Alimentos que devem compor a sua dieta

Publicado em 22/02/2015 por galdinopinto em Alimentação Conheça 8 alimentos que devem compor a sua dieta e a de qualquer pessoa. Existem determinados alimentos que são, de modo implacável, deixados em segundo e terceiro planos quando se pensa em legumes e frutas. Curiosamente, a maioria sequer é conhecida do paladar dos brasileiros. Mas, sempre é bom descobrir novos aromas e se surpreender. Às vezes surge um ingrediente com aparência ou nome estranho, mas mesmo assim vale a pena seguir em frente e experimentá-los, pois todos a seguir são extremamente nutritivos e preciosos sob diversos aspectos. Acompanhe mais detalhas na sequência. A lentilha Muito consumida durante o período de comemorações do fim de ano, a lentilha está longe de ser a preferência nacional. No entanto, não deveria ser assim. As lentilhas mereceriam outro tratamento, já que são fundamentais para o enrijecimento dos músculos, além de conter substâncias que prestam auxílio durante os processos de cicatrização de ferimentos. Por fim, sua relevância também se deve ao fato de ser uma ótima fonte de ferro e fibras. Em virtude de tudo isso, é altamente aconselhável trocar, de vez em quando, o tradicional feijão pela lentilha. A batata doce Há quem goste, mas a grande maioria dispensa a batata doce. Os nutricionistas não negam que em comparação com a dita “batata comum” a versão doce detém uma concentração bem superior de calorias, o dobro para ser exato. Entretanto, eles recomendam o seu consumo devido ao conjunto de elementos que a constituem, tais como o potássio, as fibras e a vitamina C, diferentemente do que é apresentado pela outra batata. O inhame Como possui uma elevada concentração de proteínas, fósforo e potássio, o inhame é um dos alimentos que não podem faltar na lista, pois ajuda a evitar complicações oriundas de cálculos renais, osteoporose e artrite. Esse tubérculo também aparece bastante em massas, pães e cereais. Isso se torna possível porque ele é muito rico em fibras e carboidratos. Para obter todos esses nutrientes da forma correta, o melhor é consumir o inhame após ele passar por cozimento. Contudo, os nutricionistas avisam que eles não devem permanecer por muito tempo sob ação do fogo, pois isso favorece a perda de suas principais propriedades. O rabanete Por ser uma ótima fonte de diversos nutrientes, tais como fósforo, potássio, cálcio e magnésio, esse legume concede força extra ao sistema imunológico, melhora o trânsito do sistema respiratório e ainda aperfeiçoa as funções executadas dentro do aparelho digestivo. A nêspera O nome exótico costuma produzir caretas quando é pronunciado. Entretanto, trata-se da popular ameixa amarela, uma fruta que contém elevada concentração de cálcio, sais minerais, fósforo e vitamina C. Além de prestar uma valiosa colaboração para se evitar o desenvolvimento do diabetes, a nêspera também atua diretamente sobre as vias respiratórias, contribuindo para uma sensível melhora nos quadros de sinusite, asma, rinite e até bronquite. Esse efeito ocorre em razão de uma substância chamada triterpenos, capaz de sintetizar óxido nítrico. A beterraba Já esse legume não é tão raro assim na mesa dos brasileiros, pois possui muitos apreciadores. Mesmo assim, está um pouco distante de ser unanimidade. Esse pensamento deve mudar porque a beterraba desempenha um importante papel em relação ao consumo de oxigênio. Essa característica faz com que o corpo não sofra as consequências ocasionadas pela fadiga. Isso ficou comprovado mediante estudos científicos efetuados pelos cientistas britânicos da Universidade de Exeter. O nabo O nabo, por sua vez, é rico em potássio e cálcio, além das vitaminas A, B e C. Some-se a isso a sua contribuição sobre o fluxo do intestino e a ajuda quanto à prevenção de determinados cânceres. A chicória Como é composta por oligossacarídeos (carboidratos constituídos por até 6 monossacarídeos), o consumo da chicória se justifica pela provisão alimentar que é direcionada às bactérias que sobrevivem no intestino, os populares prebióticos. A presença destes no intestino é de suma importância, uma vez que eles ajudam a aliviar o fluxo do órgão ao mesmo tempo em que eliminam toxinas extremamente agressivas. Os nutricionistas também recomendam a ingestão regular de chicória porque essa planta gerencia os teores de triglicérides na corrente sanguínea, além de melhorar a rapidez de absorção dos sais minerais por parte do organismo. Por fim, a chicória também possui elevadas doses das vitaminas A, B, C e D e detém um baixíssimo nível de calorias. fonte : http://saudeemalta.net.br

Inesquecíveis Sylvia Telles e Luiz Bonfá

Eu vi, a água do rio correr, canoa do Nego passar, a chuva no vento chegar, eu vi sem poder reclamar.. “Cendi” meu cigarro e fumei, lembrei meu passado e chorei, peguei na viola e pontiei, tirei um cochilo e sonhei… Sonhei com você junto a mim, olhando meu rosto a sorrir, que grande alegria senti em ve-lo ao meu lado cantar.. Fiquei em silêncio a ouvir, seu canto saudoso chamar. Seus lábios tão doces beijei, do sonho bonito acordei… (“Meu sonho” – Luiz Bonfá e Sylvia Telles – )

How We Could Actually Build a Space Colony

In our cosmic megastructures series, Popular Mechanics explores some of the key engineering and design challenges in constructing gigantic structures for use by humankind in space. Today, three classic space-colony concepts.  Name: Bernal sphere; Stanford torus; O'Neill cylinder   Named For: Respectively, British scientist John Desmond Bernal, who proposed the idea in 1929; a summer study program held by NASA in 1975 at Stanford University; Princeton physicist Gerard K. O'Neill in a 1976 book on space colonization. Selected Science Fiction Portrayals: Stanford torus–like space stations are depicted in the 1968 film 2001: A Space Odyssey and 2013's Elysium. A modified O'Neill cylinder served as the basis of the Babylon 5 space station in the 1990s TV series of the same name, and in Arthur C. Clarke's Rama novels. The desire to live in new places has driven our species to settle Earth's harshest climes, from deserts to tundras. Someday, that same urge (or, less optimistically, devastation to our home world) might drive us to colonize the toughest environment of all: space. Although they sound unfathomably futuristic, space stations housing many thousands of people are actually well within our technical and engineering know-how. Scientists have argued that permanent space outposts conceivably could be built for less than what the United States spends annually on its military. Back in the 1970s, for example, NASA-funded researchers investigated the feasibility of multiple colony designs. And they had to do it for less than $35 billion (north of $200 billion in today's dollars). "Everything had to be based on what was available at the time," said Jerry Stone, leader of the British Interplanetary Society's Project SPACE (Study Project Advancing Colony Engineering), which is now updating the decades-old designs to take new materials such as carbon fiber into account, as well as modern robots and computing power. That 1970s workshop yielded three distinct design concepts that are still widely referenced today: the Bernal sphere, the Stanford torus, and the O'Neill cylinder. So we'll use them as our guide to what it would take to build a thriving colony in space. All three designs essentially contain a living space rotated to induce gravity, with the key difference being the shape used. The Bernal Sphere A Bernal sphere exterior. (Photo Credit: National Space Society) A Bernal sphere is essentially a globe about a third of a mile in diameter that rotates almost twice per minute to provide Earthlike gravity along its equator. (This feeling of artificial gravity would peter out near the poles.) Around 10,000 people could populate the interior space, their buildings lining the curve and appearing overhead clear across the sphere's expanse.   A Bernal sphere interior. (Photo Credit: Rick Guidice/NASA) The Stanford Torus A Stanford torus, a donut-shaped tube 430 feet thick with a diameter spanning 1.1 miles, spins once per minute to produce its gravity. The inner portion of the tube is open, as in the movie Elysium, or enclosed by a transparent material to let in light. The exterior of a Stanford torus. A mirror, situated above the torus, directs sunlight into the habitat ring. (Photo Credit: Don Davis/NASA) The torus would shelter a similar number of colonists as the sphere. Horizons would slope away, upwards, and the ring of the inhabited landscape soaring overhead would make newcomers swoon. Six spokes connect the habitat ring to a central hub where spacecraft can dock. A mass estimate: 10 million tons.   The interior of a Stanford torus. (Photo Credit: Don Davis/NASA) The O'Neill Cylinder The third shape is the O'Neill cylinder, the main body of which is about 5 miles wide and 20 miles long. Three strips of land would stretch along the interior, with three equal-size, interspersed strips serving as giant, sealed windows. The cylinder's huge size means a gentle spin of one revolution every minute and a half would be enough for terrestrial gravity. One problem, though, is that objects want to rotate about their long axes, so an active control system would be needed to maintain the desirable short-axis spin rate. O'Neill also envisioned that the cylinders would always come in counter-rotating pairs to offset destabilizing, gyroscopic effects that would cause the cylinders to stray from their intended, Sun-facing angles.   O'Neill cylinder interior. (Photo Credit: Rick Guidice/NASA) While any of these space colonies would be far more vast than humanity's biggest space infrastructure project to date, the International Space Station, their designs would not pose insurmountable engineering challenges. "From an engineering standpoint, the structure is very easy—the engineering calculations are totally valid," says Anders Sandberg, a research fellow at Oxford University's Future of Humanity Institute, who has studied megastructure concepts. Mining the Moon The bigger issue is the logistics. Rocketing enough material into space to build a colony would cost big bucks. A better bet: establishing simple manufacturing facilities in space designed to use raw materials mined from the moon or asteroids. The real cost-saver O'Neill envisioned would be installing a large electromagnetic catapult on the moon. Popular among hobbyists as coilguns, these devices use electromagnets to propel a magnetizable payload down a shaft. Thanks to the moon's weak gravity, only one-sixth of Earth's, throwing ample material into space would be a piece of cake. "The nice thing about an electromagnetic launcher, once it's been constructed, the launch costs are pretty much zero," Stone says. "You don't have to provide fuel, just electricity, and you get that from the sun by solar energy." The raw lunar or asteroidal ingredients could be fashioned molecule by molecule, thanks to 3D-printing technology, into most of the components needed for the colony. "We know from Apollo samples the composition of moon rocks and soil," Stone says. "There's lots of oxygen, which we need for breathing; lots of aluminum, which is needed for structural parts; there's silicon, for the windows; and magnesium and titanium and other useful stuff." Other key structural items would include solar panels for energy, and mirrors to angle reflected sunlight into habitat enclosures through their windows. Robots could handle much of the construction itself, guided by humans or working autonomously. Soil and other Earth-specific items, such as wildlife, would, with some difficulty, need to be shipped aloft. Colonies Built to Last The completed colonies would reside in the Lagrangian point known as L5, an island of stability where gravitational attraction from our planet, the moon, and the sun balance out. Dedicated agricultural areas (located in additional tori outside the Bernal sphere, or in the O'Neill cylinder's end caps, with optimized environmental controls) would keep colonists well-fed with fresh food. Trade with other colonies and Earth would supply any unavailable wares. To protect the colonies from meteorite impacts, leftover slag from manufacturing could be built up as padding on the colony's exterior. In general, the experts says, meteorites should be a manageable nuisance. "A meteorite with enough kinetic velocity to break a window panel might happen every three years," Stone says, based on studies of the issue. The windows would be made of many small panels, so one getting smashed now and then, no problem—it would take centuries for the colony's air to leak out. Shielding residents from harmful space radiation, though, is trickier. Cosmic rays from deep space could not reasonably be stopped if humans lived outside the protection of our planet's atmosphere. Space residents would have slightly elevated cancer risks, mitigable by frequent screenings, Stone says. As for radiation from the sun, several inches of water shielding would block most of it. During rarely intense solar flares, colonists could take refuge in thickly shielded "storm shelters"—not unlike precautions for major weather events here on Earth. One benefit: Space colonies would be immune to Earthly natural disasters. "In the colonies there would be no Marsquakers, no hurricanes, no tsunamis, no volcanoes," Stone says. "Plus, you pretty much control the weather in an O'Neill cylinder. Because it's so big, you would have natural rain clouds forming in there." That level of control—and the chance to thrive in the final frontier—should motivate humankind to leave our planetary home. As O'Neill wrote in Physics Today in 1974: "I believe we have now reached the point where we can, if we so choose, build new habitats far more comfortable, productive and attractive than is most of Earth."

O Professor Pardal ataca novamente.

Professor Sparrow strikes again…. Até agora eu conhecia como fontes geradoras de energia elétrica, a força do vento utilizada em geradores com imensas hélices e capazes de gerar uma potência da ordem de megawatts, outra que tem o maior potencial como fonte segura de geração de energia,  é a energia solar, e que ainda deve passar por várias etapas de desenvolvimento tecnológico,  em contraposição à energia nuclear que pode gerar uma potência enorme mas que apresenta os riscos já por demais conhecidos, a força gerada por usinas hidroelétricas e as baterias de lítio que estão cada vez mais eficientes. Recentemente eu tomei conhecimento de um gerador que utiliza a força das ondas do mar quando publiquei esse artigo, e compreendi rápidamente seu mecanismo de ação. O único ponto espinhoso nesse sistema é a necessidade de cabos para levar a corrente elétrica gerada até a praia ou costa oceânica, e isso talvez possa ser modificado no futuro. Talvez embarcações ancoradas próximas ao conjunto de bóias e providas de torres com cabos que levariam a energia gerada até à praia, Teria que haver uma fila dessas embarcações, e os cabos balançariam muito mas como elas estarão ancoradas no fundo do mar, isso não representaria problema.  Eu não sei a que distãncia da costa ficam essas bóias e se não ficarem muito distante, talvez no futuro torres fixadas no fundo do mar possam levar o cabo até a costa. Mas existe uma força natural que ainda não foi explorada, pelo menos não li até agora nada à respeito. Trata-se da força da gravidade. Se construirmos uma torre bem alta e no seu interior for fixado um tubo de metal, vertical, desde o topo até a metade da altura da torre, Dentro do tubo uma peça de metal com dentes em um dos seus lados, pesada o suficiente para fazer girar um alternador colocado no ponto central da torre, tendo uma polia também dentada para que a peça de metal engrene nessa polia e faça girar o alternador gerando assim uma corrente elétrica. Isso tudo é apenas o fundamento da minha idéia. Nesse ponto alguém perguntaria : E quando a barra de metal chegar ao chão como ela voltaria para o alto? Eu dei tratos á bola para descobrir uma maneira, e em pouco tempo cheguei à um resultado. No lugar da torre que evidentemente não funcionaria, uma roda. Como protótipo, uma roda de 6 metros de diâmetro, com um suporte fixado no chão, um alternador em seu centro e várias peças de metal denteada (umas 5 peças mais ou menos)  As peças de metal deslizariam em tubos como na torre, fazendo o alternador girar. Quando fossem chegando no lado oposto do raio da roda, um dispositivo faria com que esta girasse até o ponto em que a peça de metal subsequente começasse a deslizar, e ao  mesmo tempo engrenasse novamente com o alternador. Existe o problema da velocidade exigida pelo alternador para produzir uma voltagem. Isso poderia ser resolvido com uma caixa de engrenagens que aumentasse grandemente a velocidade. A peça de metal não iria então ser acoplada diretamente ao alternador, mas sim ao lado primário da caixa de engrenagens. No lado de saida iria ser acoplada o alternador já com a velocidade adequada. O alternador tem imãs em seus polos fazendo com que fique pesado para ser rotacionado. Isso é o que o peso da peça de metal descendo pelo tubo iria resolver. Tudo isso é apenas um esboço da idéia. Seria preciso calcular o peso que as peças de metal teriam que ter para que pudessem fazer girar o alternador, um que gerasse uma potência de 1200W, 120V e 10A, para uso doméstico. Muito teria que ser resolvido nesse projeto para que funcionasse, mas eu acredito que possa. E nem tenho idéia do tamanho que teria um alternador que produzisse a potência de 1200W, como também não tenho idéia do peso das peças de metal. Só mesmo engenheiros na área de eletricidade e mecânica poderiam dizer se essa minha engenhoca funcionaria. As imagens abaixo servem apenas para preencher o vazio, nada tendo a ver com o tema da postagem,mas valem a pena porque são imagens belíssimas. Se você não concordou com a minha idéia, tem as imagens abaixo para não dizer que perdeu tempo abrindo este post.

Dando uma “mãozinha” para a NASA…

O máximo em tecnologia, creio eu, pode ser encontrada na NASA. Mas eles parecem não se importar muito com edição de fotografias, notadamente em fotos de foguetes e módulos espaciais, naquelas salas imensas e imaculadamente limpas.  Na postagem anterior à esta salvei uma foto do Magnetospheric Multiscale (MMS), creio que na etapa final de preparação para o lançamento. Mas vendo a foto não editada, com uma distorção de lente bem acentuada, resolvi dar uma arrumada na imagem com meu velho e bom GIMP 2.6. Aqui embaixo a imagem original, reparem que o foguete à direita e mais um outro grande objeto à esquerda parecem estar quase tombando.   Não é fácil arrumar isso porque quando se tenta verticalizar qualquer um da esquerda ou da direita, o oposto inclina-se mais ainda, mas depois de várias tentativas consegui melhorar. Perde-se um pouco no tamanho da imagem, mas os elementos principais ficaram intactos.    Aqui embaixo a mesma imagem corrigida ao máximo, incluindo ajustes no brilho e contraste. O foguete “engordou” um bocado, mas pelo menos ficou mais verticalizado. O pessoal de branco também ficou mais na vertical.  Contudo, palmas para a NASA.     Esta imagem menor acima foi salva durante o processo de edição. Os triângulos brancos é a parte da imagem que se perde.

Magnetospheric Multiscale Observatories Processed for Launch

NASA's Magnetospheric Multiscale (MMS) observatories are processed for launch in a clean room at the Astrotech Space Operations facility in Titusville, Florida. MMS is an unprecedented NASA mission to study the mystery of how magnetic fields around Earth connect and disconnect, explosively releasing energy via a process known as magnetic reconnection. MMS consists of four identical spacecraft that work together to provide the first three-dimensional view of this fundamental process, which occurs throughout the universe. The mission observes reconnection directly in Earth's protective magnetic space environment, the magnetosphere. By studying reconnection in this local, natural laboratory, MMS helps us understand reconnection elsewhere as well, such as in the atmosphere of the sun and other stars, in the vicinity of black holes and neutron stars, and at the boundary between our solar system's heliosphere and interstellar space. MMS is a NASA mission led by the Goddard Space Flight Center. The instrument payload science team consists of researchers from a number of institutions and is led by the Southwest Research Institute. Launch of the four identical observatories aboard a United Launch Alliance Atlas V rocket from Space Launch Complex 41 on Cape Canaveral Air Force Station is managed by Kennedy Space Center’s Launch Services Program. Liftoff is currently targeted for 10:44 p.m. EDT on March 12. Image Credit: NASA/Ben Smegelsky

Clef wants to change the way we log into websites

Clef uses an animation instead of an unlock code   It's had a good run, but the password's time is up. Remembering a unique unlock code for dozens of websites and apps is no longer very practical or very safe, and many different companies are exploring what comes next. One of those companies is Clef, which has developed a two-step verification system that uses an animated wave on your phone to confirm your identity. Two-step verification, now available on accounts with Google, Apple, Microsoft, Dropbox and many others, adds an additional security measure on top of a password. But existing methods typically rely on numerical codes and can be time-consuming to configure, which is why Clef thinks its new, streamlined approach has the edge. The technology is currently powering more than 40,000 sites and the company says it's now targeting larger organizations after securing US$1.6 million in investment funding. Clef apps are available for Android and iOS From the user end, you simply wave your phone at the screen and you're in (though a PIN or Touch ID confirmation is required initially). It can work over Wi-Fi or cell networks (handy when one is available but not the other) and as a fallback it's possible to scan the phone screen using a laptop camera. There are no codes to remember and there's nothing to type in: The unique wave generated by your phone confirms that you are who you say you are. "No weak passwords, frustrating tokens, or clunky dongles," promise the founders of Clef, which is based in Oakland, California. There's also the option to securely log out of your accounts with a single tap on your smartphone, should you spot any suspicious activity or suspect that someone else has been able to log into a site or app as you. Clef is far from the only company looking to revolutionize the login process. In recent months and years we've seen a wearable that uses your heartbeat as a password, an iris-scanning gadget to log you in securely and various alternatives to the mobile phone PIN.   Source: Clef via TechCrunch

SkyProwler combines a quadcopter and a fixed-wing airplane in one device

The SkyProwler ready for some speed, with its quadcopter props retracted Arizona-based start-up Krossblade is developing a five-passenger "flying car"-type vehicle known as the SkyCruiser. Among other things, plans call for it to take off and land like a quadcopter, while transitioning to faster, more efficient fixed-wing flight while en route. Will you ever be able to buy one? Well, that's hard to say, but if Krossblade's current Kickstarter campaign is a success, you will soon be able to buy a functioning miniature prototype known as the SkyProwler. Like a quadcopter, the SkyProwler has four horizontal propellers that allow it to perform vertical take-offs and landings, and to hover in mid-air. Whereas a copter has to tilt its nose down in order to move forward, however, the SkyProwler uses an additional two vertical props in the rear to push itself forward. This allows it to minimize its frontal area while moving through the air. If users want to make it really sleek and fast, though, they can instruct the aircraft to retract its landing gear and pull its four copter props into the sides of its body, switchblade-style. It's then being powered solely by the two rear props, maintaining lift using its wings. This allows it to cover greater distances using less battery power, and to keep up with fast-moving subjects – its top speed in this configuration is 83 mph (134 km/h). On the other hand, if users know that they're only going to use it for slow-speed flight and hovering, they can lighten it up by temporarily pulling off the wings and tail. Flight time ranges from 24 minutes in quadcopter configuration to 40 minutes when flying fixed-wing. The drone also features interchangeable nose cones, one of which allows it to carry a third-party camera. Another cone, however, contains Krossblade's own gimbal-mounted 4K/30fps EyeHD camera (seen above), which is said to be much more aerodynamic than something like a GoPro. Additionally, because it's mounted right on the nose, the camera can actually be aimed upwards – something that isn't possible on a quadcopter. The SkyProwler is controlled using a radio remote control unit, that comes with an optional live-streaming video screen. If users wish, however, they can remove the GPS module from that unit and carry it with them in a radio arm band, the aircraft then automatically following them by homing in on that module. In that mode (or when using the full remote control, for that matter), they can relay simple commands such as "take off" and "land" via voice prompts. Additionally, using an accompanying app, users can plot a flight path on a map, which the aircraft will subsequently follow on its own. If you're interested in a complete ready-to-fly package, be prepared to pledge US$899 – this includes a 1080p/30fps version of the camera. A model with the 4K camera will set you back $1,399. Shipping is scheduled for July, assuming all goes according to plans. . For examples of military-grade drones that utilize a similar design (except without retractable props), check out the Quadrotor UAV and the Arcturus. Sources: Krossblade, Kickstarter

CorPower system gives wave power the gears

CorPower Ocean's wave power-harnessing buoys utilize a geared drivetrain instead of hydraulics (Image: CorPower Ocean) Harnessing wave power can be a tricky business. It's one thing to build a device that simply moves up and down with the waves, but another to build one that's efficient enough to be cost-effective. Swedish company CorPower Ocean claims to have done just that, however. Its wave energy converter buoys reportedly generate five times more energy per ton of device, at a third the cost of other wave power systems. The CorPower setup is what's known as a point absorber system. Here's how it works ... A buoy floats on the surface of the ocean, moving up and down with the waves. That buoy is moored to the sea floor, although sitting on the line part way between the buoy and its anchor is the actual wave energy converter mechanism. In some other point absorber systems, this consists of a hydraulic pump that generates electricity as it's pulled up and released by the buoy. In the CorPower system, however, there's a geared drivetrain, developed at Sweden's KTH Royal Institute of Technology. That drivetrain uses multiple small pinion wheels to convert linear motion into rotation, spinning up a flywheel. Additionally, the drivetrain is said to enhance the buoy's movements, allowing it to rise and fall more while staying in sync with the rhythm of the waves. According to CorPower CEO Patrik Möller, this means that the system harnesses wave motion "all the way between the wave crest and wave trough and back in an optimal way, no matter how long or high the waves are." Energy is temporarily stored onboard, before being output at a smooth and consistent rate via electrical cables running to the shore. According to KTH, the buoys/converters are lightweight, compact, and relatively inexpensive to manufacture. One 8-meter (26-ft)-diameter buoy should be able to produce 250-300 kilowatts in a "typical Atlantic environment." The technology was recently awarded €100,000 at MIT's Building Global Innovators Demo Day. A pilot project using the buoys is planned for this November. Sources: KTH, CorPower Ocean

Deflation can be a good thing. But today’s version is pernicious

Feb 21st 2015 | From the print edition FALLING prices sound like something to cheer. In 1950 talk was not cheap. It cost $3.70 to place a five-minute call between New York and San Francisco—or $36.35 in today’s money. Now that same call costs you nothing. The emergence of the sharing economy is driving down the price of a taxi ride and a bed for the night. More recently tumbling prices for natural resources, especially oil, have boosted the spending power of consumers from Detroit to Delhi. Mark Carney, the governor of the Bank of England, reckons that falling energy prices are “unambiguously good” for the British economy. Mr Carney is not wrong. Nonetheless, the world is grievously underestimating the danger of deflation. The problem is that aggregate prices are dipping in so many places at once. Deflationary pressures are visible far beyond food and energy, and in countries that cannot claim to be leading the charge towards the new economy. In the euro zone, where deflation grips tightest, consumer prices fell by 0.6% in the year to January; Germany, Italy and Spain all saw falls. Prices in Greece have been declining for 23 months. Ultra-low inflation is also widespread. America, Britain and China each have inflation rates of less than 1%. This looks less like a welcome jolt to prices than a sign of entrenched weak demand. Deflation poses several risks, some well-understood, one not (see article). One familiar danger is that consumers will put off spending in the expectation that things will get even cheaper, further muting demand. Likewise, if prices fall across an economy but wages do not, then firms’ margins will be squeezed and employment will stagnate or decline. (Neither of these dangers is yet visible; indeed, America and Britain are seeing strong employment growth.) A third, well-known risk is debt deflation: debts become more onerous because the amount that is owed does not fall, even as earnings do. This is a big worry in the euro zone, where many banks are already stuffed with dud loans. The least-understood danger is also the most serious, because it is already here. Deflation makes it harder to loosen monetary policy. When inflation is at 4%, the central bank can take real (ie, inflation-adjusted) rates well below zero, to -4%, by keeping headline rates at zero. But as inflation falls and turns negative, low real rates get harder and harder to achieve—just when you need them most. Most rich-world central banks have already cut their main policy rates near to zero in order to pep up demand. A growing number of European economies are using negative interest rates to encourage spending, although charging people to put money in the bank will eventually prompt them to use the mattress instead (see article). All of which means that policymakers risk having precious little room for manoeuvre when the next recession hits. And sooner or later it will—because of a sharp slowdown in China, say, or the effect of a rising greenback on dollar-denominated corporate debt, or from some shock that comes out of the blue. The Federal Reserve has cut its policy rate by an average of 3.9 percentage points in the six recessions since 1971. That would not be possible today. The break-glass-in-case-of-emergency option of depreciating the currency massively against a fast-growing trading partner is of limited use when so few big economies are growing rapidly and prices are falling, or close to it, in so many places. Change the target Policymakers should be more worried than they appear to be, and their actions to avert deflation should be bolder. Governments need to boost demand by spending more on infrastructure; central banks should err on the side of looseness. (Next month the ECB will start quantitative easing—and about time too.) Now is also the moment to consider revising the monetary rule book—in particular, to switch the central bankers’ target from the inflation rate that most now favour to a goal for the level of nominal GDP, the total value of spending in an economy before adjusting for inflation. With such a target there is no need to distinguish between good and bad price shocks. And the change in rules would itself send a signal that policymakers are serious about banishing the threat of deflation. Central bankers change course slowly, and their allegiance to inflation targets runs deep. Conservatism often serves them well. But in this case it could cost the world economy dearly. From the print edition: Leaders source – www.economist.com