ABOVE — The motto on Niels Bohr’s coat of arms: CONTRARI SUNT COMPLEMENTA (Opposites Are Complementary). Formulated by Niels Bohr, a leading founder of quantum mechanics, the complementarity principle holds that objects have certain pairs of complementary properties which cannot all be observed or measured simultaneously. Niels Bohr (1885–1962) received the Nobel Prize in Physics in 1922 for foundational contributions to understanding of atomic structure and quantum theory. In 1947, Niels Bohr was awarded the Order of the Elephant, a prestigious Danish award normally reserved for royalty or distinguished generals. The only other Danish scientist who received that honor was Tycho Brahe in 1578. As part of the award, the laureate’s family coat of arms is carved into the wall of the national Hall of Fame (pictured above). Bohr’s family, though, did not have a coat of arms, so Bohr got to design one himself. You will notice that he choose the ancient Chinese Taoist Yin-Yang symbol for the centerpiece. He did not do this lightly. Thus he chose to represent his Principle of Complementarity as the centrepiece of his coat of arms.
ON THE FUNDAMENTAL NATURE OF EXISTENCE
What is “reality” ? Let me define “reality” as all that which validly exists. Initially, I wanted to title this essay “On the Fundamental Nature of Reality”. However, the opposite of the term “reality” is “unreality”, referring to that which is unreal. Being a skeptical experimental “realist”, I aspire to concern myself only with that which is real, as per my above definition, because that which is unreal does not exist, and only appears to us to exist indirectly via paradoxes, and various kinds of illusions. Paradoxes and illusions do exist, but that which they struggle to show us, does not.
Why would the above distinction be important? We may forever argue whether consciousness and all properties of our mind, like for instance intelligence, are real or not, in which sense, and to what extent, but it would be difficult to believe that our mind (consciousness) does not exist at all, simply because we are under strong impression of using it to solve our everyday problems, and to make great scientific discoveries, like Albert Einstein had done.
Scientific materialists argue that consciousness does not exist in a sense that it is not physical, as opposed to all that which is subject of modern experimental physics. And I completely agree with them! Consciousness is not physical. Then, would it only follow that our mind (consciousness) is simply an illusion, a mere epiphenomenon of brain’s physical processes?
Was Albert Einstein a genius with an above average (mental) intelligence, or were all his scientific achievements merely by luck, being a byproduct of his brain’s deterministic physical processes conditioned by his genetic makeup? And what exactly is this in a genetic makeup that does make one a potential genius? Is it nature, or nurture?
Let me try to offer some basis for possible clarification stemming from my interpretation of the Yin-Yang symbol. I will argue, strictly based on the Quantum Field Theory (the latest and the greatest in physics),
that in addition to all that which is considered to physically exist by modern experimental science, there also equally and validly exists that which is not physical, and that both are inseparably connected, like ice floating in water.
From my extensive studies of various Eastern philosophies, I have found one almost universal tenet stating that everything that exists must always be composed of some parts. Mathematical point is partless and dimensionless by definition, but it is not physical. “Partless particles are simply physically impossible”, exclaim in unison Eastern mystics from their dark and cold mountain caves! Have they obtain a doctoral degrees in experimental quantum mechanics? Nope. So, what do they know, really. We know better! We have the LHC at CERN, and the standard model of elementary particles, and they don’t.
The minimum number of parts are two, and according to my interpretation, the Yin-Yang symbol not only expresses this simple and obvious fact, but also suggests, not necessarily that each of these parts is also composed of two parts, but rather that each of these parts has a dual nature.
For example, if we think of electromagnetism, it is composed of inseparable electric and magnetic fields. Electricity is defined by its negative and positive charges (electric dipole), and magnetism by its magnetic poles (magnetic dipole). The Yin-Yang symbol happens to be the perfect metaphor in this instance. Coincidence?
Let’s try to apply the above mentioned intuitive insight to the nature of entire existence. My conjecture is that everything that validly exists can be conceptually divided into physical and non-physical phenomena. Both are inseparably connected, and as per the Yin-Yang principle, the smaller dots in each one suggest that both, the physical and the non-physical can only exist in the context of their polar opposites. For example, some polar opposites of the physical could be expressed in terms of matter and energy, particle and wave, matter and antimatter, gravity and antigravity, or as already above mentioned electric charges, and magnetic poles.
The Yin-Yang principle naturally suggested to me the necessary physical existence of the most fundamental sub-quantum element that is both, concentrated like a particle, and spread-out like a wave, which naturally resolves the mystery of particle-wave duality. A self-contained, discrete, yet very flexible fragment of energy:
Some polar opposites of the non-physical could be expressed in terms of conscious and unconscious, passive (mental space) and active (subtle mental energies in that mental space), knowing and not knowing, wisdom and ignorance, selfishness and altruism, suffering and pleasure, love and hate, truth and falsehood, or good and evil. What I mean by “mental space” is the space we see in our dreams, the equivalent of the space we see in our waking state.
In general, the “space” of existence, and for existence, is the space between polar opposites. Between top and bottom, between left and right, between north and south, and between east and west. Otherwise, when polar opposites would converge and merge, there would only remain one partless and dimensionless physical point, i.e. the physical non-existence. But to exist, space must be made of something. What empty space is made of ?!
IS THERE, BY ANY CHANCE, SOMETHING NON-PHYSICAL LURKING DEEP DOWN IN THE VERY HEART OF QUANTUM FIELD THEORY ?!
Let’s have a short introduction to Quantum Field Theory (QFT) by Kathryn Jepsen:
Sean Carroll thinks it’s time you learned the truth: All of the elementary particles you know are actually quantum fields. When scientists talk to non-scientists about particle physics, they talk about the smallest building blocks of matter: what you get when you divide cells and molecules into tinier and tinier bits until you can’t divide them any more. That’s one way of looking at things. But it’s not really the way things are, said Caltech theoretical physicist Sean Carroll in a lecture at Fermilab. “To understand what is going on, you actually need to give up a little bit on the notion of particles.” Instead, think in terms of fields. You’re already familiar with some fields. When you hold two magnets close together, you can feel their attraction or repulsion before they even touch—an interaction between two magnetic fields [ see down below on this page ]. Likewise, you know that when you jump in the air, you’re going to come back down. That’s because you live in Earth’s gravitational field. Carroll’s stunner, at least to many non-scientists, is this: Every particle is actually a field. The universe is full of fields, and what we think of as particles are just excitations of those fields, like waves in an ocean. An electron, for example, is just an excitation of an electron field. This may seem counterintuitive, but seeing the world in terms of fields actually helps make sense of some otherwise confusing facts of particle physics. When a radioactive material decays, for example, we think of it as spitting out different kinds of particles. Neutrons decay into protons, electrons and neutrinos. Those protons, electrons and neutrinos aren’t hiding inside neutrons, waiting to get out. Yet they appear when neutrons decay. If we think in terms of fields, this sudden appearance of new kinds of particles starts to make more sense. The energy and excitation of one field transfers to others as they vibrate against each other, making it seem like new types of particles are appearing. The LHC smashes bunches of energetic protons into one another, and scientists study those collisions. “There’s an analogy that’s often used here,” Carroll said, “that doing particle physics is like smashing two watches together and trying to figure out how watches work by watching all the pieces fall apart. “This analogy is terrible for many reasons,” he said. “The primary one is that what’s coming out when you smash particles together is not what was inside the original particles. Instead, it’s like you smash two Timex watches together and a Rolex pops out.” What’s really happening in LHC collisions is that excitations of a field—the energetic protons—are vibrating together and transfering their energy to adjacent fields, forming new excitations that we see as new particles.
I will use the above mentioned analogy of quantum fields being like an ocean, spanning entire Universe. The reason there are waves in the ocean is because various energies disturb and excite its water. The ocean has never been calm and flat. We can think of these waves as particles, and of the ocean as their quantum field. Had there been no ocean, there would not have been any waves possible. But we could have ocean without waves, a quantum field with undisturbed energy. This has been well known in physics as the Zero Point Energy field.
As long as the energy of the quantum field remains unexcited, there are no particles, which are excitations of this energy field. Waves are shapes of water, and particles are shapes of energy of their respective Zero Point Energy quantum fields.
Quantum field is an ocean of energy (ZPE) from which particles can be shaped by exciting it, just like exciting calm waters of the ocean produces waves. Ocean is water, and waves are water.
This makes complete sense. The analogy is perfect.
The Zero Point Energy of quantum field is the undisturbed ocean. But how deep is this ocean? How much of Zero Point Energy is contained in the undisturbed quantum field ?!
There are only various gross estimates. Hypothetically, this ocean could be infinitely deep, because nobody has seen any “bottom” to the Universe yet. However, physics correctly rejects the possibility of existence of any infinite physical quantities. Presently, most physicists theoretically estimate this energy to be unbelievably huge. Prof. Matt Visser of Washington University in St. Louis clarifies:
The Zero Point Energy (ZPE) is an intrinsic and unavoidable part of quantum physics. The ZPE has been studied, both theoretically and experimentally, since the discovery of quantum mechanics in the 1920s and there can be no doubt that the ZPE is a real physical effect. The “vacuum energy” is a specific example of ZPE which has generated considerable doubt and confusion. In a completely empty flat universe, mathematical calculations of the vacuum energy yield infinite value.
One could try to argue that a step from the impossibly infinite value all the way down to a merely unbelievably huge value would be good enough to do the trick, but it turns out that it is still absolutely unacceptable.
Exactly how unacceptable is it? It is like calculating the size of a hydrogen atom, instead of being infinitely large, to be the size of an average galaxy. No kidding. We have a long way to go!
Surprisingly, there is a very simple scientific method to precisely measure the exact amount of Zero Point Energy in any given limited volume of vacuum of empty space, and it has already been calculated by Frank Wilczek, a Nobel Prize-winning physicist at the Massachusetts Institute of Technology. Let Frank Wilczek describe it for us in his own words:
Richard Feynman looked tired when he wandered into my office. It was the end of a long, exhausting day in Santa Barbara, sometime around 1982. Events had included a seminar that was also a performance, lunchtime grilling by eager postdocs, and lively discussions with senior researchers. The life of a celebrated physicist is always intense. But our visitor still wanted to talk physics. We had a couple of hours to fill before dinner. I described to Feynman what I thought were exciting if speculative new ideas such as fractional spin and anyons. Feynman was unimpressed, saying: “Wilczek, you should work on something real.” Looking to break the awkward silence that followed, I asked Feynman the most disturbing question in physics, then as now: “There’s something else I’ve been thinking a lot about: Why doesn’t empty space weigh anything?” Feynman, normally as quick and lively as they come, went silent. It was the only time I’ve ever seen him look wistful. Finally he said dreamily, “I once thought I had that one figured out. It was beautiful.” And then, excited, he began an explanation that crescendoed in a near shout: “The reason space doesn’t weigh anything, I thought, is because there is NOTHING there.”
The above two Nobel Prize-winning physicists, Feynman and Wilczek, both do agree, although only privately behind closed doors, that the answer to the most disturbing question in physics, then as now, why doesn’t empty space weigh anything, is simply because there is NOTHING there. No energy in the Zero Point Energy quantum field, at all?! Then, what else such Zero Point Energy quantum field could be made of? We would have to agree that this field is made of nothing. It simply does not exist. Physically, that is.
What is non-physical in Quantum Field Theory is the quantum field itself, this allegedly physical fabric that all subatomic elementary particles are shaped of. And that, in turn, would make the entire so-called “physical reality” non-physical by extension.
But let us critically and skeptically question this answer. Had any limited volume of the vacuum of empty space been filled with the Zero Point Energy of quantum field, this energy would have to be equivalent of mass, as per Einstein’s mass-energy equivalence principle, the famous E=mc2. That was the precise scientific reason behind Frank Wilczek’s most disturbing question in physics, then as now, why doesn’t empty space weigh anything. And it doesn’t. How much the “NOTHING“ could possibly weigh?!
Energy is equivalent of mass, as per E=mc2, and mass produces gravity. Since the energy of the vacuum of empty space, even in a very tiny volume of one cubic centimeter, is theoretically estimated to be unbelievably huge, then empty space of the Universe would be producing unbelievably more gravity than all the combined matter in the Universe.
If it doesn’t strike you as a grave theoretical disaster of cosmic proportions, then you should know that even in mainstream science it is called: “The worst theoretical prediction in the history of physics“, or simply the CATASTROPHE:
The only logical conclusion that can be drawn from this obvious experimental fact is that the Zero Point Energy of quantum fields does not exist physically.
Had the quantum field energy not been there at all, like the ocean, then the elementary particles that are composed of real energy could not form (something from nothing). And they do. Beyond any reasonable doubt. The energy of UV photons can burn our skin painfully.
“ ‘Particles’ are what we measure in detectors. We start slipping into the language of saying that it’s the quantum fields that are real, and particles are excitations. We talk about virtual particles, all this stuff — but it does not go click, click, in anyone’s detector.” — Nima Arkani-Hamed
The only possible solution to this apparent paradox is that the Zero Point Energy of quantum fields is not physically real. Are you profoundly shocked yet? Well, then what is real?
Could everything we call real be made of things that cannot be regarded as real ?!
But how could we sufficiently substantiate this extraordinary claim? Do Extraordinary Claims Require Extraordinary Evidence?
My above claim is not extraordinary, because I will prove it by the following most ordinary evidence of a simple magnetic field. Ordinary magnetic field, being a pure instance of a quantum field, is in fact clearly non-physical, beyond any reasonable doubt. Speaking of hiding in plain sight.
How do we know that magnetic field exists at all? We need to stick something into it, and see if anything physical happens. If it happens, something physical must be there!
In general, in terms of QFT, this would result in an appearance of a particle. Strictly speaking, there are no particles of magnetic field, like magnetons, this being the reason why there are no magnetic monopoles. Magnetic poles are not particles.
Nevertheless, a disturbance in a non-physical magnetic field will result in a real physical interaction, akin to a disturbance in other non-physical quantum fields resulting in an appearance of a real physical particle. This would be a painfully glaring paradox, i.e. something from nothing, and that is the only reason why physicists feel under pressure to keep insisting that undisturbed quantum fields must obviously be made of real physical energy, despite the obvious fact that this stubbornness produces “the worst theoretical prediction in the history of physics“, i.e. the CATASTROPHE.
Otherwise, such non-physical physics could turn into mere philosophical metaphysics right in front of their wide open eyes. And who would need that? Ghost hunters:
We imagine that the undisturbed magnetic field must be made of real physical energy that is waiting, ready to cause physical interaction upon disturbance. If so, what exactly would be this energy of undisturbed magnetic field? Photons? Electromagnetic waves? What else? Maybe virtual photons, or mathematical probabilities? Only that both are clearly non-physical.
We have already determined above that there are no particles of magnetic field. If photons were to be particles of magnetic field, then magnetic field could glow in the dark, in the vacuum. Does it? The magnetic quantum energy field cannot be made of electromagnetic waves either, simply because magnetic field is static, and electromagnetic waves are not. What else?
Magnetic field is the greatest mystery in physics that is hiding in plain sight, in your kitchen, on the fridge’s door.
Or, the ordinary magnetic field, being a pure instance of a quantum field, is in fact non-physical, like every other undisturbed static Zero Point Energy quantum field, for one simple reason that empty space does not weigh anything.
I claim that magnetic field, being static, is in essence an instance of undisturbed quantum field, because when quantum field becomes excited, this give raise to appearance of particles. There being no particles of magnetic field, like magnetons, it would suggest that magnetic field is an undisturbed quantum field having only its basic Zero Point Energy that amounts to physical zero, which means that undisturbed quantum fields do not exist physically.
Being honest, self-critical, and self-skeptical, I see an opportunity to prove my above conjecture wrong. To experimentally falsify it, we would have to weight an undisturbed volume of magnetic field to see if it in fact weighs anything. The specific method of weighting should be such that it shall not disturb this volume of magnetic field. And disturbance of magnetic field happens only when it comes in contact with something physical. You are welcome to suggest a method of weighting in the comment section below.
What we observe is not nature in itself but nature exposed to our method of questioning, wrote German quantum physicist Werner Heisenberg, who was the first to fathom the uncertainty inherent in quantum physics. To those who think of science as a direct path to the truth about the world, this quote must be surprising, perhaps even upsetting. Is Heisenberg saying that our scientific theories are contingent on us as observers? If he is, and we take him seriously, does this mean that what we call scientific truth is nothing but a big illusion?
Unfortunately, the physical existence of undisturbed quantum fields and their Zero Point Energy is merely a hypothesis that cannot ever be experimentally verified. Not even in principle, because it is nothing more than a baseless wishful thinking.
In addition to all that which is considered to physically exist by modern experimental science, there also equally and validly exists that which is not physical (opposites are complementary — Yin-Yang), and both are inseparably connected, like ice floating in water. In our metaphor, ice stands for elementary particles, and water stands for non-physical energy of quantum fields.
So, what exactly is this “non-physical energy”, that validly exists, made of? The “non-physical” cannot simply be nothing. The only “non-physical” that I could think of, that could validly exist, are our conscious minds.
It is certainly conceivable that the clarity we perceive in the world is something we bring to the world, not something that is there independent of us. The clarity of the natural world is a metaphysical belief that we unconsciously impose on the situation. We consider it to be obvious that the natural world is something exterior of us and independent of our thoughts and sense impressions; we believe in a mind-independent reality. Paradoxically, we do not recognize that the belief in a mind-independent reality is itself mind-dependent. Logically, we cannot work our way free of the bubble we live in, which consists of all of our sense impression and thoughts. The pristine world of clarity, the natural world independent of the observer, is merely a hypothesis that cannot, in principle, ever be verified. To say that the natural world is ambiguous is to highlight this assumption. It is to emphasize that the feeling that there is a natural world ‘out there’ that is the same for all people at all times, is an assumption that is not self-evident. This is not to embrace a kind of solipsism and to deny the reality of the world. It is to emphasize that the natural world is intimately entangled with the world of the mind.
The non-physical Zero Point Energy of all quantum fields spanning entire Universe is nothing else than the inseparably connected collective consciousness of all living beings. Really? Could this collective global consciousness be able to affect anything physical? Is there any experimental scientific evidence of that? Yes, and from Princeton University in New Jersey:
A long-term, continuing scientific experiment is designed to assess the possibility that correlations may occur in synchronized random data streams generated during major world events. The project is motivated by numerous past scientific experiments that suggest that the behavior of random systems can be altered by directed mental intention, and related experiments showing subtle physical changes associated with mental coherence of groups of people. Since 1998, the Global Consciousness Project (GCP) has maintained a global network of random number generators (RNGs), recording parallel sequences of random data at 65 sites around the world. A rigorous experiment tests the hypothesis that data from the RNG network will deviate from expectation during times of “global events,” defined as transitory episodes of widespread mental and emotional reaction to major world events. An ongoing replication experiment measures correlations across the network during the designated events, and the result from over 345 formal hypothesis tests departs substantially from expectation. A composite statistic for the replication series rejects the null hypothesis by more than six standard deviations. Secondary analyses reveal evidence of a second, independent correlation, as well as temporal and spatial structure in the data associated with the events. Controls exclude conventional physical explanations or experimental error as the source of the measured deviations. The experimental design constrains interpretation of the results: they suggest that some aspect of human consciousness is involved as a source of these physical effects.
Could psychokinesis (PK) be really possible? I can’t do it, but there is a much easier new experiment available to general public that have already produced beyond amazing results for tens of thousands of people, such that it is hard to believe all the reported stories!!!
But physics is not about blind belief. Physics is about consistent experimental results that anyone can count on by replicating them for oneself. Be open-minded, and give it an honest try. It has a potential to change the world:
According to scientific experiments performed by the US government’s researchers, psychokinesis has been verified beyond any reasonable doubt:
What else could possibly be able to excite the calm non-physical energy of all quantum fields in the Universe, if not our non-physical thoughts, emotions, intentions, visualizations, meditation, and our conscious and unconscious mental activity in general?
And thus our non-physical minds create our collective physical reality:
I can imagine that it may be difficult for you to instantly believe all of the above after your first reading, without fact-checking and due examination of presented issues, but try to ask yourself, out of the following two options, which one seems to be more impossible:
- that the empty space really weighs nothing, we are at liberty to make up our minds, and all our non-physical minds create our collective physical reality,
- or that Zero Point Energy of a quantum field in a tiny volume of empty space has an unbelievably huge value, a hydrogen atom is really the size of an average galaxy, and you have no free will, because instead of your non-physical mind, you only have a deterministic physical brain.
It is either the one, or the other.
The choice is yours.
THE YIN AND YANG OF HYDROGEN
“To understand hydrogen is to understand all of physics!” an exuberant colleague once exclaimed, crediting the aphorism to Victor Weisskopf. I asked Vicky, but he denied having coined it. Then, after a pause, he added “But I wish I had.” Most physicists understand Vicky’s sentiment for most physicists are reductionists who aim to understand nature in the simplest possible terms, and hydrogen is a reductionist’s dream. For me, hydrogen holds an almost mystical attraction, possibly because I am among the small band of physicists who actually confront it more or less daily.
As an object of obsession, one could do worse than hydrogen. In its special role as the simplest of all atoms, hydrogen has starred in some great episodes in the history of science. Much of what we know about the universe has come from looking at hydrogen, and it cannot be denied that the universe itself is made almost entirely of hydrogen at any rate most of the universe that we can see. We might also note hydrogen’s technological triumphs, which range from balloons to atomic clocks. One could call hydrogen an atom for all seasons. But the seasons include fall and winter as well as spring and summer, and hydrogen, too, has its dark side as well as its light side. In the timeless metaphor of the Chinese book of wisdom and philosophy known as the I Ching, hydrogen has its yin and hydrogen has its yang.
The concept of yin and yang celebrates the complementary nature of things: passive and active, earthbound and airborne, shadowy and luminous. Yin encompasses heavy, dark and earthborne qualities; yang encompasses light, luminous and ascendent qualities. Yin are the lakes; yang are the clouds. Together, yin and yang embody the principle of perpetual change and interchange. By reconciling opposites and extolling flux, the twin concept yin and yang provides a framework for viewing society, history, nature and life itself.
My colleague Thomas J. Greytak and I learned much about hydrogen’s yin and yang during our search to see it undergo Bose-Einstein condensation. We set out in that search, full of hope. Others also set out, and they, too, were full of hope. The search took much longer than any of us expected, more than 20 years, long enough to constitute a new chapter in the history of hydrogen. Knowing something of that history was good for the spirit when progress was slow.
The history of hydrogen unfolds in a world of yang, for hydrogen is the lightest of all gases and so luminous that the whole universe is suffused in its radiation. A good starting point is June 1783, when Charles Blagden, assistant to Henry Cavendish, visited Antoine-Laurent Lavoisier in Paris to described how Cavendish had created water by burning “inflammable air”. The facts were clear but Cavendish’s explanation dephlogistinization — was not. Lavoisier immediately repeated the experiment. The consequences were monumental, not because Lavoisier merely confirmed Cavendish’s work but because the experiment inspired him to create the concept of a chemical reaction. “Inflammable air” and oxygen join to form water. The very next day, 24 June 1783, Lavoisier reported his results to the Royal Academy of Sciences. The name of hydrogen was born in that event, and so was modern chemistry.
June 1783 was a month of excitement for Paris. The reason, however, was not Lavoisier’s discovery (like most important discoveries it was unremarked at the time) but because on 5 June the Montgolfier brothers had flown the first balloon. They filled their balloon with smoke and it floated away on a short flight that caused an absolute sensation throughout France. As to the reason why the balloon floated, however, there was confusion. The Montgolfiers’ rationale for filling the balloon with smoke was merely that smoke was the most cloudlike vapor one could obtain.
Jacques-Alexandre-Cesar Charles understood buoyancy, and after Lavoisier’s report to the Royal Academy, hydrogen was, so to speak, in the air. Charles immediately set about constructing a hydrogen-filled balloon, raising a public subscription to pay the costs. On 27 August the balloon lifted from the Champs de Mars and ascended a thousand meters. So, barely two months after the news of hydrogen had been announced, it was put to practical use. Possibly this was the quickest case of spin-off from basic research in the history of science. In any case, in the 18th century, just as today, there was no better way to earn society’s appreciation than by simply entertaining it.
Hydrogen’s buoyant and ascendent nature has been evident ever since Charles’ triumphant balloon flight. The optical spectrum of hydrogen first displayed itself imprinted on sunlight. In 1817, Joseph Fraunhofer discovered absorption lines in the sun’s spectrum, and 50 years later the Swedish spectroscopist A. J. Angstrom showed that Fraunhofer’s C and F lines were due to hydrogen. In 1885, J. J. Balmer used Angstrom’s data to derive the empirical formula that provided the linchpin for Niels Bohr’s 1913 paper on the structure of hydrogen. Bohr triggered the search for a new mechanics. Fifteen years later that search culminated in the work of P.A.M. Dirac. Once again hydrogen played a staring role, for the hydrogen spectrum provided the critical test of the Dirac theory. Two decades later, the spectroscopy of hydrogen was extended into the microwave regime by magnetic resonance techniques, and its precision was increased many-fold. The first microwave measurements of hydrogen’s hyperfine and fine structure revealed that things were amiss with the Dirac theory. That dilemma was resolved by the creation of relativistic quantum electrodynamics, now the paradigm of field theories, the most precise and precisely tested theory in all of physics.
Hydrogen seems almost aware of its illustrious history for the atom behaves in a regal fashion. Just as monarchs never travel unescorted, hydrogen atoms never arrive alone: If you order a tank of hydrogen what you get is a tank not of atoms, but of molecules. Every research group has its own favored technique for breaking the molecules apart, usually with an electric discharge. If you have seen a hydrogen discharge, you will have been struck by its exuberantly rich and unmistakably royal magenta glow.
This history of hydrogen has been told as a tale of yang, but there is no yang without yin and hydrogen has secretive as well as exuberant properties. At the very center of the atom dwells the almost but not totally point-like proton. At an advanced level of precision, that little knot of hadronic mischief mocks hydrogen’s perfection. The proton’s finite size shifts the energy of hydrogen only by about one part in 10^9, but the precision of today’s measurements has reached a few parts in 10^13. Ignorance about the proton is balking comparison of the most precise experiment in all of physics (spectroscopy of hydrogen’s 1S-2S transition frequency) with the most precise theory in all of physics. The lesson from this conundrum is that understanding hydrogen requires understanding the proton’s inner world of quarks and gluons. Such an unfolding of inner worlds can be viewed either as the glory or the despair of the reductionist vision. One might paraphrase the aphorism as, “To understand hydrogen, one must understand all of physics. “
On a more prosaic level, hydrogen has what might be charitably described as some minor character defects. Experimentally, the atom behaves more like a prima donna than a member of royalty. Hydrogen can be impossible to find when you want it. Alkali metal atoms, in contrast, conveniently signal their presence by spontaneously ionizing if they hit a hot tungsten filament, or fluorescing brilliantly under laser excitation. Neither strategy works with hydrogen. Hydrogen demands a bravura laser system if it is to be excited optically, for its principal transition, the Lyman-alpha line, lies at a wavelength beyond the reach of today’s laser. And practically every experimenter who produces the atom using an electrical discharge source has experienced the sinking sensation that occurs when the discharges goes into a tempermental funk, its magenta color replaced by watery blue light. The atom flow falters and the experiment must be halted until the discharge can be coaxed back into operation. By then, so much time has passed that the experimental run probably needs to be started over from scratch.
Notwithstanding these defects, hydrogen continues to hold a special attraction for physicists. Undoubtedly this is one of the reasons that my colleagues and I became swept up in the search for Bose-Einstein condensation (BEC) of an atomic gas. The search employed hydrogen because the atom has a remarkable property: If its electron spin is polarized so as to prevent the formation of molecules, the gas is the most noble gas of all, even more inert than helium. Helium liquefies at a temperature of 4.2 K. Spin-polarized hydrogen never liquefies: It remains a gas at temperatures down to absolute zero.
When the search for BEC started, hydrogen seemed almost perfectly suited to the task. There was no mystery about the required temperature and density. The condensation takes place when the atom’s deBroglie wavelength is approximately the distance between atoms. Because of hydrogen’s low mass and correspondingly long deBroglie wavelength, for a given density the transition would occur at a much higher temperature than for any other atom. Another advantage was atomic hydrogen’s close to ideal behavior: its collision cross section is so small that finite size effects can be reliably calculated. Finally, it seemed possible that hydrogen could be cooled to subkelvin temperatures merely by letting the gas make contact with a liquid helium surface. Of all atoms, only hydrogen could be cooled this way, for only hydrogen interacts so weakly with helium that it would remain in the gas phase at temperatures down to roughly 0.1K.
All these yang-like features of hydrogen attracted us to the search for BEC. That was in 1977. Inspired by hydrogen’s yang, we ran into hydrogen’s yin. To jump forward to 1995, the discovery of BEC in atomic gases is now a well known story, the most exciting single development in atomic physics since the invention of the laser. The condensates, however, were composed not of hydrogen but of alkali metal atoms. As far as BEC is concerned, hydrogen’s glamorous attractions proved to be mostly an illusion.
Although hydrogen could indeed be cooled to cryogenic temperatures, it turned out that alkali metal atoms could be cooled to much lower temperatures by laser cooling techniques. At such temperatures, these common-place atoms should rightfully be in a useless solid phase. However, when they are isolated in a trap, they remain in the gas phase. (The reason is this: The first step in the gas-to-solid transition is for two atoms to form a molecule. However, because atoms collide elastically, molecular formation requires that three atoms collide simultaneously. At the densities for BEC, such three-body collisions are so rare that the system lives on as a metastable gas.) The final stage of cooling employs forced evaporation. In this process, hydrogen’s small cross section is not a virtue but an almost fatal vice. Evaporative cooling needs collisions to maintain thermal equilibrium by redistributing the energy after the most energetic atoms escape from the system. Unfortunately, the cross section for hydrogen is more than a thousand times smaller than for the alkali metal atoms. Alkali metal atoms practically rush to low temperatures: hydrogen must be reluctantly coaxed.
In spite of hydrogen’s shortcomings, we pressed on toward BEC even after condensation was achieved in the alkali metal atoms. If BEC could be achieved with hydrogen the conditions would be different from those in all other experiments, and in any case hydrogen continued to possess its special attraction. Nevertheless, with a now aged and unreliable apparatus that was relentlessly breaking down, and little assurance that condensation could be achieved, it took considerable faith for our students to stick with the search.
Late one night last June, a phone call from the lab implored me to come quickly. I had a pretty good idea of what was up because BEC in hydrogen had seemed imminent for more than a week. As I drove in the deep night down Belmont Hill toward Cambridge, still dopey with sleep, the blackness of the sky suddenly gave way to a golden glow. I was not surprised because I had a premonition that the heavens would glow when BEC first occurred in hydrogen. Abruptly, streamers of Bose-Einstein condensates shot across the sky, shining with the deep red of rubidium and brilliant yellow of sodium. Small balls of lithium condensates flared and imploded with a brilliant red pop. Stripes of interference fringes criss-crossed the zenith; vortices grew and disappeared; blimp-shaped condensates drifted by, swaying in enormous arabesques. The spectacle was exhilarating but totally baffling until I realized what was happening: The first Bose-Einstein condensates were welcoming hydrogen into the family! For hydrogen, I thought, this was truly a night of yin, a night of yang.