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Imagine youre a copper miner in southeastern Europe in the year 3900 BCE. Day after day you haul copper ore through the mines sweltering tunnels. Youve resigned yourself to the grueling monotony of mining life. Then one afternoon, you witness a fellow worker doing something remarkable. With an odd-looking contraption, he casually transports the equivalent of three times his body weight on a single trip. As he returns to the mine to fetch another load, it suddenly dawns on you that your chosen profession is about to get far less taxing and much more lucrative. What you dont realize: Youre witnessing something that will change the course of historynot just for your tiny mining community, but for all of humanity. Despite the wheels immeasurable impact, no one is certain as to who invented it, or when and where it was first conceived. The hypothetical scenario described above is based on a 2015 theory that miners in the Carpathian Mountains (now Hungary) first invented the wheel nearly 6,000 years ago as a means to transport copper ore. The theory is supported by the discovery of more than 150 miniaturized wagons by archaeologists working in the region. These pint-size, four-wheeled models were made from clay, and their outer surfaces were engraved with a wickerwork pattern reminiscent of the basketry used by mining communities at the time. Carbon dating later revealed that these wagons are the earliest known depictions of wheeled transport to date. This theory also raises a question of particular interest to me, an aerospace engineer who studies the science of engineering design. How did an obscure, scientifically naive mining society discover the wheel, when highly advanced civilizations, such as the ancient Egyptians, did not? A controversial idea It has long been assumed that wheels evolved from simple wooden rollers. But until recently no one could explain how or why this transformation took place. Whats more, beginning in the 1960s, some researchers started to express strong doubts about the roller-to-wheel theory. Evolution of the wheel-and-axle system. (a) Frictionless bilateral rolling with two spent rollers shown on the left of the image, (b) unilateral rolling with grooved rollers held in place by semi-circular sockets, and blue arrows indicating sliding at the friction surface, (c) a wheelset with two spokeless wheels fixed to the ends of a slender axle forming a monolithic structure and (d) a partially assembled multi-body wheel-and-axle system in which the wheels rotate independently of the axle. [Image: Kai James] After all, for rollers to be useful, they require flat, firm terrain and a path free of inclines and sharp curves. Furthermore, once the cart passes them, used rollers need to be continually brought around to the front of the line to keep the cargo moving. For all these reasons, the ancient world used rollers sparingly. According to the skeptics, rollers were too rare and too impractical to have been the starting point for the evolution of the wheel. But a minewith its enclosed, human-made passagewayswould have provided favorable conditions for rollers. This factor, among others, compelled my team to revisit the roller hypothesis. A turning point The transition from rollers to wheels requires two key innovations. The first is a modification of the cart that carries the cargo. The carts base must be outfitted with semicircular sockets, which hold the rollers in place. This way, as the operator pulls the cart, the rollers are pulled along with it. This innovation may have been motivated by the confined nature of the mine environment, where having to periodically carry used rollers back around to the front of the cart would have been especially onerous. The discovery of socketed rollers represented a turning point in the evolution of the wheel and paved the way for the second and most important innovation. This next step involved a change to the rollers themselves. To understand how and why this change occurred, we turned to physics and computer-aided engineering. Simulating the wheels evolution To begin our investigation, we created a computer program designed to simulate the evolution from a roller to a wheel. Our hypothesis was that this transformation was driven by a phenomenon called mechanical advantage. This same principle allows pliers to amplify a users grip strength by providing added leverage. Similarly, if we could modify the shape of the roller to generate mechanical advantage, this would amplify the users pushing force, making it easier to advance the cart. Our algorithm worked by modeling hundreds of potential roller shapes and evaluating how each one performed, both in terms of mechanical advantage and structural strength. The latter was used to determine whether a given roller would break under the weight of the cargo. As predicted, the algorithm ultimately converged upon the familiar wheel-and-axle shape, which it determined to be optimal. During the execution of the algorithm, each new design performed slightly better than its predecessor. We believe a similar evolutionary process played out with the miners 6,000 years ago. Progression of the wheelset design during execution of the topology optimization algorithm. The iteration numbers are given in the bottom left corner of each image. [Image: Kai James] It is unclear what initially prompted the miners to explore alternative roller shapes. One possibility is that friction at the roller-socket interface caused the surrounding wood to wear away, leading to a slight narrowing of the roller at the point of contact. Another theory is that the miners began thinning out the rollers so that their carts could pass over small obstructions on the ground. Either way, thanks to mechanical advantage, this narrowing of the axle region made the carts easier to push. As time passed, better-performing designs were repeatedly favored over the others, and new rollers were crafted to mimic these top performers. Consequently, the rollers became more and more narrow, until all that remained was a slender bar capped on both ends by large discs. This rudimentary structure marks the birth of what we now refer to as the wheel. According to our theory, there was no precise moment at which the wheel was invented. Rather, just like the evolution of species, the wheel emerged gradually from an accumulation of small improvements. This is just one of the many chapters in the wheels long and ongoing evolution. More than 5,000 years after the contributions of the Carpathian miners, a Parisian bicycle mechanic invented radial ball bearings, which once again revolutionized wheeled transportation. Ironically, ball bearings are conceptually identical to rollers, the wheels evolutionary precursor. Ball bearings form a ring around the axle, creating a rolling interface between the axle and the wheel hub, thereby circumventing friction. With this innovation, the evolution of the wheel came full circle. This example also shows how the wheels evolution, much like its iconic shape, traces a circuitous pathone with no clear beginning, no end, and countless quiet revolutions along the way. Kai James is a professor of aerospace engineering at the Georgia Institute of Technology. This article is republished from The Conversation under a Creative Commons license. Read the original article.
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You arent alone; according to a recent survey, more than two-thirds of employees said they have to deal with rude coworkers, bosses, or clients.
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Two different groups of Americans are expected to march through the streets today. As thousands of troops march and dozens of tanks roll through Washington, D.C., for a military parade celebrating the Armys 250th anniversary on President Donald Trumps 79th birthday, millions of Americans nationwide are expected to protest against his administration, in what organizers believe will be the largest turnout yet since Trump took office in January for a second term. Here’s what to know about the No Kings Day protests: Why are people protesting? The No Kings Day protest movement builds on this spring’s massive May Day and Hands Off! rallies. They come after days of nationwide demonstrations against controversial federal immigration raids and deportations in Los Angeles and a number of other U.S. cities, which are part of the Trump administration’s ramped-up enforcement efforts. How big will the rallies be and where will they take place? Organizers expect 2,000 rallies to take place on Saturday in all 50 states and most major cities, from city blocks to small towns, from courthouse steps to community parks.” Protesters say they are “taking action to reject authoritarianismand show the world what democracy really looks like.” To avoid clashes with the Armys anniversary celebrations, protest gatherings will bypass the nation’s capital. (Trump has threatened to use “heavy force” against any protesters at the parade, comments the White House later attempted to clarify by asserting that the president supports “peaceful” protests.) The No Kings groups have created an extensive interactive map that includes the protest locations and times. The map is embedded on the No Kings website and is searchable by zip code. Who is behind the protest movement? Indivisible is the lead organizer of Saturday’s No Kings protests, along with a broad coalition of 180-plus partner organizations, including the American Civil Liberties Union, Common Cause, Greenpeace, Physicians for Social Responsibility, and Standing Up for Science. A number of labor unions, including the Communication Workers of America and teacher federations, are also involved in the effort. Who will be speaking? The group 50501, another organizer of the protests, told Fast Company that some of the major speakers planned nationwide include former Democratic VP candidate Minnesota Governor Tim Walz, in St. Paul; Martin Luther King Jr.’s son, Martin Luther King III, and his wife, Arndrea Waters King, in Philadelphia; No Kings Indivisible’s Leah Greenberg and Ezra Levin, also in Philadelphia; Democratic Representative Rashida Tlaib in Detroit; former Republican Representative Joe Walsh (who became a registered Democrat last week) in Charleston; and progressive political commentator Brian Tyler Cohen in downtown Los Angeles. What else is there to know? In addition to rallies around the U.S., protests are also expected in several other countries, including the U.K., Mexico, and Germany.
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