Some time ago, via a certain orange website, I came across a report about a mission to recover nuclear material from a former Soviet test site. I don't know what you're doing here, go read that instead. But it brought up a topic that I have only known very little about: Hydronuclear testing. One of the key reasons for the nonproliferation concern at Semipalatinsk was the presence of a large quantity of weapons grade material. This created a substantial risk that someone would recover the material and either use it directly or sell it---either way giving a significant leg up on the construction of a nuclear weapon. That's a bit odd, though, isn't it? Material refined for use in weapons in scarce and valuable, and besides that rather dangerous. It's uncommon to just leave it lying around, especially not hundreds of kilograms of it. This material was abandoned in place because the nature of the testing performed required that a lot of weapons-grade material be present, and made it very difficult to remove. As the Semipalatinsk document mentions in brief, similar tests were conducted in the US and led to a similar abandonment of special nuclear material at Los Alamos's TA-49. Today, I would like to give the background on hydronuclear testing---the what and why. Then we'll look specifically at LANL's TA-49 and the impact of the testing performed there. First we have to discuss the boosted fission weapon. Especially in the 21st century, we tend to talk about "nuclear weapons" as one big category. The distinction between an "A-bomb" and an "H-bomb," for example, or between a conventional nuclear weapon and a thermonuclear weapon, is mostly forgotten. That's no big surprise: thermonuclear weapons have been around since the 1950s, so it's no longer a great innovation or escalation in weapons design. The thermonuclear weapon was not the only post-WWII design innovation. At around the same time, Los Alamos developed a related concept: the boosted weapon. Boosted weapons were essentially an improvement in the efficiency of nuclear weapons. When the core of a weapon goes supercritical, the fission produces a powerful pulse of neutrons. Those neutrons cause more fission, the chain reaction that makes up the basic principle of the atomic bomb. The problem is that the whole process isn't fast enough: the energy produced blows the core apart before it's been sufficiently "saturated" with neutrons to completely fission. That leads to a lot of the fuel in the core being scattered, rather than actually contributing to the explosive energy. In boosted weapons, a material that will fusion is added to the mix, typically tritium and deuterium gas. The immense heat of the beginning of the supercritical stage causes the gas to undergo fusion, and it emits far more neutrons than the fissioning fuel does alone. The additional neutrons cause more fission to occur, improving the efficiency of the weapon. Even better, despite the theoretical complexity of driving a gas into fusion¸ the mechanics of this mechanism are actually simpler than the techniques used to improve yield in non-boosted weapons (pushers and tampers). The result is that boosted weapons produce a more powerful yield in comparison to the amount of fuel, and the non-nuclear components can be made simpler and more compact as well. This was a pretty big advance in weapons design and boosting is now a ubiquitous technique. It came with some downsides, though. The big one is that whole property of making supercriticality easier to achieve. Early implosion weapons were remarkably difficult to detonate, requiring an extremely precisely timed detonation of the high explosive shell. While an inconvenience from an engineering perspective, the inherent difficulty of achieving a nuclear yield also provided a safety factor. If the high explosives detonated for some unintended reason, like being struck by canon fire as a bomber was intercepted, or impacting the ground following an accidental release, it wouldn't "work right." Uneven detonation of the shell would scatter the core, rather than driving it into supercriticality. This property was referred to as "one point safety:" a detonation at one point on the high explosive assembly should not produce a nuclear yield. While it has its limitations, it became one of the key safety principles of weapon design. The design of boosted weapons complicated this story. Just a small fission yield, from a small fragment of the core, could potentially start the fusion process and trigger the rest of the core to detonate as well. In other words, weapon designers became concerned that boosted weapons would not have one point safety. As it turns out, two-stage thermonuclear weapons, which were being fielded around the same time, posed a similar set of problems. The safety problems around more advanced weapon designs came to a head in the late '50s. Incidentally, so did something else: shifts in Soviet politics had given Khrushchev extensive power over Soviet military planning, and he was no fan of nuclear weapons. After some on-again, off-again dialog between the time's nuclear powers, the US and UK agreed to a voluntary moratorium on nuclear testing which began in late 1958. For weapons designers this was, of course, a problem. They had planned to address the safety of advanced weapon designs through a testing campaign, and that was now off the table for the indefinite future. An alternative had to be developed, and quickly. In 1959, the Hydronuclear Safety Program was initiated. By reducing the amount of material in otherwise real weapon cores, physicists realized they could run a complete test of the high explosive system and observe its effects on the core without producing a meaningful nuclear yield. These tests were dubbed "hydronuclear," because of the desire to observe the behavior of the core as it flowed like water under the immense explosive force. While the test devices were in some ways real nuclear weapons, the nuclear yield would be vastly smaller than the high explosive yield, practically nill. Weapons designers seemed to agree that these experiments complied with the spirit of the moratorium, being far from actual nuclear tests, but there was enough concern that Los Alamos went to the AEC and President Eisenhower for approval. They evidently agreed, and work started immediately to identify a suitable site for hydronuclear testing. While hydronuclear tests do not create a nuclear yield, they do involve a lot of high explosives and radioactive material. The plan was to conduct the tests underground, where the materials cast off by the explosion would be trapped. This would solve the immediate problem of scattering nuclear material, but it would obviously be impractical to recover the dangerous material once it was mixed with unstable soil deep below the surface. The material would stay, and it had to stay put! The US Army Corps of Engineers, a center of expertise in hydrology because of their reclamation work, arrived in October 1959 to begin an extensive set of studies on the Frijoles Mesa site. This was an unused area near a good road but far on the east edge of the laboratory, well separated from the town of Los Alamos and pretty much anything else. More importantly, it was a classic example of northern New Mexican geology: high up on a mesa built of tuff and volcanic sediments, well-drained and extremely dry soil in an area that received little rain. One of the main migration paths for underground contaminants is their interaction with water, and specifically the tendency of many materials to dissolve into groundwater and flow with it towards aquifers. The Corps of Engineers drilled test wells, about 1,500' deep, and a series of 400' core samples. They found that on the Frijoles Mesa, ground water was over 1,000' below the surface, and that everything above was far from saturation. That means no mobility of the water, which is trapped in the soil. It's just about the ideal situation for putting something underground and having it stay. Incidentally, this study would lead to the development of a series of new water wells for Los Alamos's domestic water supply. It also gave the green light for hydronuclear testing, and Frijoles Mesa was dubbed Technical Area 49 and subdivided into a set of test areas. Over the following three years, these test areas would see about 35 hydronuclear detonations carried out in the bottom of shafts that were about 200' deep and 3-6' wide. It seems that for most tests, the hole was excavated and lined with a ladder installed to reach the bottom. Technicians worked at the bottom of the hole to prepare the test device, which was connected by extensive cabling to instrumentation trailers on the surface. When the "shot" was ready, the hole was backfilled with sand and sealed at the top with a heavy plate. The material on top of the device held everything down, preventing migration of nuclear material to the surface. The high explosives did, of course, destroy the test device and the cabling, but not before the instrumentation trailers had recorded a vast amount of data. If you read these kinds of articles, you must know that the 1958 moratorium did not last. Soviet politics shifted again, France began nuclear testing, negotiations over a more formal test ban faltered. US intelligence suspected that the Soviet Union had operated their nuclear weapons program at full tilt during the test ban, and the military suspected clandestine tests, although there was no evidence they had violated the treaty. Of course, that they continued their research efforts is guaranteed, we did as well. Physicist Edward Teller, ever the nuclear weapons hawk, opposed the moratorium and pushed to resume testing. In 1961, the Soviet Union resumed testing, culminating in the test of the record-holding "Tsar Bomba," a 50 megaton device. The US resumed testing as well. The arms race was back on. US hydronuclear testing largely ended with the resumption of full-scale testing. The same safety studies could be completed on real weapons, and those tests would serve other purposes in weapons development as well. Although post-moratorium testing included atmospheric detonations, the focus had shifted towards underground tests and the 1963 Partial Test Ban Treaty restricted the US and USSR to underground tests only. One wonders about the relationship between hydronuclear testing at TA-49 and the full-scale underground tests extensively performed at the NTS. Underground testing began in 1951 with Buster-Jangle Uncle, a test to determine how big of a crater could be produced by a ground-penetrating weapon. Uncle wasn't really an underground test in the modern sense, the device was emplaced only 17 feet deep and still produced a huge cloud of fallout. It started a trend, though: a similar 1955 test was set 67 feet deep, producing a spectacular crater, before the 1957 Plumbbob Pascal-A was detonated at 486 feet and produced radically less fallout. 1957's Plumbbob Rainier was the first fully-contained underground test, set at the end of a tunnel excavated far into a hillside. This test emitted no fallout at all, proving the possibility of containment. Thus both the idea of emplacing a test device in a deep hole, and the fact that testing underground could contain all of the fallout, were known when the moratorium began in 1959. What's very interesting about the hydronuclear tests is the fact that technicians actually worked "downhole," at the bottom of the excavation. Later underground tests were prepared by assembling the test device at the surface, as part of a rocket-like "rack," and then lowering it to the bottom just before detonation. These techniques hadn't yet been developed in the '50s, thus the use of a horizontal tunnel for the first fully-contained test. Many of the racks used for underground testing were designed and built by LANL, but others (called "canisters" in an example of the tendency of the labs to not totally agree on things) were built by Lawrence Livermore. I'm not actually sure which of the two labs started building them first, a question for future research. It does seem likely that the hydronuclear testing at LANL advanced the state of the art in remote instrumentation and underground test design, facilitating the adoption of fully-contained underground tests in the following years. During the three years of hydronuclear testing, shafts were excavated in four testing areas. It's estimated that the test program at TA-49 left about 40kg of plutonium and 93kg of enriched uranium underground, along with 92kg of depleted uranium and 13kg of beryllium (both toxic contaminants). Because of the lack of a nuclear yield, these tests did not create the caverns associated with underground testing. Material from the weapons likely spread within just a 10-20' area, as holes were drilled on a 25' grid and contamination from previous neighboring tests was encountered only once. The tests also produced quite a bit of ancillary waste: things like laboratory equipment, handling gear, cables and tubing, that are not directly radioactive but were contaminated with radioactive or toxic materials. In the fashion typical of the time, this waste was buried on site, often as part of the backfilling of the test shafts. During the excavation of one of the test shafts, 2-M in December 1960, contamination was detected at the surface. It seems that the geology allowed plutonium from a previous test to spread through cracks into the area where 2-M was being drilled. The surface soil contaminated by drill cuttings was buried back in hole 2-M, but this incident made area 2 the most heavily contaminated part of TA-49. When hydronuclear testing ended in 1961, area 2 was covered by a 6' of gravel and 4-6" of asphalt to better contain any contaminated soil. Several support buildings on the surface were also contaminated, most notably a building used as a radiochemistry laboratory to support the tests. An underground calibration facility that allowed for exposure of test equipment to a contained source in an underground chamber was also built at TA-49 and similarly contaminated by use with radioisotopes. The Corps of Engineers continued to monitor the hydrology of the site from 1961 to 1970, and test wells and soil samples showed no indication that any contamination was spreading. In 1971, LANL established a new environmental surveillance department that assumed responsibility for legacy sites like TA-49. That department continued to sample wells, soil, and added air sampling. Monitoring of stream sediment downhill from the site was added in the '70s, as many of the contaminants involved can bind to silt and travel with surface water. This monitoring has not found any spread either. That's not to say that everything is perfect. In 1975, a section of the asphalt pad over Area 2 collapsed, leaving a three foot deep depression. Rainwater pooled in the depression and then flowed through the gravel into hole 2-M itself, collecting in the bottom of the lining of the former experimental shaft. In 1976, the asphalt cover was replaced, but concerns remained about the water that had already entered 2-M. It could potentially travel out of the hole, continue downwards, and carry contamination into the aquifer around 800' below. Worse, a nearby core sample hole had picked up some water too, suggesting that the water was flowing out of 2-M through cracks and into nearby features. Since the core hole had a slotted liner, it would be easier for water to leave it and soak into the ground below. In 1980, the water that had accumulated in 2-M was removed by lifting about 24 gallons to the surface. While the water was plutonium contaminated, it fell within acceptable levels for controlled laboratory areas. Further inspections through 1986 did not find additional water in the hole, suggesting that the asphalt pad was continuing to function correctly. Several other investigations were conducted, including the drilling of some additional sample wells and examination of other shafts in the area, to determine if there were other routes for water to enter the Area 2 shafts. Fortunately no evidence of ongoing water ingress was found. In 1986, TA-49 was designated a hazardous waste site under the Resource Conservation and Recovery Act. Shortly after, the site was evaluated under CERCLA to prioritize remediation. Scoring using the Hazard Ranking System determined a fairly low risk for the site, due to the lack of spread of the contamination and evidence suggesting that it was well contained by the geology. Still, TA-49 remains an environmental remediation site and now falls under a license granted by the New Mexico Environment Department. This license requires ongoing monitoring and remediation of any problems with the containment. For example, in 1991 the asphalt cover of Area 2 was found to have cracked and allowed more water to enter the sample wells. The covering was repaired once again, and investigations made every few years from 1991 to 2015 to check for further contamination. Ongoing monitoring continues today. So far, Area 2 has not been found to pose an unacceptable risk to human health or a risk to the environment. NMED permitting also covers the former radiological laboratory and calibration facility, and infrastructure related to them like a leach field from drains. Sampling found some surface contamination, so the affected soil was removed and disposed of at a hazardous waste landfill where it will be better contained. TA-49 was reused for other purposes after hydronuclear testing. These activities included high explosive experiments contained in metal "bottles," carried out in a metal-lined pit under a small structure called the "bottle house." Part of the bottle house site was later reused to build a huge hydraulic ram used to test steel cables at their failure strength. I am not sure of the exact purpose of this "Cable Test Facility," but given the timeline of its use during the peak of underground testing and the design I suspect LANL used it as a quality control measure for the cable assemblies used in lowering underground test racks into their shafts. No radioactive materials were involved in either of these activities, but high explosives and hydraulic oil can both be toxic, so both were investigated and received some surface soil cleanup. Finally, the NMED permit covers the actual test shafts. These have received numerous investigations over the sixty years since the original tests, and significant contamination is present as expected. However, that contamination does not seem to be spreading, and modeling suggests that it will stay that way. In 2022, the NMED issued Certificates of Completion releasing most of the TA-49 remediation sites without further environmental controls. The test shafts themselves, known to NMED by the punchy name of Solid Waste Management Unit 49-001(e), received a certificate of completion that requires ongoing controls to ensure that the land is used only for industrial purposes. Environmental monitoring of the TA-49 site continues under LANL's environmental management program and federal regulation, but TA-49 is no longer an active remediation project. The plutonium and uranium is just down there, and it'll have to stay.

In a previous life, I worked for a location-based entertainment company, part of a huge team of people developing a location for Las Vegas, Nevada. It was COVID, a rough time for location-based anything, and things were delayed more than usual. Coworkers paid a lot of attention to another upcoming Las Vegas attraction, one with a vastly larger budget but still struggling to make schedule: the MSG (Madison Square Garden) Sphere. I will set aside jokes about it being a square sphere, but they were perhaps one of the reasons that it underwent a pre-launch rebranding to merely the Sphere. If you are not familiar, the Sphere is a theater and venue in Las Vegas. While it's know mostly for the video display on the outside, that's just marketing for the inside: a digital dome theater, with seating at a roughly 45 degree stadium layout facing a near hemisphere of video displays. It is a "near" hemisphere because the lower section is truncated to allow a flat floor, which serves as a stage for events but is also a practical architectural decision to avoid completely unsalable front rows. It might seem a little bit deceptive that an attraction called the Sphere does not quite pull off even a hemisphere of "payload," but the same compromise has been reached by most dome theaters. While the use of digital display technology is flashy, especially on the exterior, the Sphere is not quite the innovation that it presents itself as. It is just a continuation of a long tradition of dome theaters. Only time will tell, but the financial difficulties of the Sphere suggest that follows the tradition faithfully: towards commercial failure. You could make an argument that the dome theater is hundreds of years old, but I will omit it. Things really started developing, at least in our modern tradition of domes, with the 1923 introduction of the Zeiss planetarium projector. Zeiss projectors and their siblings used a complex optical and mechanical design to project accurate representations of the night sky. Many auxiliary projectors, incorporated into the chassis and giving these projectors famously eccentric shapes, rendered planets and other celestial bodies. Rather than digital light modulators, the images from these projectors were formed by purely optical means: perforated metal plates, glass plates with etched metalized layers, and fiber optics. The large, precisely manufactured image elements and specialized optics created breathtaking images. While these projectors had considerable entertainment value, especially in the mid-century when they represented some of the most sophisticated projection technology yet developed, their greatest potential was obviously in education. Planetarium projectors were fantastically expensive (being hand-built in Germany with incredible component counts) [1], they were widely installed in science museums around the world. Most of us probably remember a dogbone-shaped Zeiss, or one of their later competitors like Spitz or Minolta, from our youths. Unfortunately, these marvels of artistic engineering were mostly retired as digital projection of near comparable quality became similarly priced in the 2000s. But we aren't talking about projectors, we're talking about theaters. Planetarium projectors were highly specialized to rendering the night sky, and everything about them was intrinsically spherical. For both a reasonable viewing experience, and for the projector to produce a geometrically correct image, the screen had to be a spherical section. Thus the planetarium itself: in its most traditional form, rings of heavily reclined seats below a hemispherical dome. The dome was rarely a full hemisphere, but was usually truncated at the horizon. This was mostly a practical decision but integrated well into the planetarium experience, given that sky viewing is usually poor near the horizon anyway. Many planetaria painted a city skyline or forest silhouette around the lower edge to make the transition from screen to wall more natural. Later, theatrical lighting often replaced the silhouette, reproducing twilight or the haze of city lights. Unsurprisingly, the application-specific design of these theaters also limits their potential. Despite many attempts, the collective science museum industry has struggled to find entertainment programming for planetaria much beyond Pink Floyd laser shows [1]. There just aren't that many things that you look up at. Over time, planetarium shows moved in more narrative directions. Film projection promised new flexibility---many planetaria with optical star projectors were also equipped with film projectors, which gave show producers exciting new options. Documentary video of space launches and animations of physical principles became natural parts of most science museum programs, but were a bit awkward on the traditional dome. You might project four copies of the image just above the horizon in the four cardinal directions, for example. It was very much a compromise. With time, the theater adapted to the projection once again: the domes began to tilt. By shifting the dome in one direction, and orienting the seating towards that direction, you could create a sort of compromise point between the traditional dome and traditional movie theater. The lower central area of the screen was a reasonable place to show conventional film, while the full size of the dome allowed the starfield to almost fill the audience's vision. The experience of the tilted dome is compared to "floating in space," as opposed to looking up at the sky. In true Cold War fashion, it was a pair of weapons engineers (one nuclear weapons, the other missiles) who designed the first tilted planetarium. In 1973, the planetarium of what is now called the Fleet Science Center in San Diego, California opened to the public. Its dome was tilted 25 degrees to the horizon, with the seating installed on a similar plane and facing in one direction. It featured a novel type of planetarium projector developed by Spitz and called the Space Transit Simulator. The STS was not the first, but still an early mechanical projector to be controlled by a computer---a computer that also had simultaneous control of other projectors and lighting in the theater, what we now call a show control system. Even better, the STS's innovative optical design allowed it to warp or bend the starfield to simulate its appearance from locations other than earth. This was the "transit" feature: with a joystick connected to the control computer, the planetarium presenter could "fly" the theater through space in real time. The STS was installed in a well in the center of the seating area, and its compact chassis kept it low in the seating area, preserving the spherical geometry (with the projector at the center of the sphere) without blocking the view of audience members sitting behind it and facing forward. And yet my main reason for discussing the Fleet planetarium is not the the planetarium projector at all. It is a second projector, an "auxiliary" one, installed in a second well behind the STS. The designers of the planetarium intended to show film as part of their presentations, but they were not content with a small image at the center viewpoint. The planetarium commissioned a few of the industry's leading film projection experts to design a film projection system that could fill the entire dome, just as the planetarium projector did. They knew that such a large dome would require an exceptionally sharp image. Planetarium projectors, with their large lithographed slides, offered excellent spatial resolution. They made stars appear as point sources, the same as in the night sky. 35mm film, spread across such a large screen, would be obviously blurred in comparison. They would need a very large film format. Fortuitously, almost simultaneously the Multiscreen Corporation was developing a "sideways" 70mm format. This 15-perf format used 70mm film but fed it through the projector sideways, making each frame much larger than typical 70mm film. In its debut, at a temporary installation in the 1970 Expo Osaka, it was dubbed IMAX. IMAX made an obvious basis for a high-resolution projection system, and so the then-named IMAX Corporation was added to the planetarium project. The Fleet's film projector ultimately consisted of an IMAX film transport with a custom-built compact, liquid-cooled lamphouse and spherical fisheye lens system. The large size of the projector, the complex IMAX framing system and cooling equipment, made it difficult to conceal in the theater's projector well. Threading film into IMAX projectors is quite complex, with several checks the projectionist must make during a pre-show inspection. The projectionist needed room to handle the large film, and to route it to and from the enormous reels. The projector's position in the middle of the seating area left no room for any of this. We can speculate that it was, perhaps, one of the designer's missile experience that lead to the solution: the projector was serviced in a large projection room beneath the theater's seating. Once it was prepared for each show, it rose on near-vertical rails until just the top emerged in the theater. Rollers guided the film as it ran from a platter, up the shaft to the projector, and back down to another platter. Cables and hoses hung below the projector, following it up and down like the traveling cable of an elevator. To advertise this system, probably the greatest advance in film projection since the IMAX format itself, the planetarium coined the term Omnimax. Omnimax was not an easy or economical format. Ideally, footage had to be taken in the same format, using a 70mm camera with a spherical lens system. These cameras were exceptionally large and heavy, and the huge film format limited cinematographers to short takes. The practical problems with Omnimax filming were big enough that the first Omnimax films faked it, projecting to the larger spherical format from much smaller conventional negatives. This was the case for "Voyage to the Outer Planets" and "Garden Isle," the premier films at the Fleet planetarium. The history of both is somewhat obscure, the latter especially. "Voyage to the Outer Planets" was executive-produced by Preston Fleet, a founder of the Fleet center (which was ultimately named for his father, a WWII aviator). We have Fleet's sense of showmanship to thank for the invention of Omnimax: He was an accomplished business executive, particularly in the photography industry, and an aviation enthusiast who had his hands in more than one museum. Most tellingly, though, he had an eccentric hobby. He was a theater organist. I can't help but think that his passion for the theater organ, an instrument almost defined by the combination of many gizmos under electromechanical control, inspired "Voyage." The film, often called a "multimedia experience," used multiple projectors throughout the planetarium to depict a far-future journey of exploration. The Omnimax film depicted travel through space, with slide projectors filling in artist's renderings of the many wonders of space. The ten-minute Omnimax film was produced by Graphic Films Corporation, a brand that would become closely associated with Omnimax in the following decades. Graphic was founded in the midst of the Second World War by Lester Novros, a former Disney animator who found a niche creating training films for the military. Novros's fascination with motion and expertise in presenting complicated 3D scenes drew him to aerospace, and after the war he found much of his business in the newly formed Air Force and NASA. He was also an enthusiast of niche film formats, and Omnimax was not his first dome. For the 1964 New York World's Fair, Novros and Graphic Films had produced "To the Moon and Beyond," a speculative science film with thematic similarities to "Voyage" and more than just a little mechanical similarity. It was presented in Cinerama 360, a semi-spherical, dome-theater 70mm format presented in a special theater called the Moon Dome. "To the Moon and Beyond" was influential in many ways, leading to Graphic Films' involvement in "2001: A Space Odyssey" and its enduring expertise in domes. The Fleet planetarium would not remain the only Omnimax for long. In 1975, the city of Spokane, Washington struggled to find a new application for the pavilion built for Expo '74 [3]. A top contender: an Omnimax theater, in some ways a replacement for the temporary IMAX theater that had been constructed for the actual Expo. Alas, this project was not to be, but others came along: in 1978, the Detroit Science Center opened the second Omnimax theater ("the machine itself looks like and is the size of a front loader," the Detroit Free Press wrote). The Science Museum of Minnesota, in St. Paul, followed shortly after. The Carnegie Science Center, in Pittsburgh, rounded out the year's new launches. Omnimax hit prime time the next year, with the 1979 announcement of an Omnimax theater at Caesars Palace in Las Vegas, Nevada. Unlike the previous installations, this 380-seat theater was purely commercial. It opened with the 1976 IMAX film "To Fly!," which had been optically modified to fit the Omnimax format. This choice of first film is illuminating. "To Fly!" is a 27 minute documentary on the history of aviation in the United States, originally produced for the IMAX theater at the National Air and Space Museum [4]. It doesn't exactly seem like casino fare. The IMAX format, the flat-screen one, was born of world's fairs. It premiered at an Expo, reappeared a couple of years later at another one, and for the first years of the format most of the IMAX theaters built were associated with either a major festival or an educational institution. This noncommercial history is a bit hard to square with the modern IMAX brand, closely associated with major theater chains and the Marvel Cinematic Universe. Well, IMAX took off, and in many ways it sold out. Over the decades since the 1970 Expo, IMAX has met widespread success with commercial films and theater owners. Simultaneously, the definition or criteria for IMAX theaters have relaxed, with smaller screens made permissible until, ultimately, the transition to digital projection eliminated the 70mm film and more or less reduce IMAX to just another ticket surcharge brand. It competes directly with Cinemark xD, for example. To the theater enthusiast, this is a pretty sad turn of events, a Westinghouse-esque zombification of a brand that once heralded the field's most impressive technical achievements. The same never happened to Omnimax. The Caesar's Omnimax theater was an odd exception; the vast majority of Omnimax theaters were built by science museums and the vast majority of Omnimax films were science documentaries. Quite a few of those films had been specifically commissioned by science museums, often on the occasion of their Omnimax theater opening. The Omnimax community was fairly tight, and so the same names recur. The Graphic Films Corporation, which had been around since the beginning, remained so closely tied to the IMAX brand that they practically shared identities. Most Omnimax theaters, and some IMAX theaters, used to open with a vanity card often known as "the wormhole." It might be hard to describe beyond "if you know you know," it certainly made an impression on everyone I know that grew up near a theater that used it. There are some videos, although unfortunately none of them are very good. I have spent more hours of my life than I am proud to admit trying to untangle the history of this clip. Over time, it has appeared in many theaters with many different logos at the end, and several variations of the audio track. This is in part informed speculation, but here is what I believe to be true: the "wormhole" was originally created by Graphic Films for the Fleet planetarium specifically, and ran before "Voyage to the Outer Planets" and its double-feature companion "Garden Isle," both of which Graphic Films had worked on. This original version ended with the name Graphic Films, accompanied by an odd sketchy drawing that was also used as an early logo of the IMAX Corporation. Later, the same animation was re-edited to end with an IMAX logo. This version ran in both Omnimax and conventional IMAX theaters, probably as a result of the extensive "cross-pollination" of films between the two formats. Many Omnimax films through the life of the format had actually been filmed for IMAX, with conventional lenses, and then optically modified to fit the Omnimax dome after the fact. You could usually tell: the reprojection process created an unusual warp in the image, and more tellingly, these pseudo-Omnimax films almost always centered the action at the middle of the IMAX frame, which was too high to be quite comfortable in an Omnimax theater (where the "frame center" was well above the "front center" point of the theater). Graphic Films had been involved in a lot of these as well, perhaps explaining the animation reuse, but it's just as likely that they had sold it outright to the IMAX corporation which used it as they pleased. For some reason, this version also received new audio that is mostly the same but slightly different. I don't have a definitive explanation, but I think there may have been an audio format change between the very early Omnimax theaters and later IMAX/Omnimax systems, which might have required remastering. Later, as Omnimax domes proliferated at science museums, the IMAX Corporation (which very actively promoted Omnimax to education) gave many of these theaters custom versions of the vanity card that ended with the science museum's own logo. I have personally seen two of these, so I feel pretty confident that they exist and weren't all that rare (basically 2 out of 2 Omnimax theaters I've visited used one), but I cannot find any preserved copies. Another recurring name in the world of IMAX and Omnimax is MacGillivray Freeman Films. MacGillivray and Freeman were a pair of teenage friends from Laguna Beach who dropped out of school in the '60s to make skateboard and surf films. This is, of course, a rather cliché start for documentary filmmakers but we must allow that it was the '60s and they were pretty much the ones creating the cliché. Their early films are hard to find in anything better than VHS rip quality, but worth watching: Wikipedia notes their significance in pioneering "action cameras," mounting 16mm cinema cameras to skateboards and surfboards, but I would say that their cinematography was innovative in more ways than just one. The 1970 "Catch the Joy," about sandrails, has some incredible shots that I struggle to explain. There's at least one where they definitely cut the shot just a couple of frames before a drifting sandrail flung their camera all the way down the dune. For some reason, I would speculate due to their reputation for exciting cinematography, the National Air and Space Museum chose MacGillivray and Freeman for "To Fly!". While not the first science museum IMAX documentary by any means (that was, presumably, "Voyage to the Outer Planets" given the different subject matter of the various Expo films), "To Fly!" might be called the first modern one. It set the pattern that decades of science museum films followed: a film initially written by science educators, punched up by producers, and filmed with the very best technology of the time. Fearing that the film's history content would be dry, they pivoted more towards entertainment, adding jokes and action sequences. "To Fly!" was a hit, running in just about every science museum with an IMAX theater, including Omnimax. Sadly, Jim Freeman died in a helicopter crash shortly after production. Nonetheless, MacGillivray Freeman Films went on. Over the following decades, few IMAX science documentaries were made that didn't involve them somehow. Besides the films they produced, the company consulted on action sequences in most of the format's popular features. I had hoped to present here a thorough history of the films were actually produced in the Omnimax format. Unfortunately, this has proven very difficult: the fact that most of them were distributed only to science museums means that they are very spottily remembered, and besides, so many of the films that ran in Omnimax theaters were converted from IMAX presentations that it's hard to tell the two apart. I'm disappointed that this part of cinema history isn't better recorded, and I'll continue to put time into the effort. Science museum documentaries don't get a lot of attention, but many of the have involved formidable technical efforts. Consider, for example, the cameras: befitting the large film, IMAX cameras themselves are very large. When filming "To Fly!", MacGillivray and Freeman complained that the technically very basic 80 pound cameras required a lot of maintenance, were complex to operate, and wouldn't fit into the "action cam" mounting positions they were used to. The cameras were so expensive, and so rare, that they had to be far more conservative than their usual approach out of fear of damaging a camera they would not be able to replace. It turns out that they had it easy. Later IMAX science documentaries would be filmed in space ("The Dream is Alive" among others) and deep underwater ("Deep Sea 3D" among others). These IMAX cameras, modified for simpler operation and housed for such difficult environments, weighed over 1,000 pounds. Astronauts had to be trained to operate the cameras; mission specialists on Hubble service missions had wrangling a 70-pound handheld IMAX camera around the cabin and developing its film in a darkroom bag among their duties. There was a lot of film to handle: as a rule of thumb, one mile of IMAX film is good for eight and a half minutes. I grew up in Portland, Oregon, and so we will make things a bit more approachable by focusing on one example: The Omnimax theater of the Oregon Museum of Science and Industry, which opened as part of the museum's new waterfront location in 1992. This 330-seat boasted a 10,000 sq ft dome and 15 kW of sound. The premier feature was "Ring of Fire," a volcano documentary originally commissioned by the Fleet, the Fort Worth Museum of Science and Industry, and the Science Museum of Minnesota. By the 1990s, the later era of Omnimax, the dome format was all but abandoned as a commercial concept. There were, an announcement article notes, around 90 total IMAX theaters (including Omnimax) and 80 Omnimax films (including those converted from IMAX) in '92. Considering the heavy bias towards science museums among these theaters, it was very common for the films to be funded by consortia of those museums. Considering the high cost of filming in IMAX, a lot of the documentaries had a sort of "mashup" feel. They would combine footage taken in different times and places, often originally for other projects, into a new narrative. "Ring of Fire" was no exception, consisting of a series of sections that were sometimes more loosely connected to the theme. The 1982 Loma Prieta earthquake was a focus, and the eruption of Mt. St. Helens, and lava flows in Hawaii. Perhaps one of the reasons it's hard to catalog IMAX films is this mashup quality, many of the titles carried at science museums were something along the lines of "another ocean one." I don't mean this as a criticism, many of the IMAX documentaries were excellent, but they were necessarily composed from painstakingly gathered fragments and had to cover wide topics. Given that I have an announcement feature piece in front of me, let's also use the example of OMSI to discuss the technical aspects. OMSI's projector cost about $2 million and weighted about two tons. To avoid dust damaging the expensive prints, the "projection room" under the seating was a positive-pressure cleanroom. This was especially important since the paucity of Omnimax content meant that many films ran regularly for years. The 15 kW water-cooled lamp required replacement at 800 to 1,000 hours, but unfortunately, the price is not noted. By the 1990s, Omnimax had become a rare enough system that the projection technology was a major part of the appeal. OMSI's installation, like most later Omnimax theaters, had the audience queue below the seating, separated from the projection room by a glass wall. The high cost of these theaters meant that they operated on high turnovers, so patrons would wait in line to enter immediately after the previous showing had exited. While they waited, they could watch the projectionist prepare the next show while a museum docent explained the equipment. I have written before about multi-channel audio formats, and Omnimax gives us some more to consider. The conventional audio format for much of Omnimax's life was six-channel: left rear, left screen, center screen, right screen, right rear, and top. Each channel had an independent bass cabinet (in one theater, a "caravan-sized" enclosure with eight JBL 2245H 46cm woofers), and a crossover network fed the lowest end of all six channels to a "sub-bass" array at screen bottom. The original Fleet installation also had sub-bass speakers located beneath the audience seating, although that doesn't seem to have become common. IMAX titles of the '70s and '80s delivered audio on eight-track magnetic tape, with the additional tracks used for synchronization to the film. By the '90s, IMAX had switched to distributing digital audio on three CDs (one for each two channels). OMSI's theater was equipped for both, and the announcement amusingly notes the availability of cassette decks. A semi-custom audio processor made for IMAX, the Sonics TAC-86, managed synchronization with film playback and applied equalization curves individually calibrated to the theater. IMAX domes used perforated aluminum screens (also the norm in later planetaria), so the speakers were placed behind the screen in the scaffold-like superstructure that supported it. When I was young, OMSI used to start presentations with a demo program that explained the large size of IMAX film before illuminating work lights behind the screen to make the speakers visible. Much of this was the work of the surprisingly sophisticated show control system employed by Omnimax theaters, a descendent of the PDP-15 originally installed in the Fleet. Despite Omnimax's almost complete consignment to science museums, there were some efforts it bringing commercial films. Titles like Disney's "Fantasia" and "Star Wars: Episode III" were distributed to Omnimax theaters via optical reprojection, sometimes even from 35mm originals. Unfortunately, the quality of these adaptations was rarely satisfactory, and the short runtimes (and marketing and exclusivity deals) typical of major commercial releases did not always work well with science museum schedules. Still, the cost of converting an existing film to dome format is pretty low, so the practice continues today. "Star Wars: The Force Awakens," for example, ran on at least one science museum dome. This trickle of blockbusters was not enough to make commercial Omnimax theaters viable. Caesars Palace closed, and then demolished, their Omnimax theater in 2000. The turn of the 21st century was very much the beginning of the end for the dome theater. IMAX was moving away from their film system and towards digital projection, but digital projection systems suitable for large domes were still a nascent technology and extremely expensive. The end of aggressive support from IMAX meant that filming costs became impractical for documentaries, so while some significant IMAX science museum films were made in the 2000s, the volume definitely began to lull and the overall industry moved away from IMAX in general and Omnimax especially. It's surprising how unforeseen this was, at least to some. A ten-screen commercial theater in Duluth opened an Omnimax theater in 1996! Perhaps due to the sunk cost, it ran until 2010, not a bad closing date for an Omnimax theater. Science museums, with their relatively tight budgets and less competitive nature, did tend to hold over existing Omnimax installations well past their prime. Unfortunately, many didn't: OMSI, for example, closed its Omnimax theater in 2013 for replacement with a conventional digital theater that has a large screen but is not IMAX branded. Fortunately, some operators hung onto their increasingly costly Omnimax domes long enough for modernization to become practical. The IMAX Corporation abandoned the Omnimax name as more of the theaters closed, but continued to support "IMAX Dome" with the introduction of a digital laser projector with spherical optics. There are only ten examples of this system. Others, including Omnimax's flagship at the Fleet Science Center, have been replaced by custom dome projection systems built by competitors like Sony. Few Omnimax projectors remain. The Fleet, to their credit, installed the modern laser projectors in front of the projector well so that the original film projector could remain in place. It's still functional and used for reprisals of Omnimax-era documentaries. IMAX projectors in general are a dying breed, a number of them have been preserved but their complex, specialized design and the end of vendor support means that it may become infeasible to keep them operating. We are, of course, well into the digital era. While far from inexpensive, digital projection systems are now able to match the quality of Omnimax projection. The newest dome theaters, like the Sphere, dispense with projection entirely. Instead, they use LED display panels capable of far brighter and more vivid images than projection, and with none of the complexity of water-cooled arc lamps. Still, something has been lost. There was once a parallel theater industry, a world with none of the glamor of Hollywood but for whom James Cameron hauled a camera to the depths of the ocean and Leonardo DiCaprio narrated repairs to the Hubble. In a good few dozen science museums, two-ton behemoths rose from beneath the seats, the zenith of film projection technology. After decades of documentaries, I think people forgot how remarkable these theaters were. Science museums stopped promoting them as aggressively, and much of the showmanship faded away. Sometime in the 2000s, OMSI stopped running the pre-show demonstration, instead starting the film directly. They stopped explaining the projectionist's work in preparing the show, and as they shifted their schedule towards direct repetition of one feature, there was less for the projectionist to do anyway. It became just another museum theater, so it's no wonder that they replaced it with just another museum theater: a generic big-screen setup with the exceptionally dull name of "Empirical Theater." From time to time, there have been whispers of a resurgence of 70mm film. Oppenheimer, for example, was distributed to a small number of theaters in this giant of film formats: 53 reels, 11 miles, 600 pounds of film. Even conventional IMAX is too costly for the modern theater industry, though. Omnimax has fallen completely by the wayside, with the few remaining dome operators doomed to recycling the same films with a sprinkling of newer reformatted features. It is hard to imagine a collective of science museums sending another film camera to space. Omnimax poses a preservation challenge in more ways than one. Besides the lack of documentation on Omnimax theaters and films, there are precious few photographs of Omnimax theaters and even fewer videos of their presentations. Of course, the historian suffers where Madison Square Garden hopes to succeed: the dome theater is perhaps the ultimate in location-based entertainment. Photos and videos, represented on a flat screen, cannot reproduce the experience of the Omnimax theater. The 180 horizontal degrees of screen, the sound that was always a little too loud, in no small part to mask the sound of the projector that made its own racket in the middle of the seating. You had to be there. IMAGES: Omnimax projection room at OMSI, Flickr user truk. Omnimax dome with work lights on at MSI Chicago, Wikimedia Commons user GualdimG. Omnimax projector at St. Louis Science Center, Flickr user pasa47. [1] I don't have extensive information on pricing, but I know that in the 1960s an "economy" Spitz came in over $30,000 (~10x that much today). [2] Pink Floyd's landmark album Dark Side of The Moon debuted in a release event held at the London Planetarium. This connection between Pink Floyd and planetaria, apparently much disliked by the band itself, has persisted to the present day. Several generations of Pink Floyd laser shows have been licensed by science museums around the world, and must represent by far the largest success of fixed-installation laser projection. [3] Are you starting to detect a theme with these Expos? the World's Fairs, including in their various forms as Expos, were long one of the main markets for niche film formats. Any given weird projection format you run into, there's a decent chance that it was originally developed for some short film for an Expo. Keep in mind that it's the nature of niche projection formats that they cannot easily be shown in conventional theaters, so they end up coupled to these crowd events where a custom venue can be built. [4] The Smithsonian Institution started looking for an exciting new theater in 1970. As an example of the various niche film formats at the time, the Smithsonian considered a dome (presumably Omnimax), Cinerama (a three-projector ultrawide system), and Circle-Vision 360 (known mostly for the few surviving Expo films at Disney World's EPCOT) before settling on IMAX. The Smithsonian theater, first planned for the Smithsonian Museum of Natural History before being integrated into the new National Air and Space Museum, was tremendously influential on the broader world of science museum films. That is perhaps an understatement, it is sometimes credited with popularizing IMAX in general, and the newspaper coverage the new theater received throughout North America lends credence to the idea. It is interesting, then, to imagine how different our world would be if they had chosen Circle-Vision. "Captain America: Brave New World" in Cinemark 360.

Air traffic control has been in the news lately, on account of my country's declining ability to do it. Well, that's a long-term trend, resulting from decades of under-investment, severe capture by our increasingly incompetent defense-industrial complex, no small degree of management incompetence in the FAA, and long-lasting effects of Reagan crushing the PATCO strike. But that's just my opinion, you know, maybe airplanes got too woke. In any case, it's an interesting time to consider how weird parts of air traffic control are. The technical, administrative, and social aspects of ATC all seem two notches more complicated than you would expect. ATC is heavily influenced by its peculiar and often accidental development, a product of necessity that perpetually trails behind the need, and a beneficiary of hand-me-down military practices and technology. Aviation Radio In the early days of aviation, there was little need for ATC---there just weren't many planes, and technology didn't allow ground-based controllers to do much of value. There was some use of flags and signal lights to clear aircraft to land, but for the most part ATC had to wait for the development of aviation radio. The impetus for that work came mostly from the First World War. Here we have to note that the history of aviation is very closely intertwined with the history of warfare. Aviation technology has always rapidly advanced during major conflicts, and as we will see, ATC is no exception. By 1913, the US Army Signal Corps was experimenting with the use of radio to communicate with aircraft. This was pretty early in radio technology, and the aircraft radios were huge and awkward to operate, but it was also early in aviation and "huge and awkward to operate" could be similarly applied to the aircraft of the day. Even so, radio had obvious potential in aviation. The first military application for aircraft was reconnaissance. Pilots could fly past the front to find artillery positions and otherwise provide useful information, and then return with maps. Well, even better than returning with a map was providing the information in real-time, and by the end of the war medium-frequency AM radios were well developed for aircraft. Radios in aircraft lead naturally to another wartime innovation: ground control. Military personnel on the ground used radio to coordinate the schedules and routes of reconnaissance planes, and later to inform on the positions of fighters and other enemy assets. Without any real way to know where the planes were, this was all pretty primitive, but it set the basic pattern that people on the ground could keep track of aircraft and provide useful information. Post-war, civil aviation rapidly advanced. The early 1920s saw numerous commercial airlines adopting radio, mostly for business purposes like schedule coordination. Once you were in contact with someone on the ground, though, it was only logical to ask about weather and conditions. Many of our modern practices like weather briefings, flight plans, and route clearances originated as more or less formal practices within individual airlines. Air Mail The government was not left out of the action. The Post Office operated what may have been the largest commercial aviation operation in the world during the early 1920s, in the form of Air Mail. The Post Office itself did not have any aircraft; all of the flying was contracted out---initially to the Army Air Service, and later to a long list of regional airlines. Air Mail was considered a high priority by the Post Office and proved very popular with the public. When the transcontinental route began proper operation in 1920, it became possible to get a letter from New York City to San Francisco in just 33 hours by transferring it between airplanes in a nearly non-stop relay race. The Post Office's largesse in contracting the service to private operators provided not only the funding but the very motivation for much of our modern aviation industry. Air travel was not very popular at the time, being loud and uncomfortable, but the mail didn't complain. The many contract mail carriers of the 1920s grew and consolidated into what are now some of the United States' largest companies. For around a decade, the Post Office almost singlehandedly bankrolled civil aviation, and passengers were a side hustle [1]. Air mail ambition was not only of economic benefit. Air mail routes were often longer and more challenging than commercial passenger routes. Transcontinental service required regular flights through sparsely populated parts of the interior, challenging the navigation technology of the time and making rescue of downed pilots a major concern. Notably, air mail operators did far more nighttime flying than any other commercial aviation in the 1920s. The post office became the government's de facto technical leader in civil aviation. Besides the network of beacons and markers built to guide air mail between cities, the post office built 17 Air Mail Radio Stations along the transcontinental route. The Air Mail Radio Stations were the company radio system for the entire air mail enterprise, and the closest thing to a nationwide, public air traffic control service to then exist. They did not, however, provide what we would now call control. Their role was mainly to provide pilots with information (including, critically, weather reports) and to keep loose tabs on air mail flights so that a disappearance would be noticed in time to send search and rescue. In 1926, the Watres Act created the Aeronautic Branch of the Department of Commerce. The Aeronautic Branch assumed a number of responsibilities, but one of them was the maintenance of the Air Mail routes. Similarly, the Air Mail Radio Stations became Aeronautics Branch facilities, and took on the new name of Flight Service Stations. No longer just for the contract mail carriers, the Flight Service Stations made up a nationwide network of government-provided services to aviators. They were the first edifices in what we now call the National Airspace System (NAS): a complex combination of physical facilities, technologies, and operating practices that enable safe aviation. In 1935, the first en-route air traffic control center opened, a facility in Newark owned by a group of airlines. The Aeronautic Branch, since renamed the Bureau of Air Commerce, supported the airlines in developing this new concept of en-route control that used radio communications and paperwork to track which aircraft were in which airways. The rising number of commercial aircraft made in-air collisions a bigger problem, so the Newark control center was quickly followed by more facilities built on the same pattern. In 1936, the Bureau of Air Commerce took ownership of these centers, and ATC became a government function alongside the advisory and safety services provided by the flight service stations. En route center controllers worked off of position reports from pilots via radio, but needed a way to visualize and track aircraft's positions and their intended flight paths. Several techniques helped: first, airlines shared their flight planning paperwork with the control centers, establishing "flight plans" that corresponded to each aircraft in the sky. Controllers adopted a work aid called a "flight strip," a small piece of paper with the key information about an aircraft's identity and flight plan that could easily be handed between stations. By arranging the flight strips on display boards full of slots, controllers could visualize the ordering of aircraft in terms of altitude and airway. Second, each center was equipped with a large plotting table map where controllers pushed markers around to correspond to the position reports from aircraft. A small flag on each marker gave the flight number, so it could easily be correlated to a flight strip on one of the boards mounted around the plotting table. This basic concept of air traffic control, of a flight strip and a position marker, is still in use today. Radar The Second World War changed aviation more than any other event of history. Among the many advancements were two British inventions of particular significance: first, the jet engine, which would make modern passenger airliners practical. Second, the radar, and more specifically the magnetron. This was a development of such significance that the British government treated it as a secret akin to nuclear weapons; indeed, the UK effectively traded radar technology to the US in exchange for participation in US nuclear weapons research. Radar created radical new possibilities for air defense, and complimented previous air defense development in Britain. During WWI, the organization tasked with defending London from aerial attack had developed a method called "ground-controlled interception" or GCI. Under GCI, ground-based observers identify possible targets and then direct attack aircraft towards them via radio. The advent of radar made GCI tremendously more powerful, allowing a relatively small number of radar-assisted air defense centers to monitor for inbound attack and then direct defenders with real-time vectors. In the first implementation, radar stations reported contacts via telephone to "filter centers" that correlated tracks from separate radars to create a unified view of the airspace---drawn in grease pencil on a preprinted map. Filter center staff took radar and visual reports and updated the map by moving the marks. This consolidated information was then provided to air defense bases, once again by telephone. Later technical developments in the UK made the process more automated. The invention of the "plan position indicator" or PPI, the type of radar scope we are all familiar with today, made the radar far easier to operate and interpret. Radar sets that automatically swept over 360 degrees allowed each radar station to see all activity in its area, rather than just aircraft passing through a defensive line. These new capabilities eliminated the need for much of the manual work: radar stations could see attacking aircraft and defending aircraft on one PPI, and communicated directly with defenders by radio. It became routine for a radar operator to give a pilot navigation vectors by radio, based on real-time observation of the pilot's position and heading. A controller took strategic command of the airspace, effectively steering the aircraft from a top-down view. The ease and efficiency of this workflow was a significant factor in the end of the Battle of Britain, and its remarkable efficacy was noticed in the US as well. At the same time, changes were afoot in the US. WWII was tremendously disruptive to civil aviation; while aviation technology rapidly advanced due to wartime needs those same pressing demands lead to a slowdown in nonmilitary activity. A heavy volume of military logistics flights and flight training, as well as growing concerns about defending the US from an invasion, meant that ATC was still a priority. A reorganization of the Bureau of Air Commerce replaced it with the Civil Aeronautics Authority, or CAA. The CAA's role greatly expanded as it assumed responsibility for airport control towers and commissioned new en route centers. As WWII came to a close, CAA en route control centers began to adopt GCI techniques. By 1955, the name Air Route Traffic Control Center (ARTCC) had been adopted for en route centers and the first air surveillance radars were installed. In a radar-equipped ARTCC, the map where controllers pushed markers around was replaced with a large tabletop PPI built to a Navy design. The controllers still pushed markers around to track the identities of aircraft, but they moved them based on their corresponding radar "blips" instead of radio position reports. Air Defense After WWII, post-war prosperity and wartime technology like the jet engine lead to huge growth in commercial aviation. During the 1950s, radar was adopted by more and more ATC facilities (both "terminal" at airports and "en route" at ARTCCs), but there were few major changes in ATC procedure. With more and more planes in the air, tracking flight plans and their corresponding positions became labor intensive and error-prone. A particular problem was the increasing range and speed of aircraft, and corresponding longer passenger flights, that meant that many aircraft passed from the territory of one ARTCC into another. This required that controllers "hand off" the aircraft, informing the "next" ARTCC of the flight plan and position at which the aircraft would enter their airspace. In 1956, 128 people died in a mid-air collision of two commercial airliners over the Grand Canyon. In 1958, 49 people died when a military fighter struck a commercial airliner over Nevada. These were not the only such incidents in the mid-1950s, and public trust in aviation started to decline. Something had to be done. First, in 1958 the CAA gave way to the Federal Aviation Administration. This was more than just a name change: the FAA's authority was greatly increased compared tot he CAA, most notably by granting it authority over military aviation. This is a difficult topic to explain succinctly, so I will only give broad strokes. Prior to 1958, military aviation was completely distinct from civil aviation, with no coordination and often no communication at all between the two. This was, of course, a factor in the 1958 collision. Further, the 1956 collision, while it did not involve the military, did result in part from communications issues between separate distinct CAA facilities and the airline's own control facilities. After 1958, ATC was completely unified into one organization, the FAA, which assumed the work of the military controllers of the time and some of the role of the airlines. The military continues to have its own air controllers to this day, and military aircraft continue to include privileges such as (practical but not legal) exemption from transponder requirements, but military flights over the US are still beholden to the same ATC as civil flights. Some exceptions apply, void where prohibited, etc. The FAA's suddenly increased scope only made the practical challenges of ATC more difficult, and commercial aviation numbers continued to rise. As soon as the FAA was formed, it was understood that there needed to be major investments in improving the National Airspace System. While the first couple of years were dominated by the transition, the FAA's second director (Najeeb Halaby) prepared two lengthy reports examining the situation and recommending improvements. One of these, the Beacon report (also called Project Beacon), specifically addressed ATC. The Beacon report's recommendations included massive expansion of radar-based control (called "positive control" because of the controller's access to real-time feedback on aircraft movements) and new control procedures for airways and airports. Even better, for our purposes, it recommended the adoption of general-purpose computers and software to automate ATC functions. Meanwhile, the Cold War was heating up. US air defense, a minor concern in the few short years after WWII, became a higher priority than ever before. The Soviet Union had long-range aircraft capable of reaching the United States, and nuclear weapons meant that only a few such aircraft had to make it to cause massive destruction. Considering the vast size of the United States (and, considering the new unified air defense command between the United States and Canada, all of North America) made this a formidable challenge. During the 1950s, the newly minted Air Force worked closely with MIT's Lincoln Laboratory (an important center of radar research) and IBM to design a computerized, integrated, networked system for GCI. When the Air Force committed to purchasing the system, it was christened the Semi-Automated Ground Environment, or SAGE. SAGE is a critical juncture in the history of the computer and computer communications, the first system to demonstrate many parts of modern computer technology and, moreover, perhaps the first large-scale computer system of any kind. SAGE is an expansive topic that I will not take on here; I'm sure it will be the focus of a future article but it's a pretty well-known and well-covered topic. I have not so far felt like I had much new to contribute, despite it being the first item on my "list of topics" for the last five years. But one of the things I want to tell you about SAGE, that is perhaps not so well known, is that SAGE was not used for ATC. SAGE was a purely military system. It was commissioned by the Air Force, and its numerous operating facilities (called "direction centers") were located on Air Force bases along with the interceptor forces they would direct. However, there was obvious overlap between the functionality of SAGE and the needs of ATC. SAGE direction centers continuously received tracks from remote data sites using modems over leased telephone lines, and automatically correlated multiple radar tracks to a single aircraft. Once an operator entered information about an aircraft, SAGE stored that information for retrieval by other radar operators. When an aircraft with associated data passed from the territory of one direction center to another, the aircraft's position and related information were automatically transmitted to the next direction center by modem. One of the key demands of air defense is the identification of aircraft---any unknown track might be routine commercial activity, or it could be an inbound attack. The air defense command received flight plan data on commercial flights (and more broadly all flights entering North America) from the FAA and entered them into SAGE, allowing radar operators to retrieve "flight strip" data on any aircraft on their scope. Recognizing this interconnection with ATC, as soon as SAGE direction centers were being installed the Air Force started work on an upgrade called SAGE Air Traffic Integration, or SATIN. SATIN would extend SAGE to serve the ATC use-case as well, providing SAGE consoles directly in ARTCCs and enhancing SAGE to perform non-military safety functions like conflict warning and forward projection of flight plans for scheduling. Flight strips would be replaced by teletype output, and in general made less necessary by the computer's ability to filter the radar scope. Experimental trial installations were made, and the FAA participated readily in the research efforts. Enhancement of SAGE to meet ATC requirements seemed likely to meet the Beacon report's recommendations and radically improve ARTCC operations, sooner and cheaper than development of an FAA-specific system. As it happened, well, it didn't happen. SATIN became interconnected with another planned SAGE upgrade to the Super Combat Centers (SCC), deep underground combat command centers with greatly enhanced SAGE computer equipment. SATIN and SCC planners were so confident that the last three Air Defense Sectors scheduled for SAGE installation, including my own Albuquerque, were delayed under the assumption that the improved SATIN/SCC equipment should be installed instead of the soon-obsolete original system. SCC cost estimates ballooned, and the program's ambitions were reduced month by month until it was canceled entirely in 1960. Albuquerque never got a SAGE installation, and the Albuquerque air defense sector was eliminated by reorganization later in 1960 anyway. Flight Service Stations Remember those Flight Service Stations, the ones that were originally built by the Post Office? One of the oddities of ATC is that they never went away. FSS were transferred to the CAB, to the CAA, and then to the FAA. During the 1930s and 1940s many more were built, expanding coverage across much of the country. Throughout the development of ATC, the FSS remained responsible for non-control functions like weather briefing and flight plan management. Because aircraft operating under instrument flight rules must closely comply with ATC, the involvement of FSS in IFR flights is very limited, and FSS mostly serve VFR traffic. As ATC became common, the FSS gained a new and somewhat odd role: playing go-between for ATC. FSS were more numerous and often located in sparser areas between cities (while ATC facilities tended to be in cities), so especially in the mid-century, pilots were more likely to be able to reach an FSS than ATC. It was, for a time, routine for FSS to relay instructions between pilots and controllers. This is still done today, although improved communications have made the need much less common. As weather dissemination improved (another topic for a future post), FSS gained access to extensive weather conditions and forecasting information from the Weather Service. This connectivity is bidirectional; during the midcentury FSS not only received weather forecasts by teletype but transmitted pilot reports of weather conditions back to the Weather Service. Today these communications have, of course, been computerized, although the legacy teletype format doggedly persists. There has always been an odd schism between the FSS and ATC: they are operated by different departments, out of different facilities, with different functions and operating practices. In 2005, the FAA cut costs by privatizing the FSS function entirely. Flight service is now operated by Leidos, one of the largest government contractors. All FSS operations have been centralized to one facility that communicates via remote radio sites. While flight service is still available, increasing automation has made the stations far less important, and the general perception is that flight service is in its last years. Last I looked, Leidos was not hiring for flight service and the expectation was that they would never hire again, retiring the service along with its staff. Flight service does maintain one of my favorite internet phenomenon, the phone number domain name: 1800wxbrief.com. One of the odd manifestations of the FSS/ATC schism and the FAA's very partial privatization is that Leidos maintains an online aviation weather portal that is separate from, and competes with, the Weather Service's aviationweather.gov. Since Flight Service traditionally has the responsibility for weather briefings, it is honestly unclear to what extend Leidos vs. the National Weather Service should be investing in aviation weather information services. For its part, the FAA seems to consider aviationweather.gov the official source, while it pays for 1800wxbrief.com. There's also weathercams.faa.gov, which duplicates a very large portion (maybe all?) of the weather information on Leidos's portal and some of the NWS's. It's just one of those things. Or three of those things, rather. Speaking of duplication due to poor planning... The National Airspace System Left in the lurch by the Air Force, the FAA launched its own program for ATC automation. While the Air Force was deploying SAGE, the FAA had mostly been waiting, and various ARTCCs had adopted a hodgepodge of methods ranging from one-off computer systems to completely paper-based tracking. By 1960 radar was ubiquitous, but different radar systems were used at different facilities, and correlation between radar contacts and flight plans was completely manual. The FAA needed something better, and with growing congressional support for ATC modernization, they had the money to fund what they called National Airspace System En Route Stage A. Further bolstering historical confusion between SAGE and ATC, the FAA decided on a practical, if ironic, solution: buy their own SAGE. In an upcoming article, we'll learn about the FAA's first fully integrated computerized air traffic control system. While the failed detour through SATIN delayed the development of this system, the nearly decade-long delay between the design of SAGE and the FAA's contract allowed significant technical improvements. This "New SAGE," while directly based on SAGE at a functional level, used later off-the-shelf computer equipment including the IBM System/360, giving it far more resemblance to our modern world of computing than SAGE with its enormous, bespoke AN/FSQ-7. And we're still dealing with the consequences today! [1] It also laid the groundwork for the consolidation of the industry, with a 1930 decision that took air mail contracts away from most of the smaller companies and awarded them instead to the precursors of United, TWA, and American Airlines.

You know sometimes a technology just sort of... comes and goes? Without leaving much of an impression? And then gets lodged in your brain for the next decade? Let's talk about one of those: the iBeacon. I think the reason that iBeacons loom so large in my memory is that the technology was announced at WWDC in 2013. Picture yourself in 2013: Steve Jobs had only died a couple of years ago, Apple was still widely viewed as a visionary leader in consumer technology, and WWDC was still happening. Back then, pretty much anything announced at an Apple event was a Big Deal that got Big Coverage. Even, it turns out, if it was a minor development for a niche application. That's the iBeacon, a specific solution to a specific problem. It's not really that interesting, but the valance of it's Apple origin makes it seem cool? iBeacon Technology Let's start out with what iBeacon is, as it's so simple as to be underwhelming. Way back in the '00s, a group of vendors developed a sort of "Diet Bluetooth": a wireless protocol that was directly based on Bluetooth but simplified and optimized for low-power, low-data-rate devices. This went through an unfortunate series of names, including the delightful Wibree, but eventually settled on Bluetooth Low Energy (BLE). BLE is not just lower-power, but also easier to implement, so it shows up in all kinds of smart devices today. Back in 2011, it was quite new, and Apple was one of the first vendors to adopt it. BLE is far less connection-oriented than regular Bluetooth; you may have noticed that BLE devices are often used entirely without conventional "pairing." A lot of typical BLE profiles involve just broadcasting some data into the void for any device that cares (and is in short range) to receive, which is pretty similar to ANT+ and unsurprisingly appears in ANT+-like applications of fitness monitors and other sensors. Of course, despite the simpler association model, BLE applications need some way to find devices, so BLE provides an advertising mechanism in which devices transmit their identifying info at regular intervals. And that's all iBeacon really is: a standard for very simple BLE devices that do nothing but transmit advertisements with a unique ID as the payload. Add a type field on the advertising packet to specify that the device is trying to be an iBeacon and you're done. You interact with an iBeacon by receiving its advertisements, so you know that you are near it. Any BLE device with advertisements enabled could be used this way, but iBeacons are built only for this purpose. The applications for iBeacon are pretty much defined by its implementation in iOS; there's not much of a standard even if only for the reason that there's not much to put in a standard. It's all obvious. iOS provides two principle APIs for working with iBeacons: the region monitoring API allows an app to determine if it is near an iBeacon, including registering the region so that the app will be started when the iBeacon enters range. This is useful for apps that want to do something in response to the user being in a specific location. The ranging API allows an app to get a list of all of the nearby iBeacons and a rough range from the device to the iBeacon. iBeacons can actually operate at substantial ranges---up to hundreds of meters for more powerful beacons with external power, so ranging mode can potentially be used as sort of a lightweight local positioning system to estimate the location of the user within a larger space. iBeacon IDs are in the format of a UUID, followed by a "major" number and a "minor" number. There are different ways that these get used, especially if you are buying cheap iBeacons and not reconfiguring them, but the general idea is roughly that the UUID identifies the operator, the major a deployment, and the minor a beacon within the deployment. In practice this might be less common than just every beacon having its own UUID due to how they're sourced. It would be interesting to survey iBeacon applications to see which they do. Promoted Applications So where do you actually use these? Retail! Apple seems to have designed the iBeacon pretty much exclusively for "proximity marketing" applications in the retail environment. It goes something like this: when you're in a store and open that store's app, the app will know what beacons you are nearby and display relevant content. For example, in a grocery store, the grocer's app might offer e-coupons for cosmetics when you are in the cosmetics section. That's, uhh, kind of the whole thing? The imagined universe of applications around the launch of iBeacon was pretty underwhelming to me, even at the time, and it still seems that way. That's presumably why iBeacon had so little success in consumer-facing applications. You might wonder, who actually used iBeacons? Well, Apple did, obviously. During 2013 and into 2014 iBeacons were installed in all US Apple stores, and prompted the Apple Store app to send notifications about upgrade offers and other in-store deals. Unsurprisingly, this Apple Store implementation was considered the flagship deployment. It generated a fair amount of press, including speculation as to whether or not it would prove the concept for other buyers. Around the same time, Apple penned a deal with Major League Baseball that would see iBeacons installed in MLB stadiums. For the 2014 season, MLB Advanced Marketing, a joint venture of team owners, had installed iBeacon technology in 20 stadiums. Baseball fans will be able to utilize iBeacon technology within MLB.com At The Ballpark when the award-winning app's 2014 update is released for Opening Day. Complete details on new features being developed by MLBAM for At The Ballpark, including iBeacon capabilities, will be available in March. What's the point? the iBeacons "enable the At The Ballpark app to play specific videos or offer coupons." This exact story repeats for other retail companies that have picked the technology up at various points, including giants like Target and WalMart. The iBeacons are simply a way to target advertising based on location, with better indoor precision and lower power consumption than GPS. Aiding these applications along, Apple integrated iBeacon support into the iOS location framework and further blurred the lines between iBeacon and other positioning services by introducing location-based-advertising features that operated on geofencing alone. Some creative thinkers did develop more complex applications for the iBeacon. One of the early adopters was a company called Exact Editions, which prepared the Apple Newsstand version of a number of major magazines back when "readable on iPad" was thought to be the future of print media. Exact Editions explored a "read for free" feature where partner magazines would be freely accessible to users at partnering locations like coffee shops and book stores. This does not seem to have been a success, but using the proximity of an iBeacon to unlock some paywalled media is at least a little creative, if probably ill-advised considering security considerations we'll discuss later. The world of applications raises interesting questions about the other half of the mobile ecosystem: how did this all work on Android? iOS has built-in support for iBeacons. An operating system service scans for iBeacons and dispatches notifications to apps as appropriate. On Android, there has never been this type of OS-level support, but Android apps have access to relatively rich low-level Bluetooth functionality and can easily scan for iBeacons themselves. Several popular libraries exist for this purpose, and it's not unusual for them to be used to give ported cross-platform apps more or less equivalent functionality. These apps do need to run in the background if they're to notify the user proactively, but especially back in 2013 Android was far more generous about background work than iOS. iBeacons found expanded success through ShopKick, a retail loyalty platform that installed iBeacons in locations of some major retailers like American Eagle. These powered location-based advertising and offers in the ShopKick app as well as retailer-specific apps, which is kind of the start of a larger, more seamless network, but it doesn't seem to have caught on. Honestly, consumers just don't seem to want location-based advertising that much. Maybe because, when you're standing in an American Eagle, getting ads for products carried in the American Eagle is inane and irritating. iBeacons sort of foresaw cooler screens in this regard. To be completely honest, I'm skeptical that anyone ever really believed in the location-based advertising thing. I mean, I don't know, the advertising industry is pretty good at self-deception, but I don't think there were ever any real signs of hyper-local smartphone-based advertising taking off. I think the play was always data collection, and advertising and special offers just provided a convenient cover story. Real Applications iBeacons are one of those technologies that feels like a flop from a consumer perspective but has, in actuality, enjoyed surprisingly widespread deployments. The reason, of course, is data mining. To Apple's credit, they took a set of precautions in the design of the iBeacon iOS features that probably felt sufficient in 2013. Despite the fact that a lot of journalists described iBeacons as being used to "notify a user to install an app," that was never actually a capability (a very similar-seeming iOS feature attached to Siri actually used conventional geofencing rather than iBeacons). iBeacons only did anything if the user already had an app installed that either scanned for iBeacons when in the foreground or registered for region notifications. In theory, this limited iBeacons to companies with which consumers already had some kind of relationship. What Apple may not have foreseen, or perhaps simply accepted, is the incredible willingness of your typical consumer brand to sell that relationship to anyone who would pay. iBeacons became, in practice, just another major advancement in pervasive consumer surveillance. The New York Times reported in 2019 that popular applications were including SDKs that reported iBeacon contacts to third-party consumer data brokers. This data became one of several streams that was used to sell consumer location history to advertisers. It's a little difficult to assign blame and credit, here. Apple, to their credit, kept iBeacon features in iOS relatively locked down. This suggests that they weren't trying to facilitate massive location surveillance. That said, Apple always marketed iBeacon to developers based on exactly this kind of consumer tracking and micro-targeting, they just intended for it to be done under the auspices of a single brand. That industry would obviously form data exchanges and recruit random apps into reporting everything in your proximity isn't surprising, but maybe Apple failed to foresee it. They certainly weren't the worst offender. Apple's promotion of iBeacon opened the floodgates for everyone else to do the same thing. During 2014 and 2015, Facebook started offering bluetooth beacons to businesses that were ostensibly supposed to facilitate in-app special offers (though I'm not sure that those ever really materialized) but were pretty transparently just a location data collection play. Google jumped into the fray in their Signature Google style, with an offering that was confusing, semi-secret, incoherently marketed, and short lived. Google's Project Beacon, or Google My Business, also shipped free Bluetooth beacons out to businesses to give Android location services a boost. Google My Business seems to have been the source of a fair amount of confusion even at the time, and we can virtually guarantee that (as reporters speculated at the time) Google was intentionally vague and evasive about the system to avoid negative attention from privacy advocates. In the case of Facebook, well, they don't have the level of opsec that Google does so things are a little better documented: Leaked documents show that Facebook worried that users would 'freak out' and spread 'negative memes' about the program. The company recently removed the Facebook Bluetooth beacons section from their website. The real deployment of iBeacons and closely related third-party iBeacon-like products [1] occurred at massive scale but largely in secret. It became yet another dark project of the advertising-industrial complex, perhaps the most successful yet of a long-running series of retail consumer surveillance systems. Payments One interesting thing about iBeacon is how it was compared to NFC. The two really aren't that similar, especially considering the vast difference in usable ranges, but NFC was the first radio technology to be adopted for "location marketing" applications. "Tap your phone to see our menu," kinds of things. Back in 2013, Apple had rather notably not implemented NFC in its products, despite its increasing adoption on Android. But, there is much more to this story than learning about new iPads and getting a surprise notification that you are eligible for a subsidized iPhone upgrade. What we're seeing is Apple pioneering the way mobile devices can be utilized to make shopping a better experience for consumers. What we're seeing is Apple putting its money where its mouth is when it decided not to support NFC. (MacObserver) Some commentators viewed iBeacon as Apple's response to NFC, and I think there's more to that than you might think. In early marketing, Apple kept positioning iBeacon for payments. That's a little weird, right, because iBeacons are a purely one-way broadcast system. Still, part of Apple's flagship iBeacon implementation was a payment system: Here's how he describes the purchase he made there, using his iPhone and the EasyPay system: "We started by using the iPhone to scan the product barcode and then we had to enter our Apple ID, pretty much the way we would for any online Apple purchase [using the credit card data on file with one's Apple account]. The one key difference was that this transaction ended with a digital receipt, one that we could show to a clerk if anyone stopped us on the way out." Apple Wallet only kinda-sorta existed at the time, although Apple was clearly already midway into a project to expand into consumer payments. It says a lot about this point in time in phone-based payments that several reporters talk about iBeacon payments as a feature of iTunes, since Apple was mostly implementing general-purpose billing by bolting it onto iTunes accounts. It seems like what happened is that Apple committed to developing a pay-by-phone solution, but decided against NFC. To be competitive with other entrants in the pay-by-phone market, they had to come up with some kind of technical solution to interact with retail POS, and iBeacon was their choice. From a modern perspective this seems outright insane; like, Bluetooth broadcasts are obviously not the right way to initiate a payment flow, and besides, there's a whole industry-standard stack dedicated to that purpose... built on NFC. But remember, this was 2013! EMV was not yet in meaningful use in the US; several major banks and payment networks had just committed to rolling it out in 2012 and every American can tell you that the process was long and torturous. Because of the stringent security standards around EMV, Android devices did not implement EMV until ARM secure enclaves became widely available. EMVCo, the industry body behind EMV, did not have a certification program for smartphones until 2016. Android phones offered several "tap-to-pay" solutions, from Google's frequently rebranded Google Wallet^w^wAndroid Pay^w^wGoogle Wallet to Verizon's embarrassingly rebranded ISIS^wSoftcard and Samsung Pay. All of these initially relied on proprietary NFC protocols with bespoke payment terminal implementations. This was sketchy enough, and few enough phones actually had NFC, that the most successful US pay-by-phone implementations like Walmart's and Starbucks' used barcodes for communication. It would take almost a decade before things really settled down and smartphones all just implemented EMV. So, in that context, Apple's decision isn't so odd. They must have figured that iBeacon could solve the same "initial handshake" problem as Walmart's QR codes, but more conveniently and using radio hardware that they already included in their phones. iBeacon-based payment flows used the iBeacon only to inform the phone of what payment devices were nearby, everything else happened via interaction with a cloud service or whatever mechanism the payment vendor chose to implement. Apple used their proprietary payments system through what would become your Apple Account, PayPal slapped together an iBeacon-based fast path to PayPal transfers, etc. I don't think that Apple's iBeacon-based payments solution ever really shipped. It did get some use, most notably by Apple, but these all seem to have been early-stage implementations, and the complete end-to-end SDK that a lot of developers expected never landed. You might remember that this was a very chaotic time in phone-based payments, solutions were coming and going. When Apple Pay was properly announced a year after iBeacons, there was little mention of Bluetooth. By the time in-store Apple Pay became common, Apple had given up and adopted NFC. Limitations One of the great weaknesses of iBeacon was the security design, or lack thereof. iBeacon advertisements were sent in plaintext with no authentication of any type. This did, of course, radically simplify implementation, but it also made iBeacon untrustworthy for any important purpose. It is quite trivial, with a device like an Android phone, to "clone" any iBeacon and transmit its identifiers wherever you want. This problem might have killed off the whole location-based-paywall-unlocking concept had market forces not already done so. It also opens the door to a lot of nuisance attacks on iBeacon-based location marketing, which may have limited the depth of iBeacon features in major apps. iBeacon was also positioned as a sort of local positioning system, but it really wasn't. iBeacon offers no actual time-of-flight measurements, only RSSI-based estimation of range. Even with correct on-site calibration (which can be aided by adjusting a fixed RSSI-range bias value included in some iBeacon advertisements) this type of estimation is very inaccurate, and in my little experiments with a Bluetooth beacon location library I can see swings from 30m to 70m estimated range based only on how I hold my phone. iBeacon positioning has never been accurate enough to do more than assert whether or not a phone is "near" the beacon, and "near" can take on different values depending on the beacon's transmit power. Developers have long looked towards Bluetooth as a potential local positioning solution, and it's never quite delivered. The industry is now turning towards Ultra-Wideband or UWB technology, which combines a high-rate, high-bandwidth radio signal with a time-of-flight radio ranging protocol to provide very accurate distance measurements. Apple is, once again, a technical leader in this field and UWB radios have been integrated into the iPhone 11 and later. Senescence iBeacon arrived to some fanfare, quietly proliferated in the shadows of the advertising industry, and then faded away. The Wikipedia article on iBeacons hasn't really been updated since support on Windows Phone was relevant. Apple doesn't much talk about iBeacons any more, and their compatriots Facebook and Google both sunset their beacon programs years ago. Part of the problem is, well, the pervasive surveillance thing. The idea of Bluetooth beacons cooperating with your phone to track your every move proved unpopular with the public, and so progressively tighter privacy restrictions in mobile operating systems and app stores have clamped down on every grocery store app selling location data to whatever broker bids the most. I mean, they still do, but it's gotten harder to use Bluetooth as an aid. Even Android, the platform of "do whatever you want in the background, battery be damned," strongly discourages Bluetooth scanning by non-foreground apps. Still, the basic technology remains in widespread use. BLE beacons have absolutely proliferated, there are plenty of apps you can use to list nearby beacons and there almost certainly are nearby beacons. One of my cars has, like, four separate BLE beacons going on all the time, related to a phone-based keyless entry system that I don't think the automaker even supports any more. Bluetooth beacons, as a basic primitive, are so useful that they get thrown into all kinds of applications. My earbuds are a BLE beacon, which the (terrible, miserable, no-good) Bose app uses to detect their proximity when they're paired to another device. A lot of smart home devices like light bulbs are beacons. The irony, perhaps, of iBeacon-based location tracking is that it's a victim of its own success. There is so much "background" BLE beacon activity that you scarcely need to add purpose-built beacons to track users, and only privacy measures in mobile operating systems and the beacons themselves (some of which rotate IDs) save us. Apple is no exception to the widespread use of Bluetooth beacons: iBeacon lives on in virtually every apple device. If you do try out a Bluetooth beacon scanning app, you'll discover pretty much every Apple product in a 30 meter radius. From MacBooks Pro to Airpods, almost all Apple products transmit iBeacon advertisements to their surroundings. These are used for the initial handshake process of peer-to-peer features like Airdrop, and Find My/AirTag technology seems to be derived from the iBeacon protocol (in the sense that anything can be derived from such a straightforward design). Of course, pretty much all of these applications now randomize identifiers to prevent passive use of device advertisements for long-term tracking. Here's some good news: iBeacons are readily available in a variety of form factors, and they are very cheap. Lots of libraries exist for working with them. If you've ever wanted some sort of location-based behavior for something like home automation, iBeacons might offer a good solution. They're neat, in an old technology way. Retrotech from the different world of 2013. It's retro in more ways than one. It's funny, and a bit quaint, to read the contemporary privacy concerns around iBeacon. If only they had known how bad things would get! Bluetooth beacons were the least of our concerns. [1] Things can be a little confusing here because the iBeacon is such a straightforward concept, and Apple's implementation is so simple. We could define "iBeacon" as including only officially endorsed products from Apple affiliates, or as including any device that behaves the same as official products (e.g. by using the iBeacon BLE advertisement type codes), or as any device that is performing substantially the same function (but using a different advertising format). I usually mean the latter of these three as there isn't really much difference between an iBeacon and ten million other BLE beacons that are doing the same thing with a slightly different identifier format. Facebook and Google's efforts fall into this camp.