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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.'”
Categories
Analysis Scicomm

Journalistic entropy

Say you need to store a square image 1,000 pixels wide to a side with the smallest filesize (setting aside compression techniques). The image begins with the colour #009900 on the left side and, as you move towards the right, gradually blends into #1e1e1e on the rightmost edge. Two simple storage methods come to mind: you could either encode the colour-information of every pixel in a file and store that file, or you could determine a mathematical function that, given the inputs #009900 and #1e1e1e, generates the image in question.

The latter method seems more appealing, especially for larger canvases of patterns that are composed by a single underlying function. In such cases, it should obviously be more advantageous to store the image as an output of a function to achieve the smallest filesize.

Now, in information theory (as in thermodynamics), there is an entity called entropy: it describes the amount of information you don’t have about a system. In our example, imagine that the colour #009900 blends to #1e1e1e from left to right save for a strip along the right edge, say, 50 pixels wide. Each pixel in this strip can assume a random colour. To store this image, you’d have to save it as an addition of two functions: ƒ(x, y), where x = #009900 and y = #1e1e1e, plus one function to colour the pixels lying in the 50-px strip on the right side. Obviously this will increase the filesize of the stored function.

Even more, imagine if you were told that 200,000 pixels out of the 1,000,000 pixels in the image would assume random colours. The underlying function becomes even more clumsy: an addition of ƒ(x, y) and a function R that randomly selects 200,000 pixels and then randomly colours them. The outputs of this function R stands for the information about the image that you can’t have beforehand; the more such information you lack, the more entropy the image is said to have.

The example of the image was simple but sufficiently illustrative. In thermodynamics, entropy is similar to randomness vis-à-vis information: it’s the amount of thermal energy a system contains that can’t be used to perform work. From the point of view of work, it’s useless thermal energy (including heat) – something that can’t contribute to moving a turbine blade, powering a motor or motivating a system of pulleys to lift weights. Instead, it is thermal energy motivated by and directed at other impetuses.

As it happens, this picture could help clarify, or at least make more sense of, a contemporary situation in science journalism. Earlier this week, health journalist Priyanka Pulla discovered that the Indian Council of Medical Research (ICMR) had published a press release last month, about the serological testing kit the government had developed, with the wrong specificity and sensitivity data. Two individuals she spoke to, one from ICMR and another from the National Institute of Virology, Pune, which actually developed the kit, admitted the mistake when she contacted them. Until then, neither organisation had issued a clarification even though it was clear both individuals are likely to have known of the mistake at the time the release was published.

Assuming for a moment that this mistake was an accident (my current epistemic state is ‘don’t know’), it would indicate ICMR has been inefficient in the performance of its duties, forcing journalists to respond to it in some way instead of focusing on other, more important matters.

The reason I’m tending to think of such work as entropy and not work per se is such instances, whereby journalists are forced to respond to an event or action characterised by the existence of trivial resolutions, seem to be becoming more common.

It’s of course easier to argue that what I consider trivial may be nontrivial to someone else, and that these events and actions matter to a greater extent than I’m willing to acknowledge. However, I’m personally unable to see beyond the fact that an organisation with the resources and, currently, the importance of ICMR shouldn’t have had a hard time proof-reading a press release that was going to land in the inboxes of hundreds of journalists. The consequences of the mistake are nontrivial but the solution is quite trivial.

(There is another feature in some cases: of the absence of official backing or endorsement of any kind.)

So as such, it required work on the part of journalists that could easily have been spared, allowing journalists to direct their efforts at more meaningful, more productive endeavours. Here are four more examples of such events/actions, wherein the non-triviality is significantly and characteristically lower than that attached to formal announcements, policies, reports, etc.:

  1. Withholding data in papers – In the most recent example, ICMR researchers published the results of a seroprevalence survey of 26,000 people in 65 districts around India, and concluded that the prevalence of the novel coronavirus was 0.73% in this population. However, in their paper, the researchers include neither a district-wise breakdown of the data nor the confidence intervals for each available data-point even though they had this information (it’s impossible to compute the results the researchers did without these details). As a result, it’s hard for journalists to determine how reliable the results are, and whether they really support the official policies regarding epidemic-control interventions that will soon follow.
  2. Publishing faff – On June 2, two senior members of the Directorate General of Health services, within India’s Union health ministry, published a paper (in a journal they edited) that, by all counts, made nonsensical claims about India’s COVID-19 epidemic becoming “extinguished” sometime in September 2020. Either the pair of authors wasn’t aware of their collective irresponsibility or they intended to refocus (putting it benevolently) the attention of various people towards their work, turning them away from the duo deemed embarrassing or whatever. And either way, the claims in the paper wound their way into two news syndication services, PTI and IANS, and eventually onto the pages of a dozen widely-read news publications in the country. In effect, there were two levels of irresponsibility at play: one as embodied by the paper and the other, by the syndication services’ and final publishers’ lack of due diligence.
  3. Making BS announcements – This one is fairly common: a minister or senior party official will say something silly, such as that ancient Indians invented the internet, and ride the waves of polarising debate, rapidly devolving into acrimonious flamewars on Twitter, that follow. I recently read (in The Washington Post I think, but I can’t find the link now) that it might be worthwhile for journalists to try and spend less time on fact-checking a claim than it took someone to come up with that claim. Obviously there’s no easy way to measure the time some claims took to mature into their present forms, but even so, I’m sure most journalists would agree that fact-checking often takes much longer than bullshitting (and then broadcasting). But what makes this enterprise even more grating is that it is orders of magnitude easier to not spew bullshit in the first place.
  4. Conspiracy theories – This is the most frustrating example of the lot because, today, many of the originators of conspiracy theories are television journalists, especially those backed by government support or vice versa. While fully acknowledging the deep-seated issues underlying both media independence and the politics-business-media nexus, numerous pronouncements by so many news anchors have only been akin to shooting ourselves in the foot. Exhibit A: shortly after Prime Minister Narendra Modi announced the start of demonetisation, a beaming news anchor told her viewers that the new 2,000-rupee notes would be embedded with chips to transmit the notes’ location real-time, via satellite, to operators in Delhi.

Perhaps this entropy – i.e. the amount of journalistic work not available to deal with more important stories – is not only the result of a mischievous actor attempting to keep journalists, and the people who read those journalists, distracted but is also assisted by the manifestation of a whole industry’s inability to cope with the mechanisms of a new political order.

Science journalism itself has already experienced a symptom of this change when pseudoscientific ideas became more mainstream, even entering the discourse of conservative political groups, including that of the BJP. In a previous era, if a minister said something, a reporter was to drum up a short piece whose entire purpose was to record “this happened”. And such reports were the norm and in fact one of the purported roots of many journalistic establishments’ claims to objectivity, an attribute they found not just desirable but entirely virtuous: those who couldn’t be objective were derided as sub-par.

However, if a reporter were to simply report today that a minister said something, she places herself at risk of amplifying bullshit to a large audience if what the minister said was “bullshit bullshit bullshit”. So just as politicians’ willingness to indulge in populism and majoritarianism to the detriment of society and its people has changed, so also must science journalism change – as it already has with many publications, especially in the west – to ensure each news report fact-checks a claim it contains, especially if it is pseudoscientific.

In the same vein, it’s not hard to imagine that journalists are often forced to scatter by the compulsions of an older way of doing journalism, and that they should regroup on the foundations of a new agreement that lets them ignore some events so that they can better dedicate themselves to the coverage of others.

Featured image credit: Татьяна Чернышова/Pexels.

Categories
Life notes Science

Time and the pandemic

There is this idea in physics that the fundamental laws of nature apply the same way for processes moving both forwards and backwards in time. So you can’t actually measure the passage of time by studying these processes. Where does our sense of time, rather the passage of time, come from then? How do we get to tell that the past and future are two different things, and that time flows from the former to the latter?

We sense time because things change. Clock time is commonly understood to be a way to keep track of when and how often things change but in physics, time is not the master: change doesn’t arise because of time but time arises because of change. So time manifests in the laws of nature through things that change in time. One of the simplest such things is entropy. Specifically, the second law of thermodynamics states that as time moves forward, the entropy of an isolated system cannot decrease. Entropy thus describes an arrow of time.

This is precisely what the pandemic is refusing to do, at least as seen through windows set at the very back of a newsroom. Many reporters writing about the coronavirus may have the luxury of discovering change, and therefore the forward march of time itself, but for someone who is somewhat zoomed out – watching the proceedings from a distance, as it were – the pandemic has only suffused the news cycle with more and more copies of itself, like the causative virus itself.

It seems to me as if time has stilled. I have become numb to news about the virus, which I suspect is a coping mechanism, like a layer of armour inserted between a world relentlessly pelting me with bad news and my psyche itself. But the flip side of this protection is an inability to sense the passage of time as well as I was able before.

My senses are alert to mistakes of fact, as well as mostly of argument, that reporters make when reporting on the coronavirus, and of course to opportunities to improve sentence construction, structure, flow, etc. But otherwise, and thanks in fact to my limited engagement with this topic, it feels as if I wake up every morning, my fingers groaning at the prospect of typing the words “lockdown”, “coronavirus”, “COVID-19”, “herd immunity” and whatever else1. And since this is what I feel every morning, there is no sense of change. And without change, there is no time.

1. I mean no offence to those suffering the pandemic’s, and the lockdown’s, brutal health, economic, social, cultural and political consequences.

I would desperately like to lose my armour. The bad news will never stop coming but I would still like to get back to bad news that I got into journalism to cover, the bad news that I know what to do about… to how things were before, I suppose.

Oh, I’m aware of how illogical this line of introspection is, yet it persists! I believe one reason is that the pandemic is a passing cloud. It leapt out of the horizon and loomed suddenly over all of us, over the whole world; its pall is bleak but none of us doubts that it will also pass. The pandemic will end – everybody knows this, and this is perhaps also why the growing desperation for it to dissipate doesn’t feel misplaced, or unjustified. It is a cloud, and like all clouds, it must go away, and therefrom arises the frustration as well: if it can go away, why won’t it?

Is it true that everything that will last for a long time also build up over a long time? Climate change, for example, doesn’t – almost can’t – have a single onset event. It builds and builds all around us, its effects creeping up on us. With each passing day of inaction, there is even less that we can do than before to stop it; in fact, so many opportunities have been squandered or stolen by bad actors that all we have left to do is reduce consumption and lower carbon emissions. So with each passing day, the planet visits us with more reminders of how we have changed it, and in fact may never have it back to the way it once was.

Almost as if climate change happened so slowly, on the human scale at least, that it managed to weave itself into our sense of time, not casting a shadow on the clock as much as becoming a part of the clock itself. As humankind’s grandest challenge as yet, one that we may never fully surmount, climate change doesn’t arise because of time but time arises because of climate change. Perhaps speed and surprise is the sacrifice that time demands of that which aspires to longevity.

The pandemic, on the other hand, likely had a single onset… right? At least it seems so until you realise the pandemic is in fact the tip of the proverbial iceberg – the thing jutting above the waterline, better yet the tip of the volcano. There is a complicated mess brewing underground, and out of sight, to which we have all contributed. One day the volcano shoots up, plastering its surroundings with lava and shooting smoke and soot kilometres into the air. For a time, the skies are a nuclear-winter grey and the Sun is blotted out. To consider at this time that we could stave off all future eruptions by pouring tonnes of concrete into the smouldering caldera would be folly. The pandemic, like magma, like the truth itself, will out. So while the nimbuses of each pandemic may pass, all the storm’s ingredients will persist.

I really hope the world, and I do mean the world, will heed this lesson as the novel coronavirus’s most important, if only because our sense of time and our expectations of what the passage of time could bring need to encompass the things that cause pandemics as much as they have come to encompass the things that cause Earth’s climate to change. We’ve become used to thinking about this outbreak, and likely the ones before it, as transitory events that begin and end – but really, wrapped up in our unrelenting yearning for the pandemic to pass is a conviction that the virus is a short-lived, sublunary creature. But the virus is eternal, and so our response to it must also transform from the mortal to the immortal.

Then again, how I wish my mind submitted, that too just this once, to logic’s will sans resistance. No; it yearns still for the pandemic to end and for ‘normal’ to recommence, for time to flow as it once did, with the promise of bringing something new to the threshold of my consciousness every morning. I sense there is a line here between the long- and the short-term, between the individual and the collective, and ultimately between the decision to change myself and the decision to wait for others before I do.

I think, as usual, time will tell. Heh.

Categories
Scicomm

A journey through Twitter and time, with the laws of physics

Say you’re in a dark room and there’s a flash. The light travels outward in all directions from the source, and the illumination seems to expand in a sphere. This is a visualisation of how the information contained in light becomes distributed through space.

But even though this is probably what you’d see if you observed the flash with a very high speed camera, it’s not the full picture. The geometry of the sphere captures only the spatial component of the light’s journey. It doesn’t say anything about the time. We can infer that from how fast the sphere expands but that’s not an intrinsic property of the sphere itself.

To solve this problem, let’s assume that we live in a world with two spatial dimensions instead of three (i.e. length and breadth only, no depth). When the flash goes off in this world, the light travels outward in an expanding circle, which is the two-dimensional counterpart of a sphere. At 1 second after the flash, say the circle is 2 cm wide. After 2 seconds, it’s 4 cm wide. After 3 seconds, it’s 8 cm wide. After 4 seconds, it’s 16 cm wide. And so forth.

If you photographed the circles at each of these moments and put the pictures together, you’d see something like this (not to scale):

And if you looked at this stack of circles from under/behind, you’d see what physicists call the light cone.

Credit: Stib/Wikimedia Commons, CC BY-SA 3.0

The cone is nothing but a stack of circles of increasing diameter. The circumference of each circle represents the extent to which the light has spread out in space at that time. So the farther into the future of an event – such as the flash – you go, the wider the light cone will be.

(The reason we assumed we live in a world of two dimensions instead of three should be clearer now. In our three-dimensional reality, the light cone would assume a four-dimensional shape that can be quite difficult to visualise.)

According to the special theory of relativity, all future light cones must be associated with corresponding past light cones, and light always flows from the past to the future.

To understand what this means, it’s important to understand the cones as exclusionary zones. The diameter of the cone at a specific time is the distance across which light has moved in that time. So anything that moves slower – such as a message written on a piece of paper tied to a rock thrown from A to B – will be associated with a narrower cone between A and B. If A and B are so far apart that even light couldn’t have spanned them in the given time, then B is going to be outside the cone emerging from A, in a region officially called elsewhere.

Now, light is just one way to encode information. But since nothing can move faster than at the speed of light, the cones in the diagram above work for all kinds of information, i.e. any other medium will simply be associated with narrower cones but the general principles as depicted in the diagram will hold.

For example, here’s something that happened on Twitter earlier today. I spotted the following tweet at 9.15 am:

When scrolling through the replies, I noticed that one of Air Vistara’s senior employees had responded to the complaint with an apology and an assurance that it would be fixed.

https://twitter.com/TheSanjivKapoor/status/1154223981358018561

Taking this to be an admission of guilt, and to an admission of there actually having been a mistake by proxy, I retweeted the tweet at 9.16 am. However, only a minute later, another account discovered that the label of ‘professor’ didn’t work with the ‘male’ option either, ergo the glitch didn’t have so much to do with the user’s gender as much as the algorithm was just broken. A different account brought this to my attention at 9.30 am.

So here we have two cones of information that can be recast as the cones of causality, intersecting at @rath_shyama’s tweet. The first cone of causality is the set of all events in the tweet’s past whose information contributed to it. The second cone of causality represents all events in whose past the tweet lies, such as @himdaughter’s, the other accounts’ and my tweets.

As it happens, Twitter interferes with this image of causality in a peculiar way (Facebook does, too, but not as conspicuously). @rath_shyama published her tweet at 8.02 am, @himdaughter quote-tweeted her at 8.16 am and I retweeted @himdaughter at 9.16 am. But by 9.30 am, the information cone had expanded enough for me to know that my retweet was possibly mistaken. Let’s designate this last bit of information M.

So if I had un-retweeted @himdaughter’s tweet at, say, 9.31 am, I would effectively have removed an event from the timeline that actually occurred before I could have had the information to act on it (i.e., M). The issue is that Twitter doesn’t record (at least not publicly anyway) the time at which people un-retweet tweets. If it had, then there would have been proof that I acted in the future of M; but since it doesn’t, it will look like I acted in the past of M. Since this is causally impossible, the presumption arises that I had the information about M before others did, which is false.

This serves as an interesting commentary on the nature of history. It is not possible for Twitter’s users to remember historical events on its platform in the right order simply because Twitter is memoryless when it comes to one of the actions it allows. As a journalist, therefore, there is a bit of comfort in thinking about the pre-Twitter era, when all newsworthy events were properly timestamped and archived by the newspapers of record.

However, I can’t let my mind wander too far back, lest I stagger into the birth of the universe, when all that existed was a bunch of particles.

We commonly perceive that time has moved forward because we also observe useful energy becoming useless energy. If nothing aged, if nothing grew weaker or deteriorated in material quality – if there was no wear-and-tear – we should be able to throw away our calendars and pretend all seven days of the week are the same day, repeated over and over.+

Scientists capture this relationship between time and disorderliness in the second law of thermodynamics. This law states that the entropy – the amount of energy that can’t be used to perform work – of a closed system can never decrease. It can either remain stagnant or increase. So time does not exist as an entity in and of itself but only seems to as a measure of the increase in entropy (at a given temperature). We say a system has moved away from a point in its past and towards a point in its future if its entropy has gone up.

However, while this works just fine with macroscopic stuff like matter, things are a bit different with matter’s smallest constituents: the particles. There are no processes in this realm of the quantum whose passage will tell you which way time has passed – at least, there aren’t supposed to be.

There’s a type of particle called the B0 meson. In an experiment whose results were announced in 2012, physicists found unequivocal proof that this particle transformed into another one faster than the inverse process. This discrepancy provides an observer with a way to tell which way time is moving.

The experiment also remains the only occasion till date on which scientists have been able to show that the laws of physics don’t apply the same forward and backward in time. If they did, the forward and backward transformations would have happened at the same rate, and an observer wouldn’t have been able to tell if she was watching the system move into the future or into the past.

But with Twitter, it would seem we’re all clearly aware that we’re moving – inexorably, inevitably – into the future… or is that the past? I don’t know.

+ And if capitalism didn’t exist: in capitalist economies, inequality always seems to increase with time.

Categories
Science

Why a pump to move molten metal is awesome

The conversion of one form of energy into another is more efficient at higher temperatures.1 For example, one of the most widely used components of any system that involves the transfer of heat from one part of the system to another is a device called a heat exchanger. When it’s transferring heat from one fluid to another, for example, the heat exchanger must facilitate the efficient movement of heat between the two media without allowing them to mix.

There are many designs of heat exchangers for a variety of applications but the basic principle is the same. However, they’re all limited by the explicit condition that entropy – “the measure of disorder” – is higher at lower temperatures. In other words, the lower the temperature difference within the exchanger, the less efficiently the transfer will happen. This is why it’s desirable to have a medium that can carry a lot of heat per unit volume.

But this is not always possible for two reasons. First: there must exist a pump that can move such a hot medium from one point to another in the system. This pump must be made of materials that can withstand high temperatures during operation as well as not react with the medium at those temperatures. Second: one of the more efficient media that can carry a lot of heat is liquid metals. But they’re difficult to pump because of their corrosive nature and high density. Both reasons together, this is why medium temperatures have been limited to around 1,000º C.

Now, an invention by engineers from the US has proposed a solution. They’ve constructed a pump using ceramics. This is really interesting because ceramics have a good reputation for being able to withstand extreme heat (they were part of the US Space Shuttle’s heat shield exposed during atmospheric reentry) but an equally bad reputation for being very brittle.2 So this means that a ceramic composition of the pump material accords it a natural ability to withstand heat.

In other words, the bigger problem the engineers would’ve solved for would be to keep it from breaking during operation.

DOI: 10.1038/nature24054
DOI: 10.1038/nature24054

Their system consists of a motor (not visible in the image above but positioned to the right of the shaft, made of an insulating material), the gearbox, a piping network and a reservoir of liquid tin. When the motor is turned on, the pump receives liquid tin from the bottom of the reservoir. Two interlocking gears inside the pump (shown left bottom) rotate. As the tin flows between the blades, it is compressed into the space between them, creating a pressure difference that sucks in more tin from the reservoir. After the tin moves through the blades, it is let out into another pipe that takes it back to the reservoir.

The gearbox. Source: https://www.youtube.com/watch?v=Y_6K-Xo4nH8
The gearbox. Source: https://www.youtube.com/watch?v=Y_6K-Xo4nH8

The blades are made of Shapal, an aluminium nitride ceramic made by the Tokuyama Corporation in Japan with the unique property of being machinable. The pump seals and piping network are made of graphite. High-temperature pumps usually have pipes made of polymers. Graphite and such polymers are similar in that they’re both very difficult to corrode. But graphite has an upper hand in this context because it can also withstand higher temperatures before it loses its consistency.

Using this setup, the engineers were able to operate the pump continuously for 72 hours at an average temperature of 1,200º C. For the first 60 hours of operation, the flow rate varied between 28 and 108 grams per second (at an rpm in the lower hundreds). According to the engineers’ paper, this corresponds to an energy transfer of 5-20 kW for a vat of liquid tin heated from 300º C to 1,200º C. They extrapolate these numbers to suggest that if the gear diameter and thickness were enlarged from 3.8 cm to 17.1 cm and 1.3 cm to 5.85 cm (resp.) and operated at 1,800 rpm, the resulting heat transfer rate would be 100 MW – a jump of 5,000x from 20 kW and close to the requirements of a utility-scale power plant.

And all of this would be on a tabletop setup. This is the kind of difference having a medium with a high energy density makes.

The engineers say that their choice of temperature at which to run the pump – about 1,200ºC – was limited by whatever heaters they had available in their lab. So future versions of this pump could run for cheaper and at higher temperatures by using, say, molten silicon and higher grade ceramics than Shapal. Such improvements could have an outsize effect in our world because of the energy capacity and transfer improvements they stand to bring to renewable energy storage.

1. I can attest from personal experience that learning the principles of thermodynamics is easier through application than theory – an idea that my college professors utterly failed to grasp.

2. The ceramics used to pave the floor of your house and the ceramics used to pad the underbelly of the Space Shuttle are very different. For one, the latter had a foamy internal structure and wasn’t brittle. They were designed and manufactured this way because the ceramics of the Space Shuttle wouldn’t just have to withstand high heat – they would also have to be able to withstand the sudden temperature change as the shuttle dived from the -270º C of space into the 1,500º C of hypersonic shock.

Featured image credit: Erdenebayar/pixabay.