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In ordinary visible light, this cluster of galaxies doesn’t look like much. There are bigger clusters with larger and more dramatic-looking galaxies in them. But there’s more to this image than galaxies, even in visible light. The gravity from the cluster magnifies and distorts light passing near it, and mapping that distortion reveals something about a substance ordinarily hidden from us: dark matter.
This collection of galaxies is famously called the “Bullet Cluster,” and the dark matter inside it was detected through a method called “weak gravitational lensing.” By tracking distortions in light as it passes through the cluster, astronomers can create a sort of topographical map of the mass in the cluster, where the “hills” are places of strong gravity and “valleys” are places of weak gravity. The reason dark matter—the mysterious substance that makes up most of the mass in the universe—is so hard to study is because it doesn’t emit or absorb light. But it does have gravity, and thus it shows up in a topographical map of this kind.
The Bullet Cluster is one of the best places to see the effects of dark matter, but it’s only one object. Much of the real power of weak gravitational lensing involves looking at thousands or millions of galaxies covering large patches of the sky.
To do that, we need big telescopes capable of mapping the cosmos in detail. One of these is the Large Synoptic Survey Telescope (LSST), which is under construction in Chile, and should begin operations in 2022 and run until 2032. It’s an ambitious project that will ultimately create a topographical map of the universe.
“[LSST] is going to observe roughly half of the sky over a ten-year period,” says LSST deputy director Beth Willman. The observatory has “a broad range of science goals, from dark energy and weak [gravitational] lensing, to studying the solar system, to studying the Milky Way, to studying how the night sky changes with time.”Artist’s rendering of the Large Synoptic Survey Telescope, currently under construction in Chile (Michael Mullen Design, LSST Corporation)
To study the structure of the universe, astronomers employ two basic strategies: going deep, and going wide. The Hubble Space Telescope, for example, is good at going deep: its design lets it look for some of the faintest galaxies in the cosmos. LSST, on the other hand, will go wide.
“The size of the telescope itself isn't remarkable,” says Willman. LSST will be 27 feet in diameter, which puts it in the middle range of existing telescopes. “The unique part of LSST's instrumentation is the field of view of [its] camera that's going to be put on it, which is roughly 40 times the size of the full moon.” By contrast, a normal telescope the same size as LSST would view a patch of the sky less than one-quarter of the moon’s size.
In other words, LSST will combine the kind of big-picture image of the sky you’d get by using a normal digital camera, with the depth of vision provided by a big telescope. The combination will be breathtaking, and it’s all due to the telescope’s unique design.
LSST will employ three large mirrors, where most other large telescopes use two mirrors. (It’s impossible to make lenses as large as astronomers need, so most observatories use mirrors, which can technically be built to any size.) Those mirrors are designed to focus as much light as possible onto the camera, which will be a whopping 63 inches across, with 3.2 billion pixels.
Willman says, “Once it's put together and deployed onto the sky, it will be the largest camera being used for astronomical optical observations.”
While ordinary cameras are designed to recreate the colors and light levels that can be perceived by the human eye, LSST’s camera will “see” five colors. Some of those colors overlap those seen by the retinal cells in our eyes, but they also include light in the infrared and ultraviolet part of the spectrum.
After the Big Bang, the universe was a hot mess—of particles. Soon, that quagmire cooled and expanded to the point where the particles could begin attracting each other, sticking together to form the first stars and galaxies and forming a huge cosmic web. The junctions of which grew into large galaxy clusters, linked by long thin filaments, and separated by mostly-empty voids. At least that’s our best guess, according to computer simulations that show how dark matter should clump together under the pull of gravity.
Weak gravitational lensing turns out to be a really good way to test these simulations. Albert Einstein showed mathematically that gravity affects the path of light, pulling it slightly out of its straight-line motion. In 1919, British astronomer Arthur Eddington and his colleagues successfully measured this effect, in what was the first major triumph for Einstein’s theory of general relativity.
The amount light bends depends on the strength of the gravitational field it encounters, which is governed by the source’s mass, size and shape. In cosmic terms, the sun is small and low in mass, so it nudges light by only a small amount. But galaxies have billions and billions of stars, and galaxy clusters like the Bullet Cluster consist of hundreds or thousands of galaxies, along with plenty of hot plasma and extra dark matter holding them all together and the cumulative affect on light can be quite significant. (Fun fact: Einstein didn’t think lensing would actually be useful, since he only thought of it in terms of stars, not galaxies.)A dark matter map, created by Japanese astronomers using weak lensing (Satoshi Miyazaki, et al.)
Strong gravitational lensing is produced by very massive objects that take up relatively little space; an object with the same mass but spread out over a larger volume will still deflect light, but not as dramatically. That’s weak gravitational lensing—usually just called “weak lensing”—in essence.
Every direction you look in the universe, you see lots of galaxies. The most distant galaxies may be too faint to see, but we still see some of their light filtering through as background light. When that light reaches a closer galaxy or galaxy cluster on its way to Earth, weak lensing will make that light a little brighter. This is a small effect (that’s why we say “weak”, after all), but astronomers can use it to map the mass in the universe.
The 100 billion or so galaxies in the observable universe provide a lot of opportunities for weak lensing, and that’s where observatories like LSST come in. Unlike most other observatories, LSST will survey large patches of the sky in a set pattern, rather than letting individual astronomers dictate where the telescope points. In this way it resembles the Sloan Digital Sky Survey (SDSS), the pioneering observatory that has been a boon to astronomers for nearly 20 years.
A major goal of projects like SDSS and LSST is a census of the galactic population. How many galaxies are out there, and how massive are they? Are they randomly scattered across the sky, or do they fall into patterns? Are the apparent voids real—that is, places with few or no galaxies at all?
The number and distribution of galaxies gives information about the biggest cosmic mysteries. For example, the same computer simulations that describe the cosmic web tell us we should be seeing more small galaxies than show up in our telescopes, and weak lensing can help us find them.
Additionally, mapping galaxies is one guide to dark energy, the name we give the accelerating expansion of the universe. If dark energy has been constant all the time, or if it has different strengths in different places and times, the cosmic web should reflect that. In other words, the topographical map from weak lensing may help us answer one of the biggest questions of all: just what is dark energy?
Finally, weak lensing could help us with the lowest-mass particles we know: neutrinos. These fast-moving particles don’t stick around in galaxies as they form, but they carry away energy and mass as they go. If they take away too much, galaxies don’t grow as big, so weak lensing surveys could help us figure out how much mass neutrinos have.
Like SDSS, LSST will release its data to astronomers regardless of whether they’re members of the collaboration, enabling any interested scientist to use it in their research.
“Running the telescope in survey mode, and then getting those extensive high-level calibrated data products out to the entire scientific community are really gonna combine to make LSST be the most productive facility in the history of astronomy,” says Willman. “That's what I'm aiming for anyway.”
The power of astronomy is using interesting ideas—even ones we once thought wouldn’t be useful—in unexpected ways. Weak lensing gives us an indirect way to see invisible or very tiny things. For something called “weak,” weak lensing is a strong ally in our quest to understand the universe.
At 2 p.m. on February 16, 1968, a special red telephone rang at the police station in Haleyville, Alabama. Rather than a police officer, U.S. Congressman Tom Bevill answered the call. On the other end of the line was Alabama Speaker of the House Rankin Fite, calling from the mayor’s office (actually located in another part of the same building). Bevill’s simple answer of “hello” may not rank alongside Samuel Morse’s “What hath God wrought,” but it ushered in an important part of daily life, one that has saved countless American lives over the past 50 years. The call marked the first use of the emergency number 9-1-1, a technological answer to a life-and-death question—how do you get help quickly in the event of an emergency? Americans wrestling with the problem have experimented with many innovative solutions over the years.
In the late 18th and early 19th centuries, getting to the scene of a fire as quickly as possible was the best defense against a damaging conflagration. Just as today, time was of the essence. Watchmen would alert the populace with wooden rattles and raise the alarm by shouting through the streets (sometimes known as “hallooing fire”). Citizens and volunteer firefighters alike would grab leather buckets, hooks, axes, and other necessary equipment and head in the direction of the clamor. A simple fire pumper might be drawn by hand to the scene as well. But finding a fire fast, especially in a warren of urban streets, could be difficult.
The citizens of Philadelphia tried one solution when they restored the steeple of the Pennsylvania State House (better known as Independence Hall) in 1828. They hung a new bell and put a watchman on duty to keep a lookout for fires. Franklin Peale, son of painter Charles Willson Peale, suggested an alarm system for the new bell that would direct fire companies to the scene of a blaze. In the event of a fire near the State House itself, the bell in the steeple was rung continuously. One peal at regular intervals indicated a fire to the north, two peals meant a fire to the south, three to the east, four to the west, and so on. This system is preserved in the decoration on the top of a fire hat from Philadelphia in the museum collections. A compass rose, with a bell at the center, displays the alarm code. Bell codes were used in other cities as well, like New York. In Boston, the city was divided into fire districts, and church bells would peal the number of a district where a fire was discovered. However, the 19th century saw American cities growing in size and population, and a better system was needed to pinpoint the location of an emergency.
William F. Channing and Moses Farmer were both obsessed with the potential for electromagnetism and telegraphy. Specifically, both believed it could be harnessed to create a reliable and near-instantaneous fire alarm system throughout the city of Boston. The two collaborated to lobby city officials to fund “the Application of the Electric Telegraph to signalizing Alarms of Fire” (as their presentation was titled) and received $10,000 to develop and establish their system.
After running nearly 50 miles of wire throughout the city, connected to dozens of alarm boxes and bells, Channing and Farmer’s system was ready in the spring of 1852. If someone opened an alarm box and turned a small crank, the special-purpose telegraph would send out a pulsating electric current to electromagnets that pulled and released the bell clappers, producing alarms both at the scene of the emergency and at the central station, where the location was recorded. The first attempt by the public to use the system was on April 29, 1852. Unfortunately, the helpful citizen cranked too fast, such that the message could not be read, and the man had to run to the central signal office to alert them of the fire in person. Nevertheless, Channing and Farmer would continue to refine their system, and within months it proved a reliable tool in raising the alarm in Boston.
Channing and Farmer made a joint application for a patent for their system, and a patent was issued on May 19, 1857 (Patent No. 17355). Their patent model resides today in the Electricity Collections here at the museum, along with earlier prototypes.
It was at a Smithsonian Institution lecture in March 1855 that emergency alarms took another step. At that lecture, William Channing described the details and merits of the Channing and Farmer system, humbly noting theirs was “a higher system of municipal organization than any which has heretofore been proposed or adopted.” Despite this lofty claim, both men had failed to sell their system to other cities and municipalities, and Channing was falling into debt.
Attending the lecture was John Nelson Gamewell, a postmaster and telegraph operator from Camden, South Carolina. Seeing an opportunity, Gamewell raised the funds to buy the rights to market the Channing and Farmer system. Beginning in 1856, he sold the system to several American cities, including New Orleans, St. Louis, and Philadelphia. By 1859 Gamewell obtained the full rights and patents to the system and was on the verge of creating a fire alarm empire when the Civil War broke out. The U.S. government seized the patents from the Confederate Gamewell, and John Kennard, a fire official from Boston, bought them on the cheap in 1867.
After the war, Gamewell moved north and partnered with Kennard to create a new company to manufacture and sell fire alarms. Building on their success, Gamewell established the Gamewell Fire Alarm Telegraph Company, and its logo—a fist holding a clutch of lightning bolts—would soon be found on alarm boxes throughout North America. By 1890 Gamewell systems were installed in nearly 500 cities in the United States and Canada.
While Gamewell boxes became a common sight on public streets and buildings in the early 20th century, more and more Americans were installing a new device in their homes and businesses: the telephone. Before the advent of rotary dial phones (ask your parents, kids), all calls went through with operator assistance, and emergency calls could be directed to the appropriate party. With dial service, a person with an emergency had to call direct to their local police station, hospital, or fire department. Experiments with a universal emergency number in the UK in the 1930s prompted the National Association of Fire Chiefs to recommend such a system for the United States in 1957. On January 12, 1968, after a decade of study and debate and presidential commissions, the Federal Communications Commission and AT&T announced the selection of 9-1-1 as a national emergency number. One FCC member boasted at the time that 911 would be better remembered than 007.
The number was indeed easy to remember, quick to dial when needed, particularly on rotary phones (did you ask?), and difficult to dial in error. AT&T had already established special three-digit numbers—4-1-1 for directory assistance and 6-1-1 for customer service—so the new emergency number fit the existing system.
Some 2,000 independent phone companies in the United States had been left out of the decision, many preferring “0” as the standard number. Nevertheless, one such company decided get behind 9-1-1 in a big way. Bob Gallagher, the president of the Alabama Telephone Company (ATC), decided his company would beat “Ma Bell” to the punch. ATC staff picked Haleyville as the best location and worked after hours to design and implement the infrastructure. Almost exactly one month after AT&T’s announcement, Speaker Fite and Congressman Bevill spoke over the first dedicated 9-1-1 line. Nome, Alaska, would debut a 9-1-1 system about a week later.
It would take time for the system to grow in the United States, so publicity like that which surrounded the Haleyville call helped to spread the idea. Twenty years later, only half the U.S. population had access to a 9-1-1 system. By the end of the last century, that number had grown to well over 90%. Today an estimated 240 million calls a year are made to 9-1-1. Upwards of 80% of these calls now come from wireless devices, something almost impossible to consider 50 years ago, just as the watchman with a wooden rattle might not envision an alarm traveling over electrical wires.
Tim Winkle is the deputy chair of the Division of Home and Community Life and the curator of the Firefighting and Law Enforcement Collection.
Edvard Munch’s “The Scream” is iconic—but it's also mysterious. Why is the stressed-out subject screaming, anyway? A Norwegian scientist has an intriguing new theory, reports the BBC’s Jonathan Amos: Perhaps the scream was inspired by an atmospheric phenomenon called mother-of-pearl clouds.
The rare clouds got their nickname from the abalone shells they resemble. Also known as nacreous or polar stratospheric clouds, they’re iridescent and pretty unusual. They form in northerly latitudes during the winter when the dry stratosphere cools down.
Normally, the stratosphere is so dry that it can’t sustain clouds, but when temperatures get beneath about 108 degrees below zero, all of the scant moisture in the air gets chilly enough to form ice crystals. When the sun hits the perfect place along the horizon, those ice crystals reflect its rays, causing a shimmering, pearly effect.
Helene Muri, a meteorologist and cloud expert, recently gave a talk at this year's European Geosciences Union General Assembly about how the wavy mother-of-pearl clouds could be portrayed in Munch’s painting. “As an artist, they no doubt could have made an impression on him,” she tells Amos.The clouds form in icy temperatures and can be viewed only at certain latitudes and times of day. (Wikimedia Commons)
Though the sky in "The Scream" is outlandish, the painting is widely believed to be autobiographical. Munch himself struggled with tragedy and fragile health that scholars believe could have informed the painting’s colors and themes. In a poem in his diary, Munch recalls the sky turning “blood red” after he felt “a wave of sadness” while walking with some friends. He put a similar poem on the frame of one of his versions of the painting.
That description has prompted other scientists to use natural phenomena to explain the origin of the painting. In 2004, physicists theorized that the clouds were created when Krakatoa erupted in Indonesia—an event that caused spectacular sunsets throughout Europe. But it’s tricky to ascribe a particular date, time, or event to a piece of art, especially since painting is by nature so subjective.
It turns out that mother-of-pearl clouds have a dark side: As Nathan Case explains for The Conversation, they cause the ozone layer to further break down by stoking a reaction that produces free radicals, which can destroy atmospheric ozone. That’s something to scream about—but until scientists invent artistic time machines, their theories about the weather events that precipitated history’s greatest paintings will remain mere suppositions.
Sir Arthur Conan Doyle died in 1930, but his most famous work—stories about the English detective Sherlock Holmes—has lived on. Thanks to copyright law, those stories have also continued to benefit Doyle's heirs for the past 84 years. Every time someone wanted to write a story or film a movie about Sharlock Holmes, the Doyle estate would collect a fee. A legal ruling announced this week, however, has set Holmes free: the character and all his companions (as penned by Doyle) are now in the public domain.
The legal case of Klinger v. Conan Doyle Estate that settled the claim actually rested on an interesting issue, whether a copyright claim can persist on a character even if the works depicting that character have fallen out of copyright. The defense of the Doyle estate went something like this: sure, Arthur Conan Doyle's stories are now at least 90 years old, but other stories about Sherlock Holmes are still under copyright, therefore Sherlock Holmes is still under copyright.
Judge Richard Posner didn't buy the argument, and he ruled that Sherlock Holmes, the character, is now in the public domain.
Part of the motivation for the Judge's decision, says Molly Van Houweling for the Authors Alliance, was a consideration of what the larger ramifications of extending the copyright on Holmes would have on art in general. Holmes' lasting popularity is a rarity among fictional characters—most fall out of favor within years, not decades. Creating a longer term on copyright for characters would reduce the number of works flowing into the public domain. This, in turn, would make it more difficult or more expensive for future artists to work, since a great deal of art draws on earlier works.
There's another interesting facet to the case, too. The Doyle estate's argument hinged on the idea that Sherlock Holmes was a complex and defined character, one whose characteristics were set down by Doyle. But that argument, say Parker Higgins and Sarah Jeong in their 5 Useful Articles newsletter, really just isn't the case:
Posner's opinion has much to commend, but one area it does not delve into is how the character of Sherlock Holmes—as we know him—is the construct of many authors, artists, and even film-makers. As Authors Alliance co-founder Molly Van Houweling points out, the phrase "elementary, my dear Watson," never appears in any of Doyle's works. And Doyle himself never described Holmes wearing his signature funny hat, this pop culture impression of the detective came about through a series of others' interpretations—first, in a few original illustrations by Sidney Paget, which probably influenced the stage actor William Gilette's depiction of Holmes, whose photo inspired American illustrator Frederic Dorr Steele to consistently draw the character in a deerstalker cap, an artistic choice that made its way into a number of cinematic versions.
So what adventures should Sherlock and Watson get up to next? It's time to get your fan fiction juices flowing.
Gawking at the love lives of public figures–from Brangelina to Eliot Spitzer–is something of a national pastime these days, and things weren't much different during the lifetime of celebrated American artist Winslow Homer (1836-1910).
While prolific in depicting the outside world, Homer adamantly refused to reveal his inner landscape to an increasingly curious public throughout his career. Perhaps that is why, nearly a century after his death, we're still interested: Secrecy often suggests something worth concealing.
Homer himself hinted at this sentiment in a 1908 note to a would-be biographer: "I think that it would probably kill me to have such a thing appear–and as the most interesting part of my life is of no concern to the public I must decline to give you any particulars in regard to it."
Although Homer remained a bachelor for all of his 74 years, after his death, one of his close friends told biographer Lloyd Goodrich that the artist "had the usual number of love affairs." No conclusive evidence is available about any of these, but a thin trail of emotional clues exists amid Homer's correspondence with friends and family, as well as in his work.
The first such clue comes in a March 1862 letter to his father, Charles Savage Homer. The young Homer is planning to travel to Washington to illustrate Civil War action for Harper's Weekly, and mentions a comment made by his editor: "He thinks (I am) smart and will do well if (I) meet no pretty girls down there, which he thinks I have a weakness for."
Homer spent ten months in France in 1866-7, and had an active social life there, if his vivacious engravings of Parisian dance halls are any indication (see above sketch). For the next five or six years, back in America, he continued to paint generally cheerful, lively scenes, often featuring pretty young women.
"The numerous portrayals of fetching women suggest a longing for feminine company…these scenes may have been this shy man's way of safely bringing women closer," Randall Griffin wrote in his 2006 book Winslow Homer: An American Vision.
Specifically, it seems the painter yearned to be closer to Helena De Kay, an art student and the sister of Homer's friend Charles De Kay. She was the apparent model for several of Homer's works in the early 1870s, until she married the poet and editor Richard Watson Gilder in 1874.
As fine arts scholar Sarah Burns explained in a 2002 article for The Magazine ANTIQUES, Helena De Kay's correspondence shows how Homer may have tried to court her. Homer often asked her to visit his studio, an invitation he rarely extended to anyone, and she is the only painter he ever offered to instruct (though there is no evidence she accepted). In one note, he even compared a photo of her to a Beethoven symphony, "as any remembrance of you will always be."
Perhaps Homer's circa 1872 oil "Portrait of Helena De Kay" reflects his realization that he would likely lose his beloved to Gilder, who began courting her that year. It was an unusual work for Homer's style up to then – a somber, formal portrait, and an uncommissioned one at that.
In the painting, DeKay is seated on a couch in profile, dressed in black and looking down at a closed book in her hands. The indoor setting, presumably Homer's studio, is dark and empty but for a small spot of color on the floor–a discarded and dying rose; a few of its petals scattered nearby.
It is "a very suggestive picture, and unlike any other he painted," says Nicolai Cikovsky Jr., a Homer biographer and retired National Gallery of Art curator. "I'd say she is the most nameable candidate (for a love interest), certainly."
A letter from Homer to De Kay in December 1872 indicates that something had come between them. He asks her to pick up a sketch he had made of her, adding a few cryptic words of reassurance: "I am very jolly, no more long faces. It is not all wrong."
The next year, another of Homer's notes alludes to his feelings by what it omits: "My dear Miss Helena, I have just found your picture. I think it very fine. As a picture I mean, not because, etc."
It is unclear whether Homer ever actually proposed to De Kay, but he painted a picture of a proposal scene in 1872, with the telling title, "Waiting For an Answer," and in 1874 he painted an almost identical scene minus the young suitor ("Girl in an Orchard"), suggesting that the girl's answer had been to send the boy away. Around the same time, he painted several other pictures of "thwarted love," as Burns describes it.
Some scholars think he fell in love again a few years later, when he was around 40 years old. He visited friends in rural Orange County, New York, and painted several pictures of women there. One of them, titled "Shall I Tell Your Fortune?" shows a saucy-looking lass seated barefoot on the grass, holding playing cards in one hand. Her other hand rests palm-up on her hip, and her direct gaze seems to be asking the painter much more than the title suggests.
A similar woman appears in other Homer paintings from the mid to late 1870s, and this may have been the schoolteacher referred to by Homer's grandniece, Lois Homer Graham, in a piece she wrote for the book Prout's Neck Observed decades later: "The year 1874 found all of the Homer sons well established in their careers…Winslow had courted a pretty school teacher, but lost her to his career."
It does seem clear that Homer wanted a major change of scenery and lifestyle rather suddenly at the end of the 1870s. As Cikovsky puts it, "something was stirring in Homer's life, and I think some sort of intimacy gone wrong was part of that."
The artist withdrew from society, moving first to an island off Gloucester, Mass., then the remote fishing village of Cullercoats, England, and finally in 1883 to Prout's Neck, Maine, where he stayed the rest of his life. He developed a reputation as a grumpy recluse, discouraging visitors and turning down most social invitations, although he remained close to his family. His personal life may have suffered, but his professional life flourished in these years, as the seacoast inspired some of his best works.
Interestingly, Homer never attempted to sell the painting of the fortune-telling girl. It was still on an easel in his Prout's Neck studio when he died in 1910.
But before you get too wrapped up in the romance of that idea, keep in mind that alternate theories abound. Homer scholar Philip Beam thinks the mystery woman was no woman at all, but rather a boy modeling as a woman for the "girl-shy" painter.
At least one reviewer has argued that Homer was homosexual, though most art historians now reject the theory. Others, including Beam, think he was simply married to his work.
"To an artist of Homer's caliber much is given, but if he is to put his great gift to its fullest use, much is also demanded. So much that there is little time left to share with a wife," Beam wrote in Winslow Homer at Prout's Neck (1966).
The truth, it seems, remains as stubbornly elusive as the artist himself.
“Inventing Utamaro: A Japanese Masterpiece Rediscovered,” open recently at the Smithsonian’s Arthur M. Sackler Gallery, is a challenging exhibition, says Julian Raby, The Dame Jillian […]
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