“It should be possible to explain the laws of physics to a barmaid.”
“When forced to summarize the general theories of relativity in one sentence: Time and space and gravitation have no separate existence from matter.”
-Albert Einstein
Scientists are deeply invested in the next generation of quantum materials, searching any uncharted classes of enigmatic materials to exploit in the creation of new, innovative technology. One such candidate, known as the ‘strange’ metals, are catching the eye of researchers, particularly the compound YbAlB4, made of the elements ytterbium, aluminium and boron, affectionately known as ‘Y-Ball’.
Strange metals are so called as their behaviour drastically deviates from the familiar properties of metals. They do not obey the standard electrical conventions, they share mysterious similarities to black holes and they challenge and contradict elements of Quantum Theory.
1. Their resistance increases linearly with temperature. In normal metals, the resistance increases until it plateaus, becoming constant at high temperatures in accord with Fermi liquid theory, a model composed of interacting fermions in a low temperature system, which describes the normal state of most metals. Resistance in metals arises when the flow of free electrons is hindered in some way, by the vibrating atomic structure of the material or through collisions with other electrons, leading to electron scattering. Fermi-liquid theory dictates a maximum rate at which the scattering of these electrons can occur. But strange metals don’t follow the Fermi-liquid rules, puzzling material scientists around the world.
2. Strange metals are high-temperature superconductors, with negligible resistance. When strange metals are cooled to low temperatures, they too often become superconductors. Most normal metals are not superconductors, at any temperature!
3. The conductivity of strange metals is linked to both Planck’s constant and Boltzmann’s constant, both of which are fundamental constants of nature, suggesting understanding strange metals may lead to deeper insights into the laws of nature.
4. Strange metals are a new state of matter, existing between two known phases of matter, Mott insulators, materials expected to conduct electricity according to electronic band theories but instead act as insulators, typically at low temperatures, and Fermi liquids, similar in properties to a Fermi gas but with differences which are too lengthy to discuss here.
Fig. 1. Phase Diagram of Strange Metals. Source: Strange metals: New state of matter shares properties with black holes (newatlas.com)
5. Strange metals challenge and push the theories of quantum mechanics to their limit. As the electrical resistance has a linear relationship with temperature, strange metals lose their energy with a rate just within the constraints that the laws of quantum mechanics allow. There exists an unusually slow rate of fluctuations in the electrical charge of Y-Ball.
Using Mossbauer spectroscopy, scientists at Rutgers Centre for Materials Theory bombarded Y-ball with gamma rays, in order to measure the rate at which it’s electrical charge fluctuated. In normal metals, electrons hop in and out of the atoms, causing their electrical charge to fluctuate, but at a rate that is thousands of times too fast to be seen by Mossbauer spectroscopy. In the case of Y-Ball, the fluctuations happened in a nanosecond, which is exceedingly slow in the quantum world. The team at Rutgers reasoned that “each time an electron hops into an ytterbium atom, it stays there long enough to attract the surrounding atoms, causing them to move in and out. This synchronized dance of the electrons and atoms slows the whole process so that it can be seen by the Mossbauer.”
No one can predict the future, but we may guess with some confidence that quantum materials, such as strange metals, will play a tremendous role in the next generation of technology. These oddities of the metallic family may hold the key to understanding high superconductivity in many materials, aiding researchers to develop more and more efficient methods of energy transfer, reducing the waste of power occurring in transit. Professors working in this field of research believe that decoding the secrets of Y-Ball will give them new ideas and will help humanity design, develop and discover new materials.
As strange metals have similar properties to black holes, they could be the door to unlocking further secrets of the universe, exploring their erratic behaviour may shed light on the base truths of how the physical world works.
Our Earth is teeming with millions of diverse life forms. From the domestic to the feral, bipedal, quadrupedal, insects and reptiles, the natural world hosts an incredible abundance of animalia. The Bumble (Bombus) or Honey Bee (Apis) are among the very few species of animals who can boast to have baffled the minds of mathematicians and physicists alike for centuries. At a glance, the bee appears much too heavy and stout for flight. It’s wings are too small with respect to their round bodies, which already seem poorly aligned with traditional aerodynamic models and pale in comparison with other airborne creatures. Bees, of course, with secrets of their own, turn these impossibilities to trivialities. In recent years, however, with our current physical knowledge and computational advancements, these secrets have been unraveled, and we can now decisively pinpoint the physics of the flight of the bumblebee.
I generalize this blog to the bumble or honey bee, but these physics apply to all bees under the Apoidean superfamily. The basis of bee flight is founded on two core aspects. Firstly, we must directly examine the concept of flight unique to the bee in this case, and how it contrasts other modes of aviation found in birds or airplanes. We have all seen man-made plane wings before, or can imagine the great pinions of an eagle in flight. They are blunt and rounded in the direction of the air flow, designed to make the air flow on top of the wing flow faster than the air on the bottom of the wing. This creates a pressure differential in the air, which is balanced out by an upward force on the wing, which pulls the plane upward. The bee’s wing, on the other hand, is much more akin to a thin foil, and as such, it can manipulate the airflow around its wings, creating tiny tornadoes or vortexes at their tips. These are known as Leading Edge Vortices (LEVs), and are a core factor in the flight of bees, wasps, moths and many other insects.
Figure 1: The effect of the leading-edge vortex.
As can be seen in the above diagram, the Leading edge vortex provides the minibeast with an “induced downwash” of air. This accounts for a major portion of the creature’s weight and offers it a huge amount of stability mid-flight. It is through this method that bees are capable of hovering in place, it is also worth noting that all insects that fly in this manner must beat their wings hundreds of times a second to achieve this feat. This stunning amount of motion in a short time frame is what causes the signature buzz of the bee.
Crucially, these leading-edge vortices allow the bee to maintain a distinct wing path. Rather than just flapping them up and down, the bee is able to follow a curved loop with its appendages. These are not rigid appendages, and can bend and twist at will; this enables not only a way of directional influence in the bee’s flight, but is in fact paramount to the performance of the aforementioned wing path. The LEVs produced at the tips of its wings allow the bee to angle its wings higher against the air, this higher angle ingrained into the wing path provides the insect with enough force to become airborne. There is a delicate yet essential pressure difference again between the top and the bottom of the wing, maintained exactly and constantly by these vortices. (3)
Figure 2 : The wing path of the bee.
In a way, one can see that the flight of a humble bumble bee and a Boeing 747 are (perhaps) not too dissimilar after all. The natural solution to flight is both wonderfully elegant and simple. By means of updrafts, induced downwashes and differences in pressure, advanced aerodynamics, muscle control or jet fuel, the bee, bird and Boeing 747 are all capable of achieving flight in their own unique way.
References : Figure 1): https://doi.org/10.1038/35089159
Figure 2): https://askabiologist.asu.edu/how-do-bees-fly
(3) : https://doi.org/10.1098/rsif.2017.0159
Atoms, the building blocks which make up our universe, are made up of 3 important elements: the proton, the neutron and the electron. You may have recognize this image from the Big bang Theory.
The protons are the particles in red and have a positive electric charge, the neutrons in blue and have no charge. Together they comprise the nucleus. The grey particles are the electrons, which have negative charge, and attracted to the protons, much like the moon is attracted to the Earth. They execute an orbital motion around the nucleus.
When a very high energy ray of light comes near an atom, it has a chance to spontaneously disappear and leave behind an electron and a positron (the antimatter counterpart of the electron. Like an electron, except with a positive charge). This is called pair production. At first glance, this is a very strange prospect, that a ray of light can spontaneously turn into matter and antimatter. But this process obeys all of the laws of physics (obviously, because it happens), i.e. conservation of momentum, conservation of charge and conservation of energy. Conservation of energy is achieved when you take into account the rest energy of the proton and the electron.
Einstein figured out that matter is a form of bundled up energy, which is described by the famous equation E = m, which says that the energy from an electron or a positron existing is equal to its mass multiplied by the speed of light squared. So if the energy of the light ray is more than twice m, with m being the mass of the electron or positron (both have the same mass), then conservation of energy is satisfied.
The figure above shows the light ray coming from the left near the atom, and transforming into the electron positron pair on the right. So it obeys the laws of physics, but why does it happen? And why does it have to happen near an atom?
Well it has to happen near an atom due to a subtle interaction between the atom and the light ray. Every atom produces electromagnetic fields, which the ray interacts with. The result of this interaction is probabilistic, the probability is determined by taking into account the total number of possible outcomes. It turns out, through the study of a field called quantum electrodynamics, that the probability that pair production occurs depends on the energy of the light ray, the higher the energy the more likely, and with the square of the number of protons in the nucleus, again, the more there are, the more likely. This interaction with the atom through its electromagnetic field includes it in the equation for the conservation of energy and momentum, which is why it is seen in the figure to have an extra momentum after the interaction.
Pair production is also a process which can happen backwards, in a process called pair annihilation. If you imagine running the process in the graph above backwards in time, i.e. the electron and the positron run into each other near an atom and annihilate each other to create a gamma ray, with all of the various conservation laws being obeyed.
References:
Image 1: Big bang theory: Why Leonard & Sheldon Spent exactly 139.5 hours rebuilding the model, https://screenrant.com/big-bang-theory-leonard-sheldon-139-hours-model-why/ , Accessed May 2020
Image 2: Conversion of energy into mass, https://www.jick.net/~jess/hr/skept/EMC2/node9.html , accessed May 2020
TIME CRYSTALS!!! A name and concept that seem to come straight out of a science fiction or fantasy novel. But are they as fictional as we expect them to be?
A time crystal is a novel phase of matter. It is a system which oscillates repeatedly from one stable ground state to another without absorbing or “burning” any energy in the process. Despite being a constantly evolving system, a time crystal is perfectly stable. Analogous to regular crystals in space which break the spacial-translational symmetry, time crystals spontaneously break time-translational symmetry – the usual rule that a stable system will remain the same throughout time. No work is carried out by such systems and no usable energy can be extracted from them, so finding them would not violate the well-established principles of thermodynamics.
In 2012, the Nobel laureate in physics, Frank Wilczek proposed the existence of the titular time crystals. Wilczek envisioned a diamond-like multi-part object which breaks the time-translation symmetry in its equilibrium, moving in periodic, continuous motion and eventually returning to its initial state. However, this model turn out to be impossible as laws of thermodynamics dictate that in order to minimise their energy, quantum particles in the thermodynamic limit prefer to stop rather than to move. Scientists had to come up with other, slightly different models to make the creation of time crystals more plausible.
“If you think about crystals in space, it’s very natural also to think about the classification of crystalline behavior in time,”
– Frank Wilczek
Over the past few years, researchers have tried to developed various methods and approaches to create systems which very closely resemble the theorised time crystals. Such systems require some “ingredients” or specific techniques to be constructed. Consider a one-dimensional chain of spins. First, particles such as electrons are prepared in a polarised spin state. Naturally, these particles will try to settle into an arrangement which minimalised their energy. However, random destructive interference will trap them in higher-energy configurations. Our system is now experiencing a many-body localisation. These many-body localised systems exhibit a very special kind of order: if you flip the spin orientation of each particle, you will create another stable many-body localised state.
If you act on our system with a periodic driver such as a very specific laser, you will find that the spin orientations will flip back and forth, repeatedly and indefinitely moving between two many-body localised states. It is important to note that the particles do not heat up and absorb any net energy from the driving laser. By definition, our system has formed a time crystal.
In 2021, a new development in the fields of quantum computing and theoretical condense matter physics made the headlines. Researches at Google and physicists Stanford and Princeton and other universities were able to demonstrate the existence of such time crystals using Google’s revolutionary quantum computers.
Quantum computers operate on qubits – controllable quantum particles. The controllable aspects of the qubits prove to be especially useful in creating a time crystal. We can randomise the interaction strengths between the qubits, creating the necessary destructive interference between them, which in turn, allows us to achieve the many-body localisation. In this experiment, microwave lasers act as our periodic drivers, flipping the spins of the qubits. By running thousands of such demonstrations for various initial configurations, the researchers were able to observe that the spins were flipping back and forth between two many-body localised states. During these processes the particles never absorbed or dissipated any energy from the microwave laser, keeping the entropy of the system unchanged. They were able to create an extremely stable time crystal within a quantum computer.
“Something that’s as stable as this is unusual, and special things become useful,”
– Roderich Moessner, director of the Max Planck Institute for the Physics of Complex Systems in Dresden, Germany and co-author of the Google quantum computer time crystal paper.
Time crystals have the potential to finally allow us to take our condense matter research into the fourth dimension. They may help us create a whole new generation of novel devices and technologies. Their applications might include: being used as a new techniques of more precise timekeeping, simulating ground states in quantum computing schemes and even being implemented as a robust method of storing memory in quantum computers. However, due to the exotic nature of these systems and our poor knowledge of their physics, it might be a while until we will be able to grasp time itself in the palm of our hands.
Quantum mechanics is regarded as one of the crowning achievements of 20th century physics with it’s predictions backed up by countless experiments in the decades since its formulation in the 1920’s. Along with it’s success as a physical theory for all things microscopic it has also garnered notoriety in the mainstream for its perceived complicated and abstract subject matter and it’s reputation for being impenetrable to any layman. The reason for this singling out of quantum mechanics from the great canon of physical theories is due to its unique philosophical position in relation to the physics it describes, or better put: it’s not necessarily what quantum mechanics tells us, rather how we interpret what we are told.
To begin this discussion of interpretations of quantum mechanics it is best to start with the most widely accepted and universally taught interpretation, The probabilistic interpretation. This is the belief that quantum mechanics doesn’t tell us what has happened in a given system but more precisely how likely it is to happen in a given system. Within this framework we can imagine that all possible results of a measurement of a quantum system have assigned to them a particular probability which represents how likely one is to find the system in that arrangement when measured.
To clarify this idea we can consider a widely understood concept, Pokémon cards! We know that the only way to ‘measure’ what Pokémon we have is to remove the card from the pack and ‘observe’ it. If we know beforehand that there are only 3 types of Pokémon available, let’s say, fire, water and electric and we have heard from others who have bought the same cards that 20% of people get fire cards, 50% get water cards and 30% get electric cards. We can describe our card before we open it as follows:
(card type) = 0.2 (fire) + 0.5 (water) + 0.3 (electric).
All information about the card is represented in this statement (i.e. the type of card and the probability of getting it). We also know that after we open the card and ‘observe’ it we will only possess a single card belonging to only a single card type and it will not change. Therefore, (assuming we got a fire card) after it has been opened the card can be described as:
(card type) = 1.0 (fire)
This change in the description of the card is fundamental to this interpretation of quantum mechanics and is said to take place instantly upon measurement.
The many worlds interpretation of quantum mechanics is an alternate interpretation which proposes a different view on the ‘collapse’ of the description of quantum systems. It states that every possible result of an observation is realised in it’s own universe. Using this point of view, at the moment when the card is opened we can imagine the arrow of time branching into 3 distinct paths and in each new path a different type of card was obtained.
This interpretation was formulated in the 1970’s with contributions from physicists such as Hugh Everett and Bryce DeWitt and aimed to resolve some of the paradoxes of quantum mechanics, the most famous of which being Schrödinger’s cat. While sounding like nothing more than a purely science fiction concept it remains a very real and respected academic hypothesis to this day.
At this stage Albert Einstein is a household name across the globe, his name being synonymous with the word ‘genius’. His theories and thought experiments have had an immense impact on our understanding of physics, and he seemed able to imagine ideas that no one else possibly could. This post tells the story of how, in 1929, Einstein retracted one of his theories – calling it the “biggest blunder” of his life.
Einstein had included in his equations of gravity what he called ‘the cosmoligical constant’, a constant represented by capital lambda, which allowed him to describe a static universe. This model of the universe complied with what was the generally accepted theory at the time in 1917, that the universe was indeed stationary.
Then, in 1929, Edwin Hubble (whom the Hubble telescope is named for) presented convincing evidence that the universe is in fact expanding. This caused Einstein to abandon his cosmological constant (i.e. presuming its value to be zero), believing it to be a mistake.
But that wasn’t the end of the story. Years went by and physicists repeatedly inserted, removed and reinserted lambda into the equations describing the universe, unable to decide whether or not it was necessary. Finally, in 1997/8, two teams of theorists, one led by Saul Perlmutter, published papers outlining the need for Einstein’s cosmological constant.
Through their analysis of the most distant supernovae ever observed – one of which was SN1997ap – and their redshifts, they had reached the conclusion that the distant supernovae were roughly fifteen percent farther away than where the prior models placed them. This could only mean they were accelerating away from us. The only known thing that ‘naturally’ accounts for this acceleration was Einstein’s lambda, and so it was reinserted into Einstein’s equations one last time. Einstein’s equations now perfectly matched the observed state of the universe.
So while Einstein’s initial use for the cosmological constant was incorrect, it proved vital to forming an accurate picture of our world. The great theorist had once again foreseen a factor no one else could – this time a good 70 years before anyone, including himself, was able to prove it.
As a rule, the universe tends towards disorder. It can seem like a rather depressing fact to some, but no matter how concerted and deliberate you try to be, physics guarantees that your actions will always act to increase the overall amount of disorder in the world. Want to have a spoon of sugar in your tea? You’ve just ruined your sweetener’s fine crystal structure by letting it dissolve. Take it without sugar? In boiling the kettle you’ve already set the water molecules in your drink into ever faster and disordered motion just by heating them up. There’s no stopping it. This universal law is codified physically in the second law of thermodynamics, which dictates that after carrying out any irreversible process (irreversible in the sense that you cannot stir the sugar out of your tea), entropy, a measure of disorder, must necessarily have increased.
Beyond the depression, at first this principle can seem somewhat illusive. Why does Nature decide things must be messied? The answer lies in probability. Take again the example of our cup of tea and sugar. Each sugar molecule, given the chance, can move relatively freely through the tea. They’ll bump into a water molecule here or there, another sugar molecule, or potentially a caffeine molecule (should you not take decaf), but on average, over time, they get around the entire cup. If you consider the probability of different arrangements of the sugar molecules, you can see that an unmixing of a spoon of sugar is incredibly unlikely. For this to happen, we’d need every sugar molecule from all around the cup to conspire to all at once stick back to our spoon, meanwhile enough of the water molecules would have to decide to get out of the way to make room for our spoonful (presuming your sugar was dry to begin with). The odds of this happening are staggeringly small. They’re so astronomically small in fact that in principle we can say it’ll essentially never happen, even if we stood and stared diligently at our cup for a few billion years. The second law of thermodynamics, under this guise, and once we note that generally there’s just a higher chance of things being disordered, is simply a statement that Nature does the most probable.
Now, in 1867, James Clerk Maxwell, feeling rather devious, proposed a simple thought experiment regarding entropy that went without a complete solution by physicists for some 115 years. What Maxwell tried to do was concoct a system whose entropy would decrease rather than increase over time, thus becoming more ordered and flying in the face of the second law of thermodynamics. To do this he imagined a container split in two. One side of the container, say the right, is completely empty to start, the other is full of gas, and the two are separated by an impenetrable wall with a small tap to let gas flow between the containers. First, we open the tap and let things progress according to the laws of physics. Predictably, the gas spreads out between the two containers, diffusing out from the left portion into the right until everything settles down into equilibrium, the gas pressure now having gone down due to its expansion. This so far is completely ordinary. If we run and check that nothing has broken yet, we’ll be assured that everything is in order. The system has undergone an irreversible process (the gas won’t magically saunter back into its original place on one side of the container), and so it should be more disordered than before, with a higher entropy. This we find to be true, since in having spread out the positions of all the molecules making up the gas are now inherently more random. The second law remains law and we have no problems so far.
Now comes the demon. Maxwell allows for a tiny creature, you can imagine them with horns if you like, to open and close the tap at will. This demon, conspiring to annoy physicists, decides it rather liked things the way they were before. It decides that should it see a particle moving to the left from the right side of the container it will open the tap and let it into the left side, whereas if it sees a particle moving to the right from the left side it’ll refuse to budge the tap. Over time, this leads to a gradual return to our original situation; all the gas is back on the left, whereas there’s nothing but vacuum on the right. Thus our demon, through a slight bit of trickery wiggling a tap open and closed, seems to have restored order and reversed entropy! Even more startling still is that if we had placed a small turbine at the tap that spins as gas flows between the containers, we could have harvested some of the energy from our experiment and, since we’ve returned everything back to its starting position, there’s no stopping us doing that again, and again, and again. We’d get more energy out of the system each time, and a free lunch.
There’s no such thing of course. The solution to the problem of Maxwell’s demon lies not in trying to manufacture a replica in a lab and generate infinite power using little devilish creatures and boxes of gas, rather it lies in trying to prove that either no such demon could exist, or in as much as they could they don’t break the laws of physics. One idea first tried out on the problem was that the demon would necessarily have to actually be able to see the gas molecules in order to know when to open the tap, and to do this it’d have to shoot light at them, using up energy and thus squashing our hopes of a sustainable future being powered by Satan. Equally, this light must reflect off the molecules, jostling them about thus increasing the randomness of their motion. This solution falls through however, since the demon, outwitting us, can always decide to use lower and lower intensity light to sense the particles, and thus use an absolute minimum of energy, eeking out an advantage and still breaking physics (this might mean they’re worse at seeing the particles, but they’ve got time and can miss a few so long as overall gas only ever travels one way through the tap).
The beginnings of a solution to the problem interestingly came from the work of pioneering computer scientist Claude Shannon. In 1948, Shannon showed that the information content of any message could be directly quantified mathematically by what he called information entropy. The more information a message holds, the higher its information entropy. On the face of it Shannon’s notion of information entropy seems quite some distance from what physicists mean when they talk about entropy. What’s the connection between the amount of information stored in a text message and how disordered my cup of tea is? The answer lies in a distinction between the measurements us physicists normally take of systems and measurements of their exact states. Normally, we don’t measure where every single gas molecule is in a system, in fact normally we can’t possibly do this. To store all the position data for just one gram of hydrogen gas at one instant in time would require something like a quadrillion gigabytes of storage. Every bit of data storage on the planet currently amounts to less than 3% of that, and that’s just for a snapshot of the particles at an instant. We’d be in an even worse state trying to measure how the particles move over time. What we normally measure in a lab are things like pressure, temperature, or volume, which all come from the behaviour of large numbers of particles rather than individual ones, and so require much less data to store. Physicists say that what we typically measure is the macrostate of systems, or how they appear on a macroscopic scale, rather than their microstate, or how they appear down to the level of atoms and molecules. In general, many different microstates can correspond to the same macrostate, since they give the same pressure, temperature, etc., just with the particles moved around a bit. Information entropy, when applied to a gas in a box, is a measurement of how much additional information we’d need to figure out the exact microstate our gas is in (where all the molecules are, how fast they’re moving, etc.) once we know what macrostate it’s in. Thus, if we know all the particles are on the left side of the box, we’d need to know less information to figure out exactly where they are, and thus the system has lower entropy than if they were spread out over the entire box.
Information entropy alone doesn’t solve the problem, however. The second step was made by physicist Rolf Landauer who, in 1961, showed that theoretically there is a lower limit to the energy efficiency of any form of computation, in what’s known as Landauer’s principle. What Landauer proved is that if a computer is to perform a calculation, whether that be adding two numbers, running a line of code, or even something as simple as storing or deleting data, there is a quantifiable minimal energy cost in doing so, and a corresponding entropy increase for having gone to the bother. This entropy increase comes from the fact that, in using up some power, whatever circuit we run our computations on must heat up, and thus either it or its surroundings must become more disordered, since this heat causes its molecules to jiggle about in more random motion.
With all of this at hand, it still took another 21 years for physicists to finally come up with a solution to Maxwell’s demon when, in 1982, Charles Bennett finally figured it out. Bennett’s stroke of genius was to reduce the demon down to its core function; an information-processing machine connected to a tap. The tap connection isn’t too important, since we can always in principle minimise its energy consumption and corresponding entropy increase, and so the solution comes directly from considering the information-processing (the problem isn’t in the demon’s body, just whatever they have between the ears). Bennett reasoned that the demon is going to need to store some data, since they need to record both where the particles near it are and how they’re moving, alongside when they have to open and close the tap to let the right ones through. He equally reasoned that the demon doesn’t have infinite storage space, and so will eventually run out of room and have to start overwriting their storage to record when next to open the tap. This overwriting, however, must take at least the theoretical minimum of energy given my Landuer’s principle, and this must correspond to a least corresponding increase in entropy. This entropy increase, when calculated, will always exceed the decrease the demon gets out of playing with the tap, and thus the demon is thwarted and the second law persists.
Maxwell’s demon is one of the many striking examples in physics of the power of a simple thought experiment and particularly how their solutions, sometimes taking years, can draw in results from seemingly unrelated fields of study entirely into a unified whole. Physicists from Galileo to Newton to Einstein have all pondered mock setups like this in their minds, daydreaming about lobbing cannonballs into orbit, jumping in elevators, or poisoning cats, and from these imaginings has sprung some of the greatest developments in the history of science and physics, alongside ever deeper insights into the minutiae of the Universe. The whole process of carrying out thought experiments, or Gedankenexperiment as Einstein liked to call them, runs down to the core of what physicists do; simplify the world to its most fundamental parts, play with them, learn something, then build it back up again.
When it comes to science and the supernatural, the common consensus is that the two areas are polar opposites and will never meet. The area of quantum mechanics, which is approaching the ripe old age of 200 years, continues to provide a great deal of confusion within the scientific community as to what it is that makes such an utterly baffling concept possible.
Quantum in a Nutshell
Quantum mechanics is, at its core, an explanation of why particles act the way they do. In classical mechanics a wave will always act like a wave, that is, it will always travel at the speed of light with some frequency and respective wavelength and will experience effects such as refraction, reflection and diffraction. Similarly, a particle in classical mechanics will always act like a particle; a solid mass with a momentum. Quantum mechanics is used to explain the motion of particles that are so small they do not act like a particle or a wave, but rather as both.
Now you may be thinking “big deal, particle go brrr” but I can assure you it gets weirder. In order to illustrate why the scientific community was and remains to be so perplexed by this field, we must first observe the results of the double slit experiment, the first example of wave-particle duality.
The Double-Slit Experiment
First performed by Thomas Young in 1802, the double slit experiment, as the name suggests, uses two slits in the surface of a solid material to create and interference pattern from an incident beam of light. This experiment was revolutionary in observing the physical properties of wave motion.
Figure 1: Young’s Double Slit Experiment. Credit: [1] eiu.edu
In 1927, in an experiment performed at Western Electric by Clinton Davisson and Lester Germer, it was proven that electrons could undergo diffraction and produce a diffraction pattern, thus proving the hypothesis of wave-particle duality, a fundamental building block of modern-day quantum mechanics. In 1961, the double slit experiment was carried out using a beam of electrons instead of light in order to see if they would produce the same result. Sure enough, the electrons produced an interference pattern on the screen.
So Young’s experiment shows us that electrons behave like waves. But we know that electrons interact with other particles in the same way a particle would. This wave-particle duality is what gives rise to the quantum-mechanical theory. An electron may act as either a particle or a wave at any given time. The real question is does an electron know when it has to act like one or the other? A common thought experiment details a detector being placed at the two slits so that the electron is observed going through the slit. Hypothetically, the interference pattern would not appear on the other side as before since the electron is observed passing through the slit in the form of a particle and therefore must continue to act like a particle. Richard Feynman used this thought experiment to prove that an electron must always act like a wave in this circumstance since this thought experiment cannot possibly be performed due to the impossibly small scale ([2] Harrison, 2006).
Varying Interpretations
Feynman’s thought experiment can cause some confusion as it gives the impression that an electron could choose to act like a particle at the slit because it somehow knows it is being observed. Similar to other natural phenomena, if left unexplained by physics, many will jump to believe that a higher power could control such behaviour. Science has always been used to explain natural phenomena that were previously considered to be acts of witches, gods or the supernatural.
The idea that a particle could be granted some form of consciousness by a higher power is something that would very much excite those who believe in or are searching for a god. Simply put, however, that’s not how it works. The particle does not “choose” its state, it simply is. If placed in a certain condition where a wave will experience a certain effect (as in the double slit experiment) it will do so and will undergo the same process as anything else with wave motion. Like when a non-Newtonian fluid is put under stress, it will alter its form to adapt to its surroundings. An electron is still a particle but simply acts like a wave sometimes.
The probabilistic nature of quantum mechanics does give rise to some theories about alternate worlds in which fundamental particles were to act like particles where they would act like waves in our world. This “Many Worlds” theory is more the stuff of science fiction as there is truly no way for it to be proven. The fact that it cannot be disproven, however, is an interesting notion that finds itself appearing more in cinemas than in the lab.
The Final Message
The scientific community’s interpretations of quantum mechanics vary from the perfectly normal to the apparently bizarre. The notion that this field of study could prove the existence of parallel dimensions seems to be pulled directly out of science fiction. The idea that a particle can choose its state of being gives rise to a plethora of philosophical and potentially religious questions.
Quantum mechanics is clearly the most vital area of physics today and the sooner we can come to an explanation that can be understood by all, the better.
References
[1] Dr. Doug Davis, Adventures in Physics, 20.2 Young’s Double Slit, East Illinois University. https://ux1.eiu.edu/~cfadd/3050/Adventures/chapter_20/ch20_2.htm
[2] David M Harrison, 2006, The Feynman Double Slit, Dept. of Physics, University of Toronto. https://faraday.physics.utoronto.ca/PVB/Harrison/DoubleSlit/DoubleSlit.html
A quark is defined as any component of a set of primary subatomic particles that interact via the strong force and are thought to be among the fundamental components of matter. Protons and neutrons are formed by quarks interacting with one another via this strong force, much like atomic nuclei are formed by the latter particles combining in various proportions. Quarks are classified into six kinds, known as flavours, based on their mass and charge properties. There are three pairings of quark flavours: up and down, charm and weird, and top and bottom. Quarks appear to be actual elementary particles, with no discernible structure nor the ability to be resolved into smaller particles. However, quarks appear to invariably combine with other quarks or antiquarks, which are their antiparticles, to generate all hadrons—the so-called strongly interacting particles that include both baryons and mesons.
Quark (Particle)
James Joyce isn’t generally the first name that comes to mind when we think about particle physics. In 1963, when physicist Murray Gell-Man offered a term for his hypothesis of a fundamental particle of matter smaller than a proton or a neutron, Joyce was not on his mind. There was no spelling for the phrase he pronounced “quork” since it had never been written down.
James Joyce
According to Gell-Man’s own account, he had a propensity of calling strange items “squeak” and “squork,” and “quork” was one of them. He stumbled upon a phrase from Joyce’s ‘Finnegan’s Wake‘ a few months later:
“Three quarks for Muster Mark!
Sure he has not got much of a bark
And sure any he has it’s all beside the mark.”
Joyce clearly intended quark to rhyme with Mark, bark etc. However, this didn’t sound anything like the “kwork” in Gell-Mann’s thoughts. The physicist used some imagination and recreated the statement as a request for drinks at the bar:
“Muster Mark gets three quarts!”
Pronouncing the term like kwork “might not be wholly irrational” with this change, notes Gell-Mann in his 1994 book ‘The Quark and the Jaguar’. “The recipe for producing a neutron or proton out of quarks is, roughly speaking, ‘Take three quarks,” thus the allusion to three seemed appropriate.
Murray Gell-Man
The name quark comes from an old English phrase that means “to croak.” In the tale of Tristan and Iseult, a bird choir mocks King Mark of Cornwall, and the above-quoted verses are about that. However, there is a persistent mythology, particularly in German-speaking regions of the world, that Joyce got it from the word Quark, a German word of Slavic origin that is often translated as “cottage cheese” but is also a slang phrase for “trivial nonsense.” According to folklore, he heard it in a peasant market in Freiburg during a visit to Germany.
Quark (Dairy Product)
https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=12307&button=recent