The names of smartness

Something leapt in my heart when I read Kangana Ranaut’s latest repartee to Saif Ali Khan’s misguided notes on nepotism and eugenics. There were many reasons for this but one in particular was to see the name ‘Terence Tao’ mentioned among the examples Ranaut picked to describe the world’s smartest people (flipside: no women on the list):

You also spoke of eugenics — which means controlled breeding of the human race. So far, I believe that the human race hasn’t found the DNA that can pass on greatness and excellence. If it had, we would’ve loved to repeat the greatness of Einstein, Da Vinci, Shakespeare, Vivekananda, Stephen Hawking, Terence Tao, Daniel Day-Lewis, or Gerhard Richter.

The names of Einstein and Hawking are so popular that people include them in rosters of greatness often without being aware of what they have achieved. Tao, on the other hand, isn’t yet that well-known. Not everyone has heard of him, and most of those who have are likely to be aware of his stature as a mathematician.

This isn’t any kind of a comment on Ranaut, who has done everyone a good turn with her letter, but more a confession of my own cynicism. Cynicism that people are likelier than not to know the name of Einstein than of Tao, of Isaac Newton than of Pierre-Simon Laplace, of even Rosalind Franklin than of Rosalyn Yalow.

Featured image credit: jinsngjung/pixabay.

Why Titan is awesome #9

Featured image: Four of the 66 antennae of the ALMA array. Credit: Carlos Padilla – AUI/NRAO.

Editions onetwothreefourfivesixseven and eight

In edition #8 of ‘why Titan is awesome’, we visited a lake near Titan’s north pole, named Ligeia Mare, and how it could sport long lines of tiny – ~2 cm – waves. In a new study, scientists have uncovered evidence that Ligeia Mare also has enough vinyl cyanide dissolved in its waters liquid methane to be able to form 30 million biological cells per millilitre.

Does this mean we know that there’s life on Titan?+ No. We only know that if there is life on Titan in the form of microbes, then there could be 30 million cells per millilitre of Ligeia Mare with membranes composed of vinyl cyanide (with the additional assumption that each of these cells is 10 micrometers wide). But in spite of the particularity of this statement, it’s an exciting discovery nonetheless. To make it, scientists did not use the Cassini probe, although they were inspired enough to undertake follow-up studies by Cassini data published in 2007 that showed signs of vinyl cyanide in Titan’s atmosphere.

Much of what we think we know about Titan comes from computational models generated by labs on Earth. Some of the data for these models comes from space-borne observatories like Cassini and powerful telescopes on the ground. The remaining data is predicted by scientists based on what they know about how a a large body like Titan evolves over time. Even in the new study, published in the journal Science Advances on July 28, scientists used telescopes – technically called antennae – part of the Atacama Large Millimetre/submillimetre Array (ALMA), Chile, to infer that there is a certain quantity of vinyl cyanide in Titan’s atmosphere. But as the abstract of their paper continues:

Radiative transfer modeling suggests that most of the C2H3CN emission originates at altitudes of ≳200 km, in agreement with recent photochemical models. The vertical column densities implied by our best-fitting models lie in the range of 3.7 × 1013 to 1.4 × 1014 cm−2. The corresponding production rate of vinyl cyanide and its saturation mole fraction imply the availability of sufficient dissolved material to form ~107 cell membranes/cm3 in Titan’s sea Ligeia Mare.

The presence of vinyl cyanide itself does not indicate that cell membranes will be formed with it. Instead, this thesis is based on a study published in 2015, which said that the integrity of cell membranes forming in cold methane lakes – like the ones on Titan – would depend on certain electrochemical properties of molecules of nitrogen. The study’s authors referred to such membranes as ‘azotosomes’ – akin to the liposomevesicles that make up all cell membranes on Earth. And the new study’s authors surmise that vinyl cyanide is one such molecule of nitrogen that could lead to the formation of azotosomes (‘azote’ is the French name for nitrogen).


Image: What ALMA saw. The blue ring is Titan; the vertical dot-dashed blue line is the polar axis and the dashed white line represents Titan’s equator. The colour intensity denotes the flux density of the vinyl cyanide emission. Source: Palmer et al., Sci. Adv. 2017;3: e1700022

Another feature of the study that provides wonderful insight into how Titan ‘works’ is where the vinyl cyanide forms. The scientists used a photochemical model to determine this using data obtained by Cassini and ALMA, and figured the substance was forming at least 200 km above Titan’s surface, in the reaction:

CN + C2H4 → C2H3CN + H
(cyanide ion + ethylene → vinyl cyanide + hydrogen)

At a lower altitude (~100 km), their models also predicted that vinyl cyanide was forming in much lower quantities by the reaction:

HCN + C2H3 → C2H3CN + H
(Hydrogen cyanide + vinyl radical → vinyl cyanide + hydrogen)

From there, it is carried in a steady stream by “a rain of haze particles” to the surface. This isn’t new: Titan is the only body in the Solar System, apart from Earth, known to have a fully functional counterpart of our water cycle; there, it is a methane cycle. To obtain all this data, scientists used ALMA to record 11 observations of Titan as the moon transited the antennae’s gaze between February and May 2014, when it was between 8.9 and 9.7 AU (1.3 and 1.4 billion km) away.

Ah, Titan.

+This assessment excludes questions arising from the possibility that there is an ocean of liquid water and ammonia some 55-80 km below Titan’s surface.

Quasiparticles: A useful perspective

Recently, an international team of researchers claimed that it had discovered particles called Majorana fermions in a topological superconductor. The international press went gaga but, unfortunately, there wasn’t much discussion on whether what had been found was a particle or a quasiparticle. Many news outlets assumed that they were one and the same – but they’re really not. One physicist even thinks that the quasiparticle that was found in the superconductor could’ve been of synthetic origin, not natural. I asked condensed-matter physicist Vijay Shenoy, whose lab at IISc has been doing some great work on topological materials, about this. His replies are presented in full below.

Can all quasiparticles be treated as particles?

VS: The idea of a ‘quasiparticle’ is a very subtle one. At the risk of being technical, let me try this:

An excitation is called a particle if, for a given momentum of the excitation, there is a well-defined energy. Quite remarkably, this definition of a particle embodies what we conventionally think of as a particle: small hard things that move about.

Now, to an example. Consider a system made of atoms at a very low density. It will be in a gaseous state. Due to their kinetic energy, the atoms will be freely moving about. Such a system has particle-like excitations. These particle-like excitations correspond to the behaviour of individual atoms.

Now consider the system at a higher density. The atoms will be strongly interacting with each other and, therefore, make up a solid. You will never “see” these atoms as low-energy excitations. There will now be new type of excitations that are made of the collective motion of atoms and which will be particle-like (since there is a well-defined energy for a given momentum). These particle-like excitations are called phonons. Note that the phonon excitation is very different from the atom that makes up the solid. For example, phonons carry sound within a solid – but when the sound propagates, you don’t have atoms being carried from place to place!

A ‘quasiparticle’ excitation is one that is very nearly a particle-like excitation: for the given momentum, it is a small spread of energy about some average value. The manifestation is such that, for practical purposes, if you watch this excitation over longer durations, it will behave like a particle in an experiment…

Other examples: neutrons and protons are particle-like excitations of the quark-gluon system!

If I find a quasiparticle with certain unique properties, can I also be sure that I will also be able to find a particle with the same properties?

VS: I assume by “find a particle” you mean like a ‘fundamental particle’. I know examples where this is (as far as we know) not true. For example, the 1/3-filled Landau level has Laughlin quasiparticles that have a charge 1/3rd that of an electron! Other filling factors will have excitations with other fractional charges. We do not know any fundamental particle that could have these properties.

Actually, the idea of a ‘fundamental particle’ is itself not a very useful concept in physics. Something may look fundamental to us at scales of energies that are accessible to us – but if we probe at higher energy scales, we may see that it is also made up of other even more fundamental things (neutrons/protons are really quarks held together by gluons). We will then say that the original ‘fundamental particle’ is a quasiparticle excitation of the system of ‘even more fundamental things’! You could actually ask where this will end, at what energy scales… We really do not know the answer to this question. This is why the concept of a ‘fundamental particle’ is not a very useful concept in physics.

Not for me a distinction between opinions and reportage

(Note: There’s some text beyond the postscript at the bottom.)

A recent discussion with some of my peers alerted me to a need I’ve either been deaf to or just don’t buy: readers, at least some of them, prefer to be presented with a clear distinction between opinion and reported pieces on a news website. Now, I’m not sure how anyone can draw a clear line between these two kinds of pieces. Even in a news report, there is a subjective choice being made by the reporter in her choice of interviewees, sources, topics, etc. And in many areas of media coverage – both geographically (India, US, Europe, etc.) and topically (politics, finance, science, etc.) – these choices have to be made very carefully because even a small misstep can land the report on the wrong side of the political spectrum. You, its author, will at least be branded “insensitive” etc.

Hell, even when I’m writing about topological phases of matter, I consider it a matter of opinion when I choose to speak about the Indian context or not, when I choose to highlight practical applications or not.

To me, everything is contested, to the point that there no longer seems to be any point in making a distinction between opinion and reportage if my opinion is going to be just my voice in my piece and my reportage is going to be just my choice of voices in my piece. A more important, and more meaningful, declaration to make would be that of my own PoV. That is, for me to tell the reader that I, Vasudevan Mukunth, am on the political Left more than half the time, that I believe we shouldn’t always talk about the applications of research because I think that debases the ‘wonder’ and ‘curiosity’ aspects of science+, that in fact I don’t think there is an opinion-neutral position when it comes to covering certain topics, e.g. GM foods, etc.

By not making a distinction between opinion and reportage, I believe the reader will also be forced to consider each piece more seriously. Instead of declaring upfront that a following piece is an oped, it would be better to follow certain rules of writing that allow an uninitiated reader to separate facts from opinions. I say this based on two assumptions, the second more important than the first:

  1. Facts are immutable
  2. The reader should know better

By the latter, I mean that the reader should question everything she reads, learn only to trust a few well-defined sources, and understand overall that the presumption of there being a single truth regarding anything in this world is a myth. This is true even in science – or should I say more so in science, thanks to there being more at stake when scientists promise a single truth to an audience that usually doesn’t know better. To me, the act of conveying the news stopped being stripped of opinions at least three years ago. And to others – wanting to have a caution of some sort that a piece contains opinions is in some sense a confession that you think news reports are otherwise not opinionated. That’s disappointing.

TL;DR: A label like ‘opinion’ is only a horse-blinder.

+In a developed nation with higher levels of social security, spending on blue sky research is, from the vantage point of a populist, more “forgivable” than it is to her counterpart in a developing nation, where the level of social security is lower. Would this not affect how we choose to portray the purpose of scientific research in the mainstream media?

Update (three hours later):

A counterpoint, courtesy myself: Isn’t there some value in targeting a reader who wantsto read a piece of a certain type (e.g. one that can be classified as “reportage” over one that can be classified as “opinion) – and therefore in labelling a piece as “reportage” or “opinion”?

This is likely because the reportage/opinion distinction still exists in most readers’ minds, at least in the form of a bimodal distribution. One mode represents the sort of piece that has only one voice and few references; the other mode represents the sort of piece that has multiple voices, multiple references or both. And getting rid of this modality will be difficult, a major reason being that time is limited. Readers only want to spend a certain fraction of their day reading something, and in that time, publishers would like the readers to be able to find the pieces they want. So in order to improve their content’s discoverability, editors have to consider branding it “reportage”, “opinion” or whatever.

(And this in turn will lead to a self-fulfilling retrenchment of the “reportage”/”opinion” modality in the readers’ minds.)

Featured image credit: Schmid-Reportagen/pixabay.

Of armchair critics, journalists and sportspersons

You remember the criticism that former Indian men’s ODI cricket captain M.S. Dhoni received when a member of the press, Sam Ferris, asked him a question about his retirement during a presser, got invited to the front by the sportsman and got snubbed in front of everyone? Shortly after, Arun Venugopal wrote an open letter to Dhoni on ESPN Cricinfo:

At worst it was a clichéd question – if it makes you feel better the media gets clichéd answers all the time – but not one that deserved the patronising response it got. All it needed was a straightforward answer – “I don’t have plans to retire yet”, or “I will make it public when I plan to”, or even a “no comment,” if you really didn’t wish to answer it. You probably expected an Indian journalist to ask the question, because you trotted out the response anyway.

I don’t speak on behalf of all the journalists; I speak merely as one of many. You are free to ascribe any intent to any question, but our job is about seeking answers and reporting on them just as yours is playing cricket. Some would accuse us journalists of taking ourselves too seriously. I am all for taking the mickey, pulling a leg or two – just so long as mutual respect and professionalism is a two-way street.

§

Now, I grant you that playing tennis can be physically excruciating, that almost nobody likes getting unsolicited advice, that Wimbledon’s strict dress code for playing women is stupid and that hecklers are jerks.

But tell my why, it’s different from what Dhoni did – or even hilarious, as The West Australian claims – when another sportsperson, Kim Clijsters at Wimbledon, invites a critic from the stands to show him why he can’t play tennis and that that disqualifies him from offering suggestions from his seat. I say it’s worse, too, to make a point about some in-game strategy against a monumentally weaker opponent as well as to state that suggestions are not welcome, and that if they still seem forthcoming, they will be turned into jokes at the makers’ expense.

Does this mean journalists or critics can run their mouths against sportspersons? Absolutely not: they must recognise that the people on the field are trying to do their best and that no one’s trying to be lazy or a fool. However, the compact doesn’t end here: sportspersons must also recognise that not all journalists or apparent bystanders are fools or trolls. If they’re asking questions or making suggestions that the sportsperson disagrees with, then they can be asked to pipe down (if that’s appropriate), be told that the question/suggestion is meaningless or ignore it entirely.

“Ignore it entirely?! You think that’s easy?!” Of course not, but that doesn’t excuse you when you don’t do it; in fact, by all means, ask for brownie points that you held your composure and answered levelheadedly.

There is something to be said against criticism that does not emerge from lived experience – but it does not apply all the time, especially in situations that have acquired a diverse set of nuances. Not all pursuits are founded on physical labour. This is why armchair critics are not always privileged or in the wrong – and this is why you can’t always score an argumentative point by pointing out that one is an armchair critic. An extreme example: Much as some sportspersons might like to decry or even deny, the outcomes of some games can be predicted using techniques that ignore individual choices and rely instead on statistical possibilities that emerge from macroscopic analyses. This is why you have strategists who may themselves be lousy at playing a game but are quite good at predicting how it will evolve. You’ve watched/read Moneyball, you know what I’m talking about.

Finally, Clijsters was doubly wrong to have invited over that man in the stands onto the court, squeezed him into an outfit many sizes smaller and played against him. Irrespective of the validity of his suggestion, Clijsters turned him into a joke. I only applaud him for having been a sport about it, and not Clijsters because what she did was immature. I’m not sure if that man’s suggestion – something about playing a “body serve” – was valid but the question asked by Ferris was both politely phrased and perfectly valid. Neither non-participant deserved what they got – from the sportspersons, the media at large and from a majority of the video’s consumers.

The remembering of Maryam Mirzakhani

Four p.m. I was blinking out of my afternoon siesta and scrolling down my Twitter feed catching up on whatever I’d missed when an RT by Thony Christie caught me quite by surprise: “Mathematics genius Maryam Mirzakhani has passed away”. It really jolted me out of my reverie. I vaguely remembered her fair, soft face, a pair of blue eyes, from an image in the news from two, maybe three years ago.

Words from a Quanta profile flashed in my mind, another by The Guardian about her wanting to become a writer… Yet another by someone else more obscure about the significance of the moment. A woman had won the Fields Medal! Were we celebrating or ruing the fact that it had taken, what, eight decades? And then I felt that twinge of shame I – we? – have become so good at ignoring: how many Indian women mathematicians did I know? And how many mathematicians did I – again, we? – know outside of the rosters of various prizes?


What caught me by surprise was the outpouring of grief – by people I met over the course of the evening, by people on Facebook and Twitter, by people I never knew knew about Maryam Mirzakhani or any of her work. But they did, showing up as if crawling out of the woodwork. They knew her as a brilliant young mathematician. They spoke of her as an inspiration for millions of girls and even more mathematicians besides. They collectively called her loss tragic, shared articles and anecdotes, and revealed what little joy they had tucked away in August 2014.

In a sense, the experience was an affirmation that even if the world moved on, if readers and listeners seemed to not care as much when Mirzakhani won the Fields Medal, they would remember. It was as if people were looking out, noticing some souls out of the corner of their eyes, lodging their names in some corner of their memories, not airing them too much but preserving them, remembering, and mourning when they pass on.

RIP, Maryam.

Featured image credit: Stanford University.

Goopy junk

Gwyneth Paltrow’s goop, a wellness brand that has recently come under fire for advertising almost-certainly pseudoscientific “lifestyle” products like $66 jade eggs for women to insert into their vaginas to strengthen their pelvic floors, put up three notes in their defence: two by doctors and one by ‘Team goop’. The ‘Team goop’ note was the usual defence of pseudoscience that we’re all familiar with: that they’re keeping an open mind and seeking autonomous control over their bodies while remaining blissfully deaf to how this diverts the limited resources of many misinformed people who are desperately seeking solutions to health problems away from legitimate, and more reliable, solutions as well as to the capitalist overtones of their beliefs, an irony given Paltrow & co. insist the alternating modes they’re parroting are “Eastern traditions”.

Some of the coverage that goop receives suggests that women are lemmings, ready to jump off a cliff whenever one of our doctors discusses checking for EBV, or Candida, or low levels of vitamin D—or, heaven forbid, take a walk barefoot. As women, we chafe at the idea that we are not intelligent enough to read something and take what serves us, and leave what does not. We simply want information; we want autonomy over our health. That’s why we do unfiltered Q&As, so you can hear directly from doctors; we see no reason to interpret or influence what they’re saying, to tell you what to think.

And speaking of doctors, we are drawn to physicians who are interested in both Western and Eastern modalities and incorporate the best from both, as they generally believe that while traditional medicine can be really good at saving lives, functional medicine is more adept at tackling issues that are chronic. These are the doctors we regularly feature on goop: doctors who publish in peer-reviewed journals; doctors who trained at the best institutions; doctors who are repeatedly at the forefront of medicine; doctors who persistently and aggressively maintain an open mind. The thing about science and medicine is that it evolves all the time. Studies and beliefs that we held sacred even in the last decade have since been proven to be unequivocally false, and sometimes even harmful. Meanwhile, other advances in science and medicine continue to change and save lives. It is not a perfect system; it is a human system.

(The part in bold – not sure where that dichotomy comes from.)

In fact, the jade eggs are less problematic than goop’s other misdemeanours, such as advertising “healing stickers” that goop said was backed by NASA tech – and which NASA called BS on. It’s bad enough that an org with goop’s clout and money is going to market snake oil but it’s worse if it’s going to bill itself as a marketplace for all snake-oil vendors. Anyway, goop’s principal target in their tirade was Jen Gunter, an articulate doctor with a blog, a peculiar choice given the brand and Paltrow have both come under worse fire by major news outlets with millions of social media followers. Good job picking on the small people. And late last evening (or early this morning IST), Gunter published the post everyone was waiting for:

Regarding Aviva Room [doctor #2] I have frankly never heard of her, but she appears to be a vaccine skeptic so there’s that. Dr. Steven Gundry [doctor #1], however, is a special kind of patriarchal prick. I have devoted one sentence in my writing career to his pet project lectins and somehow this earned me a proper mansplaining about both potty mouth and evidence based medicine. Dr. Gundry even wants me to know he is pals with Dr. Oz (that is where I burst out laughing on the train), yes, he brags about being associated with the same Dr. Oz who was scolded by a Senate panel for abusing his national platform to push snake oil. …

To GOOP I say medicine is not subjective. There are facts and biological plausibility. Of course there are unknowns, but not in the way you present it. For example it is fact that sea sponges contain dirt and are completely untested for menstruation. It is highly biologically plausible that sea sponges could have a significant risk of toxic shock syndrome as they may be more absorbent than tampons, may introduce more oxygen than tampons, and be impossible to clean in a way that removes the toxic shock syndrome toxin or even staph aureus. If you disagree with this information it doesn’t mean you have a different opinion, it means you are choosing to be uninformed or the potential risk of being uninformed matters less to you. Subjective would be preferring tampons with a plastic applicator over a cardboard one.

To use a phrase coined by Tim Caulfield, a health law and policy professor at the University of Alberta, it seems the tragedies that “science-free celebrities” perpetrate usually centre around believing that there’s more than one way to interpret what constitutes scientific evidence, taking the suspicion of Western medicine to another level while assuming it has had no successes, taking feminism to mean anything that’s pro-women while ignoring the need to empower women, and wearing the traditionalism of Eastern medicine as a cloak to hide from not being able to produce scientific evidence.

Featured image credit: YouTube.

The photon that wasn't teleported

Last month, Chinese researchers announced that they had performed two amazing feats. First, they had performed an experiment recreating the spooky phenomenon called quantum entanglement. To borrow a clunky but sufficient explanation from the MIT Tech Review article tweeted above:

[Entanglement] occurs when two quantum objects, such as photons, form at the same instant and point in space and so share the same existence. In technical terms, they are described by the same wave function. The curious thing about entanglement is that this shared existence continues even when the photons are separated by vast distances. So a measurement on one immediately influences the state of the other, regardless of the distance between them.

While the phenomenon has been demonstrated in (not-large) labs around the world, the Chinese launched a satellite adept at receiving and measuring the properties of photons, and then created pairs of entangled particles from the ground and fired one half of them to the satellite. When they measured the properties of one of these photons, the other photon also changed accordingly. Effectively, they’d realised entanglement over more than 500 km.

The second feat they performed was to generate some information – and not just bland photons – and instantaneously access that information through the use of entangled photons across large distances. This feat made for the first proper precursor to an information transfer system protected by quantum cryptography, which isn’t susceptible to conventional means of hacking because there is no information flow, just instantaneous information access at the two endpoints of a channel.

Now, while both experiments were great, neither the Tech Review article nor BBC article got it completely right. Both their headlines speak of an object having been teleported; this is wrong. No objects were teleported but information was, and this is a crucial difference because the advent of quantum entanglement has not changed what it means to be teleported. In the continuing regular use of the word, teleportation requires the selfsame object to disappear, or disintegrate, at one point and reappear at another instantaneously. It is the travel of the object through a large distance in space but almost no distance in time. The Chinese photons did not do this. The information contained by them did.

Two afterthoughts:

  1. Would acknowledging this difference have made for a less “sexy” headline? E.g., Information teleported to Earth’s orbit. I don’t think so. I think it sounds just as cool because teleportation is always cool.
  2. If you’re thinking the headlines might just be admissible because you subscribe to the physicist John Wheeler’s idea that “everything is information”, you’re wrong. Relevant bit:

… as the physicist Rolf Landauer liked to say, all information is physical – that is, all information is embodied in physical things or processes – but that doesn’t mean that all things physical are reducible to information. The concept of information makes no sense in the absence of something to be informed – that is, a conscious observer capable of choice, or free will.

Featured image credit: skeeze/pixabay.

Maintaining cabin pressure

Call me nitpicky or misguided but, as silly as this WhatsApp message sounds…

 

… how many people stop to check how cabin pressure really works? Clearly the message is wrong but where does our impression that “it’s wrong” come from? Does it come from the fact that

  1. it’s an unqualified WhatsApp forward?
  2. its author appears to be a ‘bhakt’?
  3. our experience travelling on flights seems so very at odds with what’s being described?, or
  4. one knowing how cabin pressure is maintained on aircrafts?

I think it’s a combination of the first three, and the third one more so, and I admit I’m quite cynical that it’s the fourth one. This isn’t an accusation that some people don’t know that air comes in from somewhere and leaves from elsewhere, and that there’s a pump that regulates this – but more a suspicion that, to the same people, the “somewhere” and the “elsewhere” might be irrelevant parts of the explanation.

Consider the following. There are two possible kinds of rebuttals to the WhatsApp message. First, the intuitive, and possibly experiential, kind that contrasts the great – and anecdotal – complexity of keeping an aircraft airborne and the almost abject mundanity of the drag caused by flatulent passengers. Second, the more technical kind that describes how an aircraft works with an engineer’s rectitude and, on occasion, authority. The first kind is a recourse to faith; the second is a recourse to knowledge. My contention is that the first kind (also as an encapsulation of the first three reasons from above) excuses us from dealing with the science and the engineering in a way that imposes some cognitive stress, which the second kind does.

When you receive such a WhatsApp message, the point is to disqualify it through the most effective means possible; from the outset, there is no diktat as to how it can be achieved (even if I’d disagree on principle), there is a preference for the faith-based mode of reasoning over the knowledge-based mode of reasoning. And over time, this preference builds tendency, which builds into bias through ignorance.

“What’s the point of learning the science?” Learning how cabin pressure is maintained (see below) isn’t going to help you in any way (unless your work has something to do with it) – but it is the lowest epistemological substrate upon which all faith-based reasoning on the topic can be founded. This isn’t to indemnify science against its many flaws as much as to suggest that without the foundation of knowledge-based reasoning, faith-based reasoning turns meaningless, and that the other way will never come to be. So why not begin with an awareness of the engineering behind maintaining cabin pressure so we remain forever sure about the provenance of our faith in it, at least?


Maintaining cabin pressure

The “somewhere” that the air comes into the cabin is first sucked in from the atmosphere by ‘taps’ installed on jet-engine compressors. They are then processed for humans by modifying their humidity and temperature using air-cycle machines, and fed into the fuselage. The “elsewhere” that air leaves the fuselage from is the set of outflow valves at the rear end of the aircraft. The air-cycle machines work constantly while the outflow valves regulate pressure within the cabin by opening and shutting accordingly.

When more air is let out than what’s coming in, the cabin will depressurise, and vice versa. This is because the ratio of cabin pressure to the aircraft’s ambient pressure is allowed to vary within only a certain range (and not too drastically when it does) as well as because the cabin itself will have been designed to be able to withstand a maximum pressure. The outflow valves are controlled by a computer.

Featured image credit: LittleVisuals/pixabay.

Why Titan is awesome #8

Editions onetwothreefourfivesix and seven.

A new study has used radar data obtained by the Cassini probe to determine that the winds blowing on Saturn’s moon Titan aren’t that strong. This is because waves on the surface of the three largest lakes near the moon’s north pole probably aren’t that high, at least in the “early summer”. The lakes are Kraken Mare, Ligeia Mare and Punga Mare. A University of Texas press release accompanying the paper has extrapolated its findings to suggest that future probes to the moon’s surface will be “in for a smooth landing”. (This is probably why Gizmodo has a weird headline for its piece discussing this work: Saturn’s Moon Titan May Have the Perfect Landing Spot For Spacecraft. I’m not sure how a study about the entire surface area of three of the largest Titanic lakes leads to talk about a tiny landing spot for a single mare explorer, but sure. PTI also, btw.)

These findings aren’t exactly pioneering. In 2008, scientists used Cassini radar data to measure the height of waves on Ontario Lacus, a lake near Titan’s south pole. In 2011, the probe was used to analyse the surfaces of Kraken Mare, one of the three lakes considered in the new study, and Jingpo Lacus (both near the north pole). In 2013, a fresh set of Cassini readings were used to study the surface of Ligeia Mare – yet another of the three lakes featured in the new study. And the new study confirms what we’ve known for the last ~decade or so: the waves on the moon’s supercold liquid-methane bodies don’t rise up by more than a few centimetres. About 1 cm, according to one reading, with the wave itself being about 20 cm long.

The real bit of novelty was two things. First, the use of a technique developed in a 2012 to determine surface roughness, called radar statistical reconnaissance (RSR), incidentally by the same person listed as the first author: a UTexas research associate named Cyril Grima (no offence to him but his name keeps making me imagine he looks like Brad Dourif). RSR uses a set of mathematical techniques to analyse the coherence, and incoherence, of radar waves reflected by rough surfaces. It was among the suite of techniques used decide a landing spot for the NASA InSight lander to be launched in May 2018. The second bit of novelty in the new study is the conclusion that the early summer period in Titan’s northern hemisphere cannot be as windy as it has been believed or the waves would be much bigger.

However, there are some caveats, as usual ignored by most media reports. The first giveaway is that RSR is a statistical technique and, sure enough, towards the end of the paper, its authors write (with ref to the image immediately below):

Credit: Earth and Planetary Science Letters
Credit: Earth and Planetary Science Letters

If smaller patches of higher roughness should occur within those tracks [shown in colour], they might not produce enough surface echoes to significantly change the trend of the amplitude distributions, making them invisible through the RSR process. In the best case, two regions with different but equally-dominant scattering regimes might produce a bi-modal distribution that is not obvious on our measurements. Hence, quiet sea surfaces might be a dominant trend during the northern early summer, but fields of waves activity might occur over local patches and/or might not be sustained over significant periods of time.

(Emphasis added.) This I think could turn the Gizmodo-type (and similar) headlines on their heads, to: “The surfaces of Titan’s lakes are usually calm – but a freak wave could sink NASA’s fancy probe.” But to be realistic, and taking a cue from the InSight paper, figuring out the perfect landing spot for a mare explorer will take a lot more analysis, especially since Cassini is going to be out of commission pretty soon. The Grima et al study is set to be published in the September 15 edition of the journal Earth and Planetary Science Letters.

TITAAAAN!