returned in July for two weeks, having about 9 days together with her before I returned to CERN for another two-week stint. During my 14 days at home, she had a collaboration meeting for her experiment. That took her to Canada. These are all perfectly normal summer activities for two research physicists in very different sub-fields. Nonetheless, this constant “apartness” wears a couple down.

34 [Days at CERN]

This is the number of days I spent at CERN this summer. It’s about a 9 hour flight to an airport in Europe, followed by a two(-ish) hour connecting flight to Geneva. I mixed it up this summer, going first from JFK airport to Geneva (after visiting my parents in Connecticut) and the second time from Dallas to Geneva. In both cases, I went via London. In both cases, the trips were their usual “long” but thankfully also mostly “uneventful”. As I told anyone who would listen this summer, I’d be very happy if airlines gassed me to knock me out for all of these flights and revived me at my destination. At least, then, I would get some goddamned sleep on these flights.

Flying from JFK (NY) to Heathrow (London) on my way to CERN. The gold stars mark places I have visited over my life (and spent more than 24 hours there, and not only in an airport).

The first block of time at CERN was a carefully planned list of specific activities, many of which were tossed to the side when it was decided to push for a summer result in the big analysis on which we work, the study of the direct interaction of the Higgs particle and the bottom quark. The second block of time at CERN was also carefully planned, a “cleanup operation” after the first block to sweep up projects that fell to the side. It was also completely shaken up by the need to complete a highly time-sensitive task in the realm of the ATLAS trigger system. We did it, but by the time I returned home I was way behind on a bunch of other stuff that also needed my attention.

A view along a road inside CERN, bordering a vineyard on the south side. The sun is setting over the Jura Mountains.

Still, 34 days at CERN made for some amazing accomplishments and memories for this summer, and really for this entire year. My graduate students are both in excellent positions to launch the final stages of their Ph.D. work. My most recent post-doc is moving forward into a data science position in industry, and I’m in the process of hiring another scientist to work with me on Higgs physics and to collaborate with and supervise the students. And, to boot, my summer research undergraduate made some amazing progress in learning to simulate the behaviors of gluons, behaviors we’ll need for the project that is the basis of her senior thesis work.

14 [Pounds I won’t miss]

This is the number of pounds I lost this summer thanks to a renewed focus on foods and exercise. I made a regular habit (4-5 days each week) of exercising for at least 30 minutes with aerobic impact (getting my heart rate high and keeping it there). I gently extended my runs (running was my primary exercise) over a period of months, until recently I could comfortably achieve 5-6 mile runs at a single shot. At my peak, over a year ago, I could run between 10-11 miles… but this was also a time when I was not stretching enough or recovering enough between long runs, and I injured my hip, hamstring, and later my right foot. It took about a year to recover from all of that, setting me back quite a bit.

My weight, tracked using electronic devices. You can see the creep upward during my stressful and inactive spring, and the push downward as I altered my diet and exercise back to healthy norms.

However, once I recommitted this summer I made good progress toward my long-term goal of (1) sustained exercise, (2) a normal and balanced diet with emphasis on fruits and vegetables, and (3) a goal-weight of 175lbs. That final goal, which is really just a number to shoot for, has been my goal since 2012 when I made my first sustained attempt to alter my lifestyle. Since then. I’ve knocked off 5-15 lbs per year, depending on the year. This summer began with me around 202 lbs, up from my low of about 190 lbs over a year ago. Now I am sitting at 188 lbs. The most important thing I that I have endurance and clarity as a result of the balanced portfolio of work, exercise, and diet.

2 [Discoveries]

This is the number of discoveries that resulted from projects I’m involved in this summer. It’s pretty hard for a physicist on a large experiment to take sole credit for anything, and I don’t deserve sole credit for these even in my wildest dreams. But to be part of two major discoveries in one summer was a hallmark of a pretty damned good summer. 

A representation of the data ATLAS used in 2018 to observe the direct interaction of the Higgs particle and bottom quark.

The first I’ve written about here before, because it’s the easier-to-care-about one: the direct observation of the Higgs particle and the Bottom quark (the second-heaviest quark) interacting with each other. This could not be observed during the first run of the LHC; despite the fact that this is the strongest and most prevalent interaction of the Higgs particle with a building block of nature (at least, in a direct sense), seeing this behavior required much more data and a vastly sharper “lens” than we had available in Run 1. By Run 2, we had honed our ability to understand and fight background processes that obscure the signal; we had improved our ability to sharpen the reconstructed properties of the Higgs boson, making them easier to see even on top of a noisy pile of confounding data; we performed vastly more simulation of the worst backgrounds, those most likely to “fake” the signature of this process and confuse our observations; we combined our work with independent searches for the same process from within the ATLAS experiment, effectively multiplying the data by a little to boost the signal. All of this together pushed us over the threshold for observation. It was a wondrous thing to see in the data.

A 12 minute animation explaining the observation of the direct interaction of the Higgs particle and the bottom quark.

The second discovery was a bit more esoteric, but no less important. In combining our measurements with other independent measurements from within the ATLAS experiment, we also discovered definitively a specific means of production of the Higgs particle. 

Prior to this, the most prevalent means of production, dubbed “Gluon Fusion,” had already been observed in the first run of the LHC. Given the fact that we smash protons into protons, and at these energies protons are mostly sticky bags of gluons, it’s no surprise that this is the first means by which we saw Higgs particles definitively produced.

The second means of production, surmised before the start of the LHC and evidenced in Run 1 (with definitive observation in Run 2) was “Vector Boson Fusion,” the analog of gluon fusion except this time it’s the exchange of massive “vector bosons” by quarks inside the proton that results in the production of a Higgs particle.

The fourth-largest means of production was observed earlier this year when the direct interaction of Higgs particles and top quarks was seen first by the CMS Experiment, and then by ATLAS. How did we skip to fourth? Well, while the Higgs and bottom quark interaction results in the most frequent decay of the Higgs particle, the bare coupling of the Higgs and the top quark (the largest such bare coupling in the Standard Model), combined with the unique signature of top quarks, a bit harder to miss than the Higgs and bottom quark interaction. This production mechanism is known as “Top Quark-Associated Production.”

As part of the Higgs and bottom quark observation, we also observed the third-largest production mechanism: “Vector Boson-Associated Production,” also known as “Higgsstrahlung.” What does this mean? It’s a production mechanism by which one first makes a vector boson, such as W or Z. That’s relatively copious at the LHC. It’s what happens next that is more rare. Not quite at the right mass-energy, the vector boson radiates a particle and “drops down” to its happiest mass-energy state. In this case, what is radiated is a whopping great Higgs particle. Thus the name “Vector Boson-Associated Production” of the Higgs particle. Why “Higgsstrahlung?” Well, “Bremsstrahlung” – the root word for this nomenclature – is German for “Braking Radiation.” It’s the radiation (light) emitted by charged particles (especially electrons) when they are forced to alter their flight trajectories, like brake lights flashing on when a car has to hit the brakes and swerve to avoid a collision. “Higgstrahlung” is an honorary name for the process of a vector boson (a cousin of the photon of light) radiating a Higgs particle. 

3 [Major things I actually did myself this summer]

“What is it you say you do here?”

Bob Slydell to Tom Smykowski, “Office Space” (1999)

What do faculty do? It’s an often repeated question, whispered behind the back of faculty by students, undergraduate and graduate alike. Do faculty just sit in their offices all day, waiting for students to walk in and interrupt their train of thought with a question? Do faculty spend most of their time writing grant proposals, failing to get grants, and complaining about grant proposals? Are they faking it? I bet they’re faking it.

Here’s what I did this summer, to justify my existence as a scientist, that didn’t involve telling other people what to do:

  1. I took over as developer and maintainer of StudyTrigTracks, a software framework for performing simulation- and data-based studies of bottom-quark-initiated jet triggers. I immediately fixed some redundancy in the code and made it a but more stumble-proof than it had been. I should know. I am very good at stumbling. Mostly I have to protect myself from me.
  2. Using StudyTrigTracks, I reproduced an analysis originally developed in 2017 to assess the performance, in data, of bottom-quark-initiated jet triggers. This resulted in a new assessment of the performance of the same triggers in 2018 data, using about 16/fb of data. This, in turn, resulted in a public plot for all ATLAS physicists (and anyone else) to use in presentations and posters. This is the first time I have personally generated such a public plot to stand alone on its own.

    From this and the 2017 figure, I made (privately) the morphing animation below (my own creation, not officially from ATLAS). Note the stability of the algorithms.
  3. I rewrote a bunch of code for a paper I am co-authoring with a former student, now a Ph.D. student at Stanford. She and I never had a chance to finish this paper 2 years ago, but we have the chance now. This involved adding a bunch of new inputs to the code, verifying the original code (written by my colleague), and generating updated figures for our paper using some new tools: MatPlotLib, Pandas, Seaborn, and SciPy. I had a LOT of fun working on this. We expect to wrap this paper up in the next couple of months.
A morphing animation of the 2017 and 2018 data performances of b-jet triggers. These were supposed to be flat with increasing proton-proton collisions (they are) and stable from year to year (they are).

Unknown [Number of Lines of Code Written this Summer]

If progress in software-based physics can be proxied by the number of lines of code you write in one block of time, then let’s just go with “innumerable”. I mean, I could use git to count the lines of code contributed across the half-dozen packages I worked on this summer. But… no. It’s the end of summer. I need a break.

A graph from Gitlab of my activity levels in software development during May-August. Darker blue means more active (this is a “heat map” plot). Grey means inactive.

10 [Postcards sent from CERN]

This is the number of postcards I sent from CERN this summer. 8 of these were for my four nieces and nephews (2 for each of them the two separate blocks of time I was at CERN this summer). One was for one of my sisters-in-law, and one was for a person I went to school with when I was young. 

The latter is perhaps the most interesting. He was interested in the mathematics and the equations that we use to describe the universe. I sent him a “Standard Model” postcard from CERN, pictured below with my notes summarizing each piece of the equation. Of course, this is a very compact and simplified version of the Standard Model. Nonetheless, it captures the essential ingredients, even if it lacks serious detail.

The front of the postcard
The back of the postcard

A View from the Shadows: Lighthouse on the Cosmic Shore

I found myself recently standing on the shores of Lake Michigan, reflecting on the connections between these human spaces and the most vast spaces of the cosmic shores. 

The Lighthouse at Cana Island on Lake Michigan in Wisconsin.

The lighthouse on Cana Island in Door County, Wisconsin stands on the shores of Lake Michigan. At a height of 87 feet, the tower is host to a fixed light focused and beamed out into the lake by a third-order Fresnel lens. Ships on Lake Michigan will know this is the Cana Island light by the fact that it has no periodicity. As part of the light house network along the shores of this great lake, this beacon provides important navigation information to ships that may otherwise wander too close to shore, or become lost in poor weather while moving between ports on this vast body of water.

The Crab Nebula, whose gases are whipped into a fury by the pulsar at the center.

In the ocean of the cosmos, there are also lighthouses. These are built, not by engineers and masons and carpenters and lensmakers, but by the violent deaths of stars that started out a little too heavy, burned a little too bright and too fast as a result, and died in a terrific collapse. These cosmic beacons are Goldilocks corpses: not too big to collapse all the way to black holes, and not too small to simply puff off their outer atmospheres and die quietly as a white dwarf. These are the neutron stars, stellar corpses spun so fast by the uneven collapse of the star that once birthed them that they pulse rhythmically and regularly for millions of years as they slowly spin down. No two spinning neutron stars – “pulsars,” as they are also known – spin at quite the same rate when born. As a result, like the lighthouses that line coastal waters, pulsars that dot the cosmos and broadcast their periodic songs provide a kind of “cosmic carte des phares (lighthouses map)” that might, one day, allow ships capable of sailing the stars to know where they are.

A Tale of Light and Glass

People visiting historic lighthouses might be doing so for a wide variety of reasons. Few people likely realize that each of these structures represents the end of a long chain of technological marvels, the culminations of many competitions among nations to be the best, to go further with science and technology than other nations, and in doing so to preserve both blood and treasure.

One competition that lies at the heart of the Cana Island lighthouse is the battle of national secrets and the struggle between scientists to perfect optical glass. This story is partly told in the most recent “Cosmos” TV series (2014), especially in the episodes “Hiding in Light” (Episode 5) and “The Electric Boy” (Episode 10). While not central to the story arc of the TV series, peripheral mentions are made of the German perfection of optical glass under the direction of Joseph von Fraunhofer, a brilliant scientist who, among other things, observed that light spectra (the rainbows of color achieved by splitting white light into its constituent colors) are not continuous, but rather possess “gaps” or “missing colors.” These are the fingerprints of atomic structure. He would not come to understand the meaning of the observation of these dark spots in spectra – that would be left to a later generation of physicists – but Fraunhofer’s discovery was a step on the way to our modern picture of the universe and its structure. German optical glass, his own perfection, was the envy of Europe. A scientific power that wanted to rival Germany would have to unlock the secrets of such glass-making.

The French managed to make quite excellent optical glass, though it was not the better of the Bavarian glass whose secrets Fraunhofer largely took to the grave when he died in 1826 at the age of 39. In fact, the glass-making of the French, while adequate, was significantly challenged by the goal of the French state to deploy a serious and advanced network of lighthouses along French territorial coasts. What was it about this plan that provided such an obstacle to French glassmakers?

Portrait of “Augustin Fresnel”
from the frontispiece of his collected works (1866). This work is over 100 years old and is in the public domain in the country of origin.

In short, the answer is Augustin-Jean Fresnel. Fresnel was brought into the French Academy of Science thanks to his remarkable (and unpopular) ideas about describing light as a wave. Since the time of Isaac Newton, the “corpuscular” theory of light – the notion that light is made from little packets or particles – had taken hold in many scientific circles. To challenge it was to court heresy. But Fresnel had developed an extremely rigorous mathematical framework to describe that patterns of light and dark that are observed when light was shone past a sharp boundary, such as the edge of a razor blade or through a very narrow slit. Only Fresnel’s wave ideas, and especially the advanced application of calculus he developed to make calculations and predictions much easier, even for complex shapes, explained these patterns.

At the height of scientific challenges to Fresnel’s ideas, others noted that he had failed to calculate what light would do when shone down on a circular disc. When they ran the math, his framework predicted that a bright spot should appear at the center of the shadow cast by the disc. A bright spot dead center in a shadow? The idea seemed ludicrous. But an experiment staged for the benefit of the French Academy showed that Fresnel’s equations were, in fact, correct: the shadow of a circular disc contained a minute bright spot at its center. Fresnel’s equations predicted a phenomenon never before observed, and when looked for, it was found.

Fresnel’s larger story is that of a man tasked with boring engineering jobs who longed instead to play with light. He had a job to do for the French state, one which he took every opportunity to avoid doing in pursuit of his theory of light. However, the two jobs intersected when Fresnel became convinced that the way to improve lighthouses, making new ones to rival those of the English, was to switch from using reflectors that beam the light out to sea to using refractors to do the same job. Using his new theory of light, Fresnel did the math and convinced himself that a superior optical device could be constructed that, instead of letting light bounce off it and focus out to sea (losing half the light in the process of bouncing), instead could channel and bend light through a clear medium. This would make a powerful lens, with a short focal length, and would be required to have much less weight than a traditional curved lens. His idea is now known as the Fresnel Lens.

The third-order Fresnel Lens of the Cana Island Lighthouse. This lens was installed by the time the lighthouse made “first light” in 1870, and came from France.

The Fresnel Lens required very pure optical glass. Fresnel spent years before his own death micromanaging French glass makers and wrestling with their product to achieve a reliable means to cast the right glass pieces to assemble into these lenses. When he died of tuberculosis in 1827 (also at age 39, and just a year after Fraunhofer’s death… an interesting symmetry), he left behind many scientific and engineering challenges to those, including one of his own brothers, who would carry on the lighthouse project. Ultimately, those challenges would be overcome and what started as a handful of demonstration lighthouses in the “Carte des Phares” (Lighthouses Map) devised by Fresnel for the French state would blossom into the greatest optical technological advance of the 19th century. Lighthouses of significant brightness and reach prevented dozens of shipwrecks a year, evidenced by the French state’s own accounting of shipwrecks off French coasts before and after the installation of Fresnel lenses in lighthouses. Lighthouses built after this technological revolution in glass making and lens constructions demanded French-made Fresnel Lenses.

The Cana Island Lighthouse sports a Fresnel Lens that dates back to around 1869 or so. It was installed in the lighthouse and the facility achieved first light in 1870. The lens is a “third-order” Fresnel lens, which means it’s the third most powerful lens of the designs created by Fresnel before his death in 1827. While this particular lens is too young to have been crafted by Fresnel himself (who, as I mentioned, felt compelled to micromanage the construction process owing to the sense that others lacked the kind of attention to detail and precision needed for this art), nonetheless it bears the hand of the master.

It’s one of his “catadioptric” designs, with prisms at the top and bottom to internally reflect and refract light as if guided by a mirror, with central glass prisms to refract the light light a standard lens. In fact, if you stare carefully at the close-up photo below of the light coming out of the catadioptric prisms at the top of the lens, you’ll see the lake horizon and waves; that’s because the light you see was originally reflected off the waves of Lake Michigan before being totally internally reflected inside the prism and directed down toward the camera lens of my phone.

A close-up view of the catadioptric aspects of the top of the third-order Fresnel lens in the Cana Island Lighthouse. Both reflection (total internal reflection) and refraction are at play here. Light that bounced off Lake Michigan and should have missed my camera lens (because I am not aimed at the lake) is reflected and refracted inside the prism, ultimately directed down toward my camera. You can see the waves of the lake and the horizon in the distance.

Lighthouse Fresnel Lenses represent the technological might of 19th century physics and engineering. A deeper understanding of light’s wave nature allowed for the imagining and design of a lens with significant focusing power but light-weight design. Once the technological challenges were overcome, the parabolic reflecting mirrors of the previous generation of lighthouses were tossed aside in favor of this new French revolution: the Fresnel Lens.

Networks of lighthouses appeared on every major body of water, constructed over decades to aid ship navigation and improve safe passage on rough waters or during inclement weather. Countless lives were saved by this optical marvel, and countless commerce made more profitable by its employ. What made possible this advance? It wasn’t the then frontier of French optics and lighthouse engineering when Fresnel took on the challenge of the Carte des Phares. It also really wasn’t French glass-making; that was adequate but not up to the task when Fresnel needed it for his ideas. Rather, it was the idea that light could be described as a wave, an idea pushed hard by Fresnel’s mathematical confidence, that drove this particular revolution. Without Fresnel’s basic insights into light and his passion for light itself, reflectors may have ruled the design of lighthouses for many more decades and that particular revolution might have been delayed until much later. The Cana Island Lighthouse, lit in 1870, may instead have sported a dated and inefficient parabolic reflector rather than the gem of a Fresnel lens that it holds today.

Lighthouses in a cosmic sea

Our passion, as a species (dotted with intellectual lights), for understanding actual light, in all its forms, has driven many other technological revolutions. We are living through one right now: the revolution in personal, cheap telecommunications. This revolution was pushed not only by the development of small, miserly radio antennas, but also powerful but compact computers and, behind the scenes, a revolution in optical fiber communications (again, optics!) that made possible the packing of more information into the same space.

But our hunger for light in all its forms also made possible the detection of cosmic lighthouses, those stellar corpses we know as “pulsars.” The first pulsars were detected by radio astronomer Jocelyn Bell in 1967. As a young graduate student, she observed a regular repeating radio signal that appeared to originate from a non-terrestrial source. It was originally labeled “LGM-1”, standing for “Little Green Man – 1.” This was a temporary name in honor to the biased notion that such a regular, repeating radio signal must come from some intelligent origin. 

A photo of Jocelyn Bell from 1967. By Roger W Haworth – Flickr, CC BY-SA 2.0,

Today we recognize these regular signals, as well as other kinds of light, are originating from rapidly spinning “neutron stars.” If a heavy star, much heavier than our own sun, experiences a runaway collapse at the end of its life, it is possible for the remnant to form a neutron star. This happens so long as the core of such a star, the seed left over after blowing off its atmosphere, is not much lighter than about 1.5 times our sun’s mass and not much heavier than about 3 times our sun’s mass. In that sweet spot, that “Goldilocks zone,” the core of the dead star will live out its days as a neutron star.

The collapse and death of a heavy star is not pretty, nor pleasant, nor without violence and drama. This leaves a toll on the neutron star, often (it seems) in gifting the stellar corpse with an incredibly fast rotation speed. Imagine an object that is spherical in shape and about the size of a major city, like New York City, but rotating more than 1000 times each second. This dense stellar corpse also emits an unfathomably large magnetic field, and as it also spins at an equally unfathomable rate, the result is an electromagnetic whip that tears at the atoms in the surrounding space – those recently cast off by the death of the star itself. Pulsars create incredible maelstroms not visible to the human eye, but visible in radio and x-ray light.

Their regular spinning results in regular pulsing in, for instance, radio. They are light cosmic lighthouses, sweeping out a beam of light for those with the right “eyes” to see. Large radio receivers will do the trick. No two pulsars spin at quite the same rate, owing to the details of their original mass (what star they came from) and how, exactly, that star died. Therefore, much as as ship at sea can know its location near a coast by the pattern of lighthouse flashes it sees in the distance, some cosmic traveler with the right radio antennas can know where in the Milky Way galaxy they have stumbled by listening to the pulsars within their radio horizon. The first such ships would have to map these cosmic shoals, but for all the ships that came after, this Carte des Phares Cosmiques would let a captain choose the next destination… or find their way to a home thought lost long ago.


This article is part of a wider series, “A View From The Shadows,” that I began writing as a follow-on to our book, “Reality in the Shadows (or) What the Heck’s the Higgs?”, published in 2017 by YBK Publishers in New York, NY and available from fine booksellers such as

“Reality in the Shadows (or) What the Heck’s the Higgs” is meant to help a new audience come to discover a love of science and especially physics, or to welcome to the frontier those who already discovered that love a long time ago.

Freedom from Symmetry: Six Years of the Higgs Particle

A “cephalopod diagram” of Higgs decay, with vector boson final states in red and fermion final states in blue. Solid lines correspond to final states we’ve definitely seen, and dashed lines represent final states still being hunted. The area of a circle represents its relative rate to that of the bottom-quark final state, which is expected to represent 60% of all Higgs boson decays.

Six years ago on this date, the Higgs boson was (probably) discovered by the ATLAS and CMS Experiments at the Large Hadron Collider in Geneva, Switzerland. I say “probably” because, at the time, all we really knew for sure was that we had discovered a new particle, with a particular mass (about 126 times the proton mass, at the time), that appeared in our experiments in ways consistent with, but not unique to, the predicted Higgs particle.

Well, it’s been 6 years and 1 Nobel Prize in physics since then, and we’re all pretty darn sure it is the Higgs boson predicted in the early 1960s.

But wait. Is it? ATLAS and CMS continue to map out its detailed properties, including one of the biggest sets of prizes in the current data set being collected right now: how much the Higgs boson interacts with the top quark, the heaviest of the 6 known quarks, and the bottom quark, the second-heaviest quark. It’s an unfolding story.

Meanwhile, check out these blog posts from me back in July of 2012, and remind yourself of how glorious it is to see something no one has ever seen before.

Relive the moments before and after the announcement of the “bump” in the data from my friend, Aidan Randle-Conde, who was at the time a post-doctoral researcher at SMU and an avid blogger and science communicator:

“Reality in the Shadows (or) What the Heck’s the Higgs?” is meant to help a new audience come to discover a love of science and especially physics, or to welcome to the frontier those who already discovered that love a long time ago.

And, of course, with further hindsight and many more years of data to inform the discussion, learn more about just what the heck’s the Higgs in our book, “Reality in the Shadows (or) What the Heck’s the Higgs?” by S. James Gates, Jr., Frank Blitzer, and me!

While we know more about this particle since discovering it in 2012-2013, there are many mysteries left. Some prizes are big, but hard to claim in all the noise. For instance, only just a year ago, we spotted the first strong hints of the direct interaction of the Higgs particle and the bottom quark… despite the fact that this should be its favored method of decay! Learn more here:

UPDATE (July 6, 2018): Added the really nice “post-seminar analysis video” from Aidan and some more words about how data in the intervening years has shed light on some questions but left others open.