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Heurikon Historical Highlights A series of articles for The Horizon by Jeffrey Mattox Our Domiciles Over the years, Heurikon has had seven homes. We started out in the basement of Chris’s house, at 621 Sheldon Street. That’s just off Monroe Street near Wingra Park. Most of the operation, including a circuit board photo and fabrication area, was in the basement. The business phone and answering machine were on a small desk in a hallway. (That original desk is still in use; it is in the telephone equipment room.) Although some business was conducted on the dining room table (which had a good view of the kitchen sink), our most important decisions were made at the Laurel Tavern on Monroe Street. Chris and his family lived upstairs in the house, along with John Burdick (one of Heurikon’s other founders), and an attractive university coed who would occasionally walk through our dining-room office wearing only her bathrobe. Years later, we heard from one of our vendor’s representatives that he visited us often just for the chance to see her parade around. Another notable resident of the house was Chris’ dog, Brandy. She would get real excited whenever a visitor came into the house, and it wasn’t uncommon for her to end up piddling on somebody’s foot. The old story about my foot once being a target is untrue — it was John’s. He just calmly stood there and smiled. It was easy for our neighbors to recognize Heurikon’s visitors. While searching for the “factory,” confused visitors would often drive up and down the street in their expensive cars before realizing the old house at 621 was the correct place.
From One Basement to Another After a short search around Madison, we found a low-rent office in the basement of an apartment complex at 700 West Badger Road. The rent was low, in part because the space didn’t have any heat — most of our heat came in through the ceiling from the apartments above. We rarely had any problems with the other tenants — expect for the time one of them plugged up their tub and let the water run over the top. That afternoon, the ceiling above our drafting area started to sag and then it gave way with a torrent of water. The water also ran down the ceiling support rods and dripped onto our benches and desks.
West Badger Road suited us nicely until 1980. By then we needed more space which we found just across the Beltline, at 3001 Latham Drive, in the rear of Vondra Engraving’s new building. We had 3,000 square feet — and heat and restrooms and carpets, and even a hallway (luxuries absent from our Badger Road offices). There were a few undesirable features, however. The metal roof was not well insulated, and when it rained, it would be so noisy we’d have to shout to be heard. On cold winter nights, condensation would freeze on the metal ceiling, which would slowly melt during the day, causing water to drip all over the benches in the shop. The air conditioners were so loud that Deanie had to turn off the one above her desk whenever she wanted to talk on the phone. By the end of 1982, we needed more space, so, with Vondra’s permission, we cut through an interior wall and expanded to 4,500 square feet (a tenth of what we have now). We had our 1982 Christmas party in the new space (the decor was “primitive unfinished warehouse”). We grew steadily during our years at Vondra. And, we got our first copy machine, wave solder machine, and Gen Rad tester. The Bombay Bicycle Club was only a short walk away, so that served as our business bar.
By the middle of 1985, we were about to burst our walls, so we committed to the first building of our own, and moved a few blocks up the hill to 3201 Latham Drive. Much of the move was done by simply putting our equipment and furniture on carts and rolling it up the hill. From the air, it looked like a line of ants moving along. New amenities included a loading dock, break area, and conference rooms. In late-1987, to make room for our continued growth, the marketing, sales, accounting, and administration departments moved downtown to 121 East Wilson Street. Also, for a few years, we leased two trailers and attached them to the building through the outside exit of the break room. The trailers were home to cost accounting, customer support, and a few other people who managed to squeezed in. The acoustics were horrible. As you walked around in the trailers, your footsteps would resonate throughout the space. We had planned on staying at Latham Drive for ten or more years, but when we needed to expand again, we decided to move to a neighborhood more suitable to our business. The Latham Drive area was an unplanned conglomeration of warehouses, stores, and factories. There was a meat-packing plant on one side of us and a junkyard on another. It just didn’t seem like the right locale for the long-term. This concludes the Heurikon Historical Highlights series.
UPDATE July 2009: In actuallity, Heurikon/Artesyn/Emerson had operations in many more locations. My perspective was from engineering, but other departments occupied other buildings. Here's a good list submitted by Bruce Dittmer:
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One week to go and the building is nearly empty. The material things such as cubicles, chairs, and people are obviously missing. There is dead silence under the air handling system. The sound of ringing phones, printers, rolling carts, the "chip shooter", hallway gatherings, and filled conference rooms are all but gone. But even with the remaining skeleton crew helping to close this final phase of Artesyn/Heurikon, the sounds of camaraderie and friendship still speak loudly within. Respect, cooperation, and a strong sense of family still remain, and one can still feel that good things were housed under this roof. Each one of us shares those feelings, which makes this chapter the hardest to finish. Artesyn/Heurikon as a business will soon be forgotten, but all that has been shared and accomplished will forever be remembered.
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Heurikon Historical Highlights A series of articles for The Horizon by Jeffrey Mattox NIKA Corporation One of our original investors and business advisors was Ed Gray. He ran the NIKA Corporation, a Madison firm that contracted with the government and insurance companies to provide cost estimates for renovating or repairing damaged buildings in cities throughout the nation. NIKA maintained a database of material and labor rates for all building trades across the country. The process of settling an insurance claim and doing cost estimates for government rehab projects involved a lot of paperwork. Ed wanted a machine that would eliminate the paper and could be taken directly into the field. Today, the perfect solution would be a portable PC, but back then there were no such things — there weren’t any personal computers, either. We designed a 50-pound “portable” computer that included a four-slot Multibus I card rack, a 3M tape drive, a Burrows plasma display panel, three switching power supplies, and two fans. The tape drive was for loading the program and database and for saving the results of a site visit. The plasma panel was that era’s idea of a liquid crystal display, except it was made out of glass and required a lethal 250 volts to operate. Chris designed a distinctive front panel and an internal support structure for the components, and somehow managed to fit everything into a metal travel case with barely any room left over. To power the unit in the field, we built a separate Gel-Cell battery pack. (That was another 50 pounds — it had to last for four hours!) It was a masterpiece of design in many ways, and it really was a forerunner of today’s portable computers. All it lacked was low-power logic, an LCD, and modern battery technology. The Computer Drop Test... We weren’t designing the unit from written specifications. It was an interactve design that entailed frequent meetings with Ed to work out the details. One day, well into the prototype construction phase, Ed announced that he was going to do a “drop test” before he’d accept the unit. He wanted it to survive a three-foot fall off of a table. Whoa! “Over my dead body,” Chris said. “Not with our plasma display, no way!” ... And The Ultimate Crush Test Ed was very impressed with his machine; he called it the NIKA Field Scribe. He showed it to the heads of all the major insurance companies and demonstrated how it could total up the costs for anything from repairing a window or painting a wall to installing electrical cables or a new roof. After a few months, however, Ed realized that the insurance industry wasn’t ready to sign onto the new technology, so he used the machine to help trumpet his other services. It was, as they say, an idea ahead of its time. Ed visited us a few months ago, and I asked him about his Field Scribe, hoping he’d tell me about how it was still stashed somewhere in his living room. Well, I shouldn’t have asked. Ed says he removed the electronics so he could temporarily use the metal case for something else, but, while laying about in his garage, the guts were run over by a truck. I hope he got the license number. (Makes me rethink the merits of the three-foot drop test.) NEXT MONTH: Domiciles of the bench and famous. |
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Original publication date: June 1992 Heurikon Historical Highlights A series of articles for The Horizon by Jeffrey Mattox EEKK and Del-Monte Corporations In the 1970s, washing machines were not very high-tech; they certainly didn’t have computers in them. However, if the washing system was destined for a bean-packing plant, computers were in order. We were asked to build such a system by the EEKK Corporation of Schaumburg, Illinois. EEKK provided control systems and related equipment to the food processing industry, and they wanted us to build a controller for use in two Del-Monte bean-packing plants. One of the plants was in Florida, and the other was near Stevens Point, Wisconsin (just south of the city on highway 51). There are many different types of equipment in an automated bean-packing plant. There are bean sorters, washers, cutters, conveyor belts, and so on, and each piece of machinery has to be cleaned and washed once each day. However, during the short, three-month packing season each year, the plant runs 24-hour per day, and the the time it takes to clean the equipment cuts into their production time. The general washing sequence was to rinse each food-processing machine, then apply a chemical, wait for a specified amount of time for it to work, then rinse the chemical off. That sounds fairly simple, but there were two factors that made things more difficult. First, the piping system only had a limited capacity, so only one set of valves could be open at a time. Second, once the washing chemical had been applied, it had to be rinsed off within a certain time window — not too soon or too late — otherwise the chemical would not work properly. The Del-Monte plants had been shutting down operations for four to six hours each night while six workers went through each plant with water and chemical hoses and sprayed the equipment. Cleaning was a time consuming and labor intensive operation. Our Infamous MLP-8080 to the Rescue We designed a controller around our MLP-8080 board that could sequence up to 64 sets of water and chemical values. It had eight timing programs that could specify rinse, wash, wait, and final rinse times for various types of processing equipment. When the operator pushed the start button, the computer would examine the database and devise a sequence for operating the valves to wash all the equipment in the least amount of time. At some points during the sequencing, the wash and rinse cycles for different sequences would overlap. That is, the system could be rinsing a bean cutting machine, while simultaneously applying the chemical to a conveyor belt and doing a final rinse on a third machine. Once it started a chemical application, however, the computer had already determined that it would be able to rinse off the chemical during the allowed time window. As usual in those days, we wrote the program in machine language, and it was very complicated. Rolls of paper tape were strewn about the shop, and the Teletype machine gave out a constant background chatter.
I can easily recall one specific problem we had while building the system. For some reason, we couldn’t buy stranded 50-conductor ribbon cable; it only came with solid wire. I don’t think they made much stranded ribbon cable back then — and 50-conductor ribbon cable was not as widely used as it is today. The solid wire we were able to get was very hard to flex, and the crimps at the connectors were unreliable. Every time we attached or removed a ribbon cable, we ran the risk of causing a loose connection. The computer-controlled system had many advantages over the old manual system that Del-Monte had been using. After we put the new system on-line, it took only one person to start the operation and one worker to go through the plant with a hose and clean around the hard-to-get-at places. And, because of the computer’s smarts, the whole plant could be cleaned in only two hours. The plant manager at Stevens Point reports that our computer equipment was in operation there for nearly ten years. They have since switched to an Allen-Bradley sequencer. The Florida plant stopped processing beans in 1980. NEXT MONTH: Our 100-pound “portable” computer. UPDATE June 2009: I called the Stevens Point plant to see if our equipement was still there. The plant manager told me they had been using our system up until a few years ago, and it was still operational. What a nice surprise. |
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Heurikon Historical Highlights A series of articles for The Horizon by Jeffrey Mattox The MLZ-DAQ — Madison Water Utility Some of our old products were not major stars — a few were dead ends or just plain unglamorous. One of those not-so-glamorous products was the MLZ-DAQ. We designed the DAQ as an inexpensive, general-purpose, data acquisition board. It was a Multibus® I board with 32 digital I/O bits, a 32-channel analog-input multiplexer, and a 12-bit analog-to-digital converter module. It used static RAM, so we were space-limited to including only 1,024 bytes of memory. What does make this board notable, however, is that most of the MLZ-DAQs we sold back in 1978 are still in operation — and right here in Madison! In fact, you are dependent on a Heurikon MLZ-DAQ to meet many of your daily needs. Like many of our early products, The MLZ-DAQ was engineered with a particular customer in mind. In this case, it was designed for the City of Madison Water Utility. They wanted to install a control center that would be connected to the 26 water pumping stations around the city. This would permit the utility to monitor water pressures, tank levels, and various status signals, and to control water pumps, all from a central location. Their system design engineers met with us and we used their specifications to design the board. The telemetry system was put into operation in the early 1980s and has been working fine ever since. Even though there are about 32 processors in the city’s inventory, we haven’t been asked to make any service calls or repair any processors. This is because the city is doing their own maintenance. That’s probably just as well, since no one in our service department claims to remember much about this particular board. Although we only sold a few hundred MLZ-DAQ boards, that microcomputer board stayed on our price list for years. Every time we considered dropping it, some impoverished customer, such as AT&T or Boeing, would decide to order a few. The water supply for our building comes from the old pumping station on Mineral Point Road (near the high school) or the new station atop the hill on High Point Road. During the winter, the city pumps 30 million gallons per day to its customers — and 45 million gallons per day during the summer. Although most of the utility’s sites have a deep well pump and a huge water storage tank, a few locations have storage tanks only. At night, or when the overall water demand is low, the utility allows water to flow in reverse, thus refilling those storage tanks from the water mains. Also, since the water mains are all interconnected in a giant underground grid, numerous pumping stations can be off-line or under repair at the same time — and we won’t notice. When you turn on your water faucet or drive past a city pumping station, remember that Heurikon computers are being used to help keep the water flowing. The City of Madison shares the honors with Oscar Mayer Foods and Cue-Nique Micro-Logic as having the oldest Heurikon products still in use. |
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Original publication date: April 1992 Heurikon Historical Highlights A series of articles for The Horizon by Jeffrey Mattox The General Electric Company We worked on four interesting projects with General Electric during the early years. Two of them were with GE’s Large Steam Turbine-Generator (LSTG) Division in Schenectady (“Bet-You-Can’t-Pronounce-It-On-Your-First-Try”), New York — a huge factory that makes steam turbines and generators for power plants. One of their critical operations is drilling holes for coolant in the thick copper bars that form the generator rotor coils. Due to the geometry of the generator, each layer of the rotor coil is a different size and shape, but the holes in each layer still have to line up perfectly. GE asked us to build the equipment that would synchronize the numerical data as it was requested by the hole boring machines. The other project with LSTG was a welding machine controller. Most welding machines attach two pieces of metal together, but this one put down a continuous bead of chromium around critical parts of steam valves to prevent wear. Both of those projects used our MLZ-80 processor and a CRT/keyboard controller board. We custom-designed a heavy-duty pedestal enclosure so the equipment was protected from the dirt, metal chips, and oil that pervaded the factory. Another early GE project was with their Housewares Group in Allentown, Pennsylvania. That’s where they assembled their two-slice toasters. Two small calibration screws on each toaster timer had to be adjusted, but the people doing the adjustment had no way to know if they were setting the screws accurately. It could take six hours or more before the timers were actually installed in a toaster and checked, and by that time it would be too late to readjust the setscrews. So, Ben Koltisko, an engineer at GE, having heard about our work from his colleagues in Schenectady, stopped off in Madison to see us on his way back from visiting Intel about his timer calibration problem. After Ben described what he wanted, we offered to make the electronic controls for his timer calibration and testing machine. We proposed a system that had features Ben hadn’t even thought of but realized he could use. Intel, however, merely offered a basic microprocessor, and they wouldn’t do any custom work. Because we fully understood his problem from the get-go, he gave us the order. As with many projects, we were caught short on the schedule and had to innovate. For example, when we couldn’t find anybody willing to give us a short turn-around on finishing our 25 small enclosures, we took the raw computer boxes across the West Beltline to an automobile-painting company — the people there were much more accustomed to repainting vehicles and doing pin stripes, but they obliged us anyway with overnight service. The interesting part about a toaster timer is that it has to account for the residual heat inside the toaster so that the second and third toasting works as well as the first. No small trick. The mechanical timers were really two-cycle thermostats. When you started toasting, a bimetal strip was heated to a set temperature by a special heating coil. When that set temperature was reached, the thermostat clicked, the special heater went off, and the thermostat cooled down. After it cooled sufficiently (to the second setpoint), it triggered the pop-up solenoid and stopped the toaster. That click you may have heard when your toast was almost done was not just a warning for you to get ready with the butter knife; it was actually part of the timing operation. A few years ago, GE’s Housewares Division was purchased by Black & Decker, and the toasters are now sold under that name and made in Taiwan. The reassuring timer click is defunct, too — probably the result of having gone solid-state. The Versatron Toaster-Oven Our fourth GE project was for another toaster-like product, called the Versatron Toaster Oven. It had a control panel with an assortment of buttons, levers, rotary switches, neon indicator lights, and audible alarms. Our task was to build the computer controls for sequencing a pneumatic machine that would fully test all functions of the control panel, including the switches, lights, and alarm. The operator loaded a Versatron panel into the machine and the tester grabbed hold of the switches and went through a sequence of tests, monitoring the panel’s outputs, lights, and alarm. The unit even had a bed of nails, much like our Genrad. The machine took about 45 seconds to test one panel, and the mechanism clicked and clanked and hissed the whole time. Very impressive. But alas, just when we got the unit finished, GE pulled the Versatron off the market. They had started selling the toaster-ovens before they had put a service network in place, and the ovens were not operating as planned — too many needed service. The ovens were being returned for repair faster than GE could fix them. So, they paid us for our work, took the testing equipment we had built, and, for tax purposes, fed the ovens and our testers to a trash compactor (ouch!). |
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Original publication date: March 1992 Heurikon Historical Highlights A series of articles for The Horizon How Programs Were Made in the Old Days We wrote our first lengthy microcomputer programs using the computer at the University of Wisconsin’s Computer Science Department. We purchased the computer time, paying by the minute of CPU usage. We started by reprogramming their mainframe’s macro assembler so it would understand Intel 8080 instructions. When we had an 8080 program to assemble, we punched a deck of about 2,000 cards, fed the cards in via a card reader, and went to a Teletype machine where we punched a long paper tape of the resultant 8080 object code. To be more accurate, we “submitted” the deck at the computer room window, waited overnight while the job was run (the night-time rates were cheaper), and then we made the object tape. If one of the cards had a typo, it took us another day to fix it and rerun the job. That type of interaction with a computer was called “batch” mode, and it was frustratingly slow. We brought the paper tape back to our office and read it in on our ASR-33 Teletype machine. The data went into RAM, and then we made a ROM copy. Sometimes the tape would break or the teletypewriter would skip a sprocket and the program wouldn’t work — it was a very unreliable system. Patchwork Quilts After we tested the program, if we needed to change even a single line of the source code, we had to edit the card deck and repeat the whole process. To avoid doing that for simple changes, we would frequently just “patch” the ROM version of the program by manually changing certain memory locations in a RAM copy of the program. Manual changes to 8080 and Zilog Z80 programs were easy to do because the eight-bit machine-code formats used by those chips were simple to memorize. After making many patches, however, our programs would become impossible to maintain, so we ultimately had to go back to the punch cards and clean things up. Since we were writing machine-language programs (not BASIC, FORTRAN or C) and had only a limited amount of space in the small ROMs, we’d frequently hand-assemble the source code modifications we were planning and figure out on paper if the total number of bytes we were adding (less those we were removing) would overflow the ROMs. If we had too many bytes, we went on a search-and-destroy mission, looking for parts of the program that could be streamlined or eliminated. This resulted in some very interesting, but highly convoluted and hard-to-maintain code. The Teletype machine ran at only 10 characters per second, so a lengthy dump was very time-consuming. The first thing we wrote was a monitor program for the 8080 that allowed us to type commands to the Teletype so we could read and write memory locations. We called it “RAID” for Real-time Assembler and Interactive Debugger — it was supposed to kill-bugs-dead. Later, when we modified the monitor to work with Zilog’s Z80 chip, we renamed the program “ZRAID.” (That monitor served us until the 68000 came along — then we wrote Hbug.) Instead of having an RS232 voltage-level interface, teletypewriters used a 20-milliampere current loop, so our early microcomputer boards had a current loop I/O circuit. Most microcomputer manuals explained how to rewire and connect a Teletype machine, and many early CRT terminals had a current loop option. Teletype Mechanics If the Teletype would act up, we would have to stop our work, get out our tools, and try to fix it. Pete Berbee and I once spent a whole day just trying to adjust a greasy camshaft in the damn machine so it wouldn’t print gobbledegook — and we never did get around to doing any useful work that day. Through the surplus market, we came across an old seven-track magnetic tape machine. Using trial and error on a I/O connector, we figured out how to start and stop the tape motion. We wrote a short bootstrap program to control the tape machine. (The bootstrap had to be read into memory from paper tape). This allowed us to save large programs and quickly reload them a day or two later. The tape machine roared like an industrial vacuum cleaner when it was running. By the end of the 1970s, Digital Research had produced the CP/M operating system, which we quickly ported to our MLZ-80 board. CP/M gave us our first in-house capability to edit and assemble programs for our hardware. The glory days of the Teletype were ending, and we cautiously invested in our first CRT terminal. Our MLZ-80 had 4,096 bytes of RAM, which was just enough to load the operating system, and was the first Multibus I card in our market to include a floppy disk controller. A separate 32-kilobyte RAM card was needed, however, to run any programs! NEXT MONTH: Toaster-master General. |
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Original publication date: January 1992 Heurikon Historical Highlights A series of articles for The Horizon Cue-Nique Micro-Logic Manufacturing, Ltd. For a few years, we were in the point-of-sale business. Our customer was Jerry Briesath, the owner-operator of Cue-Nique Billiards, “Home of The Pool-School,” right here in Madison. Jerry wanted to build and resell computer systems that would keep track of information about parlor patrons and show the status of each table at a glance. When a billiard-player customer comes to the checkout counter to pay his or her bill, the table usage time and bar tabs have to be tallied. Sometimes players have changed tables or are leaving before the other people at their table are done playing. Rates vary by time-of-day, and there are lower rates for groups or special occasions. Check-out can be complicated, so it is easy for employees to make mistakes and ring up incorrect charges. When he came to us, Jerry was desperate to get his idea to market, but he was a bit apprehensive because he had already spent some of his money and had received nothing useful in return. Jerry showed us the previous attempt somebody had made to build his system. It was an unfinished “Box-o-Parts & Wires” — it didn’t come close to working correctly. Could microcomputers really do the job? Heurikon Comes To The Rescue! Yes. We designed a sleek point-of-sale terminal for Jerry — the prototype used our MLP-8080 microcomputer board (what a workhorse!). We built a front panel circuit board that included table status LEDs, a small keyboard, and numerous seven-segment data displays so the operator and customer could see table usage times and the dollar amounts owed.
The system also controlled an external relay box that was connected to the lights above each billiard table — whenever a table was “in use” the appropriate table lights automatically came on. Later, we added bowling alley capabilities that kept track of shoe rental charges and counted frame pulses from the pin-setters. After building 15 prototypes, we redesigned the system to reduce costs and to eliminate the need for a fan (which usually sucked in more street dirt than cool air). We put all of the electronics on a single PCB and incorporated a high-tech, new-tech switching power supply. We learned a lot more than we had anticipated about the high levels of electrical noise that switching power supplies could produce; sometimes the 8080 processor would go berserk for no apparent reason and send gobbledegook to the display instead of table data. Lessons In Conceptualization Working with Jerry was a lot of fun. He knew what he needed, but he was usually vague on the details. He came to us with general concepts of how the machine should operate, then we made a few specific implementation suggestions, to which Jerry would say: “Yeah, that sounds pretty good — make it work something like that.” After a few days, Jerry would often call back and ask if we could add another feature or two, “but only if it wasn’t too much work.” It was a very loose style, but it suited us, too. Dennis Paton joined us as we began production of the Cue-Nique units, and we kept him very busy testing and debugging the assemblies. Then, as now, Dennis always kept a beautifully neat work area — in a pinch, we could always find a needle-nose pliers and wire cutters neatly stored in his top drawer. When we moved out of the West Badger Road basement, I recall seeing Dennis’s heel dents and footprints on the wall where his bench had been located — the dents are probably still there.
We later found out one reason why the other guys were able to quote so much lower than we for an identical product. Many of the components they used were low quality. Some of the capacitors, for example, had a shelf-life of only a few years. Later, the computers started to fail and Jerry had to replace those parts. Despite those setbacks, Jerry’s computers have been a big hit — he currently has hundreds of them out in the field. Some of them might even be part of the 65 we built (Jerry isn’t sure). Jerry’s Dream Lives On Today, Jerry is developing a modern version of his system, one that runs on an IBM-PC with an attached cash drawer. Using this new approach, Jerry can sell software packages world-wide. The fellow doing his programming, Chris Madsen, worked for us back when we were building the first Cue-Nique systems. By the way, Jerry is a world-renowned billiard player and instructor. It’s a real treat to see him run the balls and perform trick shots. He worked as a technical advisor on Whoopi Goldberg’s made-for-TV movie, Kiss Shot. Next time you’re in town near State and Gorham streets, stop in at Cue-Nique Billiards and ask for Jerry. Say “ ‘Hello’ from Heurikon” — maybe you can hustle a free coke. MARCH: We sing the Teletype blues.
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Original publication date: February 1992 (But it should have been done in April. :-) Sonic Boom Lines On maps and globes of the Earth, the locations of the equator, the Arctic and Antarctic circles, and the tropics of Cancer and Capricorn are clearly shown. These circles indicate certain characteristics of the apparent journey that the sun makes over the Earth’s surface each year. There are two other conjured circles on the Earth’s surface that few people know about. They are called “sonic boom lines,” and they indicate the latitudes where the Earth’s surface velocity is equal to the speed of sound. Breaking the Barriers of Credulity You know that an aircraft produces a boom whenever it accelerates above the speed of sound (approximately 760 miles per hour at 57°F). The window-shattering sonic boom that occurs when the aircraft “breaks the sound barrier” is caused by an atmospheric shock wave that extends from the aircraft to the ground. We rarely hear sonic booms today because FAA regulations prohibit all aircraft from flying at supersonic speeds over inhabited areas. However, despite FAA and public desires, the rotation of the Earth causes many parts of the surface to spin at velocities that exceed the speed of sound. Since the circumference of the Earth is roughly 24,000 miles, the surface speed at the equator due to the rotation of the Earth is about 1,000 miles per hour (well above the speed of sound).
Unlike the equator and tropics, the exact locations of the sonic boom lines vary according to local altitude and air temperature. For example, using Heurikon’s altitude (978 feet above sea level) and average atmospheric conditions (11.83°C), the sonic boom line moves to 43° 04' 55" north latitude. Although these effects are very small, they are enough to make the exact locations of the boom lines laborious to determine and in continuous flux. That is why cartographers refuse to put these lines on their maps. Cone Heads in Our Nether Regions Technically, the sonic boom lines are the intersections of an imaginary cone with the Earth’s surface. That cone (the surface of which represents all points that are rotating at the speed of sound) extends parallel to the Earth’s poles and pierces the Earth at the two sonic boom latitudes. The supersonic atmospheric regions that are directly above locations on the Earth’s surface that are themselves outside (but near to) a sonic boom line are called, curiously, the “nether regions.” Those small areas dissipate the sonic boom shock waves into outer space, thus preventing the shock waves from causing a continuous, annoying boom to listeners on the surface. The Earth’s motion around the sun and the sun’s motion through the cosmos do not affect the sonic boom phenomenon nor produce one of their own. This is because sound waves cannot travel through the vacuum of outer space.
If you examine a map of Wisconsin, you will see that the northern sonic boom line comes near to the Madison area. In fact, the altitude- and temperature-adjusted line (at 43° 04' 55") goes right though the center of our building, piercing the flagpoles, front doors, central corridor, rear doors — even the picnic table. The wide maroon stripe in the middle of our lobby carpet lies directly over the boom line!
Is it merely a coincidence that our building straddles the northern sonic boom line, and should we be concerned? Dunno. Go figure. |
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