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John Huth | USLHC | United States

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Another Kind of Science

Thursday, May 23rd, 2013

I’ve been away from blogging for quite some time – mainly to finish a book I was working on.   The book is unrelated to particle physics, but follows a course I teach at Harvard, called Primitive Navigation.   We explore navigational techniques used by cultures like the Polynesians and Norse, in addition to looking at environmental topics like the origins of ocean currents and global weather systems.   While doing research for the book and the course, I found that humans have always been exceedingly clever in making sense of their environments and harnessing this knowledge to journey long distances.   I found that the ability of humans to develop sophisticated constructs to bring order to their environment is not limited to the lineage of Western scientific thought but is a more universal trait.

We often think of the roots of science starting with the ancient Greeks, or even further back to the Babylonians.   The canonical history is a marriage of mathematics and logic coupled with empirical observation.  The story stretches through the Arab translations of works like Euclid’s Elements during the Dark and Middle Ages, through the emergence of the scientific revolution, and culminating in the dizzying heights of modern works like quantum field theory.   This is not to say that there weren’t hiccups.   Although most scientists would dismiss astrology as quackery, astronomy and astrology were once deeply intertwined from their Western birth in Babylon through the time of Kepler.

I invite you to take a big step back and ponder the following conjecture – that Homo sapiens has always been intrinsically disposed toward scientific thinking.   This is perhaps not ‘science’ in the way we view Western science, but it still has the existence of conceptual framework on which to hang and connect observations.

In the process of doing research for the book, I interacted with a number of anthropologists who are studying the navigational schemes of Pacific Islanders.   Their work demonstrates the existence of an exceedingly sophisticated ‘toolkit’ of navigational schema that allowed them to travel huge distances across the ocean to find small target islands successfully.   Three anthropologists in particular have uncovered some amazing findings:  Cathy Pyrek, Rick Feinberg, and Joe Genz.

Most archaeological evidence points to the emergence of long-distance voyaging by a group called the Lapita people, circa 1600 BC from the Bismarck Archipelago, near New Guinea.   They built craft capable of sailing into the wind, making jumps of hundreds of miles eastward to locations like Fiji, Tonga, Tahiti and the Marquesas.   Even more astonishing was the rapid explosion of voyages of thousands of miles around AD 1000 to Hawaii and the north island of New Zealand.

In order to sail against the wind, one needs to create a sail capable of lift, like a wing and use it in combination with a hull that ‘grabs’ the water as it slices through.    The Lapita figured how to harness the complex fluid dynamics involved in lift and used it to their advantage.  In the 18th century, Captain James Cook marveled at sophisticated design of the Polynesian voyaging canoes that allowed them to travel at speeds far in excess of Western European vessels.  It wasn’t until 1904 that physicist Ludwig Prandtl laid out the theoretical basis for lift in wings, and wasn’t until the 1970’s that this theory was applied to sails.

The clever design of voyaging canoes was only part of the innovations the Pacific Islanders.   In order to sail across vast stretches of ocean, they needed viable navigational schema.    We don’t have written records from the height of the voyaging period for Polynesians (circa AD 1000), but we do have interviews with modern day practitioners of indigenous navigational techniques that hint at the ways their ancestors crossed large stretches of ocean accurately.

Anthropologists Rick Feinberg and Cathy Pyrek from Kent State have shown how indigenous navigators in eastern Solomon Islands use a ‘navigational tool-kit’, that consists of multiple signs.   Stars that are rising or setting close to the horizon form a natural star-compass.  Their rising and setting positions allow navigators to find the ‘azimuth’ or compass heading toward a destination island.   This requires the navigator to memorize a large number of stars and become familiar with their paths across the sky at different times of the year.

While a star compass may be useful, what does a navigator do during the day or in overcast weather?   Another helpful construct is a wind-compass.  Winds blowing from different directions have different characteristics.    In the eastern Solomons, the trade winds blow from the southeast, and are marked by characteristic ‘trade wind cumulus’ clouds that only grow to heights of roughly 15,000 feet and are then truncated.   These winds mark the direction ‘tonga’, or the southeast, which corresponds to the direction of the island cluster of Tonga.   Winds from the north arrive during the winter months and are associated with variable, stormy weather.

Steady winds and storm systems can also create ocean swells that act as reliable direction indicators.  Often, multiple swells can arise – for example, the Southern Ocean produces a long swell from the south, while trade winds can create shorter wavelength swells from the east.   Even if the wind shifts, the swells retain some ‘memory’ of the winds that created them allowing the navigator to maintain a steady heading.

The above tools are useful in maintaining direction under different conditions, but there’s an inherent uncertainty in the position of a vessel, and this uncertainty grows with time.   A navigator completing a 200-mile journey may only be able to establish a position to within 20 or 30 miles.   Another trick then comes into play:  birds.   Certain birds, like pelicans and frigate birds will fly some distance out to sea to feed, and then will return to their home islands in the evening.   A sailor only has to get to within 30 miles of a target island and then observe land-based birds.   The sail is dropped and when the birds fly home in the evening, a course is set.

The navigational toolkit allows for a kind of successive approximation, where the stars, wind, and swells form a rough guide, and the presence and behavior of birds provides the final precision.

A somewhat related but unique tradition is that of wave-piloting in the Marshall Islands.  Most of us are familiar with refraction and reflection of waves, whether they’re light or sound waves.   Waves on the oceans’ surface are similar, but have some notable differences.   First waves in deep-water have a speed that is proportional to the square root of the wavelength.   Second, waves in shallow water have a speed that’s proportional to the square root of the depth.   This latter relation causes waves to refract in shallow water.   When waves get into very shallow water, they’ll often break, losing much, if not all of their energy.   On the other hand, waves impinging on a steep cliff that extends underwater will reflect with very little energy lost.   Depending on the bathymetry surrounding an island, one can get very different wave patterns produced by the interaction of an incident swell with the island.

Joe Genz from the University of Hawaii studied the tradition of Marshall Island wave piloting for his doctoral thesis.   Navigators in the Marshalls have their own language for describing characteristic wave patterns around islands. Nit in kōt is the name given to a crossing pattern of waves on the lee side of an island.   If a uniform swell impinges in the eastern shore of an island, the waves passing the north shore will be refracted inside the swell-shadow toward the south and the waves passing the south shore will be refracted into the swell-shadow toward the north.   The resulting pattern of crossing waves creates a disturbed region that’s easy to identify at distances beyond which the islands are visible.

In principle, reflected ways should also give clues to the presence of an island.  Joe made the acquaintance of one Captain Korent Joel, a native Marshall Islander who was trying to revive the tradition of wave piloting.   Joe persuaded Captain Korent to demonstrate his wave piloting technique to a group of oceanographers who deployed a set of sensitive wave buoys.  As Captain Korent left the atoll of Arno, he first pointed out the incoming swell from the east, and then the reflected swell off of Arno.

There was only one problem.   No one on the boat with Captain Korent could notice the reflections, although the dominant eastern swell was clearly visible.   Even the sensitive wave buoys couldn’t detect the presence of the reflected swell.    What was going on?    Joe wondered whether Captain Korent just thought he should be seeing a reflected swell and was making this up.

In order to put Captain Korent to a sterner test, Joe waited until he (Captain Korent) was taking a nap on in the cabin.   Joe instructed the crew to motor some 30 miles to the southwest of Arno to get to a new location.   When Captain Korent woke up, Joe told him that he had taken the boat to an undisclosed location and asked him if he could identify the direction to Arno, and the kind of wave patterns he was seeing.   Captain Korent was quite certain the Arno was to the northwest, and he was also quite correct!   So, he was reading the waves properly after all!

I met Joe in person at a conference of the Association for Social Anthropology in Oceania (ASAO) in Portland Oregon in February 2012.    Joe had some videos on his laptop of Captain Korent and shared them with me.   I downloaded them to my computer.   That evening, I watched the video where Captain Korent was pointing out the reflected swell to Joe on the boat.   This was the reflected swell that Joe couldn’t see, and the oceanographer’s buoys couldn’t detect.   Joe told me what Captain Korent was saying in Marshallese about the waves.   I do some sea kayaking, and I’m often close to the water, and am a bit of an amateur wave-watcher myself.

In my first viewing of the video, I could definitely see the incoming dominant swell from the east.   But, by the third or fourth viewing, I could see a weaker reflected swell moving at slight angle against the larger incoming swell.   When I compared my observations to what Captain Korent was saying in Marshallese, they agreed completely!  By the tenth viewing, I became 100% convinced that Captain Korent was pointing out the reflected swell correctly.

 

The next day, I called Joe over, along with Cathy Pyrek, who was also attending the ASAO conference.   I pulled up the video on my laptop and showed what I saw as the reflected swell.   Joe said, “Oh yeah, now I see it”.    I turned to Cathy and asked if she really saw it, or I was just convincing them of it, but she said,“It’s definitely there, it’s strange that everyone missed it.”

We still have much to learn about how the human mind operates, but it struck me that Captain Korent’s talents show how we’re capable of picking up very weak signals in the presence of noise.   Evidently there is more information on the surface of the ocean than the oceanographer’s buoys were capable of recording.   This is perhaps not surprising, but it’s evidence that there are different frameworks of knowledge out there that are effective and are based on empiricism.   It may not be Western, but it is a kind of science.

For further reading:

Joeseph Genz, et al., “Wave Navigation in the Marshall Islands,” Oceanography, 22, June 2009, 234-245.

Joseph Genz, “Marshallese Navigation and Voyaging: Re-learning and Reviving Indigenous Knowledge of the Ocean,” (PhD diss., University of Hawaii, 2008)

John Huth, The Lost Art of Finding Our Way, (Belknap Press, Cambridge MA, 2013).

Twitter:  @JohnHuth1

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The celebrated God particle, by Mark Twain

Thursday, July 5th, 2012

Editor’s note: On midnight on the transition between July 3rd and 4th, 2012, I had a strange visitation from the ghost of Mark Twain. He wanted to write a piece about the discovery of the God particle and asked me to be his guide around CERN. Reluctantly, I agreed and asked him to meet me at the tram stop by the Geneva railroad station at 7:30 AM on the 4th. This is the report he filed.

John Huth, Twitter:  @johnhuth1

The celebrated God particle, by Mark Twain

Long have I toiled in Purgatory on the plane reserved for cynics, where daily reports of miracles on Earth are telegraphed up to provide annoyance for those assembled. This motley crew has no means of editorializing our disbelief to the masses below, hence the nature of our punishment. Lo, one day, word reached me of the imminent announcement of the discovery of an item called the “God particle”. I marveled at this. Surely it must be the second coming of the Lord, the Prince of Peace. I beseeched my captors to allow me one last chance to bear witness and editorialize before what was certainly the End of Days.

By some chance miracle, my captor-angels granted me this dispensation and directed me to a physicist as a guide. He was an experimental physicist, whom I am told is of the lowly caste, constantly soiling his britches in the muck of reality. Why I was not directed to a theorist, who I was told wore the wings of the eternal, I know not. Surely that high caste must be closer to the God particle!

I was allowed my first ghostly visitation upon the appointed guide at the stroke of midnight. I had some misgivings in my first role as an apparition, but my would-be guide shrugged it off and directed me to meet him at a public conveyance some time after daybreak.

At the appointed hour, I waited at a stop where electric-propelled trains run along the roadside to the place where this miracle was to be revealed. My guide met me, somewhat breathless, after his march across the city. The train, which I am informed, is called a ‘tram’, pulled up with the letters CERN emblazoned on the top. I asked, “Where is this CERN?” My guide told me that this was the place of the appearance of the God particle.

I inquired of him, “What manner of a place is this where God might reveal himself?” He snorted a bit and said that it was something called an accelerator where the scientists therein shoot the guts of matter together, creating tiny explosions, resembling miniature fireworks. These fireworks go off inside a chamber surrounded by an experimental device designed to record the detonations. Seeing little evident connection between the Lilliputian fireworks and the advent of the Lord, I asked further. “And, you expect the Savior to reveal himself inside one of these microscopic blasts?”

My guide laughed and explained that the particle was not really a religious manifestation, at least not the sort to which I was accustomed, but rather a kind of particle that ‘confers mass on an object’. “Oh,” I replied, “So it is something like a high priest for tiny objects?” He laughed again and pointed out my evident misunderstanding of the two uses of the term ‘mass’. His coinage of the word was the more plebian notion of the amount of stuff one encounters in daily life, like the quantity of manure piled high on a donkey cart. While he allowed that this was perhaps not the most apt of metaphors, he humored me enough to note the proper usage of the term.

Soon enough, we arrived at this CERN place. My guide ushered me to the sacred auditorium where the Truth was to be revealed. I could not contain my excitement. As we approached the place of anointment, I could see hundreds of pilgrims lined up, waiting for the exhalant moment. Some appeared to be in various states of inebriation, however, perhaps brought on by a night of revelry before.

While we patiently waited in line, I noted the evident youth of the pilgrims. I asked my guide about this. Were these really true believers, understanding the miracle that was about to be revealed to them? My guide tried to deflect the question, but this very act aroused my suspicion further. After waiting some time, a guard appeared and informed us that we had arrived too late and were turned away from the site of the miracle to come, as too many pilgrims had already filed inside.

My guide told me that we could watch the festivities remotely on an invention called the ‘internet’ that would beam images and words from the ‘Mass of mass’. I trudged with my guide down a long road, lined by trucks, factory-like buildings and all manner of detritus piled high on the roadside. Eventually we arrived at the extreme end of this CERN at a deserted factory-like building.

I accompanied him to a quiet office, where he opened up a box, and after some manipulation, a moving image of the Church of the Miracle appeared. At first, the leader of this CERN place appeared and began the solemn occasion, in the manner of a benediction. The first speaker appeared, evidently a representative of one of the experiments that bore witness to the tiny detonations. He patiently explained the workings of his apparatus and hailed the efforts of his fellow workers and the people who provided the little explosions in the first place.

This fellow, who seemed quite earnest, moved to what I gathered was the ‘punch-line’, as I could sense the rapt attention of the pilgrims in the room. When he combined the results of two kinds of fireworks, lo-and-behold!, a magic barrier was crossed.

Now, dear reader, you don’t need to know my opinion of statistics, but I will tell you that there is something called a ‘five-sigma’ effect. This manifestation of statistics is deemed by the cognoscenti to be a ‘discovery.’ My guide seemed to be glued to the screen, hanging on every word this gentleman uttered. When I inquired about the meaning of this ‘five-sigma’ miracle, he told me that if it was 4.9, it didn’t count. I was rather amazed that such a small fraction divides a miracle from a non-miracle, but he said it was thus.

At the revelation of the five-sigma miracle, there was spontaneous applause around the room where the Mass was held. The gentleman took his seat and a young woman took his place, evidently from a second experiment that bore witness to the miracle. As the gentleman that preceded her had spoken, the young woman proceeded to explain the workings of her explosion-detector and also praised the efforts of her fellow experiment builders and the managers of the explosions themselves. Toward the end of her talk, she, too, spoke of a ‘five-sigma’ effect, which again, my guide informed me was the hallmark of a discovery. Remarkably, like the previous speaker, this ‘effect’ was just over this marvelous threshold of the number five. She briefly mentioned something called a ‘look elsewhere effect’, which she pronounced quickly as something that was ‘four-something sigma’. I asked my guide whether this meant that the magic number ‘five’ had not yet been attained, but he informed me that the ‘five’ surely counted more than the ‘four-something’, but couldn’t really articulate an answer, only reaffirming some of my suspicions of this thing called statistics.

At the end of the young woman’s talk, there was spontaneous applause. The leader of this CERN stood up and pronounced it a discovery, whereupon all bedlam broke out on the floor of the chamber. My guide switched off his magic box and we were left in the silence of that deserted building.

I was grateful to spend a bit of time composing my thoughts to pen this report. While I was doing so, my guide allowed me to see some of the reportage of my living brethren journalists. As I suspected, they hunted for quotes from the high caste of theorists who pronounced it an amazing discovery. Lo, nothing was heard of the laborers who produced the explosions in the first place. Evidently it was not their place to interpret the miracle.

My guide informed me that this was not really the end. He said that he could not say whether this was really the God particle or something else. I was sorely disappointed, and yet could not yet reconcile this with the pronouncements of the theory caste. My guide shrugged his shoulders and said that the caste that made the explosions and the caste that built the experiments had more work to do. I asked, “Was this not really the advent of the Second Coming?” My guide just laughed.

I do not know what to make of this spectacle, as my captor-angels have now insisted that I must beat a hasty retreat to the Plane of Cynics in Purgatory. I can only confess that I reveled in my brief Sisyphean return to the land of the living.

Yours, Mark Twain

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The great vacuum in the sky

Thursday, March 29th, 2012

This is the zone rockets traverse in Thomas Pynchon’s novel Gravity’s Rainbow. I got e-mail from a reader who didn’t understand the concept of the vacuum. The writer didn’t think it possible, and is in good company. Neither Plato, nor Aristotle, nor even Descartes believed that a pure vacuum could exist.

A ‘vacuum’ in the most common sense is simply the absence of matter in some volume. Early experiments by physicists Torricelli and Boyle with vacuum pumps demonstrated that at least a partial vacuum was possible and could be created on earth. A standard measure of the purity of a vacuum is often expressed in the unit of pressure called a “Torr”, after Torricelli. The pressure at the surface of the earth is 760 Torr. The creation of vacuums of increasingly rarefaction has been possible with more and more powerful pumps. First, there is a mechanical pump, much like a piston engine in a car, which can achieve a pressure of about 10E-5 Torr. Then, there is a turbomolecular pump that uses a high-speed turbine to rid a chamber of gas. Beyond this, there are ion pumps, which trap atoms in a chamber by bombarding them with ionized atoms. At very low temperatures, physicists can take advantage of cryopumping where molecules can be made to stick to cold surfaces.

Why are vacuums important to the LHC? As you might be aware, we have to cool the magnets to a degree or so above absolute zero. In order to do this, we effectively have to create a giant thermos bottle to help keep the magnets cold. This uses a vacuum as the first stage of insulation from the outside world, which prevents the transmission of heat across the barrier of the vacuum.

The beam pipes of the LHC must have a very clean vacuum in order to keep protons circulating in the accelerator tubes without colliding with errant gas molecules. To do this, the pipes the protons travel through are typically maintained to a vacuum of 10E-9 Torr. At the interaction points, where the collisions take place in the middle of the detectors, extra care has to be taken to reduce the number of gas molecules even further, so more cryopumping is used to get the vacuum down to a level of 10E-11 Torr.

To give you some idea of what 10E-11 Torr is like, it’s akin to the pressure in interplanetary space. Present estimates of the vacuum of space far between galaxies is more than 1000 times lower than that, with 6 hydrogen atoms per cubic meter.

In a sense, these are all ‘partial vacuums’ – meaning that there are still atoms floating around. But, if we were able to make a perfect vacuum pump, would this mean that there’s absolutely nothing but space in such a creation?

The answer is ‘no’ and somewhat bizarre. In quantum field theory, there is a concept of ‘virtual’ particles, which are always being created and destroyed in empty space. For example, an electron and an anti-electron (called a positron) can be created momentarily in free space and can then fall back together again. If we introduced a free charge to this perfect vacuum, these electron-positron pairs would polarize and tend to screen the charge of the particle.

Beyond these virtual pairs of particles, there is something even stranger, that we sometimes associate with the Higgs boson, called a ‘vacuum expectation value’. This is to say, in a perfect vacuum we expect that there is some non-zero amount of the Higgs field floating around. Now, one may be quick to dismiss this as just some figment of a theorist’s imagination that has no consequence. Measurements of the rate of expansion of the universe, however, indicate a strange ‘dark energy’ that permeates free space and is forcing the universe to accelerate its expansion. This dark energy appears to be an energy that will inhabit space devoid of any matter whatsoever and is akin to the ‘vacuum expectation value’ in many ways. No one knows why this dark energy exists, but it is permitted by Einstein’s equations describing the large-scale structure of the universe. We just didn’t expect to see it, and it seems to lurk everywhere.

So, perhaps the ancient philosophers were right: there may not be a pure vacuum in nature after all.

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Turtles all the way down?

Tuesday, March 20th, 2012

I recently got an interesting e-mail about the Big Bang. The writer said she didn’t see how you could make something out of nothing. She collects creation myths and thought that, no matter how you sliced it, it’s always “turtles all the way down.” This is a reference to creation myths where the world is poised on top of a turtle, which is itself poised on top of something else, but raises the issue: Is there any firm ground?

This is worth addressing because it illustrates the gulf between the understandings in people’s minds about the Big Bang on one hand, and how physicists deal with it on the other. To be clear – we have a wealth of observations that support the Big Bang, but you have to be careful. We can only look back into the universe to a moment 300,000 years after the ‘start,’ as best we can discern it. At this early moment, the universe went from being opaque to transparent. Before this moment, ionized gas kept light from traveling any distance, but once protons and electrons cooled enough to form neutral hydrogen, light (photons) could travel long distances. The remnant photons from this time are seen as the so-called cosmic microwave radiation. These photons were first observed by Arno Penzias and Robert Wilson in the 1960’s and continues to be a rich source of information about the early universe.

What do we see? We see galaxies moving away from each other. The further away we look, the faster they appear to recede. Einstein’s gravity has a number of solutions for possible universe structures. One of these solutions describes the expanding universe very well, and, if taken at face value, would extrapolate back in time to an initial state when all matter in the universe existed as a single point of infinite density. But, does a point of infinite density make sense? The author of the e-mail question thinks not, that it’s like pulling a rabbit out of the hat. You can’t make something from nothing, and this apparent absurdity invalidates the Big Bang model.

The main issue is that, although our observations are very consistent with this model of a Big Bang universe, we cannot actually see the initial moment. It’s hidden from view. We strongly suspect that the laws of physics might change dramatically when distances scales and energy densities approach the conditions very close to initial moment. We know that when the classical laws of physics are combined with quantum mechanics, new phenomena emerge. This was the case of our theory of electromagnetism. When we incorporated quantum mechanics with electromagnetism, the phenomenon of anti-matter became apparent. We have yet to find a satisfactory theory of gravity that combines quantum mechanics. The manifestations of quantum mechanics in gravity will only emerge at extremely high energy densities, such as those in the very early universe, near the time of this infinite density, and will likely modify our current models. For all we know, space-time might resemble some Escher print, eluding the concept of an infinite density starting point through a twisted configuration that folds in on itself.

Rather than dealing with a concept that seems almost theological in nature, physicists try to reconcile models against data. We fully realize that our models will extrapolate to conditions that raise difficult issues, like infinite densities. More often than not, the difficult conditions are something we avoid talking about, because, largely, we cannot really test or measure these. If it is inaccessible, it is inaccessible. The work can be perhaps more likened to the work of explorers. Our job is to map new territories, and, if anything, we can only report on territories we’ve explored. What lies beyond the horizon is a matter of speculation.
Responses? Questions? Contact me on Twitter @JohnHuth1

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On the edge of the icepack

Tuesday, December 20th, 2011

Now that we might (maybe, possibly, could be, it could go away, let’s be careful about what we say here lest we put a jinx on it…) be seeing hints of a Higgs, it’s time of some cautionary tales that a ‘discovery’ is not the end of the story, it’s only the beginning.

When I was a young graduate student, Martinus Veltman gave a talk at a summer school. He had yet to share the Nobel Prize in physics with Gerard t’Hooft for work on the Standard Model. This was 1980. Veltman said, “Right now, theorists are in the driver’s seat. In fact, for the next 30 years, with the exception of the details of the masses of some particles, we know what’s going to happen. But in 30 years, we absolutely are going to need experimental guidance to make any progress in particle physics whatsoever.”

In point of fact, I don’t think anyone recorded Veltman’s words for posterity, but it made a deep impression on me in a number of ways. First and foremost to a rookie experimentalist was the realization that I had to toil in the vineyards for thirty years until something truly of note would arrive. The second thought was “What on earth is he talking about?” We were handed the Higgs boson as an article of faith.

In the current publicity about the Higgs boson, I often worry that we simplify the goals of what we’re doing to the point of trivializing it. Veltman was right: What we call the “Higgs boson” or the “God particle” is really a surrogate for a strange mechanism that bestows mass on all particles through an interaction. We have the most precise theory of anything and, yet, this absolutely crucial piece is missing. We’ve gotten to that point, 30 years later, at which we’ve found almost all of the particles theorists predicted as part of the Standard Model and are now heading into uncharted territory in higher energy ranges.

What we don’t often talk about are the odd properties that this mysterious particle is thought to have. Often times, theorists, like Veltman, feel that the current model is horribly inelegant and must therefore be completely wrong and only a pale approximation of what nature really does to bestow mass, the most elemental of properties a particle can possess.

What makes it so inelegant? In the first place, if it is as described in our simplest model, it would be the only elementary particle we know of that doesn’t possess an intrinsic property of ‘spin’, which seems to be key in the workings of our theory of fundamental forces. For more on the inherently quantum mechanical property of particles known as spin, see this post by Flip Tanedo.

Beyond its spin 0, the Higgs has a very odd property: It gives energy to the vacuum of space. We don’t really know what this means and often just ignore it. Yet, a kind of vacuum energy has been invoked to describe cosmology on very different energy scales from the energies we’re exploring at the LHC. Astrophysicists often talk about something called the “flatness problem”.

If you took a pot of boiling water just off the stove, and dumped ice into it, eventually you would see the ice and the hot water come to some equilibrium temperature. But, in order for this to happen, the ice and hot water have to physically come in contact with each other. When we look around the universe, the temperature of everything is the same to a remarkable degree, as if it was all sitting in the same pot and came to the same temperature. That would all be well and good, but one patch of the universe cannot possibly have been in contact with another part, because they’re separated by such a large distance that light itself cannot connect the two. How could the entire universe be at the same temperature?

The answer is largely thought to lie in a period called ‘inflation’. Initially the very early universe was so dense and compact that temperatures from one part could communicate to another part: everything was sitting in the same ‘pot’. Then, a mysterious vacuum energy appeared that pushed parts of the universe out of contact, but preserved the uniformity of temperature. This happened within a very early phase of the universe when temperatures and energy densities were far hotter than the conditions we’re producing at the LHC. This vacuum energy is about a trillion times larger than what we associate with the Higgs.

Astrophysicists have also invoked a vacuum energy at another, much weaker scale. You may have heard of ‘dark energy’. Our best guess is that, like the vacuum energy of the early universe, this mysterious force that seems to be pushing the universe apart also seems to be a kind of vacuum energy. Yet, in this case the energy of the vacuum is exceedingly weaker than the energies we’re exploring at the LHC. So, there’s a vacuum energy invoked to explain both the very early universe and the very late universe. At the same time, there’s a vacuum energy associated with the Higgs, but it just sits there like an orphan, of no consequence.

To deal with some of these strange properties, theorists have come up with other ideas for how the Higgs might manifest itself:

1.) Supersymmetric Higgs – The energy scale where the three main forces other than gravity, the strong, weak and electromagnetic- join together is close to the scale associated with the cosmic inflation. This is often called the ‘Grand Unification scale.’ The fact that we see two of the fundamental forces – weak and electromagnetic – joining together at the LHC energies presents a conundrum. It is very difficult to reconcile the Grand Unification scale with the LHC scale in a natural way without having some other kinds of matter arise. The constants of the theory would have to line up just perfectly, fine-tuned to a level of precision that is equivalent to balancing a pencil on its point. With Supersymmetry, a number of Higgs-like particles arise.

2.) Composite Higgs – Rather than deal with an inelegant particle with no spin, theorists have speculated that it’s actually made of multiple objects, possible pair of top quarks, tightly bound together. The opposite spins of the objects bound together in a composite Higgs would cancel out to give it zero spin.

3.) No Higgs –According to some models, the Higgs is not a particle at all, but the result of interactions that create mass. These models are sometimes called ‘technicolor’. Although they aren’t particularly favored by theorists because they’re difficult to calculate, we cannot rule them out.

Experimentalists are checking the data for all of these possibilities.

But, what if something like our vanilla-Higgs shows up with a high degree of certainty? Are we done? Hardly! Given all the possibilities and the somewhat inelegant nature of the vanilla-Higgs model, the work has just begun. We have to ask questions like: Is there only one? What is its spin? How does it interact with all the other particles? Are there any variations in its interactions from what we expect, and if so, how does that relate to other measurements we do. These are the tough questions, the one Veltman was alluding to and my betting odds are that we’ll find deviations from our vanilla-Higgs, but it won’t be easy. It may take a decade or more of data taking at the highest beam intensities and energies before we begin to understand what’s really going on.

Science may begin with blinders and theories may run aground, but eventually we do manage to figure out what’s going on.

Here’s a cautionary tale from the 19th century. It illustrates how people can be steered in the direction of one theory, but ultimately can end up with a far more powerful idea.

A German geographer named August Petermann championed a theory of a warm Polar sea. Some expeditions to the high Arctic reported seeing vast stretches of ice-free water extending off toward the horizon. An oceanographer named Silas Bent speculated the that warmth of the Gulf Stream waters flowing north, combined with the waters of a similar ocean current, called the Kurosiwa (black current) flowing off of the coast of Japan would be sufficient to warm the Polar Ocean to the point that an expedition, if it could make it through some part of the ice pack, could sail directly to the Pole. Petermann was one of the main champions of the idea.

James Gordon Bennett Jr. was the publisher of the New York Herald and tried to boost publication by underwriting adventurous expeditions. He financed Henry Morton’s Stanley’s search for David Livingston, garnering a boost in the circulation of the Herald. Hearing of Petermann’s theory of the warm polar sea, Bennett set about to finance an expedition and purchased a British gunboat, the HMS Pandora, and refitted it. He enlisted the US Navy to find a crew. Rechristened the USS Jeanette, it was captained by Lieutenant Commander George DeLong. Hoping to repeat the publicity of the famous Stanley-Livingston meeting, Bennett sent the Jeanette north through the Bering Strait in hopes of reaching the famed open Polar Sea. The Jeanette left San Francisco in July 1879, and was last heard from in late August of that year.

After crossing the Bering Strait, the Jeanette was soon frozen fast in the icepack. Trapped there for nearly two years, it slowly drifted northwest from the coast of Siberia and was ultimately crushed by the icepack. DeLong ordered his crew to abandon ship and began a trek over the frozen icepack, hauling three lifeboats in hopes of eventually reaching settlements along the delta of the Lena River in Siberia. DeLong didn’t make it out alive, perishing in the maze of channels. Some survivors did make it to settlements and eventually made it back home.

Three years later, the wreckage of the Jeanette washed up on the coast of Greenland, some three thousand miles away. This prompted many to wonder how the wreckage could travel so far across the frozen icecap. Theories about ocean current proliferated. One adventurer, Fridtjof Nansen, constructed a polar exploration vessel, the Fram. Fram had a rounded hull that allowed it to be frozen into the icepack without being crushed. Nansen and crew sailed to roughly the point where the Jeanette had been frozen in and commenced a drift across the Polar Sea. At this point, the theory of the Open Polar Sea was completely abandoned in the face of the overwhelming data to the contrary.

Although Nansen never reached the North Pole, during the Fram’s expedition, the remaining crew made detailed observations of wind patterns, drift, the ocean depths and temperatures. On its return to Norway, the Fram had a wealth of data that took years to sift through. Vagn Ekman was a student in physics at the University of Uppsala, Sweden. He was studying fluid dynamics and heard of the data from the Fram. After exploring the mathematics of the interactions of air and water flow on the surface of the rotating earth, he developed the modern theory of surface ocean currents, which bears his name: Ekman transport.

Ekman’s work remains one of the fundamental underpinnings of oceanography.

What I’m trying to point out is this: We are on a voyage of discovery. As Veltman said, experimentalists are really now the ones in the drivers seat. The vanilla-Higgs is an easy target to fire at, as there are quite specific predictions for how it will be manifested, but there are good reasons to be suspicious that the Higgs is precisely as it is described in the simplest version of the Standard Model. Like the long, meandering progression from the theory of the Open Polar Sea to the modern theory of Ocean Currents, I suspect that we’ll have many changes and false leads. As it stands now, with the performance of the LHC, we are just beginning to penetrate the icepack, and we don’t really know what to expect.

A rendering of the long retreat to the Lena River Delta by the DeLong Expedition

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Worshipping at the Fed Ex drop box

Friday, October 28th, 2011

Walking through Cambridge one Friday evening, I saw a strange sight: a man praying to a Federal Express drop box. At first it seemed odd, but then I could hear the prayer in Hebrew. I looked at my watch and saw that it was 6:04 PM, the moment of sunset for Cambridge. His orientation was facing east, so clearly he was a Hasidic man praying toward Jerusalem. The initial oddity wore off as I unraveled the mystery. He must have been en route to some destination when the sunset overtook him.

I teach a course called Primitive Navigation. The subject is how navigational strategies emerged in many cultures across the earth prior to the Scientific Revolution. As part of the course, I have students identify stars and planets, and become accustomed to their motion in the sky. I track the positions of the stars and planets as a matter of course, and can even anticipate events like the backward motion of planets called retrograde motion. Currently Jupiter is executing a retrograde motion.

Now, let’s try an experiment here. Google the words “Jupiter” and “retrograde” and look at the how many hits you have to go through before you find an astronomy, as opposed to an astrology website. You’ll go through five pages of astrology hits. That’s not all. If you read one of the websites, it will tell you that Jupiter is retrograde in Taurus. But, if I look up in the sky, I don’t see Jupiter in Taurus, I see it in Aries – quite some distance away.

What’s going on?

Most people don’t care if Jupiter is executing a retrograde motion unless it tells them whether they should buy stocks or wear heels on a blind date. The scheme used by western astrologers is based on a version of the sky that was frozen in time when the ancient Greeks made observations of the sky. Since that time, the earth’s axis had wobbled to a new orientation, but, due to tradition, the astrologers use the old locations of the zodiac as a basis for the augury.

What does any of this have to do with particle physics? Clearly the two stories – the man praying at the Fed Ex drop box, and the belief in Jupiter executing retrograde motion in Taurus are matters of faith. We might scoff at these as relics from a bygone era, but we should be cautious on two accounts: 1.) descriptions of the universe at one time saw astronomy and astrology as somewhat inseparable and 2.) even modern science rests on many assumptions that to many of us have become articles of faith.

Now, you might say, “but…science has a right to examine any and all assumptions, but things like religion and astrology take all assumptions as sacred.” The problem is ‘which assumptions?’. There are so many. When I was a graduate student, I studied something called the Dirac equation. Paul Dirac was a theoretical physicist who is best known for his famous equation describing the motion of particles like electrons. He successfully combined two pillars of modern theory: quantum mechanics, which describes particles as a wave with special relativity, which takes the speed of light to be a fundamental constant of nature.

When he put these two factors together, his equation had some strange properties. At first blush, you find that electrons have this strange motion that’s called ‘zitterbewegung’; German for ‘trembling motion’. This is a very rapid oscillation of electrons at the speed of light, which doesn’t seem to really happen and would lead to odd results. This was more or less brushed under the rug.

The second problem is that there are negative energy solutions, which should be forbidden because they would violate our cherished principle of the conservation of energy. One of my friends at graduate school laughingly called these “Dirac fairy tales.” But an odd thing happened. Dirac tried to plug up the negative energy states by saying that nature somehow filled up all the negative energy solutions, leaving behind the possibility that ‘bubbles’ in the sea could be created. These bubbles would have the same mass, but opposite charge of the electron. It was an inevitable consequence of his equations, but had never been seen and he was ready to dismiss this as he had done with the zitterbewegung. He speculated that the positively charged electron might be the proton, but was dissuaded and published a prediction of a positively charged electron. In 1932, Carl Anderson discovered the positron.

So, the zitterbewegung was discarded as meaningless, but the problem of the negative energies ended up predicting the existence of antimatter.

More articles of faith: infinite energies. You might recall that the strength of the electric field gets larger as you get closer to a charged particle. In particle physics, we like to talk about ‘point-like’ particles, meaning that they have no size. In practice, this creates a problem: right at the electron, the electric field is infinite. Energy gets tied up in the electric fields, so, in principle, the energy of the electric field of the electron is infinite. This seems like a problem, since the electron seems to move quite happily around. How do physicists deal with this?

We have a process that removes the infinite energies and renders them finite. It’s called renormalization. The main idea is that we decide, somewhat arbitrarily, that our rules of physics change at very high energy scales or very small distance scales. The scale where everything changes is so remote from the scales that we’re testing that it won’t make a difference in our calculations. We ‘kill’ the infinite energies this way and make our calculations finite. This process also provides a look at particles we have yet to see that might exert a hidden influence on the strength of forces and values of masses. This process, however contrived it might seem, has given amazingly solid predictions. Yet we don’t know what it means for the physics to change at very, very short distances. It’s a matter of faith.

Theorists say that any viable theory of particles and their interactions must be of a sort that allows us to remove the infinite energies. This requirement guides theorists to root out non-conforming theories and accept theories that avoid the infinite energies. In essence, this is the role of the Higgs boson — by being the thing that makes mass, it allows our beloved Standard Model to avoid the infinite energies and does.

Physicists rarely questions these articles of faith. Sweeping zitterbewegung under the rug is fine, but what does it mean? Is there any meaning to the process that we use to kill the infinite energies, or is it just a mathematical trick that appears to work? Although they may seem like ‘fairy tales’ as my friend said, they have become articles of faith and are rarely questioned. The problem is: we don’t know whether we will be forced to reexamine some of these, or if so, which of these we have to reexamine. Until then, we have our own Fed Ex drop box where we worship.

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