neutrinos – Close Read

The weekly linklist – July 25, 2020

I’ve decided to publish this linklist via Substack. Next weekend onwards, it will only be available on https://linklist.substack.com. And this is why the list exists and what kind of articles you can find in it.

Want to buy a parrot? Please login via Facebook. – “F-commerce emerged in Bangladesh largely because there was no major e-commerce platform to absorb all the business. But although it’s biggest there, this form of selling isn’t exclusive to the country, or even the region: globally, 160 million small stores operate on Facebook, and in countries like Thailand, almost half of all online sales happen through social media.”
The history of climate science – “The fact that carbon dioxide is a ‘greenhouse gas’ – a gas that prevents a certain amount of heat radiation escaping back to space and thus maintains a generally warm climate on Earth, goes back to an idea that was first conceived, though not specifically with respect to CO2, nearly 200 years ago. The story of how this important physical property was discovered, how its role in the geological past was evaluated and how we came to understand that its increased concentration, via fossil fuel burning, would adversely affect our future, covers about two centuries of enquiry, discovery, innovation and problem-solving.”
The story of cryptomining in Europe’s most disputed state – “In early 2018, millions of digital clocks across Europe began falling behind time. Few took notice at first as slight disruptions in the power supply caused bedside alarms and oven timers running on the frequency of electric current to begin lagging. … European authorities soon traced the power fluctuations to North Kosovo, a region commonly described as one of Europe’s last ganglands. Since 2015, its major city, Mitrovica, has been under the control of Srpska Lista, a mafia masquerading as a political party. Around the time Srpska came to power, North Kosovo’s electricity consumption surged. Officials at the Kosovo Electricity Supply Company in Prishtina, Kosovo’s capital city, told me that the region now requires 20 percent more power than it did five years ago. Eventually, it became clear why: across the region, from the shabby apartment blocks of Mitrovica to the cellars of mountain villages, Bitcoin and Ethereum rigs were humming away, fueling a shadow economy of cryptocurrency manufacturing.”
Electromagnetic pulses are the last thing you need to worry about in a nuclear explosion – “The electromagnetic pulse that comes from the sundering of an atom, potentially destroying electronics within the blast radius with some impact miles away from ground zero, is just one of many effects of every nuclear blast. What is peculiar about these pulses, often referred to as EMPs, is the way the side effect of a nuclear blast is treated as a special threat in its own right by bodies such as the Task Force on National and Homeland Security, which, despite the official-sounding name, is a privately funded group. These groups continue a decadelong tradition of obsession over EMPs, one President Donald Trump and others have picked up on.”
India’s daunting challenge: There’s water everywhere, and nowhere – “I am walking across the world. Over the past seven years I have retraced the footsteps of Homo sapiens, who roamed out of Africa in the Stone Age and explored the primordial world. En route, I gather stories. And nowhere on my foot journey—not in any other nation or continent—have I encountered an environmental reckoning on the scale of India’s looming water crisis. It is almost too daunting to contemplate.”
Here be black holes – “During the 15th and 16th centuries, when oceans were the spaces between worlds, marine animals, often so prodigious that they were termed sea monsters, were difficult to see and even harder to analyse, their very existence uncertain. Broadly construed, the history of space science is also a story of looking across and into the ocean – that first great expanse of space rendered almost unknowable by an alien environment. Deep space, like the deep sea, is almost inaccessible, with the metaphorical depth of space echoing the literal depth of oceans. These cognitive and psychic parallels also have an analogue in the practicalities of survival, and training for space missions routinely includes stints under water.”
Birds bear the warnings but humans are responsible for the global threat – “Bird omens of a sort are the subject of two recent anthropological studies of avian flu preparedness in Asia. Both Natalie Porter, in Viral Economies, and Frédéric Keck, in Avian Reservoirs, convey the ominousness suffusing poultry farming, using birds as predictors. As both demonstrate, studying how birds interact with human agriculture can provide early warnings of a grim future. Indeed, Keck in Avian Reservoirs explicitly compares public-health surveillance (which he studies in the book) to augury, tracing ‘the idea that birds carry signs of the future that humans should learn to read … back to Roman divination.'”
Fiction as a window into the ethics of testing the Bomb – “The stuff that surprised me was on the American side. For example, the assessment by Curtis LeMay [the commander who led US air attacks on Japan] where he basically says, “We’ve bombed the shit out of Japan. Hurry up with your atomic bomb, because there’s going to be nothing left if you don’t.” That shocked me, and also that they deliberately left those cities pristine because they wanted to show the devastation. They wanted, I believe, to kill innocent people, because they were already moving on to the Cold War.”
The idea of entropy has led us astray – “Perhaps physics, in all its rigors, is deemed less susceptible to social involvement. In truth, though, Darwinian and thermodynamic theories served jointly to furnish a propitious worldview—a suitable ur-myth about the universe—for a society committed to laissez-faire competition, entrepreneurialism, and expanding industry. Essentially, under this view, the world slouches naturally toward a deathly cold state of disorder, but it can be salvaged—illuminated and organized—by the competitive scrabble of creatures fighting to survive and get ahead.”
How massive neutrinos broke the Standard Model – “Niels Bohr … had the radical suggestion that maybe energy and momentum weren’t really conserved; maybe they could somehow be lost. But Wolfgang Pauli had a different — arguably, even more radical — thought: that perhaps there was a novel type of particle being emitted in these decays, one that we simply didn’t yet have the capacity to see. He named it “neutrino,” which is Italian for “little neutral one,” and upon hypothesizing it, remarked upon the heresy he had committed: ‘I have done a terrible thing, I have postulated a particle that cannot be detected.'”
How a small Arab nation built a Mars mission from scratch in six years – “When the UAE announced in 2014 that it would send a mission to Mars by the country’s 50th birthday in December 2021, it looked like a bet with astronomically tough odds. At the time, the nation had no space agency and no planetary scientists, and had only recently launched its first satellite. The rapidly assembled team of engineers, with an average age of 27, frequently heard the same jibe. ‘You guys are a bunch of kids. How are you going to reach Mars?’ says Sarah Al Amiri, originally a computer engineer and the science lead for the project.”
The pandemic has made concentrated reading difficult. How are book reviewers dealing with this? – “To read good and proper, I needed to disconnect from the terrible reality of the present – wishful thinking with the always-on-alert mode that the pandemic thrust upon us. A few pages in, my mind would wander, snapping out of the brief, quiet moment and I’d find myself reaching for my phone. … But as neuroscientists world over have told us, it’s been hard for most people to focus, with our brain in fight-or-flight mode to the threat of the virus. An activity like deep reading is especially difficult because it requires a high level of engagement and quiet. So it wasn’t just me.”
Facebook’s employees reckon with the social network they’ve built – “Why was Zuckerberg only talking about whether Trump’s comments fit the company’s rules, and not about fixing policies that allowed for threats that could hurt people in the first place, he asked. ‘Watching this just felt like someone was sort of slowly swapping out the rug from under my feet,’ Wang said. ‘They were swapping concerns about morals or justice or norms with this concern about consistency and logic, as if it were obviously the case that ‘consistency’ is what mattered most.'”

Physics Nobel rewards neutrino work, but has sting in the tail for India

As neutrino astronomy comes of age, the Nobel Foundation has decided to award Takaaki Kajita and Arthur B. McDonald with the physics prize for 2015 for their discovery of neutrino oscillations – a property which indicates that the fundamental particle has mass.

Takaaki Kajita is affiliated with the Super-Kamiokande neutrino detector in Japan. He and Yoji Totsuka used the detector to report in 1998 that neutrinos produced when cosmic rays struck Earth’s atmosphere were ‘disappearing’ as they travelled to the detector. Then, in 2002, McDonald of the Sudbury Neutrino Observatory in Canada reported that incoming electron neutrinos from the Sun were metamorphosing into muon- or tau-neutrinos. Electron-neutrino, muon-neutrino and tau-neutrino are three kinds of neutrinos (named for particles they are associated with: electrons, muons and taus).

What McDonald, Kajita and Totsuka had together found was that neutrinos were changing from one kind to another as they travelled – a property called neutrino oscillations – which is definite proof that the particles have mass. Sadly, Totsuka died in 2009, and may not have been considered for the Nobel Prize for that reason.

This was an important discovery for astroparticle physics. For one, the Standard Model group of equations that defines the behaviour of fundamental particles hadn’t anticipated it. For another, the discovery also made neutrinos a viable candidate for dark matter, which we’re yet to discover, and for what their having mass implies about the explosive deaths of stars – a process that spews copious amounts of neutrinos.

Neutrino oscillations were first predicted by the Italian nuclear physicist Bruno Pontecorvo in 1957. In fact, Pontecorvo has laid the foundation of a lot of concepts in neutrino physics whose development has won other physicists the Nobel Prize (in 1988, 1995 and 2002), though he’s never won the prize himself.

An infographic showing how the Super-Kamiokande neutrino experiment works. Source: nobelprize.org

Although it was a tremendous discovery that neutrinos have mass, a discovery that forced an entrenched theory of physics to change itself, the questions that Pontecorvo, Kajita, McDonald and others asked have yet to be fully answered: one of the biggest unsolved problems in physics today is what the neutrino-mass hierarchy is. In other words, physicists haven’t yet been able to find out – via theory or experiment – which of the three kinds neutrinos is the heaviest and which the lightest. The implications of the mass-ordering are important for physicists to understand certain fundamental predictions of the Standard Model. As it turns out, the model has many unanswered questions, and some physicists hope that a part of the answer may lie in the unexpected properties of neutrinos.

An infographic showing how the Sudbury Neutrino Observatory works. Source: nobelprize.org

Exacerbating the scientific frustration is the fact that neutrinos are notoriously hard to detect because they rarely interact with matter. For example, the IceCUBE neutrino observatory operated by the University of Wisconsin-Madison near the South Pole in Antarctica employs thousands of sensors buried under the ice. When a neutrino strikes a water molecule in the ice, the reaction produces a charged lepton – electron, muon or tau, depending on the neutrino. That lepton moves faster through the surrounding ice than the speed of light in ice, releasing energy called Cherenkov radiation that’s then detected by the sensors. Building on similarly advanced principles of detection, India and China are also constructing neutrino detectors.

At least, India is supposed to be. China on the other hand has been labouring away for about a year now in building the Jiangmen Underground Neutrino Observatory (JUNO). India’s efforts with the India-based Neutrino Observatory (INO) in Theni, Tamil Nadu have, on the other hand, ground to a halt. The working principles behind both INO and JUNO are targeted at answering the mass-ordering questions. And if answered, it would almost definitely warrant a Nobel Prize in the future.

INO’s construction has been delayed because of a combination of festering reasons with no end in sight. The observatory’s detector is a 50,000-ton instrument called the iron calorimeter that is to be buried underneath a kilometre of rock so as to filter all particles but neutrinos out. To acquire such a natural shield, the principal institutions involved in its construction – the Department of Atomic Energy (DAE) and the Institute of Mathematical Sciences, Chennai (Matscience) – have planned to hollow out a hill and situate the INO in the resulting ‘cave’. But despite clearances acquired from various pollution control boards as well as from the people living in the area, the collaboration has faced repeated resistance from environmental activists as well as politicians who, members of the collaboration allege, are only involved for securing political mileage.

Schematic view of the Underground neutrino lab under a mountain. Credit: ino.tifr.res.in

The DAE, which obtained approval for the project from the Cabinet and the funds to build the observatory, has also been taking a hands-off approach and has until now not participated in resolving the face-off between the scientists and the activists.

At the moment, the construction has been halted by a stay issued by the Madurai Bench of the Madras High Court following a petition filed with the support of Vaiko, founder of the Marugmalarchi Dravida Munnetra Kazhagam. But irrespective of which way the court’s decision goes, members of the collaboration at Matscience say that arguments with certain activists have degenerated of late, eroding their collective spirit to persevere with the observatory – even as environmentalists continue to remain suspicious of the DAE. This is quite an unfortunate situation for a country whose association with neutrinos dates back to the 1960s.

At that time, a neutrino observatory located at a mine in the Kolar Gold Fields was among the first in the world to detect muon neutrinos in Earth’s atmosphere – the same particles whose disappearance Takaaki Kajita was able to record to secure his Nobel Prize for. Incidentally, a Japanese physicist named Masatoshi Koshiba was spurred by the KGF discovery to build a larger neutrino detector in his country, called Kamioka-NDE, later colloquialised to Kamiokande (Koshiba won the Nobel Prize in 2002 for discovering the opportunities of neutrino astronomy). Kamiokande was later succeeded by Super-Kamiokande, which in the late-1990s became the site of Kajita’s discovery. The KGF observatory, on the other hand, was shut in the 1992 as the mines were closed.

For the broader physics community, brakes applied on the INO’s progress count for little because there are other neutrino detectors around the world – like JUNO – as well as research labs that can continue to look for answers to the mass-ordering question. In fact, the Nobel Prize awarded to Kajita and McDonald stands testimony to the growing realisation that, like the particles of light, neutrinos can also be used to reveal the secrets of the cosmos. However, for the Indian community, which has its share of talented theoretical physicists, the slowdown signifies a slipping opportunity to get back in the game.

The Wire
October 6, 2015

Type 1a supernova spotted in M82

(A version of this piece appeared on The Hindu, Chennai, website on January 22 as written by me.)

A Type 1a supernova was spotted a few hours ago by stargazers in the starburst galaxy M82, which is only 11.4 million light-years away from Earth (here’s an interactive map and a helpful sky-chart). This is the closest such supernova that has been detected since 1972, and is poised to give astronomers and cosmologists some invaluable insight into how such stellar explosions pan out, and what we can learn about neutrinos, gamma rays and dark energy from them.

See the bright, blinking spot of light on the galaxy's 'lower' half? That's your SN1a. — See the bright, blinking spot of light on the galaxy’s ‘lower’ half? That’s your SN1a. Animation by E. Guido, N. Howes, M. Nicolini

The supernova is a Type 1a supernova (SN1a), which means it’s not the explosion that happens when a star runs out of fuel and blows itself apart. Instead, it’s what happens when a white dwarf pulls in too much material from a nearby star and blows itself apart—having bitten off more than it could chew.

That M82 is a starburst galaxy means it’s rapidly producing stars. This also means it has a lot of old stars, many of which are continuously dying. They could either be dying as Type 2 supernovae—which is the run-out-fuel kind—or Type 1. The SN1a that’s gone off now (i.e. so many millions of years ago) has chosen to go off as Type 1a, and that’s a good thing because we haven’t spotted a Type 1a since 1972 that’s so close.

When the explosion releases light, it doesn’t immediately start its journey and head straight for Earth. Instead, the light gets trapped in the explosion behind lots of matter, and is delayed. In fact, the ‘ghost particles’ that can pass through matter almost undetected, neutrinos, get a headstart. They reach us before light from the explosion does.

However, a Type 1a supernova produces far fewer neutrinos than does a Type 2, so while the neutrinos flying our way will still be valuable, they might not be valuable enough to study a supernova with. On the other hand, the M82-SN1a could be our big chance to study SN-origin gamma rays in the best detail for the first time in more than four decades.

However, since we haven’t had our detectors trained for neutrinos from M82 particularly, how do we know when that white dwarf in M82 blew up? We measure how its brightness varies over time. Using that information, we know the thing blew up 11.4 million years ago. Because a 1a’s variation of brightness over time consistently follows a well-established pattern, white dwarfs across the universe can be used as cosmic candlesticks: astronomers use them to judge the relative distances of nearby objects.

In fact, white dwarfs did play an important role in astronomers discovering that the universe was expanding at an accelerating rate due to dark energy. Paraphrasing astronomer Katharine Mack’s tweet: “With a better estimate of the distance [as judged from their brightness], we get a better link between the distance and the universe’s expansion.”

M82’s relative closeness is useful because it provides a lot more information to work with before it could get (more) adulterated through the distance of space. In fact, according to astronomer Daniel Fischer, the supernova’s been going on for a full week now, and was missed by the bigger budget telescopes because it was, and I quote, ‘too bright’. As Brad Tucker, an astronomer from Berkeley, tweeted,

[tweet https://twitter.com/btucker22/status/425989187188187137 hide_thread=’true’]

So, hadn’t it been for amateur astronomers, who’ve made this remarkable observation, too, we wouldn’t have spotted this beauty. Already, according to Skymania’s Paul Sutherland, astronomers believe they’ve caught this supernova early in its act and think it could brighten even further.

This particular find was made by Russian amateur astronomers on January 22, and later confirmed by multiple sources. In fact, M82-SN1a seems to have appeared in the photographs taken by noted Japanese amateur astronomer Koichi Itagaki on January 14 itself (beating Patrick Wiggins by a day). And if you’re interested in reporting such discoveries, check this page out. If you want to keep up with the social media conversation over M82, follow @astrokatie. She’s going nuts (in a good way).

Itagaki's photos of M82 — Itagaki’s photos of M82