Learning the difference between trekking poles and Nordic walking poles

I didn’t know the difference, but as I read more, it’s clear that what I will want are Nordic walking poles rather than trekking poles. (I’m a city walker, not a back-country or trail hiker.) The video below is from this post.

See also “Nordic Walking Poles vs. Trekking Poles: What’s the Difference?“

Triple-Star Test Shows Einstein Was Right, Again

General relativity, like quantum mechanics, has passed every test thrown at it. Too bad we still can’t combine the two. James Geach reports in Scientific American:

It may not be intuitive, but drop a hammer and a feather and—in the absence of air resistance—they will hit the ground at exactly the same time. This is a key principle of physics known as “universal free fall”, stating that all objects accelerate identically in the same gravitational field. In fact, it’s an important theme in Albert Einstein’s immensely successful theory of general relativity, which describes how gravity works.

But although we know it holds true for hammers and feathers, it’s been unclear whether the principle extends to extreme objects such as stars. Now a new study, published in Nature, has tested the principle using a remarkably extreme astrophysical environment: a triple star system containing two white dwarfs and a pulsar (a rotating neutron star that beams radio waves). These objects are the extremely dense remnants of dead stars.

Spoiler alert: It turns out Einstein is still right, and it is getting even harder to prove him wrong.

But let’s start with the basics. Hold an object in your hand. It doesn’t matter what it is—the object will have some mass. We can think of that mass in two ways. Isaac Newton taught us that if we apply a force to a body it will undergo an acceleration, and the size of that acceleration is directly proportional to the amount of force applied—and inversely proportional to the mass itself. Give a broken-down car a push and it won’t accelerate very quickly, but apply that same push to a shopping trolley and you’ll send it careering down the aisle. When thinking about the acceleration of an object due to a force exerted on it, we think about the “inertial mass” of the body.

Any two objects with mass are attracted to each other through the gravitational force. So the object you are holding in your hand is attracted to the Earth, and the size of the force pulling it down is dependent on the mass of the object. In this case, we think about the “gravitational mass”.

If you dropped it, the object you are holding would “free fall”—the force of gravity would accelerate it towards the ground. The size of the force pulling the object down depends on the gravitational mass, but the amount of acceleration depends on the inertial mass. But is there any difference between the two types of mass? To find out, we can write down an equation of motion linking the two types of mass: inertial mass on one side of the equation and gravitational mass on the other.

The equation predicts something we can test using an experiment: if inertial mass is equivalent to gravitational mass, then all objects should fall towards the Earth with an identical acceleration regardless of their mass. That often surprises people. This is called the “Equivalence Principle”.

Galileo first noticed that plummeting objects fall at the same rate, and you can do this experiment yourself by simultaneously dropping two objects of different mass. However one problem doing this on Earth is the presence of another force acting on the falling bodies, called air resistance. If you drop a hammer and a feather, the feather will tend to gently drift down to the ground, lagging behind—the objects aren’t strictly in free fall. But go to the moon and do that experiment, as astronaut David Scott did during Apollo 15, where there is no air resistance, and the Equivalence Principle is clear to see.

Now, it has been unclear whether the theory does a good job of describing gravity in all situations. There is a lot at stake—if general relativity breaks down for certain situations then we would need a revised or modified theory of gravity. In particular, scientists have been wondering whether the universality of free fall applies to objects that have strong “self gravity”—a significant gravitational field of their own. Indeed some modified theories of gravity predict that the Equivalence Principle might be violated for strongly self-gravitating bodies in free fall, whereas general relativity says it should be universal.

DANCE OF STARS

Thanks to an extreme laboratory in space—a triple stellar system 4,200 light years away – the new study managed to test this. That name doesn’t do it justice: we’re talking about two white dwarfs and a more massive “millisecond” pulsar (a neutron star rotating about 366 times a second, and beaming radio waves like a lighthouse). One white dwarf and the pulsar are orbiting each other every 1.6 days. In turn they also orbit around the other white dwarf every 327 days.

The pulsar-white dwarf pair can be considered to be in free fall towards the other white dwarf, because an orbit is just the case of free fall without ever reaching the ground, like satellites around the Earth. Of course, the pulsar and white dwarf are very massive objects themselves, with strong self gravity. General relativity predicts that the accelerations of the white dwarf and pulsar, due to being in free fall towards the outer white dwarf, should be identical—despite differences in mass and self-gravity.

Combining observations that span six years of monitoring, the astrophysicists carefully modelled the orbits of the pair. They measured a parameter called Delta, which describes the fractional difference between the acceleration of the white dwarf and the more massive pulsar. If general relativity holds, then Delta should be equal to zero. The results indicate that, within the uncertainties of the measurements, the difference in accelerations is indeed statistically consistent with zero—we can say with 95% confidence that Delta is less than 0.0000026.

This new constraint is far better than anything previously measured. It provides valuable new empirical evidence that general relativity remains our best model of how gravity works, so we are unlikely to need any new or modified theories at this point. This come just weeks after general relativity was proven right on a galactic scale for the first time. . .

Continue reading.

The deep roots of writing

Michael Erard, writer in residence at the Max Planck Institute for Psycholinguistics in Nijmegen in the Netherlands, writes in Aeon:

Recent scholars of the history of writing describe what was first and foremost an administrative tool. According to their ‘administrative hypothesis’, writing was invented so that early states could track people, land and economic production, and elites could sustain their power. Along the way (their argument goes) writing became flexible enough, in how it captured spoken language, to be used for poetry and letters and, eventually, word games such as Mad Libs and fortune cookies.

The writing/state connection sailed out most recently in Against the Grain(2017) by James Scott, a political scientist at Yale whose goal is to overturn the usual story about how civilisation came to be. In his book, he draws from accumulated archaeological findings to show that large sedentary populations and grain agriculture existed long before the first states in both Mesopotamia and China. These operations came to be coopted by rulers, ruling classes and elite interests. The elite didn’t invent agriculture or urban living but fashioned the oft-told narrative giving them credit for these achievements. In his book, Scott assembles a political counter-narrative to up-end their story of progress and show how people were better off when they weren’t subjects.

This counter-narrative needs villains, and writing serves this purpose brilliantly, because it’s the tool of power that makes subjects subjects. ‘The state is a recording, registering, and measuring machine,’ writes Scott – and a coercive machine that makes lists of names, levies taxes, rations food, raises armies, and writes rules. ‘The coincidence of the pristine state and pristine writing,’ he writes, ‘tempts one to the crude functionalist conclusion that would-be state makers invented the forms of notation that were essential to statecraft.’ Without writing, Scott argues, there could be no state – and without the state, there could be no writing. He seems to be saying that everything that humans would come to write – myths, epic poems, love letters, essays, re-assessments of the history of civilisation – was an epiphenomenon of bureaucratic paperwork.

As far as I am concerned, however, the evidence suggests otherwise. I come to this defence of writing as an unabashed partisan of text, a diehard literate in an age pivoting to video – I barely watch television, which marks me as a philistine these days. Every week seems to bring fresh news of a dimmer future for writing, whether it’s thanks to AI-curated, voice-operated information interfaces or in the hopes pinned on emojis as a universal writing system. So after reading Scott’s book I was moved to throw some gravel at the thinking that rolls along this track: if writing is the offspring of accounting and keeps the powerful in power, then let’s unshackle ourselves and return to purity.

Who needs writing, anyway? Seen through the filter of a military analogy, writing might be like nuclear weapons (which were developed specifically by the military), or it might be like gunpowder, which was discovered by alchemists searching for life-prolonging substances hundreds of years before its use in weapons. The question is this: is writing the product of the state in every single stage of its evolution, invented de novo by administrative elites? Or is it composed of pre-existing representational practices that expanded to fill the needs of the state and complex society?

The evidence suggests that writing is actually more like gunpowder than like nuclear weapons. For one thing, in the four wellsprings of writing, it never (as far as we know) sprang forth as fully phonographic but evolved to become that – there’s usually some kind of proto-writing, and some kind of proto-proto-writing. I like to think of writing as a layered invention. First there’s the graphic invention: the notion of making a durable mark on a surface. Humans have been doing this for at least 100,000 years – the bureaucracy didn’t give humans that power. Then the symbolic invention: let’s make this mark different from all other marks and assign it a meaning that we can all agree on. Humans have been doing this for a long time, too. Then there’s the linguistic one: let’s realise that a sound, a syllable and a word are all things in the world that can be assigned a graphic symbol. This invention depends on the previous ones, and itself is made of innovations, realisations, solutions and hacks. Then comes the functional invention: let’s use this set of symbols to write a list of captives’ names, or a contract about feeding workers, or a letter to a distant garrison commander. All these moves belong to an alchemy of life that makes things go boom.

When you consider these layers of invention, you discover that early writing in Mesopotamia, for instance, had no overtly political function, as the archaeologist David Wengrow at University College London argues in What Makes Civilization? (2010). Instead, for the first 300-400 years of early cuneiform texts in the region (from about 3300-2900 BCE), Wengrow sees a bookkeeping function for managing temple-factories of the day. ‘There is hardly any use of writing for what I would view as state-like functions (eg, dynastic monuments, taxation, tribute, narratives of political events) until the Early Dynastic period,’ he told me.

This is an even stronger strike against the administrative hypothesis than it looks, because the counting that was the precursor to writing in Mesopotamia didn’t need the state to develop. In the 1960s, the archaeologist Denise Schmandt-Besserat began studying clay tokens – cylinders, pyramids, discs, balls – thousands of which had been found all over Middle Eastern archaeological sites, though no one had explained what they were. These tokens showed up in Neolithic archaeological sites from 8000 BCE, well before the earliest states emerge in Mesopotamia. Schmandt-Besserat, whom I studied with at the University of Texas at Austin in the early 1990s, argued that the tokens went back 10,000 years. She realised that they were markers for objects: one cone per unit of grain, one diamond per unit of honey, and so forth. At first, tokens that denoted goods and objects were stored in groups; one storage method was sealing them into hollow clay balls. To overcome the obvious drawback that the contents of a sealed envelope can’t be checked, early accountants pressed the tokens into the soft, wet surface of the envelope. By the fourth millennium, scribes realised that the impressed signs made the envelopes redundant – just press the tokens into the clay, or better yet, create written signs that mimicked tokens. Then one more step of abstraction completed the journey: create written signs that capture speech-sounds and word-meanings.

The implications are clear, at least for Mesopotamia. Early states functioned without writing for nearly 3,000 years before the invention of cuneiform because they had the token system for counting. And tokens didn’t need the conditions of the state to develop – they preceded the state by 2,000 years. What we have is counting that precedes complex economic organisation as well as phonetic writing that precedes political functions. Both trajectories undermine the writing/state argument.

The administrative hypothesis lacks evidence in other regions where writing developed, as well. In China, for example, the earliest writing samples, which were divination texts carved into bone and turtle shell, date to approximately 1320 BCE, but archaeologists don’t know whether there was also administrative, propagandistic or literary writing happening at the same time. And they don’t know what preceded the carved word signs, which included names, dates and items of sacrifice, though the confident shape and execution of the characters suggests a well-developed scribal class. That, in turn, points to a complex society. But was this society administered by forms of writing? There’s no evidence that it was.

Further mysteries are posed by writing in Mesoamerica. The most prominent examples are Mayan and Zapotec writing, which date to 300 BCE and 600 BCE respectively. All the existing examples of Mesoamerican writing are engravings on rock or murals; writing on other materials, such as palm leaf, were either lost to decay or destroyed by the Spanish conquerors. Before phonetic writing there was iconography, and early writing itself featured leaders, rulers, prisoner-taking, and conquests. Nothing economic or administrative exists.

Over and over, what we see is that writing is more like gunpowder than like a nuclear bomb. In each of the four sites of the independent invention of writing, there’s either no evidence one way or the other, or there’s evidence that a proto-writing pre-dated the administrative needs of the state. Even in Mesopotamia, a phonetic cuneiform script was used for a few hundred years for accounting before writing was used for overtly political purposes. As far as the reductive argument that accountants invented writing in Mesopotamia, it’s true that writing came from counting, but temple priests get the credit more than accountants do. ‘Priests invented writing’ is a reduction I can live with – it posits writing as a tool for contacting the supernatural realm, recording the movement of spirits, inspecting the inscrutable wishes of divinities.

As it turns out, the popular ‘administrative hypothesis’ has run into headwinds among other scholars too. In the afterword to the essay collection The First Writing (2004), Stephen Houston, an anthropologist at Brown University in Rhode Island, concluded that the administrative hypothesis, though tempting, ‘remains hypothetical’. Fourteen years later, things are unchanged, especially for Mesoamerica, Houston told me in a recent email. ‘The earliest writing we have appears, where we can read it, to be resolutely about kings, gods, ritual activities, fetish objects. There are plausible grounds to think they had cadastrals [listings of land parcels and who owned them] and the like, which appear in early Colonial Mexico. But we just don’t have the direct evidence.’

Other anthropologists, meanwhile, have been looking more closely at historical instances where writing emerges outside of the state – and where states emerge without writing. . .

Continue reading.

US Army reneges on its promise, quietly discharging immigrant recruits

Martha Mendoza and Garance Burke report for AP on the folly of trusting the military:

Some immigrant U.S. Army reservists and recruits who enlisted in the military with a promised path to citizenship are being abruptly discharged, the Associated Press has learned.

The AP was unable to quantify how many men and women who enlisted through the special recruitment program have been booted from the Army, but immigration attorneys say they know of more than 40 who have been discharged or whose status has become questionable, jeopardizing their futures.

“It was my dream to serve in the military,” said reservist Lucas Calixto, a Brazilian immigrant who filed a lawsuit against the Army last week. “Since this country has been so good to me, I thought it was the least I could do to give back to my adopted country and serve in the United States military.”

Some of the service members say they were not told why they were being discharged. Others who pressed for answers said the Army informed them they’d been labeled as security risks because they have relatives abroad or because the Defense Department had not completed background checks on them.

Spokespeople for the Pentagon and the Army said that, due to the pending litigation, they were unable to explain the discharges or respond to questions about whether there have been policy changes in any of the military branches.

Eligible recruits are required to have legal status in the U.S., such as a student visa, before enlisting. More than 5,000 immigrants were recruited into the program in 2016, and an estimated 10,000 are currently serving. Most go the Army, but some also go to the other military branches.

To become citizens, the service members need an honorable service designation, which can come after even just a few days at boot camp. But the recently discharged service members have had their basic training delayed, so they can’t be naturalized.

Margaret Stock, an Alaska-based immigration attorney and a retired Army Reserve lieutenant colonel who helped create the immigrant recruitment program, said she’s been inundated over the past several days by recruits who have been abruptly discharged.

All had signed enlistment contracts and taken an Army oath, Stock said. Many were reservists who had been attending unit drills, receiving pay and undergoing training, while others had been in a “delayed entry” program, she said.

“Immigrants have been serving in the Army since 1775,” Stock said. “We wouldn’t have won the revolution without immigrants. And we’re not going to win the global war on terrorism today without immigrants.” . . .

Continue reading.

It’s weird how the military talks so much about “honor.” I wonder what they mean by it. They obviously do not honor their promises.

An all-RazoRock shave: Italian flag synthetic, Zi’ Peppino, and Baby Smooth

A great shave for Friday: Zi’ Peppino’s green-tobacco fragrance is wonderful, and the lather’s not too shabby, either. The Baby Smooth is one of my favorite razors: what’s not to like.

I got out early for the walk: very cool, very quiet, and I cut a minute off my time from the beginning of the week. I can’t wait to try the trekking sticks. I had a Nordic Track for years and really loved the workout I got, and I think the trekking sticks might be reminiscent of that: arm work incorporated into a leg workout.