A gear-train for particle physics

It has come under scrutiny at various times by multiple prominent physicists and thinkers, but it’s not hard to see why, when the idea of ‘grand unification’ first set out, it seemed plausible to so many. The first time it was seriously considered was about four decades ago, shortly after physicists had realised that two of the four fundamental forces of nature were in fact a single unified force if you ramped up the energy at which it acted. (electromagnetic + weak = electroweak). The thought that followed was simply logical: what if, at some extremely high energy (like what was in the Big Bang), all four forces unified into one? This was 1974.

There has been no direct evidence of such grand unification yet. Physicists don’t know how the electroweak force will unify with the strong nuclear force – let alone gravity, a problem that actually birthed one of the most powerful mathematical tools in an attempt to solve it. Nonetheless, they think they know the energy at which such grand unification should occur if it does: the Planck scale, around 1019 GeV. This is about as much energy as is contained in a few litres of petrol, but it’s stupefyingly large when you have to accommodate all of it in a particle that’s 10-15 metres wide.

This is where particle accelerators come in. The most powerful of them, the Large Hadron Collider (LHC), uses powerful magnetic fields to accelerate protons to close to light-speed, when their energy approaches about 7,000 GeV. But the Planck energy is still 10 million billion orders of magnitude higher, which means it’s not something we might ever be able to attain on Earth. Nonetheless, physicists’ theories show that that’s where all of our physical laws should be created, where the commandments by which all that exists does should be written.

… Or is it?

There are many outstanding problems in particle physics, and physicists are desperate for a solution. They have to find something wrong with what they’ve already done, something new or a way to reinterpret what they already know. The clockwork theory is of the third kind – and its reinterpretation begins by asking physicists to dump the idea that new physics is born only at the Planck scale. So, for example, it suggests that the effects of quantum gravity (a quantum-mechanical description of gravity) needn’t necessarily become apparent only at the Planck scale but at a lower energy itself. But even if it then goes on to solve some problems, the theory threatens to present a new one. Consider: If it’s true that new physics isn’t born at the highest energy possible, then wouldn’t the choice of any energy lower than that just be arbitrary? And if nothing else, nature is not arbitrary.

To its credit, clockwork sidesteps this issue by simply not trying to find ‘special’ energies at which ‘important’ things happen. Its basic premise is that the forces of nature are like a set of interlocking gears moving against each other, transmitting energy – rather potential – from one wheel to the next, magnifying or diminishing the way fundamental particles behave in different contexts. Its supporters at CERN and elsewhere think it can be used to explain some annoying gaps between theory and experiment in particle physics, particularly the naturalness problem.

Before the Higgs boson was discovered, physicists predicted based on the properties of other particles and forces that its mass would be very high. But when the boson’s discovery was confirmed at CERN in January 2013, its mass implied that the universe would have to be “the size of a football” – which is clearly not the case. So why is the Higgs boson’s mass so low, so unnaturally low? Scientists have fronted many new theories that try to solve this problem but their solutions often require the existence of other, hitherto undiscovered particles.

Clockwork’s solution is a way in which the Higgs boson’s interaction with gravity – rather gravity’s associated energy – is mediated by a string of effects described in quantum field theory that tamp down the boson’s mass. In technical parlance, the boson’s mass becomes ‘screened’. An explanation for this that’s both physical and accurate is hard to draw up because of various abstractions. So as University of Bruxelles physicist Daniele Teresi suggests, imagine this series: Χ = 0.5 × 0.5 × 0.5 × 0.5 × … × 0.5. Even if each step reduces Χ’s value by only a half, it is already an eighth after three steps; after four, a sixteenth. So the effect can get quickly drastic because it’s exponential.

And the theory provides a mathematical toolbox that allows for all this to be achieved without the addition of new particles. This is advantageous because it makes clockwork relatively more elegant than another theory that seeks to solve the naturalness problem, called supersymmetry, SUSY for short. Physicists like SUSY also because it allows for a large energy hierarchy: a distribution of particles and processes at energies between electroweak unification and grand unification, instead of leaving the region bizarrely devoid of action like the Standard Model does. But then SUSY predicts the existence of 17 new particles, none of which have been detected yet.

Even more, as Matthew McCullough, one of clockwork’s developers, showed at an ongoing conference in Italy, its solutions for a stationary particle in four dimensions exhibit conceptual similarities to Maxwell’s equations for an electromagnetic wave in a conductor. The existence of such analogues is reassuring because it recalls nature’s tendency to be guided by common principles in diverse contexts.

This isn’t to say clockwork theory is it. As physicist Ben Allanach has written, it is a “new toy” and physicists are still playing with it to solve different problems. Just that in the event that it has an answer to the naturalness problem – as well as to the question why dark matter doesn’t decay, e.g. – it is notable. But is this enough: to say that clockwork theory mops up the math cleanly in a bunch of problems? How do we make sure that this is how nature works?

McCullough thinks there’s one way, using the LHC. Very simplistically: clockwork theory induces fluctuations in the probabilities with which pairs of high-energy photons are created at some energies at the LHC. These should be visible as wavy squiggles in a plot with energy on the x-axis and events on the y-axis. If these plots can be obtained and analysed, and the results agree with clockwork’s predictions, then we will have confirmed what McCullough calls an “irreducible prediction of clockwork gravity”, the case of using the theory to solve the naturalness problem.

To recap: No free parameters (i.e. no new particles), conceptual elegance and familiarity, and finally a concrete and unique prediction. No wonder Allanach thinks clockwork theory inhabits fertile ground. On the other hand, SUSY’s prospects have been bleak since at least 2013 (if not earlier) – and it is one of the more favoured theories among physicists to explain physics beyond the Standard Model, physics we haven’t observed yet but generally believe exists. At the same time, and it bears reiterating, clockwork theory will also have to face down a host of challenges before it can be declared a definitive success. Tik tok tik tok tik tok

Titan's chemical orgies

Titan probably smells weird. It looks like a ball of dirt. It has ponds and streams of liquid ethane and methane and lakes of the two ethanes, with nitrogen bubbling up in large patches, near its poles. It has clouds of hydrocarbons raining down more methane. And like the water cycle on Earth, Titan has a methane cycle. Its atmosphere is a stifling billow of (mostly) nitrogen. Its surface temperature often dips below -180º C, and the Sun is as bright in its sky as our moon is in ours. In all, Titan is a dank orgy of organic chemistries playing out at the size of a small planet. And it smells weird – like gasoline. All the time.

But it is also beautiful. Titan is the only other object in the Solar System known to have bodies of liquid something flowing on its surface. It has a thick atmosphere and seasons. Its methane cycle signifies a mature and stable resource recycling system, just the way a functional household allows you to have routines. Yes, it’s cold and apparently desolate, but Titan can’t help these things. Water would freeze on its surface but the Saturnian moon has made do with what wouldn’t, and it has a singularly fascinating surface chemistry to show for it. Titan has been one of the more unique moons ever found.

And new observations and studies of the moon only make it more unique. This week, scientists from the Georgia Institute of Technology reported Titan possibly has dunes of tar that, once formed, stay in formation because their ionised particles cling together. The scientists stuck naphthalene and biphenyl – two organic compounds thought to exist on Titan’s surface – into a tumbler, tumbled it around for about 20 minutes in a nitrogen chamber and then emptied it. According to a Georgia Tech press release, 2-5% of the mixture lumped up.

The idea of tarry sands is not new. The Cassini probe studying the Saturn system found strange, parallel dunes near Titan’s equator in 2006, over a hundred metres tall. Soon after, scientists were thinking about ‘sediment cohesiveness’, the tendency of certain particles to stick together because of weak but persistent static charges, to explain the dunes. These charges are much weaker among sand particles and volcanic ash on Earth. Then again, in a 2009 paper in Nature Geoscience – the same journal the Georgia Tech study was published in – planetary geologists showed that longitudinal dunes, as they were called, were known to form in the Qaidam Basin in China. A note accompanying the paper explained:

More recent models for linear dune formation are centred on two main scenarios for formation and perpetuation. Winds from two alternating directions, separated by a wide angle, result in the formation of dunes whose long axis falls somewhere between the two wind directions. Alternatively, winds blowing from a single direction along a dune surface that has been stabilized in some way, for example by vegetation, an obstacle or sediment cohesiveness, can produce the same dune form.

That the Georgia Tech study affirmed the latter possibility doesn’t mean the former has been ruled out. Scientists have shown that bi-directional winds are possible on Titan, where wind blows in one direction over a desert and then shifts by 120º and blows over the same patch, forming a longitudinal dune. One of the Georgia Tech study’s novelties is in finding a way for the dune’s particles to stick together. Previous studies couldn’t confirm this was possible because the dunes mostly occur near Titan’s equator, where the weather is relatively much drier than at the poles, where mud-like clumps can form and hold their shape.

The other novelty is in using their naphthalene-biphenyl model to explain why the longitudinal dunes are also facing away from the wind. As one of the study’s authors told New Scientist, “The winds are moving one way and the sediments are moving the other way.” This is because the longitudinal dunes accrue on existing dunes and elongate themselves backwards. And once they do form, more naphthalene and biphenyl grains stick on them thanks to the static produced by them rubbing against each other. Only storms can budge them then.

The Georgia Tech group also writes in its paper that infrared and microwave observations suggest the dune’s constituent particles don’t become available through the erosion of nearby features. Instead, the particles become available out of Titan’s atmosphere, in the form of ‘haze particles’. They write: “[Frictional] charging provides an efficient process for the aggregation of simple aromatic hydrocarbons, and may serve as a mechanism for the formation of dune grains with diameters of several hundred micrometers from micrometer-sized haze particles.”

A big-picture implication is that Titan’s surface features are shaped by agents that are almost powerless on Earth. In other words, Titan doesn’t just smell weird; it’s also sticky. Despite the moon’s being similar to Earth in many ways, there are still drastic differences arising from small mismatches, mismatches we’d think wouldn’t make a difference. They remind us of the conditions we take for granted at home that are friendly to life – and of the conditions in which we can still dream of the possibility of life. Again, studies (described here and here) have shown this is possible. One has even warned us that Titanic lifeforms, if they exist, would smell nowhere as good as their name at all.

Understanding the dunes is a way to understand Titan’s winds. This is important because future missions to the moon envisage wind-blown balloons and cruising gliders.

Featured image: Saturn in the background of Titan, its largest moon. Credit: gsfc/Flickr, CC BY 2.0.

I’d written this post originally for Gaplogs but it got published in The Wire first.

Happy Lord of the Rings Day

Just been having a bad day today – and from the midst of it all, almost forgot to blog about Lord of the Rings Day. I do this every year on the blog (I think), recalling two things: how great Lord of the Rings was, and how even better something else is. Last year, and I’m making no effort to check, it had to have been one of Steven Erikson’s books, possibly from the Malazan series. I’ve got nothing else to add this year. The Malazan series is still the best in my books, and if you’re into epic fantasy fiction and haven’t read it yet: boo. I would also highly recommend the Warcraft lore.

Customary recap: March 25 every year is Lord of the Rings Day – a.k.a. Tolkien Day and Lord of the Rings Reading Day – because, in the books, that’s the day on which the One Ring is taken into the fires of Orodruin (or Mount Doom or Amon Amarth) by Gollum/Smeagol from the finger of Frodo Baggins. It was the year 3019 of the Third Age and augured the end of the War of the Ring. On this day, let’s read a chapter or two from the trilogy and remember what an enlightening experience reading the books was.

Featured image credit: kewl/pixabay

One in a thousand

Couldn’t pull myself away from reading Rajini Krish’s posts all of yesterday. Context: Krish, or Muthukrishanan Jeevanantham, an MPhil student at JNU, reportedly hung himself to his death on the morning of March 13, 2017 (I say ‘reportedly’ because Krish’s mother has alleged that it couldn’t have been suicide). After reading his posts – on Facebook and his blog – I wrote about them for The Wire here. I couldn’t add a paragraph in it because the copy had already been passed to the editor and was being processed for publication, so I’m putting it down below. It’s about an intricate relationship between equality and self-respect, particularly epitomised by India’s elderly (though not always): when their children get married and split off into nuclear families living separately, it has become a matter of self-esteem in many households for older members to be seen to be independent, depending on no one else for their living but themselves. Similarly, in Krish’s story, he recalls a conversation he’d had with his grandmother, Sellammal, in Salem (where he lived) before he moved to Delhi. He asks Sellammal why she has to make her living cleaning “kid’s asses” at a local school, earning a paltry Rs 750, when she snaps back:

“Paiya [boy], don’t talk too much like a big man, We old people have some reasons to work here, and I don’t want to disturb my sons. That’s why I [sit] in silence, always in my room, though my sons are nearby.”

In the Tamil film Aayirathil Oruvan (‘One in a thousand’, 2010), which explores the adjacency of freedom and self-respect, a historical war between the Pandyas and the Cholas has ended with the Cholas going into hiding. When their hideout is finally discovered by three adventurers, they are appalled by what the once-resplendent kingdom has been reduced to: a collection of a few hundred people living in squalor underground, with no apparent sense of dignity and with the false belief that they are still revered by the world outside. At one point, the Chola king sings a song telling the visitors that, though it might appear humiliating to preside “over a kingdom of skulls”, and for his ‘subjects’ to see him so, his people and he have been carrying on because they are used to their freedom to determine their own fate – and intend to hold on to it even when they emerge from their cocoon. And for as long as such a deal doesn’t seem to materialise, they will continue to be the way they are. The song is called ‘Thaai thindra mannae‘ (‘The earth the mother ate’) – and its last four verses (before the final refrain) are heartrending. The lyricist was Vairamuthu.

I can only offer two lines of the four in scant consolation to the spirit and soul of Rajini Krish.

Endro oru naal vidiyum endrae iravai chumakkum naalae, azhadhe / The day holding on to the night in the hope that it will dawn someday, don’t cry

Endhan kannin kanneer kazhuva ennodazhum yaazhae, azhadhe / The youth who would cry to wash away my tears with yours, don’t cry

Some notes on empiricism, etc.

The Wire published a story about the ‘atoms of Acharya Kanad‘ (background here; tl;dr: Folks at a university in Gujarat claimed an ancient Indian sage had put forth the theory of atoms centuries before John Dalton showed up). The story in question was by a professor of philosophy at IISER, Mohali, and he makes a solid case (not unfamiliar to many of us) as to why Kanad, the sage, didn’t talk about atoms specifically because he was making a speculative statement under the Vaisheshika school of Hindu philosophy that he founded. What got me thinking were the last few lines of his piece, where he insists that empiricism is the foundation of modern science, and that something that doesn’t cater to it can’t be scientific. And you probably know what I’m going to say next. “String theory”, right?

No. Well, maybe. While string theory has become something of a fashionable example of non-empirical science, it isn’t the only example. It’s in fact a subset of a larger group of systems that don’t rely on empirical evidence to progress. These systems are called formal systems, or formal sciences, and they include logic, mathematics, information theory and linguistics. (String theory’s reliance on advanced mathematics makes it more formal than natural – as in the natural sciences.) And the dichotomous characterisation of formal and natural sciences (the latter including the social sciences) is superseded by a larger, more authoritative dichotomy*: between rationalism and empiricism. Rationalism prefers knowledge that has been deduced through logic and reasoning; empiricism prioritises knowledge that has been experienced. As a result, it shouldn’t be a surprise at all that debates about which side is right (insofar as it’s possible to be absolutely right – which I don’t think everwill happen) play out in the realm of science. And squarely within the realm of science, I’d like to use a recent example to provide some perspective.

Last week, scientists discovered that time crystals exist. I wrote a longish piece here tracing the origins and evolution of this exotic form of matter, and what it is that scientists have really discovered. Again, a tl;dr version: in 2012, Frank Wilczek and Alfred Shapere posited that a certain arrangement of atoms (a so-called ‘time crystal’) in their ground state could be in motion. This could sound pithy to you if you were unfamiliar with what ground state meant: absolute zero, the thermodynamic condition wherein an object has no energy whatsoever to do anything else but simply exist. So how could such a thing be in motion? The interesting thing here is that though Shapere-Wilczek’s original paper did not identify a natural scenario in which this could be made to happen, they were able to prove that it could happen formally. That is, they found that the mathematics of the physics underlying the phenomenon did not disallow the existence of time crystals (as they’d posited it).

It’s pertinent that Shapere and Wilczek turned out to be wrong. By late 2013, rigorous proofs had showed up in the scientific literature demonstrating that ground-state, or equilibrium, time crystals could not exist – but that non-equilibrium time crystals with their own unique properties could. The discovery made last week was of the latter kind. Shapere and Wilczek have both acknowledged that their math was wrong. But what I’m pointing at here is the conviction behind the claim that forms of matter called time crystals could exist, motivated by the fact that mathematics did not prohibit it. Yes, Shapere and Wilczek did have to modify their theory based on empirical evidence (indirectly, as it contributed to the rise of the first counter-arguments), but it’s undeniable that the original idea was born, and persisted with, simply through a process of discovery that did not involve sense-experience.

In the same vein, much of the disappointment experienced by many particle physicists today is because of a grating mismatch between formalism – in the form of theories of physics that predict as-yet undiscovered particles – and empiricism – the inability of the LHC to find these particles despite looking repeatedly and hard in the areas where the math says they should be. The physicists wouldn’t be disappointed if they thought empiricism was the be-all of modern science; they’d in fact have been rebuffed much earlier. For another example, this also applies to the idea of naturalness, an aesthetically (and more formally) enshrined idea that the forces of nature should have certain values, whereas in reality they don’t. As a result, physicists think something about their reality is broken instead of thinking something about their way of reasoning is broken. And so they’re sitting at an impasse, as if at the threshold of a higher-dimensional universe they may never be allowed to enter.

I think this is important in the study of the philosophy of science because if we’re able to keep in mind that humans are emotional and that our emotions have significant real-world consequences, we’d not only be better at understanding where knowledge comes from. We’d also become more sensitive to the various sources of knowledge (whether scientific, social, cultural or religious) and their unique domains of applicability, even if we’re pretty picky, and often silly, at the moment about how each of them ought to be treated (Related/recommended: Hilary Putnam’s way of thinking).

*I don’t like dichotomies. They’re too cut-and-dried a conceptualisation.