omenti

green flight

Two years ago the Environmental Protection Agency reported aviation accounted for about three percent of the nation's CO₂ emissions, or about twelve percent of transportation.  The international figure is about two point five percent.  These may not seem huge, but they've been growing steadily and, post pandemic, should continue their growth.  Making matters worse is the global warming contribution from the cloud-like contrails produced by the jet engines at altitude.   It's difficult to study, but indications are the contribution may double the global warming impact. 

 

A number of approaches have been suggested and are in various stages of testing.  Moving to bio-fuels isn't the greatest solution as growing and producing biofuels has issues and you're still producing contrails.  In the short term some airlines will move to it, but that may be part a PR and carbon credits game as much as anything. 

 

Electric airplanes exist and there are even a few (very) sort haul commercial flights.  The problem is the specific energy of the battery - how heavy is a battery per unit of energy storage.   Turbine fuel stores about eighty times as much energy as a safe lithium-ion battery of the same weight.  Airplanes frequently carry large amounts of fuel - the weight of fuel burned on a cross country trip is greater than that of the the passengers and crew.  The range of a battery powered airplane is severely limited even after accounting for the great efficiency of an electric motor.   We could get a lot closer with exotic batteries that aren't anywhere close to reality, but even then you're talking about a propeller driven (slower) aircraft. 

 

Hydrogen often comes up as the perfect clean fuel - the combustion product is just water.   Although it's the most common element in the universe and accounts for most of your body's atoms, we need hydrogen gas and that's extremely rare on Earth.  Hydrogen gas (H₂) must to be produced and it takes a lot of energy to create it - more than you can get out of it.  Most of it is produced from a petrochemical process that involves carbon emissions.  This is called black or grey hydrogen and, if you manage to capture most of the carbon emissions it's called blue hydrogen.  What you want is green hydrogen - hydrogen produced using electrolysis with electricity from wind, solar or nuclear power.  That seems like a nice use of excess intermittent power. 

 

It's important to think of hydrogen as an energy storage medium - a non-rechargeable battery of sorts.  It has a very low - essentially unusable energy density at atmospheric pressure.  You'd need impossibly large tanks (think about Hindenburg sized tanks) or you can compress it or liquify it and shrink your tanks to something more manageable.  In gas form at a very high but probably safe pressure it needs about five to ten times the volume of  jet fuel. Liquid hydrogen gets you down to about three and a half times the volume.  

 

Engineering is all about finding an optimal solution to several problems that generally interact.  You could convert a turboprop or turbofan to burn hydrogen and see where that takes you.  Turboprops seem to be workable on short haul routes (1,000 km or less) with small passenger loads (under 100 passengers).  They'd be slow and fly at lower altitudes than today's jets.  Turbofans present a number of problems - at altitude they're making contrails and the range and payload isn't great.  One needs to think a bit out of the box.   

 

You might use a hybrid jet fuel/hydrogen engine that climbs to cruising altitude on jet fuel as fuel consumption is much greater in that phase. Then the switch to hydrogen fuel is made when the engines are throttled back at cruise altitude.  You could also design a lifting body aircraft that has a lot of internal volume for liquid hydrogen fuel tanks without being too large for conventional airports.  Tricks might get you across the US with a few hundred passengers, but flights across the Atlantic or Pacific would require something more. 

 

The prop-driven airplanes present other opportunities. A fuel cell converts hydrogen to electricity and electric motors are more efficient that jet engines.  There are a number of little problems that can be overcome, but a fuel cell propeller airliner may just be a short to medium range solution.

 

Airbus is working on the problem - or at least they were before the pandemic.  I can believe the target date for the propeller aircraft, the lifting body is probably more than fifteen years out.

There may be a near term niche for hydrogen powered flying vehicles.  Agricultural and inspection drones are much larger than hobbyist drones.  They're limited to half hour flight times with batteries, but new fuel cell drones with small high pressure hydrogen tanks have appeared in Korea.  They can fly for hours and that may be the first practical opening for aerial hydrogen.

 

moving from noun to verb

About a week ago Apple announced its latest Watch.  While it isn't a major leap, Horace and Om wrote great pieces about something more significant - namely what it does.¹  The first few iterations were a bit muddled - now it has become a wearable assistive technology.  That's significant.

 

Assistive technology invokes images of wheelchairs, braces, crutches and so on..  adaptations to make life easier for those people with physical problems.  It's a mistake to think that way.  All of us use these technologies  (I'll ignore the distinction between assistive and adaptive) ..  utensils, chairs, shoes, door knobs, screw drivers - all of these count.  Many of us wear eye glasses - a technology that compensates for a deficiency that would be a serious handicap if not corrected.  Some people have artificial joints and pacemakers - implantable assistive technologies that are always worn.   It begs the question of who gets to be called normal and who makes the decision.  I've written about that, so back to the Apple Watch.

 

At the beginning of the nineteenth century town clocks were an adaptive technology that gave people in emerging industrial cities a sense of common time to allow for synchronized work.  Less expensive models for the home became a necessity for workers who could afford them.  People who couldn't employed a variety of other techniques including "knocker-uppers" - people you would pay to make sure you got up in time.  Towards the end of the century the need for standards and a more global time synchronization emerged - railroads were the first big driver.

 

Railroad time is to the time of the future. The Sun is no longer to boss the job. People—all 55,000,000 of them—must eat, sleep and work as well as travel by railroad time. It is a revolt, a rebellion. The sun will be requested to rise and set by railroad time. The planets must, in the future, make their circuits by such timetables as railroad magnates arrange. People will have to marry by railroad time, and die by railroad time. Ministers will be required to preach by railroad time—banks will open and close by railroad time—in fact, the Railroad Convention has taken charge of the time business, and the people may as well set about adjusting their affairs in accordance with its decree… . We presume the sun, moon and stars will make an attempt to ignore the orders of the Railroad Convention, but they, too, will have to give in at last.
—Indianapolis Sentinel, 21 November 1883

 

Synchronizing clocks turns out to be an interesting technical problem. A Swiss patent clerk named Albert Einstein specialized in clock synchronization patents by day while thinking about time more deeply after hours.  

 

With atomic clocks - some orbiting in GPS satellites - we now have very accurate time synchronization available anywhere on Earth.  It's available in your smartphone and your Apple Watch with much better accuracy than the display requires .. very accurate time is much more central to communication and location determination. 

 

So just how important is a watch as something you wear to tell you the time - the watch as a simple noun?

 

There are still synchronizations for connecting with people, transport, broadcasts and so on.  Some of that requires less synchronization.  Some of the most creative work is poorly synchronized much of the time.  Television has become streaming video at your convenience and much of radio has turned into podcasts and streaming audio.  So why wear a thick $400 piece of hardware on your wrist?

 

You wear it because it is becoming a verb.  It's stuffed full of sensors and watches you.  A growing list of health, exercise and motivation related functions.  Complex computations turn thousands of dollar of tech in a doctor's office or researcher's lab into a few one dollar sensors and software.  And all of this can be networked.  I'll mention Happy Bob - a Type 1 Diabetes app by one of you (Jutta Haaramo) that is making the lives of thousands of diabetics easier.   This is only the beginning.    The Watch overlaps a bit with the iPhone, but they mostly fill very different functions - wearable is a big deal.  It's important to note the Watch still has a lot of headroom for growth. 

 

We humans have been expanding and augmenting the basic human body for over ten thousand years and the process is accelerating.   It's exciting, but we should be thinking more deeply about what it means as well as who is normal and who decides.

__________

¹ Oxygen saturation wasn't difficult to add - it exists elsewhere.  What is important is the watch can keep a record.  A General Practitioner friend is currently testing one. If it takes good readings he's going to recommend it to patients who are in the at risk categories for Covid-19 - cheap insurance. 

That said I think the major improvement was the addition of an ultra-wideband chip. I wouldn't buy a device just for that as this is preliminary work for something that could be very big, but it's good to know new iPhones and Apple Watches have the capability now.

your partner in efficiency

As an undergrad I developed a serious bicycling habit.  Our club would take longish sixty to one hundred mile rides on weekends. These were tours rather than anything approaching racing so we talked along the way.   One of the members was obsessed with the idea of human powered flight.  His spirt was contagious and several of us volunteered labor and calculations helping to build the first prototype in quest of the Kremer Prize.  It was one of those rare challenges where the goal was just barely possible. 

 

My involvement wasn't that deep, but I quickly learned to appreciate the efficiencies required. Questions arose.  What sort of athlete would be required?  How would power move from muscles to where it could be useful?  What kind of aerodynamic design would be most efficient and what was the flight envelope?    

We knew bicycles were efficient.  A good chain drive was almost 99% efficient and you could match the power output curve of the pilot to the requirements of a propeller. That's when I learned only the pilot's legs would be used... using arms and legs wouldn't work for a couple of reasons.  And what about the nature of the leg motion?  Lots of interesting issues and answers.

 

A bit earlier an article on the cost of transportation appeared in Scientific American.  This is the famous piece that Steve Jobs loved to refer to when he pointed out a person by themselves isn't incredibly efficient, but on a bike they're spectacular.  But why?

 

There are a number of ways to approach the problem, but I'll ask a slightly different question and hopefully cover a bit more ground.  

"Why can you go faster on a bicycle than you can run?"

We have two basic models of bipedal motion: walking and running.  When you walk you straighten your knee which lifts you just a bit as your heel comes up shifting weight to the front of the foot. The other leg swings forward, staying close to the ground most of the time.  One foot doesn't lift completely until the other has landed. You don't move up and down much and most of the work is done by muscles in the upper part of your leg.

 

Running is very different.  Your body lifts further and lower leg muscles become important as the motion makes you rise up on the forward part of your foot.  Runners will go into great detail on what's happening, but basically you're launching yourself with quite a bit of force using more muscles and force than when you walk.  When a foot lands some of the energy used to break the fall is stored in tendons for release during the next launch -  a mechanical battery. Optimizing efficiency is the work of training and genetics. [ An odd thing about the efficiency of running and walking is that walking is most efficient over a very narrow speed range, while running has a much flatter efficiency curve.¹ ]

 

You can go faster running by increasing the length of your strides (or leaps), but there are limits. Your leg is a kind of double pendulum.   It takes energy to accelerate it forward and some energy to brake that motion as it starts to reach its forward limit.  It's worse if your leg is heavy.²

 

Rather than swinging legs a cyclist spins a crank.  The crank's motion is a circle about a third of a meter in diameter. A much smaller distance than walking or running strides.   Circular motion means the cyclist isn't having to waste the kinetic energy of their moving lower leg by slowing it (it does waste a some energy, but not nearly as much). The knees and thighs still need to be stopped and started, but the motion is much smaller.  The end result is less wasted energy from leg motion.³

 

Like running there's an upper limit to how fast a cyclist can move their legs and still generate their greatest power.  That's where gears come into play.  The gears and large rear wheel allow the bike to move a longer distance forward than the distance your feet travel in one revolution of the crank.  And different gear ratios allow you tailor your effort to the conditions - speed, head wind, hills ...

 

On a smooth flat road your speed is usually limited by wind resistance and the power your muscles can develop.  It's amazingly efficient.  With very little effort you can sustain a pace that no marathon runner can keep pace with.   

 

note:  I've skipped over a lot.  Human motion is a rich and not completely understood science, but hopefully this is good enough.

__________

¹ without going into great detail I show a chart here.

² To think about this consider the leg's moment of inertia and the fact that all parts of the leg aren't moving at the same speed. The upper leg moves slower - this is why fast running animals have their muscle concentrated in the upper leg.  Carbon fiber lower legs can make partial amputees faster than an otherwise similar runner with an intact leg.

Note the power your muscles generate increases as cross sectional area, while the weight increases as the volume.  Larger muscles increase in power more slowly than their weight increases.  This is why most competitive distance runners are of average height and very lean. 

³ The cyclist's center of gravity isn't moving as much either and that saves energy.

 

n95s explained

an Omenti minipost

 

Before diving in consider the bad guy. Viruses are really small. Viruses (thousands) are transported in droplets. Large droplets (0.3 micron to millimeter size) come from talking, singing, sneezing and so on. There are also laerosol droplets under a tenth of a micron that also are byproducts of talking, singing, breathing and so on. The large drops fall to the ground fairly quickly, but can shoot a fair distance. The aerosols can hang around in still air for a long time.. sometimes hours.  

 

N95s aren’t a sieve of very fine holes - or even a series of sieves. They consider of several layers of fibers… sort of a gauze of fibers - I was reminded of cotton candy (spun maple candy if you’re Canadian). The goal is not to block particles, but rather get them to stick to a fiber. The neat bit of physics is micron and smaller sized particles stick to about anything due to the van der Waals force (there’s an attractive force at small distances like these. It’s one of the reasons why IC manufacture must be done in exceptionally clean areas.) Effectively a cotton candy mass of sticky spiderweb strands.

 

All you have to do is get the particles to touch a strand.

 

BIg particles .. larger than a micron .. have a lot of momentum and behave like objects we’re used to seeing fly through the air. Their trajectory is mostly a straight line. The fact there are multiple layers mean one eventually strikes a fiber - the really big ones (millimeter size) are blocked by several fibers like a conventional mask.

 

The tiny aerosol particles are small enough to be bounced around by Brownian motion following a random path that traces out a slowly expanding region. Their random path give them a high probability of bumping into a fiber.

 

The tough ones are the intermediate size — say 0.3 to 0.5 microns. They don’t move in straight lines like the large particles and don’’t bounce around like the aerosols. Instead they follow the airflow and smoothly streamline around the fibers (technically they have a very small Reynolds number). Mmany could get through .. perhaps more than a good standard mask would permit. But the N95 has a trick up its sleeve (if a mask could have a sleeve) The fibers are made of a special material that holds an electrostatic charge for a long time… you’ve probably rubbed a balloon and watched it collect small bits of paper. These particles (and the others) feel the charge from a distance a bit larger than the space between fibers and are attracted.

 

The mask is a roach motel for virus carrying droplets.

 

The N95 rating means about 95% of these intermediate particles are trapped by the mask along with nearly 100% of the larger and smaller particles. There are N97 and N100 masks, but they’re much more expensive,

_______

Why you don’t want to wear one.

They require a tight fit that isn’t easy to achieve and they aren’t comfortable, Beards are out. They have a port that lets you exhale.. they only protect you rather than others. The important feature of mask wearing is not so much to protect yourself, but to protect others.

They have a limited shelf life (the electrostatic charge wears off)

You should only use them once and then throw them.

If there were enough to go around the trick would be to wear a good fitting cloth mask over the N95 to protect others.

 

your local replicator

minipost

I thought we were past the hype stage.  3d printing has been around for about three decades and has undergone a couple of "gee-whiz - this is the next PC .. the next Internet" hype stages.  Recently a friend mentioned a futurist was pushing it and a few other technologies as a way out of many of our problems.  It has it's place, but in the grand scheme of things it's still very much a niche player.  Once you get past prototyping or technically difficult shapes you run into the fact that it offers a limited palate of materials, is usually much more expensive than other techniques in volume and often comes with environmental and health issues. 

 

I've been playing with it as a hobbyist for about fifteen years.  I like making things and some shapes are too complex to use conventional tools.  It's fun to play with so give it a whirl if you like making.  Rather than buy a printer go with a service bureau.  Good printers are probably too expensive to justify and you don't want the noise and sometimes toxic fumes in your home. If you have some money to burn spend it on a computer controlled laser cutter or CNC milling machine...

 

The reasons why it's unlikely you'll be printing things at home rather than buying them in the next decade or three would fill a book.  Instead here's a book recommendation that will give you background and is one of those fun references almost no one has heard about.  Making It, Third Edition by Chris Lefteri.  It's aimed at designers who want to learn about manufacturing processes, but is highly readable detailed over 100 production processes at a high level.  It gives a sense of the importance of materials and dealing with scale and budget constraints.  

 

The practical openings hanging automated making are equally interesting.  Clothing is an area that could be huge.  I've written about it a few times and good progress is being made.  It also turns out to be interesting as it has great socio-economic issues.

 

Real innovation is rare.  A fun way to spend a day over the holidays is go to your library and go through Popular Mechanics and Popular Science magazines from the 50s and 60s.  These are excellent illustrations of technologies being hyped. You'll see a couple of things that worked out and hundreds that didn't.  At the same time they give a sense of how popular, and perhaps necessary, building skills were around the home then.

 

two innovations for charging into the future

Electric cars are on people's radar.  Three friends bought new cars in the last month.  Without prompting all three gave reasons why they didn't go with an electric car. It's interesting that we're at that point.  Without going into details a conventionally sized electric vehicle is a poor environmental choice if the metric is lowering carbon emissions per dollar.  Of course there may be other good reasons for going electric and the breed is improving. Battery technology is central to conventional EVs like Teslas and emerging unconventional and disruptive vehicles and change is in the air.

 

It seems every few months there's a news release announcing a dramatic breakthrough in battery development.  The problem is Lithium-ion is a huge family of battery chemistries rathe rather than a specific type of battery.  Hundreds of varieties exist all with different characteristics.  For vehicles you want low cost, high energy density, high power density (how quickly energy can be delivered), fast charging, long lifetime (thousands of charge/discharge cycles), tolerance to temperature extremes, safety and a few other things.  These translate into longer range, faster charging, extended lifetime, safety - all at a reasonable cost.  The press releases usually only address one characteristic - often at the expense of others.  Improving the breed has been a long road and fairly steady road, but two innovations are on the near-term horizon:  solid state electrolytes and lithium metal anodes.  They could change the industry.  

 

The anode is the negative terminal of a battery.  Currently most Li-Ion batteries use graphite anodes. The cathode or positive terminal is where the exotic material science is usually invoked along, but a lithium metal anode can increase the energy density (energy stored per kilogram of battery) by as much as fifty to one hundred percent.  Suddenly the weight penalty of the battery is lowered. It probably won't happen tomorrow, but seems likely on the five to ten year horizon.

 

You've probably seen videos of flaming Teslas and cellphones.  Thermal runaway causes many current Li-ion batteries to burn if they manage to get too hot (usually around 150°C) A lot of careful engineering can minimize this but, like the gasoline in a tank, it's a risk.  Solid state electrolytes are non-flammable. There are a variety of types being investigated including some that charge quickly.  Unfortunately no one has a handle on exactly how to pull it off. Toyota announced they'd have something ready by the early 2020s.  That seems a tad aggressive.  Then again it's possible a few breakthroughs could happen in the near term and they'll be on track.  It raises an interesting question.. how proprietary will the technologies be?  Will there be a class of solutions that allow many players or are we going to see the emergence of one or two very powerful players? 

 

The magic number cited for cost parity of EVs and conventional cars is around $100 per kilowatt-hour of energy storage. Exact internal costs are difficult to come by and there is more than a bit hype, but most educated guesses are in the $170 to $200 range.  This seems to be improving incrementally, but solid state electrolytes and lithium metal anodes in the next decade would disrupt the curve.  An EV with 400 to 500 mile range between charges, a safer and faster charging battery than the current crop and for the same price as a similar car with a gasoline engine. 

 

Many issues that are poorly addressed.  Recycling a vehicle batteries is going to be necessary, but is currently basically non-existent and a difficult problem.  Then there's beefing up the grid - particularly the low voltage local distribution component as electricity demand will rise significantly and could double in areas with high electric vehicle density.  Issues that will take time and money to address, but nothing insurmountable.  

 

In the meantime use whatever vehicle seems most appropriate and drive it less.  Better yet use a bike or ebike to offset some of your normal driving.  There's a short list of other environmentally meaningful steps you can take from flying less, to eating less meat (particularly beef), to voting global warming denying politicians from office. 

 

hacking creativity and collaboration

A recent Bell Labs reunion celebrating the 50^th anniversary of Unix gave me a chance to visit with old friends I hadn't seen in a long time.  Some of the people had moved into industry (Google was a popular landing place) and others found university posts.  I found myself thinking about the differences between the evaluation process of major research universities and the old Bell Laboratories.

 

In a run that lasted about five decades Bell Laboratories - call it Bell Labs Classic - was arguably the most applied research organization in the world.  There were certainly warts and missed opportunities and it effectively came to an end about five years after the mid 80s breakup of AT&T, but it was an astonishing place while it lasted.  I'm continually been struck by differences between that institution and almost everything else I've run into.

 

In universities hiring and promotion (tenure and beyond) is strongly connected to ten or so recommendation letters from leaders of the field in different universities. The authors are almost always experts in the same subspecialty as the junior researcher.  Bell Labs was different. There was an internal ranking that extended throughout the research organization. A department head would rank their people and the results were merged with the rankings from the other department heads in the same center. These rankings would then go through the same process for the next two levels up until a ranking of the entire institution existed. An expert in a field might receive fantastic marks inside their department, but do poorly further up in the process as others might be unaware of them. Interdisciplinary work would stand out and the highest ranked people tended to have one solid speciality along with work in centers far removed from their own.

 

I entered the Labs as an experimental particle physicist. There were a number of physics groups, but no particle physics. I was initially assigned to an applied physics group and found myself working with a number of other groups as I scrambled to find my way. In the process I made connections inside and outside the center and found some encouragement to trade help with others.   All researchers were given the title of  MTS  - member of the technical staff.  It resulted in a certain equality that made approaching others easy.  

 

Most researchers weren't interested in management, but there was one small step up.   If you were in the top ten percent or so for a number of years you became a distinguished member of the technical staff and given more freedom. In my case I was initially given a day a week and resources to do anything I wanted.  Those projects were all collaborations far from my home organization. 

 

Guaranteed funding for pure and applied research went away about five years after AT&T's breakup and folks had to attach their work to business units. It’s what killed Bell Labs, but realistically it was the only logical path for the company at the time. Bell Labs Classic could only exist as part of a regulated monopoly, but that’s another story.  

 

Some universities are playing around with this kind of ranking to stimulate interdisciplinary work. I don’t think it works in industrial applied research.. at least not at scale, but it might be worth considering.  Of course there are different mechanisms in other organizations - places like Pixar - but the difference between Bell Labs Classic and research universities is quite possibly the result of collaboration encouraged by a simple ranking process.

 

woodie

an Omenti mini-post

I was shocked and saddened to learn of Woodie Flowers' passing.

 

There's an interesting question you can ask about a school.  Who is the most important person?  Of course it depends on your point of view and what you think a school should be doing.  It might be an administer who has managed to turn the place around,  a remarkable alumni member who does the same, a Nobel Laurette perhaps? and for some it might be a coach who somehow energizes the place.  Is there someone who makes the place special?  Universities mean a lot of things to different people.  Ask me about MIT and I'll suggest Woodie Flowers.  He managed to light *that* spark and inspire more young engineers than you can imagine.  In light of the current ethical problems ripping apart a school on campus, he was a beacon of ethics for decades.  

 

I was lucky enough to have spent time with him on a few occasions.  He was even more optimistic and even evangelistic than what comes over in this video:

 

 

Woodie was like this in many areas.  He was responsible for developing and promoting the concept of gracious professionalism..  from an email a few years ago:

 

The election has been painful. It reminds me that we have a responsibility to help students become thoughtful citizens. Rational thought blended with empathy seems too rare everywhere.

Personal experience leads me to believe our students would be receptive to hearing us address their obligations to society. Dean Kamen founded FIRST (For Inspiration and Recognition of Science and Technology) in 1989. A couple of years later, Dean and I co-founded the FIRST Robotics Competition (FRC) patterned after the creative design exercises I had been running for many years in the Mechanical Engineering design courses. The “2.70 Contest” was anchored by “gracious professionalism,” a term I coined to celebrate the wonderful behavior prevalent among students in that course. They competed like crazy, but treated one another with respect and took pride in helping and teaching one another.

At the first FRC Kickoff, I used one slide with the term “Gracious Professionalism.” Encouraged by Dean, at the second FRC Kickoff, I used six slides featuring the phrase. Since then, Gracious Professionalism™ has become a powerful part of the ethos of the whole FIRST community. FIRST competitions have grown and have millions of alumni. Scattered over 80 countries, young people have embraced the notion that competition and kindness are compatible. At MIT, 10% of our freshman classes are FIRST alumni.

As we make the transition to digitally-enhanced learning and machine-assisted professions, I believe “uniquely-human” will be a powerful differentiator. Professionals who understand the laws of the universe and also have an emphatic response to others will be the leaders. Those who think science is a la carte will have aspirations that Mother Nature will not tolerate.

MIT students will have an obvious advantage because of their understanding of what is possible. We need to make sure they are also well equipped to manifest creativity, leadership, good judgment, and ethical behavior.

I offer Gracious Professionalism as a convenient label. It blends rigorous adherence to the laws of the universe with the human qualities we hope to see as those laws are applied by our alumni. Giving back with conscience. Blending hard knowledge with soft feelings. Facts, feeling, and fairness. The FIRST community, which includes all ages, have embraced “GP” and actually compete to “out GP” one another.

How might Gracious Professionals have voted?

Woodie Flowers

 

I'm not an engineer, but am amazed what the good ones do.  This is a big loss for MIT, engineering and the world

 

canada's beautiful new $16 million camera

My Grandmother King gave me my first camera for my eighth birthday - a Kodak Brownie.  My parents had a camera, but I wasn't allowed to use it.  This was my camera.  I also received two rolls of black and white film and a voucher for developin.  Of course I did what most eight year olds would do - I took pictures of the sky, the side of the house, my sister, the dog - twelve exposures in all.  A week later the prints came back and you can guess how bad they were.  The second roll was a bit more better, but I never developed the artistic skill.  But I did I did become fascinated with devices that capture images and have designed and built a few over the years.  

 

Some of you are excellent photographers.  My friend Om happens to be just such an artist and I believe he is writing a book on the subject.  My sister Corinne is an artist who uses photography and computers to offer quirky commentary.  I'll be content with my simple snapshots and videos enjoying the art of others.  And I'll think about the process and tools.

 

The term camera conjures up something that focuses light on film or an electronic image sensor where an image is captured.  Still or moving images, but almost always visible light.  Currently the definition is being extended to computational photography - the processing that goes on in your iPhone for example.  I stretch the definition a bit.

 

For me a camera is something that captures some event or series of events in time.  It doesn't have to be visible light, but any form of electromagnetic radiation and or something a bit more exotic - like charged particles or the shaking of space-time.

 

I first came to this way of thinking on Sulphur Mountain near Banff, Alberta.  I was almost thirteen and had gone over to a curious little shack on one of the mountains twin peaks while my parents had lunch at an observation deck a half kilometer away.   The two young men in the shack turned out to be cosmic ray physicists.  They patiently explained in kid language how they captured muons.  What they were really doing is capturing and recording part of a particle shower that came from cosmic rays striking the atmosphere twenty or so kilometers up.  They'd run these recorded events through some calculations and  would be able to say something about the shower and from that perhaps something about the Universe.  After listening I said something like "you've built a cosmic ray camera.  That tape is your film and you turn it into something like a picture"  They nodded , smiled and showed me how an image could be abstract and still give a lot of information. That day would change my life. 

 

Since then I've been around my share of particle physics detectors - essentially cameras that capture the aftermath of violent particle collisions at places like CERN.  I've also used optical and radio telescopes that, typically after a lot of computation, produce real or abstract images of places and events back in time.  It still astounds me to look at parts of the Universe as it was twelve or thirteen billion years ago.  And for fun I  even designed a homemade digital camera back in the 80s. 

 

Cameras capture images that can be meaningful.  Images that can be artistic, historical or even offer evidence of Nature's workings.   Some of the techniques are familiar and straightforwards, others are sometimes deeply computational. And if you consider the eye-brain combination a camera, as many do, there are surprises  We usually think of an image falling on an imaging surface and being turned into a more of less faithful representation of the image.   In fact there is a lot of processing that goes on between the front of the retina and the brain.  What eventually turns into an image has very little in common with what fell on the retina.  Our brain stitches together information, often out of order and spread over several seconds, to construct an approximation of reality we think of as the real thing and a sense of "now" that is equally artificial.  The comic strip is a nice example of something that is temporally impossible that happens in your brain all the time.  It turns out temporally out of order processing often happens in computational photography.    And then there are many instruments you might not think of as a camera that are much closer to the classical definition.. things like MRI, ultrasound imaging, radio telescopes and the like.  

 

Back to this $16 million Canadian camera...  

 

CHIME is a radio telescope at the Dominion Radio Astrophysical Observatory near Caleden, British Columbia.  It consists of four 100 meter by 20 meter upward facing semi-cylinders that are sort of like snowboarding half-pipes.  Sprinkled up and down the foci the semi-cylinders are 1024 radio receivers that operate between 400 and 800 MHz .. covering a frequency range similar to that of UHF television - a frequency range was chosen to detect a signal hydrogen emits.¹  That's where the name  comes from - the Canadian Hydrogen Intensity Mapping Experiment.

 

An enormous amount of computation takes place in several steps after the radios receive the signal.  The first step sets the instrument apart.  You may have a wifi router that does beam forming.  Basically you use a small array of antennas and the properties of radio waves to construct a "beam" to the source.²   CHIME creates 1024 beams listening to over 16,000 frequencies (think of them as colors) all imaged 1000 times a second.  While beam-forming adds to the computational load it dramatically decreases construction costs over a mechanically aimed antenna and for this application is a very clever strategy.  The computing just behind this is equally clever.  Sixteen million dollars to get this kind of data over what will be several decades of life is a bargain. The electronic and computer designs are elegant and if you're into that sort of thing you should look into the details.

 

The hope was it could detect an unusual recently discovered event called a fast radio burster.   At first some suggested the short radio bursts  of a thousandth of a second or so might be signals from extraterrestrials as no one had a compelling physical explanation.  They're very rare and transient.  Before CHIME only one burster called FRB121102 has been seen to repeat sending out about 100 irregularly spaced bursts since its discover in 2012.   A few hypothesis have been made, but studying a single event can lead you astray.   Then CHIME switched on for three weeks last Summer and thirteen new events were detected even though it wasn't fully functional completely.  This is far and away the most sensitive camera in the world for studying these events.  It is also well suited for mapping - making images of - hydrogen clouds in a much younger Universe, studying a special class of neutron stars called magnetars, and answering a number of other astrophysical and cosmological questions.  There's the added bonus of looking at the sky with a new type of camera.  You tend to discover things you hadn't imagined.  

 

 Human beings have become remarkably adroit at extending and even going beyond their senses as we try to understand the world.  CHIME is easily one of the most beautiful cameras ever made.

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¹ The 21 centimeter line of hydrogen is a great signal for studying the distribution of hydrogen atoms in the Universe.  It would be far too short to be detected by the telescope, but distant hydrogen is red shifted down to this frequency range..  Since the emission line is very narrow and well known, you can calculate the redshirt and therefore the distance of the gas.

² Beam forming is done by changing the signals phase at each antenna in an array in such a way that constructive and destructive interference create a pointed beam. It works well for wavelengths not much different from the antenna size.  Wifi base stations aren't very accurate, but they don't have to be. You can also do it with sound leading to some interesting pranks.

 

baseball and machine learning

A few weeks ago two of us were talking about the perception of "now".  A fusion of sensory inputs, responses and thoughts takes place and a highly edited version is assigned in what we perceive as a smooth and linear flow of time.  Consider vision.  It turns out it takes us around three tenths of a second to put together a meaningful image from the time light hits the retina. First we note color, a bit later motion and finally form.  No big deal unless you have to react very quickly.  For most of us that isn't a big deal.  For athletes it is.

 

Baseball is useful as the time it takes for the ball to travel from pitcher to bat isn't much longer than the time it takes to process an image. But baseball "works."  To examine vision in baseball consider the great women's fastpitch softball player Jenny Finch.  A few years ago she broke what the best Major League Baseball hitters are capable of. 

 

Their problem is they don't know how to "read" her.  Beginning as little kids  they learned how to hit a ball getting progressively better over time.  Early on the time of flight for the ball was so slow that human vision and reflex speeds weren't the major issue.  With practice they began to learn how to read the pitcher.  Posture, arm movements and so on.  The shards of image they formed gave them information on the physics of the ball's flight path.  They were learning all of the patterns even though they thought  that they really sensed when the ball was released and when it hit their bat - after all, that's what their mind told them.  But what their mind put together wasn't accurate.  In reality they were linking reads and other early information with ball trajectories.

 

Jenny comes along with a pitch that is over ten meters per second slower than what they're used to, but the information they receive doesn't link reliably with ball trajectories.  They either try to rely on reflexes missing the ball entirely as it flies past before they can swing or they use a mistaken trajectory from their mistaken read and strike out. They could learn... give them a lot of time working with women's fastpitch experts and they'd finally build the appropriate library.  Ultimately some of them might even play the game well.

 

There's a striking similarity with machine learning.  You show a program a huge amount of data trying to be clever and you get a program that can quickly do great pattern recognition.  At least within a restricted domain.   The richness of training datasets is often poor.  Facial recognition programs might have respectable results for white people, but completely fail with people of color.    Such biases of omission are very common, but many other types of bias exist.  (again a rich and deep subject well beyond the scope of an hour). 

 

Machine learning can be useful but is only robust when the limits of where you can use it and the types of errors it makes are well-understood.  There are many areas where it's sort of good enough even though these limits aren't well established. Other areas are more critical.  We're a long way from it being generally useful in areas the tech press considers nearly solved -  self driving vehicles come to mind.

 

Back to the athlete.  Sports are played at many levels.  At an amateur level we play because it's fun.  Beyond that most of us are watching others.  In direct competition we usually prefer watching serious pros.  Beyond the beauty of watching human motion being executed so well there are those magical times where something extraordinary happens.  Athletes at the highest level develop a deep sense of the game and, in addition to being able to react faster than their vision and reflexes would suggest, are tracking and processing other channels of information.  In some games players develop a "field sense" .. they know where the other players are and how they're moving.   You see this dramatically in beach volleyball when played at the highest level and it is common in soccer and basketball.  This gives them the ability to do the impossible. These are very beautiful human moments beyond machine learning.   And it goes beyond sport ..  think of the human experts that just out of the ordinary when the time comes - like Captain Sully Sullenberger landed in the Hudson. 

 

We tend to think about athletes as having some physical gifts and a lot of training.  Certainly those are necessary, but there's an impressive mental component.  We don't say someone is good  at foreign languages because they have a dexterous tongue.