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An Explanation for the Missing Sunspots

Smithsonian Magazine

I bet that most of you don’t know that the sunspots are missing. That’s okay. I’m sure many people don’t realize that the sun is more than just a ball of fire: it has a complex internal structure, features that vary based on multi-year cycles, and it can create solar storms that knock out power and communication here on Earth. And sometimes it behaves in ways that scientists still don’t understand well.

Sunspots are areas of intense magnetic activity on the surface of the sun. They look like dark spots to us because they are around a thousand degrees cooler than the area around them. At 4,000 to 4,500 degrees Kelvin (about 7,000 degrees Fahrenheit), though, they’re still incredibly hot. Sunspot activity cycles about every 11 years, and scientists had expected the sun to start the next cycle of heightened activity, Cycle 24, in late 2007 or 2008. Some early forecasts predicted that Cycle 24 would be especially active.

But then the sun stayed quiet—in the solar cycle’s minimum phase—for one to two years longer than expected. There hasn’t been a significant solar flare in the last two years. There had even been talk about whether we might be entering another “Maunder Minimum,” the period in the late 17th- to early 18th-century when there were only a few sunspots, compared to thousands normally, and that coincided with the Little Ice Age. That worry, at least, seems to be unfounded, as NOAA has now seen indications that Cycle 24 is nearly ready to begin, though it will likely be less active than average.

And now we have some clues about why the sun was quiet for so long. Solar scientists led by Frank Hill of the National Solar Observatory announced yesterday at a meeting in Boulder, Colorado, that the delay in the cycle start is associated with a solar jet stream deep below the sun’s surface.

The structure with the sun. The blue line in the northern and southern hemispheres is the jet stream, which runs about 1000 to 7000 km below the sun’s surface. (AAS/SPD)

These jet streams (one in the northern hemisphere, one in the south) originate at the sun’s poles, a new one every 11 years. Over the next 17 years, the jet streams migrate towards the equator, and when they reach a critical latitude of 22 degrees, they are associated with the production of sunspots. Scientists here on Earth can track these jet streams through the ripples on the sun created by the sound within, Hill said.

However, the jet streams that would be associated with Cycle 24 are a bit sluggish, taking three years to cover 10 degrees in latitude instead of the normal two years. “The flow for this cycle is taking much more time to move down to the critical latitude,” Hill said. But now that the jet streams have reached that latitude, the cycle should start right up.

Hill doesn’t know if the jet streams are a cause of the sunspot cycle or a consequence of it, though he leans towards cause. And though he says that the sluggishness was the result of other things going on under the surface of the sun, he can’t name what those things would be. “We do not fully understand the interplay of the dynamics under the surface of the sun,” he said.

I guess there’s plenty of mystery left, then, to keep the solar scientists busy.

Why We Can Blame A Warm Arctic For This Winter’s Icy Chill

Smithsonian Magazine

Warm weather thousands of miles away would seem an unlikely cause of the United Kingdom’s freakishly wet winter or the bone-deep chill experienced this year by the eastern United States. But a warming Arctic can be blamed for both, said Rutgers University atmospheric scientist Jennifer Francis at the recent AAAS Annual Meeting in Chicago, Illinois.

“It’s because the pattern this winter has been basically stuck in once place ever since early December,” Francis said. And the pattern—which has included cold, cold temperatures in the eastern United States, for instance—has been stuck because of the Arctic.

Back in 1896, the Swedish physicist Svante Arrhenius first calculated [pdf] how pumping carbon dioxide into the atmosphere would warm the planet through the greenhouse effect. That warming, he wrote, would be most pronounced in the Arctic regions, a phenomenon known as Arctic (or polar) amplification. And it is now able to be seen above the noise of the world's weather—below is a NASA animation of temperature differences compared to averages, from 1950 through 2013:

The recent amp up of Arctic warming is readily seen by the loss of summer sea ice in the Arctic Ocean. The extent of summer sea ice, in particular, has been on the decline for more than two decades, and the loss of old, thick ice has been especially pronounced (see video below).

“When you’re losing the sea ice, Arctic amplification is certainly here,” said Mark Serreze, director of the National Snow and Ice Data Center. Losing that sea ice, he said, will have impacts in the mid-latitudes, particularly on weather patterns.

The Arctic affects the rest of the planet in many ways, but the one that’s most relevant for Francis’ work is called the poleward temperature gradient—that’s the difference in temperature between the Arctic and the mid-latitudes, where the continental United States sits. That poleward temperature gradient causes air to start flowing from the North Pole southward, and a spinning Earth forces the air to move from west to east, creating the jet stream.

Frequent fliers will recognize the jet stream as the river of air that can give their airplane a boost when flying from Los Angeles to New York City. Weather fanatics, though, might be more familiar with the air pattern for its ability to move weather systems across the continent.

“When you warm the Arctic more rapidly, you’re decreasing the difference in temperature between the Arctic and the areas farther south,” and that’s weakening the poleward temperature gradient, Francis explained. A weaker gradient makes for a weaker jet stream.

 “As we weaken this difference in temperature between the Arctic and the mid-latitudes, we expect those winds from west to east to get weaker,” Francis said. “When that happens, we also expect to see that flow in the upper-level jet stream to become more wavy.” Francis compared the jet stream to a river. When a river flows down a steep mountainside, it flows quickly and its path is straight. But when the river flows over a flat plain, it’s slower and its path can begin to wander. The jet stream now sometimes meanders like that slow-moving river:

A weaker jet stream is probably more easily deflected off its path when it encounters something like a mountain range or a mass of hot air, Francis said. Those large waves increase the likelihood that a weather system—such as a particularly cold winter or a period without rain—gets blocked. “This means that the weather they create is lasting longer in your location. This leads to the more persistent weather patterns and the tendency of extreme weather of certain types to become more likely,” Francis said. “This is the hypothesis.”

And that’s the big caveat in this work—this is a hypothesis developed within the last few years by Francis and her colleague, Steve Vavrus, an atmospheric scientist at the University of Wisconsin, Madison. “Not everyone is on board,” Francis admitted.

But this appears to be a fairly new development in the evolution of the planet’s climate. The signal of Arctic amplification, first predicted back in 1896, really only became noticeable above the random ups and downs of the weather within the last 10 or 15 years, so its effects—such as the weakened jet stream—are just now starting to be experienced, Francis said.

And Francis admits that having weather pattern stuck in place by the jet stream doesn't explain all of the recent bouts of extreme weather. It will take scientists some time to figure it all out, but Francis noted that this hypothesis is backed up by a combination of observations, physics and climate models.

“There’s a lot going on in the climate system that affects the jet stream,” she said, “and figuring out how the different pieces of the puzzle fit together is a really active area of research right now.”

Art to Zoo: Tomorrow?s Forecast: Oceans and Weather (1995)

SI Center for Learning and Digital Access
Lesson plan (with printable maps and classroom/take-home activities) demonstrates how ocean currents influence weather patterns and climate. Students identify ocean currents and the relationship between currents and trade routes, conduct an experiment on the differing heat capacities of water and air, and find and label port cities around the globe.

More Evidence That Arctic Warming Is Behind the Weak Polar Vortex

Smithsonian Magazine

This past year, the U.S. Midwest and Northeast suffered through a long, cold winter. The West, in contrast, saw a warm, dry season. Yet both were symptoms of the same cause—a leaky polar vortex. This situation gets even more counterintuitive, too. A contentious idea that's been kicking around for a while posits that, as backwards as it seems, a weak polar vortex (and the resulting cold winter) might actually have been a sign of global warming. And now a new study adds evidence that this may, in fact, be the case.

Here's how it works. Normally, cold Arctic air is confined to the polar region by a strong atmospheric circulation around the pole. (That's the polar vortex.) Last year the polar vortex weakened, and the cold Arctic air spilled south, flash freezing the eastern half of the continent.

The key to making sense of how a leaky polar vortex could be tied to global warming lies in the rapid recent decreases in Arctic sea ice cover. As the sea ice melts, some researchers think, it changes how the jet stream crosses North America. The warming Arctic can mean the jet stream blows more slowly, and when that happens, the jet stream can get wobbly and “trap weather systems — including both heat waves and cold snaps — in place for an unusually long time,” says Michael Lemonick for Climate Central. (A wobbly jet stream could have consequences not just for the polar vortex, says Seth Borenstein for the Associated Press, but for a whole range of extreme weather events.)

Last winter Andrew Freedman wrote for Climate Central about the potential climate change connection of the polar vortex. Though, as Freedman and others noted, the connection is mostly correlation: there seems to be a link between melting sea ice and cold winters in the U.S., but scientists aren't really sure about how, exactly, they might be connected.

In their new study, an international team of scientists lay out what they think could be a physical mechanism that could explain the link between melting Arctic sea ice and a weakening polar vortex.

The lack of sea ice, the scientists say in their study, strips the Arctic ocean of the ice's insulating properties. This causes more heat to move from the water to the air. This change in energy flow affects the air pressure in the Arctic and changes how air moves around the region. That, in turn, could cause the polar vortex to weaken and the cold air to spill south.

Whether the recent spate of extreme weather can be tied conclusively to global climate change is still a matter of considerable scientific debate, but this new study is just another piece of evidence in the pile.

Ask Smithsonian: What Is Wind?

Smithsonian Magazine

Wind is an ever-present force. From a gentle breeze to a cold arctic blast, it is constantly shaping the landscape and the weather. But where does wind come from?

Simply put, wind is the motion of the air around us, generated by differences in pressure in the Earth's atmosphere. Air is a fluid, and just like water, it obeys the laws of fluid dynamics. It will seek to flow from a region of higher pressure to one of lower pressure, says Chris Maier, a meteorologist with the National Oceanic and Atmospheric Administration’s National Weather Service.

Earth's air-filled atmosphere is constantly but unevenly pressurized, with highs and lows at various places caused by the uneven heating of Earth’s surface by the sun. The air at the North or South Pole is colder and denser, while the air at the Equator is warmer and rises more easily. The colder, more highly pressurized polar air is constantly trying to move down to the Equator to replace the warm, rising air.

That creates Earth’s overall global circulation, says Maier. There are wind belts that circle the planet along latitudinal lines, each having particular characteristics and creating specific weather patterns.

One of those bands is the Intertropical Convergence Zone near the Equator, where the trade winds meet. Sailors named the trade winds, navigating by them because of their fairly dependable behavior.

In the Northern Hemisphere, the trade winds are created as warm air moves away from the Equator and is bent slightly right due to Earth’s rotation. This is known as the Coriolis effect. The warm air is pushed from the northeast to the southwest back toward the Equator thanks to down-rushing polar air. The same thing happens in the Southern Hemisphere, with the trade winds being pushed from the southeast toward the northwest.

As the northern and southern trade winds converge near the Equator, they create a zone with little to no wind and a tendency for short-burst intense storms full of rain. Sailors have called this zone the doldrums for eons.

In the contiguous U.S., a band known as the Westerlies is the primary force behind wind and weather, with most storms following along a west-to-east track, says Maier.

Jet streams also help direct those wind and climate patterns. The jet streams—there are at least several—range from 25,000 to 50,000 feet above Earth and “are basically fast-flowing rivers of air,” says Maier.

They help form boundaries—a counterforce to the polar air making its way toward the Equator and to the warm air moving away from the Equator, he says. The jet streams can change course, speed or altitude from day to day. The streams are often used by airlines and the military to increase speed without using more fuel.

In the U.S., the current El Niño weather pattern—in which warmer Pacific Ocean water off Peru and Ecuador creates a bubble of warmer, less-pressurized air that then moves north—is pushing North America’s usual jet stream northward and extending another jet stream across the southern part of America. That brings more snow and rain to California, more wet weather across the Gulf Coast, and milder temperatures to the East.

Wind is also noticeable on a more local level. In the winter, the air is colder, denser and more pressurized. Colder air will rush in upon the opening of a door from a heated, less-pressurized house. People who live near the mountains will notice that during the day, as the valley heats up, warm air will rise up the slopes, while in the evening, colder, denser air will push back down into the valley.

At the beach, denser air sits above cool water, while low-pressure air sits above warmer land. The colder air seeks to move inland to equalize the pressure, causing a breeze. That pattern is reversed at night, as the land cools rapidly and pushes its more pressurized air back to sea.

Storm systems, however, can upset that equilibrium. A storm undergoes many changes in pressure as it moves and often contains warmer, rising air within its confines, with cooler air pushing from behind. The stronger the difference in pressure between those systems, the more forceful the wind, as is seen with a hurricane or a tropical cyclone.

It's your turn to Ask Smithsonian.

A Big Surprise at Kilauea

National Museum of Natural History
Sometimes things just seem to be out of place. Richard Fiske from the Department of Mineral Sciences unravels the mystery of how large rocks were propelled great distances by an eruption at Kilauea and how the jet stream played a role.

Grab Your Sweaters: The Polar Vortex Is Back

Smithsonian Magazine

If you’re the type of person who piles on the blankets at the slightest hint of cold, take a deep breath—this may be hard to swallow. The United States has enjoyed an unseasonably warm autumn, but that’s about to change. Starting today, a polar vortex is poised to bring bitter cold temperatures to much of the United States, reports Doyle Rice for USA Today.

The National Weather Service Climate Prediction Center is warning of a pending polar vortex—a phenomenon that occurs when an area of low pressure and icy air surrounding both poles expands. The chill will come in two waves, writes the NWS, plunging much of the U.S. into bitter cold.

“Polar vortex” sounds (and feels) dramatic, but it’s actually a term that’s long been used by weather forecasters. As the NWS explains, the phenomenon is caused by strong air flow that usually keeps cold air close to the poles. On occasion, though, that strong circulation weakens, causing the cold air to spread out and expand south. The jet stream that usually sweeps across the northern edge of the U.S. is forced south, bringing the cold air along with it. The result: a pocket of frigid air that can engulf a city for days.

This polar vortex isn't a surprise to forecasters, but it may come as a nasty shock to people who remember the last one all too well. In January 2014, a polar vortex enveloped much of the country, contributing to record lows throughout the nation and freezing a massive 75 percent of the Great Lakes. However, the wretched winter that produced so much snow in Boston last year wasn’t due to a polar vortex; rather, the nearly 109 inches of snow that fell during the winter of 2014-15 is thought to have occurred in part because of warm ocean temperatures.

While the Midwest braces itself for what Rice calls “life-threatening cold temperatures and fierce winds” and the rest of the country wonders what the polar vortex will bring, it’s worth asking whether climate change will affect the vortex in the future. While researchers are still learning about the phenomenon, it’s thought that the jet stream is becoming more wavy over time as the Arctic warms.

As Caitlyn Kennedy of NOAA writes, a wavier jet stream means that polar air gets sucked further south than usual—and even though the connections between global warming and the polar vortex must be studied further, the speed of climate change could mean that more vortices are on the way. So grab your mittens and hunker down—it could be a wild (and very cold) ride.

See a Bubbly Nebula, an Artistic Earth and Other Spacey Treats

Smithsonian Magazine

A stellar nursery bursts with bubbles, plankton paint the North Atlantic, jets stream from a galactic merger and more in our selections for this week's best space-related images.

French Village Hits 114.6 Degrees, Setting New National Record

Smithsonian Magazine

Last week Friday, the village of Gallargues-le-Montueux located in southern France outside of Montpellier topped 114.6 degrees Fahrenheit, the highest temperature ever recorded in continental France.

That sweltering heat broke the previous record of 113.2 degrees, which was set just hours before in the village of Villevieille. And those weren’t the only hot spots. Brian Kahn at Earther reports that at least 12 weather stations in France detected temperatures above 111.4 degrees Fahrenheit, the previous hottest temperature set in 2003.

According to Agence-France Presse, the temperature spike makes France the seventh European nation to ever break the 113-degree-Fahrenheit mark, joining Bulgaria, Portugal, Italy, Spain, Greece and North Macedonia.

France was not the only nation dealing with extreme heat last week. Andorra, Luxembourg, Poland, the Czech Republic, and Germany all set record temperatures for the month of June. Germany lowered the speed limit on parts of the Autobahn, worried about buckling roads. And the heat set off the worst wildfires Spain has seen in 20 years with three major blazes burning throughout the nation. (One blaze started when improperly stored chicken manure combusted due to the heatwave.)

At least seven people died in France due to the heat with at least two fatalities in Spain and two in Italy. But that’s a far cry from 2003, when an estimated 70,000 people died in Europe, including 15,000 people in France, during a devestating heatwave, reports Sasha Ingber at NPR. After that, the French government implemented a series of measures to help protect people from the heat, including a warning system. The French weather service issued its highest warning for four regions of the country last week, leading to the closure of 4,000 schools. Public cooling rooms were also opened in cities across the country and public parks and pools stayed open for extended hours.

Though the French people seem to have weathered the heat fine, French wine is suffering. After three years of drought, many vineyards in France's southern wine country were already experiencing stress. The extreme heat pushed some over the edge, with vines withering and drying out in the oppressive temperatures. “I’ve been a winegrower for 30 years. I have never seen a vine burnt by a sudden onset of heat [until now],” Jerome Dempsey tells AFP.

On Sunday, the heatwave's grip finally broke in much of France and other parts of Europe—though it is expected to persist in Germany and parts of Eastern Europe for a day or two longer.

So what led to the massive early summer temperature spike? In an earlier article, Earther's Brian Kahn explains that the heat wave was caused by a weather phenomenon called a rex block. The weather pattern happens when stationary high pressure system over Greenland and a low pressure system over the North Atlantic contorts the jet stream, cutting off cooler air from northern latitudes from reaching Europe. The jet stream has also dipped down toward Africa, transporting hot air from the Sahara across the Mediterranean.

Karsten Haustein, a climate scientist at the University of Oxford who is affiliated with the World Weather Attribution Network, which tries to figure out how much weather events are tied to climate change, tells Carolyn Gramling at Science News that it’s hard to say how much this event is due to climate change. He says that some researchers believe the fluctuations in the jet stream may be linked to warming temperatures in the Arctic. In general, however, he says heat waves like this one are twice as likely to occur due to climate change.

Summer Heat Waves May Be Linked To Sea Ice Loss

Smithsonian Magazine

As much of the United States shivers through a cold spell, readers may be hard pressed to remember the summer heat waves that have been coming in increasing frequency. The southwestern U.S. baked during this past summer. High heat in the Midwest and East Coast in summer 2012 killed 82 people, which followed a record summer in 2011. And that came after a 2010 summer that saw high heat across the Northern Hemisphere, from Asia to Europe to North America.

These events are not random and can be blamed on the disappearance of sea ice from the Arctic Ocean and, to a lesser extent, the melting of snow cover in the Arctic, say climate scientists from the Chinese Academy of Sciences in Beijing and Rutgers University. Their study was published December 7 in Nature Climate Change.

The ice that blankets the Arctic Ocean increases in winter and shrinks in extent in the summer. Likewise, Arctic lands become covered in snow in winter, and that snow melts in warmer months. This cycle is natural, but it’s been changing in recent years. The summer ice has been shrinking more, and the winter snow has been melting more. The region is warming more quickly than the rest of the world, and it’s having a variety of consequences, from alterations to the food web to a melting of permafrost to the opening up of shipping channels.

But climate scientists are also trying to figure out if the loss of snow and ice might be having larger effects on Earth’s weather patterns. Snow and ice act like mirrors, reflecting some of the Sun’s energy back out into space. When that mirror shrinks, the darker land and ocean can suck up more heat, which not only leads to more melting and a warmer Arctic but may also alter weather far away.

Arctic sea ice reaches its smallest extent in September, and that area has declined by about 8 percent every 10 years since the 1980s. Arctic snow cover, which reaches its minimum in June, has been shrinking even faster, declining about 18 percent every decade since 1979. In the new study, the researchers linked this data, as gathered from satellite observations, with atmospheric data and found that shrinking sea ice was associated with the jet stream moving northward. Snow cover also played a role but a smaller one, even though it is disappearing faster than the sea ice.

The jet stream is a ribbon of air that flows around the Northern Hemisphere from west to east and separates cold Arctic air from warmer air masses to the south. A jet stream stuck farther in the north helps to keep unbroken the warm weather patterns to the south, “increasing the probability of extreme weather events such as heat waves and droughts,” the researchers write, particularly in the eastern half of North America, eastern Europe and eastern Asia.

This study “provides further evidence linking snow and ice loss in the Arctic with summer extreme weather in mid-latitudes,” the researchers write. “As greenhouse gases continue to accumulate in the atmosphere and all forms of Arctic ice continue to disappear, we expect to see further increases in summer heat extremes in the major population centres across much of North America and Eurasia where billions of people will be affected.”

Though a heat wave may sound like a good thing right now, as many of us look out through frost-covered windows onto snowy streets, these are expensive, deadly events that kill more people than cold, cause droughts and contribute to devastating wildfires.

But the link between changes in the Arctic and heat waves in the populous mid-latitudes isn’t certain. The study showed an association, but climate scientists have yet to figure out the mechanism that might provide the link and most remain skeptical that such a link exists. “I would have more confidence in the linkage being ‘real’ if there was a well-understood and proven mechanism to support the correlations,” James Screen, a climate researcher at the University of Exeter in England, told Climate Central. And there is evidence that Arctic melting can also be associated with extremes in winter cold.

Though climate scientists have yet to understand exactly how the changes in the Arctic may be influencing weather elsewhere in the world, there is enough evidence to convince them that they should keep investigating, climate scientist James Overland of the NOAA/Pacific Marine Environmental Laboratory in Seattle, writes in an accompanying News & Views article. “The potential for an Arctic influence remains high given the outlook for further declines in summer sea-ice and snow cover over the next few decades and Arctic amplification of global temperatures.”

Revenge of the Polar(esque) Vortex

Smithsonian Magazine

Northeasterners and Midwesterners have only just thawed out after a particularly brutal and traumatizing winter, but meteorologists are warning that an unseasonable cold snap is about to interrupt what is normally one of the hottest weeks of the summer. The meteorological phenomenon "bears a haunting resemblance" to last winter's polar vortex, the Washington Post writes, leading some to dub it "the ghost of the polar vortex" or "the polar vortex's sequel."  

The cold snap is due to a patch of cool air moving east from the Gulf of Alaska. Here's Mashable with more details about what's causing the unseasonable occurrence: 

The strange weather pattern has its roots near Hudson Bay, Canada, where so much of last winter's cold originated. The cold air will be spinning around underneath an area of low pressure at upper levels of the atmosphere, which the jet stream, which is the river of air at about 30,000 feet, is going to steer south, into the U.S., over the weekend.

The dip in the jet stream, known as a "trough," is connected via a long chain of events to once-Super Typhoon Neoguri, which struck Japan on Wednesday as a weakened tropical storm, according to Jeff Masters of Weather Underground.

As a result, places in the Great Lakes region might drop as low as the 40s on Wednesday morning, the Washington Post warns, while much of the east and northeast is predicted to experience temperatures in the 50s and 60s. Other places, such as Detroit, will drop into the low 70s - not quite as severe but still a significant change from the high 80s experienced over the past weeks. 

The low predicted temperatures are annoying for those who just want to enjoy their summer free from any reminders of the winter's horrors. But the upcoming cold snap has also ruffled some feathers at the National Weather Service. As Mashabale reports

The National Weather Service has ordered its forecasters to just quit it already with the use of the meteorological term "polar vortex" when describing a highly unusual weather event set to take place in the United States next week. 

According to the Capital Weather Gang blog, and independently confirmed by Mashable, a memo was emailed from the NWS Central Region to its central region forecast offices, which includes Chicago, telling forecasters not to use the term in any of its communications with the public.

Regardless of what it's called, however, the Washington Post warns that residents should ready their jeans and light jackets, and perhaps reconsider those mid-week trips to the beach. 

Watch How the Wind Moves Around the Earth—It's Hypnotic

Smithsonian Magazine

From North Pole to South Pole, from the surface of the planet to the top of the atmosphere, at its most basic, wind is caused by differences in pressure. The sun heats the Earth's surface unevenly and causes the air to heat unevenly, as well. Since hot air rises, the hot air lifts up and up, leaving a low pressure zone underneath. In colder places, where the pressure is higher, air rushes away, moving to balance out this difference in pressure. That's how wind happens.

Working with data from the National Oceanic and Atmospheric AdministrationFernanda Viégas and Martin Wattenberg made a stunning Wind Map, which shows real time winds as they flow around the U.S. And now computer programmer Cameron Beccario has produced an even more powerful creation—a mesmerizing tool that helps visualize the winds all over the globe and is known simply as “Earth.”

In the animated photo above, we've used Earth to show the wind conditions at 250 hectopascals, a region of the atmosphere that flows between around 30,000 and 50,000 feet, and includes the well-known northern subtropical jet stream—what you'd normally just call "the jet stream."

But Beccario's map can also be used to show what the wind is like on the surface or way high up in the stratosphere, where winds rage in massive polar vortexes. It also lets you play with different styles of map projection, from Waterman and Winkel to the super-trippy stereographic.

H/T Dan Satterfield

More from Smithsonian.com:

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Bats and Balloon Bombs: The Weird Weapons That Could Have Won WWII

Smithsonian Magazine

For most of World War II, the United States military was seriously developing a plan that would have unleashed thousands of firebomb-armed bats from planes above Japanese cities. And it could have worked, as Cara Giamio writes for Atlas Obscura.

An American dentist named Lytle S. Adams had bats on the brain, Giamio reports. When the Japanese navy attacked Pearl Harbor on December 7, 1941, Adams had just back from a vacation that included a trip to Carlsbad Cavern — and he was struck by the millions of Mexican Free-Tailed bats that roost in the caves.

Like many Americans, Adams was enraged by the Pearl Harbor attack and quickly drafted a plan to strap miniature bombs to bats and drop them over Japanese cities. At the time, the stereotypical image of Japanese buildings was of many wood-and-paper houses packed together closely. Adams imagined that the bats would stream out of bombers and instinctively flock to the rooftops and eaves of these buildings. When the timers on the bombs attached to each bat would run down, the destruction would cascade across entire neighborhoods and cities, terrorizing the populace.

With a little help from his friend, Eleanor Roosevelt, Adams’ plan eventually made it to the desks of President Franklin D. Roosevelt and his top military brass. Roosevelt thought it was “a perfectly wild idea but is worth looking into” and gathered a crack team of military experts and scientists to develop bombs small enough to execute Adams’ plan, Giamio writes. It was called “Project X-Ray.”

But as Adams and his team worked on their tiny firebombs, the Japanese military was busy with their own crazy scheme: the fu-go. In the 1920’s, a Japanese scientist named Wasaburo Oishi discovered the jet stream, and the Japanese military believes they could use it to conduct their own terror campaign against the United States, Linton Weeks reports for NPR. The fu-go plan "called for sending bomb-carrying balloons from Japan to set fire to the vast forests of America, in particular those of the Pacific Northwest. It was hoped that the fires would create havoc, dampen American morale and disrupt the U.S. war effort," James M. Powles writes for the journal World War II.

The balloon bombs were about 33 feet in diameter and made of a traditional Japanese paper called “washi.” Each fu-go carried an elaborate canopy of firebombs and sandbags, which were timed to drop off and keep the balloon drifting through the jet stream, David Kravets writes for Wired.

Project X-Ray was eventually canceled in 1944, but not because it didn’t work — in fact, early tests of the bat bombs showed that they could have been very effective. But the military decided to funnel all available funding into developing atomic weapons with the Manhattan Project and the bat bombs were given the boot. The fu-go, on the other had, were actually used and resulted in several casualties on the American mainland. However, after early reports of the bombs reached the U.S. military, it was covered up to stop the Japanese from finding out that their plan was working, Radiolab reports.

While most of the 6,000 or so balloon bombs the Japanese launched never reached the mainland, some may still be out there — and have been found by hikers as recently as 2014. If you’re hiking through the Pacific Northwest and come across a strange paper lantern, it might be best to leave it be.

Explore Every Tornado Across the United States Since 1980 Through This Interactive Map

Smithsonian Magazine

Across the United States, signs of spring are emerging, even as cold weather and a snowstorm threatens the Northeast. In most places, spring brings flower buds, balmy temperatures and a renewed green landscape, but in the central and southern United States, it also brings a force of destruction: tornado season.

Generally, these dangerous storms run from late winter to mid summer, but the season tends to vary slightly from region to region. A new interactive map from ESRI allows you to explore the history of tornadoes in your own state, region, or even backyard. The map shows every tornado to touch down in the U. S. from 1980 to 2012, and includes details on casualties and where each ranks on the Enhanced Fujita scale – a system scientists have used to rate tornadoes since 1971 (and was updated in 2007). The scale is calculated from the damage that the tornado inflicted and the wind speeds that would have been required to inflict such devastation.

So, why is spring the season of tornadoes? Here’s the highly simplified explanation behind why tornados form: warm, wet air in the lower atmosphere blows under cold, dry air in the upper atmosphere. During the spring, warm air in the jet stream coming off the Gulf of Mexico blows north and hits cold air coming out of the Arctic and off the Rocky Mountains. That year's tornado season varies based on local weather patterns and fluctuations in ocean surface temperatures. For example, warmer Pacific Ocean temperatures in 2013 shifted jet stream winds east toward Missouri and Tennessee, and away from the hotspot of Tornado Alley – from northern Texas to the lower edge of South Dakota.

A time-lapse video of annual tornado maps across the United States from 1980 to 2012. (Video: ESRI)

The United States has seen 21 category five (EF-5) tornadoes, the highest ranking on the Enhanced Fujita scale, since 1980, and eight of those hit the traditional Tornado Alley. But, the high-frequency tornado risk area extends beyond the Great Plains, east to Tennessee and south to Alabama. In terms of the most damaging tornadoes since 1980, an April 27, 2011, EF-4 twister left 1500 injured in central Alabama,and was part of a devastating tornado outbreak in the region over several days. That same year, a tornado ripped through Joplin, Missouri, killing 158 people, injuring 1150, and left $2.8 billion in property damage in its wake. The Joplin twister, an EF-5, was the deadliest tornado since 1950, and the 7th deadliest in U.S. history.

Though the traditional tornado hotspot is Tornado alley, from northern Texas to southern South Dakota, the southeastern U. S. has seen an increasing number of storms in the recent decade, and 2011 was a particularly bad year for the region. (Image: ESRI )

Like the Joplin event, most tornadoes form in extreme thunderstorms called supercells, but ESRI’s map echoes the mantra of meteorologists and wind engineers: tornadoes can form at any time and in any place. By geographical happenstance, the central United States is home to tornado-producing weather patterns, but tornadoes touch down outside the continental U. S., as well. Hawaii saw 39 tornadoes from 1950 to 2010, and some of these are waterspouts, funnels that either form on land and move to water or form over water and move to land. Even Alaska experiences a rare tornado, if the conditions are right.

For more on tornado science, see NOAA’s Tornado Q&A site compiled by Roger Edwards of the Storm Prediction Center, and for more on tornado preparedness, visit FEMA’s tornado site.

New Juno Data Gives Unprecedented Glimpse Beneath Jupiter's Stormy Shell

Smithsonian Magazine

Astronomers Galileo Galilei and Giovanni Cassini laid eyes on Jupiter's swirling surface in the 1600s. These early astronomers marveled at the giant planet’s bands and even the Great Red Spot—a storm that has swirled for centuries. Since then, despite countless observations and several successful flybys, our knowledge of the King of Planets still runs skin deep.

But now, researchers are getting their closest look yet. Four separate articles published in the journal Nature parse data from NASA’s Juno probe, giving scientists a peek into the planet’s mysterious interior, reports Jonathan Amos at the BBC. And it's nothing like we imagined.

The Juno probe was launched in 2011 and arrived at Jupiter in 2016, orbiting the solar system’s largest planet ever since. It has snapped our best photos yet of the planet and uses its array of instruments to scrutinize Jupiter's many curious features—magnetosphere, dense atmosphere, roaring winds and all.

In the first two of the new studies, researchers explore the tiny variations in the tug of Jupiter's gravity. The analysis suggests that the atmospheric storm bands swirling around the planet are not just surface features. Instead, they likely extend around 1,860 miles down.

“This solves a long-time mystery,” Juno co-investigator Tristan Guillot from the Côte d'Azur Observatory in France tells Amos. “For over 40 years we didn't know whether the bands would go all the way to the center, or whether they were just skin deep. [1,860 miles] is actually quite deep. It’s 1 percent of the mass of the planet. Jupiter’s very big so it’s about three Earth masses that are involved in this motion.”

While an atmosphere that makes up 1 percent of the planet’s mass may not sound too impressive, George Dvorsky at Gizmodo points out that Earth’s atmosphere makes up less than one millionth the mass of our planet. The new measurements will give researchers a much more detailed view of the planet, helping scientists better understand what might be powering Jupiter’s jet streams and learn more about the planet’s core, structure and origins. "It’s like going from a 2-D picture to a 3-D version in high definition, ” says lead author Yohai Kaspi of the Weizmann Institute of Science, Rehovot, Israel in a press release.

As for Jupiter’s core, this has been an enduring mystery. The third new study, however, is starting to sort this out. The analysis suggests that the interior mass of Jupiter rotates as one single body, unlike its swirling surface. The findings also suggest that the core is likely in a liquid state and is not a solid. 

“It is an almost 50-year old puzzle in planetary science that is solved,” Guillot tells Dvorsky. “We didn’t know whether a gaseous planet like Jupiter—but also Saturn, Uranus, Neptune, and giant exoplanets—rotates with zones and belts all the way to the center or whether, on the contrary, the atmospheric patterns are skin-deep. Many lab experiments, numerical simulations had been performed but with no clear picture emerging. Now, thanks to Juno’s amazing accuracy—it measured Jupiter’s gravity field 100 times better than before—we have the ground truth.”

The next revelation from Juno is a series of new photos from its Jovian Infrared Auroral Mapper, an instrument that was able to probe the weather at Jupiter’s poles as deep as 45 miles. The effort revealed an area of closely packed cyclones, some roaring at 220 miles per hour. At the north pole, eight cyclones circle around one central swirl while Juno found five of these whirls around the central cyclone of the south pole.

“Each one of the northern cyclones is almost as wide as the distance between Naples, Italy, and New York City—and the southern ones are even larger than that. They have very violent winds, reaching, in some cases, speeds as great as 220mph,” lead author Alberto Adriani of the Institute for Space Astrophysics and Planetology in Italy tells Amos. “Finally, and perhaps most remarkably, they are very close together and enduring. There is nothing else like it that we know of in the Solar System.”

Juno will likely reveal many more surprising finds about Jupiter as it continues to scan the planet until its mission ends in 2021. “The real question that we’re after is, how did it form?” Scott Bolton, Juno’s principal investigator tells Marina Koren at The Atlantic. “And what does that tell us about how the rest of the solar system formed and how other solar systems form? How are planets really made?”

Since Jupiter is likely the first planet to form in our solar system, figuring out how it came to be will help researchers understand how the rest of the planets—including Earth—lined up around the sun.

Tornadoes Are Now Ganging Up in the United States

Smithsonian Magazine

While the United States has not experienced an overall increase in tornadoes over the last several decades, more twisters are now grouping together, according to decades’ worth of tornado data analyzed by the National Oceanic and Atmospheric Administration. If the trend continues, U.S. residents could see even fewer tornado days in the coming years, but many of those days could pack a punch.

Scientists have been concerned that the atmospheric warming from climate change could somehow affect the frequency or intensity of the violent tornadoes that plague much of the United States. But it hasn’t been clear how those changes would manifest.

“We know that tornadoes form when there is lots of energy available for thunderstorms and when there is lots of wind shear,” says NOAA tornado researcher Harold Brooks. Wind shear is the change in the wind’s speed or direction as you go higher in the atmosphere, and strong shear helps give a tornado its twist. Global warming is increasing the energy available for storms to form, but it’s also expected to decrease wind shear, Brooks notes.

To see how climate change might be affecting tornadoes, scientists need to look at their historical patterns. That can be difficult, in part because there is no traditional season for tornadoes as there is for hurricanes. Twisters have struck on every calendar day of the year within the past six decades. Further complicating matters, the way twisters are observed and reported has changed over time. Scientists know that those observational differences have changed the numbers of the smallest tornadoes—those rated F0 on the Enhanced Fujita scale. These storms have increased from about 100 per year in the 1950s to some 800 annually today. Larger storms—F1 to F5—have stayed constant, numbering around 500 on average yearly, although their frequency can vary widely from year to year.

In the new study, published today in Science, Brooks and his colleagues tallied U.S. storms from 1954 to 2013, leaving out the small F0 twisters. Then they looked at the days on which those storms occurred. They found that the frequency of tornado days has declined over that time. In 1973, for instance, tornadoes formed on 187 days. By contrast, 2011 saw twisters on only 110 days—but nine of those days saw more than 30 tornadoes each.

“In effect, there is a low probability of a day having a tornado, but if a day does have a tornado, there is a much higher chance of having many tornadoes,” the researchers write. Now, about a fifth of a year’s cyclones occur on just three days of that year.

The NOAA results are similar to those of another study, published earlier this year in Climate Dynamics, that also found an increase in tornado density—twisters are clustering both in time and space. “Since we both used the same data, it is not surprising that the conclusions are the same,” says that study’s lead author James Elsner of Florida State University in Tallahassee. “It is a bit surprising to me that they do not offer speculation on the possible cause.”

The NOAA researchers are reluctant to attribute the change in tornado timing to any cause at this point, though they do not think it has anything to do with how the storms are reported. “We need to look at the distribution of favorable [tornado] conditions on small time and space scales and see how those have changed over the years, if they have changed,” Brooks says. Global climate change isn’t the only factor that may be affecting tornado patterns. Brooks says researchers should also consider changes in land-use patterns, for instance, because vegetation can affect local weather and microclimates.

But Elsner thinks that climate is probably involved. “The greater heat and moisture in the atmosphere is a direct result of a warming planet, and the warming is greater at the poles than at lower latitudes, amplifying and slowing the jet stream,” he says. That provides sufficient wind shear for the tornadoes. “Shear will decrease on average across the globe as the warming in the Arctic outpaces warming elsewhere, but sufficient shear persists regionally when the jet stream waves amplify and stall,” he says. And that could lead to clustered tornadoes.

Scientists Flew a Jet Plane Into a Thunderstorm to Study Antimatter

Smithsonian Magazine

Six years ago, Joseph Dwyer, an atmospheric physicist, flew a jet plane into the heart of a thundercloud. The plane’s trajectory was no accident — Dwyer is a lightning expert. He’s known for sending small rockets tethered to the ground by copper wire directly into storms in order to attract bolts of lightning. But despite years of work, mysteries about lightning and the storms that produce it abound. "The insides of thunder­storms are like bizarre landscapes that we have barely begun to explore," he told Davide Castelvecchi for Nature

And during that particular flight six years ago, Dwyer discovered something he still can’t fully explain. After what he calls "a wrong turn" the airplane entered into a strange cloud of antimatter.

Scientists already know that thunderstorms are breeding grounds for a particular kind of antimatter called positrons. These particles are the opposite of electrons. They carry a positive charge (hence the name) where electrons carry a negative charge. When the two meet, they annihilate each other, an event researchers can see because it throws off a flash of gamma rays. NASA’s Fermi Gamma-ray Space Telescope was able to spot these gamma ray flashes sparkling through thunderstorms soon after its launch in 2008. Each flash gives a distinct amount of energy — the signature of an electron and positron meeting.

Dwyer’s mission was therefore to look for those gamma ray flashes. He was then at the Florida Institute of Technology and was able to get a plane — the type usually flown by business executives, Castelvecchi reports — and fly off the Georgia coast in search of those gamma rays. At a fateful point the the pilots thought they had turned back towards the coast. Castelvecchi writes:

“Instead, it was a line of thunderstorms — and we were flying right through it,” Dwyer says. The plane rolled violently back and forth and plunged suddenly downwards. “I really thought I was going to die.” 

During that time however, some of the gamma ray signatures Dwyer recorded didn’t come in at the right energy level. They were slightly lower energy than he expected. In the years since the flight, they’ve tried to figure out why. Dwyer and his colleagues suspect that the rays lost energy as they traveled through the air and reached the plane. They estimate that the plane flew through a small cloud of antimatter about one to two kilometers across. 

The antimatter is still likely to be positrons, but where they were coming from is still up for debate. Instead of being created by the thunderstorm, they could have streamed in from space in the form of cosmic rays. Or, as another physicist, Aleksandr Gurevich, who was not on the team, suggests, the airplane’s wings could have gathered a charge, produced extremely intense electric fields that generated positrons.

The only way to answer all these lingering questions about the antimatter cloud is to go back to the scene of the crime — Dwyer wants to send weather balloons into the center of violent storms. Also, the U.S. National Science Foundation hopes to fly a detector that can measure gamma rays into a storm once again, this time on an armored anti-tank plane that won’t be tossed around as easily, Castelvecchi reports.  "It’s very difficult to make measurements inside the thunderstorm," Dwyer told Ira Flatow on NPR’s Science Friday in 2010. "They're big dangerous places." But not dangerous enough to stymie curiosity.

The Swirling Storm Above Saturn’s North Pole Changed Colors

Smithsonian Magazine

Jupiter’s Great Red Spot is usually the cosmic storm that gets all the attention, but the next gas giant over has a swirling weather system of its own. The massive hexagonal-shaped storm sits atop Saturn’s north pole and is big enough to swallow Earth whole. But oddly, over the last several years, the swirling shape has changed colors.

The “hexagon,” as NASA astronomers refer to the storm, is a fascinating weather system caused by six different jet streams. But since 2012, the light blue form slowly shifted to a pale gold color—the change all captured by the Cassini spacecraft, The Guardian reports.

Researchers are still investigating possible causes for the color change, but initial analysis suggests that it may have something to do with the planet's seasons, according to a NASA press release.​ 

The idea is that as the planet shifted away from the sun during its years-long winter between 1995 and 2009, and the vortex likely flushed atmospheric particulate out of the region, turning it blue. The weather patterns of the hexagon essentially barricades off the region, preventing particulate flooding back in. But now that Saturn’s northern hemisphere is starting to shift back into summer, the constant sunlight is reacting with the atmosphere to produce more particulate, turning the area gold, Samantha Mathewson reports for Space.com.

Shifting seasons may not be the only reason Saturn’s north pole is turning gold again. Wind patterns around the gas giant could change as the sun’s rays heat up Saturn’s atmosphere, according to the press release. And of course, it could be a combination of these factors.

In any case, it’s lucky that the NASA scientists were able to witness this phenomenon at all. Each year on Saturn is equal to about 29 Earth years, and Cassini has only been orbiting the gas giant since 2004. That put it in exactly the right spot to witness the color-shifting pole as it moved through its winter equinox and started back towards summer, Maddie Stone writes for Gizmodo.

Though Cassini’s mission is scheduled to come to an end next year, the wealth of data it has beamed back has given NASA scientists a fresh look at weather on a different planet. There may only be a few more months left in the craft's life, but there still potential for more discoveries to come.

Check Out New Pictures of Saturn From Cassini’s Latest Orbit

Smithsonian Magazine

After roughly 12 years of taking pictures and beaming back data about Saturn, NASA’s Cassini spacecraft's epic adventure is coming to an end. The spacecraft has recently moved into its last orbit before it takes a final plunge into Saturn’s atmosphere towards the end of 2017. Luckily, researchers here on Earth are already seeing the fruits of Cassini’s goodbye tour in a magnificent series of images of Saturn’s north pole.

"This is it, the beginning of the end of our historic exploration of Saturn,” Carolyn Porco, head researcher for the Cassini imaging team at the Space Science Institute in Boulder, Colorado, says in a statement. “Let these images—and those to come—remind you that we’ve lived a bold and daring adventure around the solar system’s most magnificent planet."

Earlier this month, Cassini entered what NASA calls its “Ring-Grazing Orbits,” which will take the little spacecraft in for a close-up look at the gas giant and it’s iconic rings. In the process, it has been able to take some of the most detailed pictures of Saturn that scientists have examined yet, including the hexagonal-shaped jet stream that caps its north pole, Paul Rincon reports for the BBC.

These images, taken on December 2 and 3, are from the first step in Cassini’s new orbit. First, the spacecraft is taking a big swing over Saturn’s north pole before it takes a steep dive down past the edge of the planet’s main rings, Loren Grush reports for The Verge. By using different filters, Cassini’s cameras were able to peer through several layers of gas to create this series of images that NASA has released as a collage.

In addition to skimming past the rings, Porco and her team are looking forward to new shots of Saturn’s moons, most of which are located near the edge of the gas giant’s main rings. In the process of taking these dives, Cassini will send back the closest-ever photographs of the planet’s rings as well as its smaller moons, Maddie Stone reports for Gizmodo.

While these are just the first images retrieved from Cassini since entering its new orbit, they are far from the last. The spacecraft is scheduled to keep diving in and out of Saturn’s rings and past the planet until April 22, when a well-timed slingshot past the moon Titan will bring Cassini into its final path. From there, it will keep circling Saturn at an even closer distance, until it finally dives into the gas giant’s atmosphere and destroys itself in the process, Rincon reports.

Until then, Cassini will continue its mission, beaming back valuable information that will help scientists better understand one of the largest planets in our cosmic backyard.

This view from NASA's Cassini spacecraft was obtained about two days before its first close pass by the outer edges of Saturn's main rings during its penultimate mission phase. (NASA/JPL-Caltech/Space Science Institute)

Cyperus anderssonii Boeckeler

NMNH - Botany Dept.

Massive Flying Wind Turbine Could Offer A New Path To Clean Energy

Smithsonian Magazine

As oil companies drill ever deeper to meet the world's thirst for fuel, a new wave of clean energy entrepreneurs are also searching far and wide for sources—but in the opposite direction.

That's because as you go higher, ground friction diminishes, giving way to increasingly stronger winds; at extreme elevations, ranging between 20,000 and 50,000 feet depending on your location, you enter what's called the jet stream, a swirling mass of air with winds upward of 100 miles per hour. As wind speeds double, the potential supply of energy grows eight-fold, so these air currents along the outer reaches of the earth's atmosphere can be thought of as a kind of vast treasure trove of renewable power.  In fact, an analysis published in the journal Energies concluded that "the total wind energy in the jet streams is roughly 100 times the global energy demand."

While the notion of tapping into the all-powerful jetstream appears to be out of reach, at least for now, a handful of wind energy start-ups are in a race to develop technologies they hope will someday take advantage of energy found at more modest altitudes. Among them is Altaeros Energies, which recently announced plans to hoist an airborne wind turbine to an unprecedented altitude of 1,000 feet above a remote site in Alaska. Over the course of 18 months, their Buoyant Airborne Turbine (BAT) prototype will supply  power to about a dozen off-the-grid homes.

Though no start date has been set for the project, the pilot is set to begin as soon as the company completes the permit process,  Altaeros Energies co-founder Adam Rein says.

"Places like Alaska are perfect for these systems we developed,"  Rein says. "At these sites, you have cold rugged conditions where the ground is frozen, which makes it difficult to put up regular turbines. If we can demonstrate that [BAT] can work in Alaska, it can work anywhere for more or less the same cost of setting up other turbines."

While the idea to create air-lifted power generators has been floated for some time now, it’s only recently that firms have assembled prototypes with the goal of producing something commercially viable. These include concepts such as the Laddermill turbine, which consists of a rotating loop of "power kites," and the Magenn Air Rotor System, a giant helium-filled rotor that its inventors has described as a "spinning Goodyear blimp.” But so far, it's only the Boston-based Altaeros that has been able to secure funding for a trial run: The pilot project is subsidized in part by the Alaska Energy Authority, which awarded the company a $1.3 million dollar grant to determine the feasibility of expanding technology to other isolated regions.

From a distance, the BAT looks a bit like a massive donut, except for a standard three-blade, horizontal axis turbine in the center. With four protruding fins for stability, the helium-filled outer shell, made from a highly-durable fabric, is attached to three high-tensile strength tethers that hold the turbine securely in place.

Once the BAT is suspended, an onboard sensor system enables the turbine to operate autonomously, even changing its position to harvest more wind energy or dock whenever it detects a severe thunderstorm. Energy is transferred to a power station on the ground, where an interface distributes power to a microgrid or grid connection.

In all, the BAT is capable of delivering two-to-three times the amount of power produced by conventional towers, Rein says. The inflatable turbine is also equipped with an emergency venting system that allows gases to be released gradually should the structure needs to be brought back to ground level. Monitoring would be done remotely; specialists would only be deployed periodically to top off any lost helium.

Altaeros hopes data collected during the 18-month pilot can be used to design commercial turbine units for niche markets, including remote military bases and  disaster zones.

Lest it sound too good to be true, there is still the issue of cost. At 18 cents per kilowatt-hour, annual energy costs of the BAT are still too high for most major markets in America, where the average consumer pays about 13.4 cents per kilowatt-hour.

But for communities located off the main power grid, airborne wind turbines offer an attractive alternative, albeit an extreme one. Alaskan residents living in these far-off rural communities sometimes pay as much as a dollar per kilowatt-hour for fuel from imported diesel housed in nearby storage tanks.

Competing designs, like the Makani's flying wing turbine, can conceivably produce power at a much lower cost, Rein says, at least at the moment. As way of boosting the technology's mainstream appeal, he says the company opted to go with the more expensive but established lift technology used to deploy Aerostat craft—used in the iconic Good Year blimp—as way of boosting its reliability. (The blimp claims to be able to withstand  hurricane force winds and lightning strikes).

"It's safe and reliable," Rein says. "No one ever worries that a blimp during a sporting even will fall into the stadium."

Besides safety, Rein says another advantage of  his company's invention is that, unlike tower turbines, inflatable structures can be transported inside small containers, making them easy to deploy in a day’s time without the need for cranes and other heavy equipment. Additional gadgets, such as wireless communication devices, can also be mounted to provide other commodities like WiFi. But the company won't attempt, at least for the forseeable future, to make a play in major markets.

"You won't see BAT sitting above the Empire State Building," he says. "There are too many community concerns in those areas. So in that sense, we’re not trying to replace traditional turbines, but rather expand access to clean power to where it typically hasn't been technologically feasible."

Celebrate Cassini's Historic Voyage in Eight Incredible Images

Smithsonian Magazine

After 20 years in space and 13 years exploring Saturn and its moons, NASA's Cassini space probe is running out of fuel. So on Friday, the craft will swing through the gap between Saturn and its famous rings and plunge into the planet's atmosphere—taking pictures and measurements along the way.

This move is a planned endeavor intended to prevent contamination of Saturn's moons, some of which have the potential to harbor life. While it's hard to say goodbye to one of humanity’s most successful exploratory missions, Cassini has left behind a legacy of data. Over the course of its explorations, it has sent back thousands upon thousands of amazing images, rewriting what we know about Jupiter as well as Saturn, its rings and most importantly its moons.

The final plunge has almost been a separate mission of its own. Since April, the craft has been in the process of making 22 loops between Saturn and its rings, giving NASA some of the closest images of the planet’s surface and new views of the ring system.

“Cassini's grand finale is so much more than a final plunge,” Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory says in a press release. “It's a thrilling final chapter for our intrepid spacecraft, and so scientifically rich that it was the clear and obvious choice for how to end the mission.”

It’s difficult to fully summarize Cassini’s contributions to science. For the full story see NASA’s timeline. But here are some of Cassini's greatest images and discoveries.

(NASA/JPL/Space Science Institute)

Jupiter Flyby

Making the 746-million-mile trip to Saturn is not easy. That’s why after its launch on October 15, 1997, Cassini spent seven years in transit, first circling the planet Venus twice using its gravity to give it a speed boost before swinging past Earth again for another lift. In December, 2000, Cassini passed Jupiter joining forces with the Galileo spacecraft already orbiting the planet. The craft was able to use its narrow-angle camera to make the most exact color images of Jupiter ever taken, picking up details as small as 75 miles across.

(NASA/JPL-Caltech/Space Science Institute)

Into Orbit

On Thursday, July 1, 2004, Cassini became the first human-created spacecraft to orbit Saturn, giving researchers the first up close images of the planet. Because a year on Saturn lasts 29.457 Earth years, Cassini has watched the angle of the sun shift over the years as the season slowly changes, giving the planet a different appearances. During its mission, Cassini witnessed winter and spring in the northern hemisphere and summer and fall in the south, recording the changes in clouds, temperature and chemistry based on the seasons. Perhaps the probe's most iconic image of the planet is "Saturn, Approaching Northern Summer," shown above, taken in May 2017 close to the summer solstice.

(NASA/JPL/University of Arizona/University of Idaho)

Landing On Titan

On January 14, 2005, the European Space Agency’s 9-foot diameter, 700-pound  Huygens lander plummeted through the atmosphere of Saturn’s giant moon Titan for 2 hours and 27 minutes. The probe, carried by Cassini, then parachuted to the moon’s surface transmitting data from six scientific instruments for 72 minutes, becoming the first probe to land on a body in the outer solar system.

As Ben Guarino at the Washington Post reports, the probe found a very Earth-like moon, with a few twists. Instead of liquid water if had liquid methane. Instead of rocks there’s chunks of frozen water and its “dirt” is made from hydrocarbon particles. Even though there are freezing temperatures, the planet could support microbial life. Over its lifetime, Cassini passed Titan more than 100 times, collecting immense amounts of images and data, including a pass in November 2015 that produced the image above, “Peering Through Titan’s Haze”

Cassini said its last goodbye to the moon on Tuesday. “Cassini has been in a long-term relationship with Titan, with a new rendezvous nearly every month for more than a decade,” Cassini Project Manager Earl Maize says in a press release. “This final encounter is something of a bittersweet goodbye, but as it has done throughout the mission, Titan's gravity is once again sending Cassini where we need it to go.”

(NASA/JPL/Space Science Institute)

Encountering Enceladus

If Cassini was in a long-term relationship with Titan, it had a torrid love affair with Saturn’s icy moon Enceladus. In March and July, 2005, Cassini made its first close passes of the moon, producing the image, “Enceladus the Storyteller,” above. The relatively small moon was a revelation with its huge clouds of water vapor, complex tectonics and fractures snaking across its southern hemisphere. Researchers also found that those fractures spray huge plumes far into space. Cassini examined those plumes, and in April researchers revealed that the jets are composed of 98 percent water along with some hydrogen and other organic chemicals. This discovery raises the possibility that life could exist at hydrothermal vents under the planet’s icy shell.

(NASA/JPL/Space Science Institute)

Rings of Information

Since Galileo first discovered Saturn’s rings in 1610, they have been a source of mystery and fascination for scientists. Cassini has helped researchers learn much more about the rings, finding that the particles in the rings range from grains of sand to mountain-sized boulders. The probe helped scientists discover that the planet’s E Ring is mainly composed of material ejected by Enceladus’s jets. On September 15, 2006, Cassini took perhaps its most dramatic image of the rings, “In Saturn’s Shadow” when the probe imaged the planet with the sun completely blocked. The picture revealed two new faint rings, one produced by the moons Janus and Epimetheus and another one by the moon Pallene.

(NASA/JPL/Space Science Institute)

The Hexagon

The Voyager probe first spotted Saturn’s strange hexagonal jet stream in the early 1980s. But Cassini was the first to produce detailed shots of the 20,000-mile wide system, which swirls around the North Pole at 200 miles per hour. While the swirl does look like a hurricane and has an eye about 50 times larger than an Earth hurricane, researchers believe it’s just the natural jet stream, which endlessly spins because, unlike on Earth, there are no mountains or other obstacles to disrupt its course.

(NASA/JPL-Caltech/Space Science Institute)

Rise of the New Moons

Besides the detailed information about Titan and Enceladus, Cassini also captured incredible images of Saturn’s many moons. When Cassini launched in 1997, researchers had only confirmed 18 of the planet’s moons. Now, Cassini and ground-based telescopes have found a total of 62 possible bodies orbiting the planet, some the size of Mercury and some just a few miles across. They come in endless shapes and sizes, many of which were captured by Cassini, including the icy moon Dione, the great canyons on Tethys, the smooth, egg-like Methone and the strange pocked surface of Hyperion. Some of the moons even crossed into pop culture, like Mimas, pictured above, which was compared to the Death Star and the tiny dumpling-like moon Pan, which, among other comparisons, many described as a space ravioli.

(NNASA/JPL-Caltech/Space Science Institute)

The Final Flights

In April, 2017, Cassini conducted the first of its 22 dives between Saturn and its rings. While it will take months or years to analyze the data, researchers have already found some surprising things, like the fact that the spaces between rings are more or less free of debris and dust. It’s also sent back new images of the Hexagon and the spiral density waves found in the planet’s B Ring.

We wish this craft well in its triumphant plunge into Saturn's atmosphere—and eagerly await the exciting discoveries that are still bound to come from the data.

Despite Dam Danger, California’s Still In a Drought

Smithsonian Magazine

As large amounts of rain and snow soaked California last week, all eyes turned toward the threat of a dam failure at Lake Oroville, a reservoir that supplies much of the state’s drinking water. But what’s getting less attention is the fact that despite the easing of drought conditions in California, the situation below ground is still dry.

Thus far, approximately 188,000 people who live near Lake Oroville remain under evacuation orders put in place when the lake’s water levels began to rise, reports the Sacramento Bee. The earthen dam, which holds 3.5 million acre-feet of water, is the tallest in the United States. But when heavy storms hit the Sierra Nevadas, the reservoir filled to its highest level ever. Such excess forced officials to use an emergency spillway that has started to erode, creating the possibility of a collapse.

The Sierra Nevadas aren’t the only place in California hit with ample precipitation this winter. Earlier this year, a series of severe storms struck Southern California, driven by a temperature anomaly in the Pacific Ocean that shifted the jet stream from its usual position. Although that’s good news for the drought-parched state, it doesn’t mean that the drought is over.

Drought conditions continue to prevail throughout much of the state. According to the United States Drought Monitor, which tracks drought conditions throughout the country, a large portion of central and southern California is still in the midst of a drought. Though much of the state’s dry segment is at a “moderate” drought level, pockets of “severe” and “extreme” drought remain despite extensive snowfall that has put statewide snowpack at 176 percent of normal.

The water below the surface, known as groundwater, also remains in crisis. According to Thomas Harter, a groundwater expert and Robert M. Hagan Endowed Chair for Water Resources Management and Policy at the University of California, Davis, this deep water offers a kind of liquid insurance for the state.

“Our groundwater is an endowment of nature,” Harter tells Smithsonian.com. Since the 1920s, water has been pumped up from beneath the surface to supplement snowpack and surface reservoirs. But during dry years, more water is pumped out of the ground than is put back in by precipitation—and the recent drought has overdrawn the groundwater account. “We have a large deficit,” explains Harter. “It will take up to six average to wet years to make up for the losses we’ve incurred over the last 15 years of groundwater storage.”

Even if it rained constantly this year, says Harter, it wouldn’t make up for the loss, especially since groundwater takes longer to accumulate underground than it does to build up in above-ground reservoirs like Lake Oroville.

In the meantime, some areas of the Central Valley are experiencing a phenomenon known as subsidence, in which rock settles in on itself and becomes more compact due to excessive groundwater pumping. Last year, scientists at the Jet Propulsion Laboratory found that some parts of central and southern California have sunk as much as 6.5 inches from subsidence.

California is working on preventing such overpumping; in 2014, the state enacted a law that regulates the practice. But it will take plenty of precipitation to bring aquifers to the right levels—and ongoing depletion can contribute to decreases in water quality, habitat loss and even a higher risk of earthquakes.

It all goes to show that the drought above is only part of the story—and California’s water crisis is far from over.

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