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Tabletop Physics May Be About to Find Answers Supercolliders Can’t
A new generation of tabletop physics devices may be the next forefront for breakthrough discoveries.
When we think of discoveries at the forefront of physics, we tend to think of massive particle accelerators like the 27-kilometer Large Hadron Collider (LHC). But it wasn’t always this way. Physics arguably began with the introduction of atoms by Leucippus and Democitrus, who logically worked out the existence of atoms around 450 BC. J. J. Thompson discovered electrons in 1897 using comparatively simple electrically charged cathode tubes; Ernest Rutherford discovered the nucleus in 1911 using a similarly modest rig.
Thompson’s cathode tube (SCIENCE MUSEUM LONDON)
Now in the 21st century, tabletop physics is making a comeback.
The value of particle accelerators is obvious, climaxing — for now anyway — with finding the Higgs Boson in 2012. But since then, meaningful findings have become scarce. But big questions remain, and simpler devices may actually be better at of finding certain answers.
One of the great mysteries of physics is why gravity is so much weaker than the three other fundamental interactions — electromagnetism and weak and strong nuclear forces — it’s the “hierarchy problem.” One prominent theory, nicknamed “ADD” after its proponents, is that gravity is losing some of its power because it’s spilling over into other, shrunken dimensions. Newton’s inverse square law of gravity says that the gravitational force between two objects is always inversely proportional to the square of the distance between them. But ADD assumes that this inter-dimensional leakage is baked into Newton’s math, and posits that the interaction between objects smaller than 100 microns apart should be stronger, since at that size, gravity wouldn’t yet have had the chance to leak away and behave as Newton observed. But making measurements at this scale is difficult.
“We are like dinosaurs. We have gotten bigger, and bigger, and bigger,” MIT physicist Janet Conrad tells Quanta Magazine. But the ease with which tabletop experiments can be tweaked and continually reconfigured to smaller and smaller scales may offer an experimental agility that big colliders can’t match. “I really do believe that this is a new field,” she said.
Eric Adelberger’s Torsion Balances
Torsion balances, or torsion pendulums, are nothing new: They were invented some time before Charles-Augustin de Coulomb started using them in 1711 to measure the electrostatic force between two charged objects.
After ADD was proposed in the late 1990s, Eric Adelberger and his team at the University of Washington — who happened to have a torsion balance on hand from an earlier experiment — decided to have a go at seeing if ADD could be proven. They’ve been publishing their results since 2001, derived from an increasingly sensitive series of four torsion balances and other pendulums. They’ve gotten their observations down to around 42 microns in 2013 — so far, there’s been no deviation from Newton’s observations. Adelberger is aiming next at about 20 microns.
One of Adelberg’s torsion balances (GUNDLACH/MERKOWITZ)
Andrew Gerachi and His Beads
Andrew Gerachi (PHYS.ORG)
Gerachi and his team have built an airless chamber inside of which is a .3-micron silica bead 300 millionths of an inch across, held in a lattice of laser light – the bead scatters light onto a detector. If the bead becomes displaced by the gravitational nudge from a nearby and similarly small object, the pattern changes and the bead’s new position can analyzed to measure the gravitational force it responded to. However, the tiny scale at which the team is working can only produce the smallest of gravitational forces. The team has demonstrated they’re capable of detecting gravitational forces that are a mere few billionths of a trillionth of a newton, the amount of gravity the Earth exerts on a falling apple. But detection isn’t measurement, and that’s harder.
Hendrick Bethlem’s Molecular Fountain
Cunfeng Cheng, Hendrick Bethlem, molecular fountain (HENDRICK BETHLEM)
Dark matter doesn’t seem to interact at all with electromagnetism or weak and strong nuclear forces. Some have theorized that it operates by means we’ve yet to detect, and that there are dark-matter force-carrying particles called axions and dark photons that do interact with standard matter, though very weakly. Hendrick Bethlem of the Free University of Amsterdam hopes to see evidence of these faint interaction in ammonia molecules.
He’s using a device called a “molecular fountain.” In it, electricity propels the ammonia molecules to the top of an air-filled chamber from which they slowly sink due to gravity. As they fall, they’re detected by a laser, and then “interrogated” by a spectroscope. The point of this is to determine the energy levels of the molecule’s electrons, and thus their mass. The mass of the molecule’s protons are also measured. These two measurements should be identical unless some other influence — such as that produced by axions or dark photons — is in effect.
Surjeet Rajendran, Peter Graham, and the Dark-Matter Radio
Surjeet Rajendran and Peter Graham (UC BERKELEY/STANFORD)
Two California physicists, Surjeet Rajendran and Peter Graham, are also on the hunt for dark matter’s axions and and dark photons, and they’ve built their own “dark-matter radio.” It’s a canister 170 cm high and 17 cm across, inside of which is a sensitive magnetometer called a SQUID, as well as a resonant circuit much like the one in a normal radio. Their theory is that axions and dark photons should produce electromagnetic waves in the radio spectrum, somewhere between a kiloHertz and a gigHertz. They plan to listen in with their radio.
They’ve also designed something they call a “CASPEr Wind.” It’s being built for them at Johannes Gutenberg University, in Mainz, Germany. It contains a cubic centimetre of liquid xenon. Should axions fly through, the xenon’s atoms’ nuclei should wobble and create a large enough magnetic field to pick up on their dark-matter radio.
To see physicists return in this way to the field’s roots with the benefit of modern knowledge makes sense. It’s a way of complimenting the ongoing work of the big guys, and what physicists are looking for are the tiniest interactions anyway. Their machinery may be more scaled-back than an LHC, but their ambitions are just as far-reaching.
The young man died nearly 2,000 years ago in the volcanic eruption that buried Pompeii.
- A team of researchers in Italy discovered the intact brain cells of a young man who died in the Mount Vesuvius eruption in A.D. 79.
- The brain's cell structure was visible to researchers (who used an electron microscope) in a glassy, black material found inside the man's skull.
- The material was likely the victim's brain preserved through the process of vitrification in which the intense heat followed by rapid cooling turned the organ to glass.
Almost 2,000 years ago, Mount Vesuvius — located on the gulf of what is today Naples in Campania, Italy — erupted, burying the ancient cities of Herculaneum and Pompeii beneath hot ash.
Recently, a team of researchers in Italy discovered the intact brain cells of a young man who died in the disaster in A.D. 79. The team studied remains that were first unearthed in the 1960s from Herculaneum, a city once nestled into the shadow of Mount Vesuvius. The man was around 25 years old when he perished and was discovered lying face-down on a wooden bed in Herculaneum's Collegium Augustalium (the College of the Augustales), located near the city's main street. The building was the headquarters of the cult of Emperor Augustus who was worshipped as a deity, a common Roman tradition at the time.
Discovery of cells
Electron microscope image of brain axons.
Credit: PLOS ONE
Now, subsequent research has described how the researchers, using an electron microscope, discovered cells in the vitrified brain. According to Petrone they were "incredibly well preserved with a resolution that is impossible to find anywhere else." Additionally, the team used another method called energy-dispersive X-ray spectroscopy to determine the chemical compounds of the glassy material. The sample was rich in carbon and oxygen, which indicates that it was organic. The researchers compared those ancient proteins to a database of proteins found in the human brain, and found that all of the discovered proteins are indeed present in human brain tissue.
Additionally, Petrone and his team suspect they also discovered vitrified nerve cells in the ancient victim's spinal cord and cerebellum based on the position of the sample in the mind of the skull and the concentration of the proteins.
These impeccable preservations of brain tissue are unprecedented and will undoubtedly open the door to new and exciting research opportunities on these ancient people and civilizations that weren't possible until now.
The Italian research team will continue to study the remains to learn more about the vitrification process, including the precise temperatures the victims were exposed to and the cooling rate of the ash. They also, according to Petrone, want to analyze proteins from the remains and their related genes.
New data have set the particle physics community abuzz.
- The first question ever asked in Western philosophy, "What's the world made of?" continues to inspire high energy physicists.
- New experimental results probing the magnetic properties of the muon, a heavier cousin of the electron, seem to indicate that new particles of nature may exist, potentially shedding light on the mystery of dark matter.
- The results are a celebration of the human spirit and our insatiable curiosity to understand the world and our place in it.
If brute force doesn't work, then look into the peculiarities of nothingness. This may sound like a Zen koan, but it's actually the strategy that particle physicists are using to find physics beyond the Standard Model, the current registry of all known particles and their interactions. Instead of the usual colliding experiments that smash particles against one another, exciting new results indicate that new vistas into exotic kinds of matter may be glimpsed by carefully measuring the properties of the quantum vacuum. There's a lot to unpack here, so let's go piecemeal.
It is fitting that the first question asked in Western philosophy concerned the material composition of the world. Writing around 350 BCE, Aristotle credited Thales of Miletus (circa 600 BCE) with the honor of being the first Western philosopher when he asked the question, "What is the world made of?" What modern high energy physicists do, albeit with very different methodology and equipment, is to follow along the same philosophical tradition of trying to answer this question, assuming that there are indivisible bricks of matter called elementary particles.
Deficits in the Standard Model
Jumping thousands of years of spectacular discoveries, we now have a very neat understanding of the material composition of the world at the subatomic level: a total of 12 particles and the Higgs boson. The 12 particles of matter are divided into two groups, six leptons and six quarks. The six quarks comprise all particles that interact via the strong nuclear force, like protons and neutrons. The leptons include the familiar electron and its two heavier cousins, the muon and the tau. The muon is the star of the new experiments.
For all its glory, the Standard Model described above is incomplete. The goal of fundamental physics is to answer the most questions with the least number of assumptions. As it stands, the values of the masses of all particles are parameters that we measure in the laboratory, related to how strongly they interact with the Higgs. We don't know why some interact much stronger than others (and, as a consequence, have larger masses), why there is a prevalence of matter over antimatter, or why the universe seems to be dominated by dark matter — a kind of matter we know nothing about, apart from the fact that it's not part of the recipe included in the Standard Model. We know dark matter has mass since its gravitational effects are felt in familiar matter, the matter that makes up galaxies and stars. But we don't know what it is.
Whatever happens, new science will be learned.
Physicists had hoped that the powerful Large Hadron Collider in Switzerland would shed light on the nature of dark matter, but nothing has come up there or in many direct searches, where detectors were mounted to collect dark matter that presumably would rain down from the skies and hit particles of ordinary matter.
Could muons fill in the gaps?
Enter the muons. The hope that these particles can help solve the shortcomings of the Standard Model has two parts to it. The first is that every particle, like a muon, that has an electric charge can be pictured simplistically as a spinning sphere. Spinning spheres and disks of charge create a magnetic field perpendicular to the direction of the spin. Picture the muon as a tiny spinning top. If it's rotating counterclockwise, its magnetic field would point vertically up. (Grab a glass of water with your right hand and turn it counterclockwise. Your thumb will be pointing up, the direction of the magnetic field.) The spinning muons will be placed into a doughnut-shaped tunnel and forced to go around and around. The tunnel will have its own magnetic field that will interact with the tiny magnetic field of the muons. As the muons circle the doughnut, they will wobble about, just like spinning-tops wobble on the ground due to their interaction with Earth's gravity. The amount of wobbling depends on the magnetic properties of the muon which, in turn, depend on what's going on with the muon in space.
Credit: Fabrice Coffrini / Getty Images
This is where the second idea comes in, the quantum vacuum. In physics, there is no empty space. The so-called vacuum is actually a bubbling soup of particles that appear and disappear in fractions of a second. Everything fluctuates, as encapsulated in Heisenberg's Uncertainty Principle. Energy fluctuates too, what we call zero-point energy. Since energy and mass are interconvertible (E=mc2, remember?), these tiny fluctuations of energy can be momentarily converted into particles that pop out and back into the busy nothingness of the quantum vacuum. Every particle of matter is cloaked with these particles emerging from vacuum fluctuations. Thus, a muon is not only a muon, but a muon dressed with these extra fleeting bits of stuff. That being the case, these extra particles affect a muon's magnetic field, and thus, its wobbling properties.
About 20 years ago, physicists at the Brookhaven National Laboratory detected anomalies in the muon's magnetic properties, larger than what theory predicted. This would mean that the quantum vacuum produces particles not accounted for by the Standard Model: new physics! Fast forward to 2017, and the experiment, at four times higher sensitivity, was repeated at the Fermi National Laboratory, where yours truly was a postdoctoral fellow a while back. The first results of the Muon g-2 experiment were unveiled on 7-April-2021 and not only confirmed the existence of a magnetic moment anomaly but greatly amplified it.
To most people, the official results, published recently, don't seem so exciting: a "tension between theory and experiment of 4.2 standard deviations." The gold standard for a new discovery in particle physics is a 5-sigma variation, or one part in 3.5 million. (That is, running the experiment 3.5 million times and only observing the anomaly once.) However, that's enough for plenty of excitement in the particle physics community, given the remarkable precision of the experimental measurements.
A time for excitement?
Now, results must be reanalyzed very carefully to make sure that (1) there are no hidden experimental errors; and (2) the theoretical calculations are not off. There will be a frenzy of calculations and papers in the coming months, all trying to make sense of the results, both on the experimental and theoretical fronts. And this is exactly how it should be. Science is a community-based effort, and the work of many compete with and complete each other.
Whatever happens, new science will be learned, even if less exciting than new particles. Or maybe, new particles have been there all along, blipping in and out of existence from the quantum vacuum, waiting to be pulled out of this busy nothingness by our tenacious efforts to find out what the world is made of.
- Benjamin Franklin wrote essays on a whole range of subjects, but one of his finest was on how to be a nice, likable person.
- Franklin lists a whole series of common errors people make while in the company of others, like over-talking or storytelling.
- His simple recipe for being good company is to be genuinely interested in others and to accept them for who they are.
Think of the nicest person you know. The person who would fit into any group configuration, who no one can dislike, or who makes a room warmer and happier just by being there.
What makes them this way? Why are they so amiable, likeable, or good-natured? What is it, you think, that makes a person good company?
There are really only two things that make someone likable.
This is the kind of advice that comes from one of history's most famously good-natured thinkers: Benjamin Franklin. His essay "On Conversation" is full of practical, surprisingly modern tips about how to be a nice person.
Franklin begins by arguing that there are really only two things that make someone likable. First, they have to be genuinely interested in what others say. Second, they have to be willing "to overlook or excuse Foibles." In other words, being good company means listening to people and ignoring their faults. Being witty, well-read, intelligent, or incredibly handsome can all make a good impression, but they're nothing without these two simple rules.
The sort of person nobody likes
From here, Franklin goes on to give a list of the common errors people tend to make while in company. These are the things people do that makes us dislike them. We might even find, with a sinking feeling in our stomach, that we do some of these ourselves.
1) Talking too much and becoming a "chaos of noise and nonsense." These people invariably talk about themselves, but even if "they speak beautifully," it's still ultimately more a soliloquy than a real conversation. Franklin mentions how funny it can be to see these kinds of people come together. They "neither hear nor care what the other says; but both talk on at any rate, and never fail to part highly disgusted with each other."
2) Asking too many questions. Interrogators are those people who have an "impertinent Inquisitiveness… of ten thousand questions," and it can feel like you're caught between a psychoanalyst and a lawyer. In itself, this might not be a bad thing, but Franklin notes it's usually just from a sense of nosiness and gossip. The questions are only designed to "discover secrets…and expose the mistakes of others."
3) Storytelling. You know those people who always have a scripted story they tell at every single gathering? Utterly painful. They'll either be entirely oblivious to how little others care for their story, or they'll be aware and carry on regardless. Franklin notes, "Old Folks are most subject to this Error," which we might think is perhaps harsh, or comically honest, depending on our age.
4) Debating. Some people are always itching for a fight or debate. The "Wrangling and Disputing" types inevitably make everyone else feel like they need to watch what they say. If you give even the lightest or most modest opinion on something, "you throw them into Rage and Passion." For them, the conversation is a boxing fight, and words are punches to be thrown.
5) Misjudging. Ribbing or mocking someone should be a careful business. We must never mock "Misfortunes, Defects, or Deformities of any kind", and should always be 100% sure we won't upset anyone. If there's any doubt about how a "joke" will be taken, don't say it. Offense is easily taken and hard to forget.
On practical philosophy
Franklin's essay is a trove of great advice, and this article only touches on the major themes. It really is worth your time to read it in its entirety. As you do, it's hard not to smile along or to think, "Yes! I've been in that situation." Though the world has changed dramatically in the 300 years since Franklin's essay, much is exactly the same. Basic etiquette doesn't change.
If there's only one thing to take away from Franklin's essay, it comes at the end, where he revises his simple recipe for being nice:
"Be ever ready to hear what others say… and do not censure others, nor expose their Failings, but kindly excuse or hide them"
So, all it takes to be good company is to listen and accept someone for who they are.
Philosophy doesn't always have to be about huge questions of truth, beauty, morality, art, or meaning. Sometimes it can teach us simply how to not be a jerk.
A recent study analyzed the skulls of early Homo species to learn more about the evolution of primate brains.