omenti

outward bound!

After two billion seconds on this planet, you tend to think about the time you've occupied and what you may occupy.  Our ability to sense scale is largely limited to what we can sense and the physical and temporal spaces we navigate.  Historians usually work with somewhat larger scales, but I'm guessing they don't have a good feel for - say - what 917 AD actually means.  Science looks at larger and smaller time scales.  I've spent a lot of time worrying about processes shorter than a femtosecond as well as those that are billions of years long.  I write down the scientific notation, but confess I don't have a physical feeling for what it means.

 

I'm particularly interested in what we can do about the future.  Dealing with global warming as a practical matter to mitigate huge biological and financial losses would see to be the big challenge (hopefully we'll see enough progress!).  On the scientific side there are projects that span decades.  Initial work on CERN's Large Hadron Collider began in the late 70s and it should run through at least the mid 2100s. Solar system exploration often looks three or more decades out.  Voyagers 1 and 2 managed to capture the public's imagination early on and they continue to provide amazing results - over 44 years from their launch.  (you can find out how far they are away and how fast they're moving at this JPL site)

 

The genesis of Voyager came when a Caltech grad student was working on a Summer project at the Jet Propulsion Laboratory in 1964.  Gary Flandro was studying techniques to send probes to the outer solar system.  Even during the space race the scale of space made this look completely blue sky.  Gary realized an alignment of Jupiter, Saturn, Uranus, and Neptune would take place in the late 70s and that it might be possible to make a "grand tour" of these planets if you used gravity assist - a mechanism that transfers a bit of the kinetic energy from a planet to a spacecraft - to speed up the journey.  Such alignments are rare on the scale of a human life - about once every two hundred years.  The project was funded and, with help from Carl Sagan, caught the public imagination with a golden record of humanity attached to the spacecraft as well as one of the most iconic images humanity has recorded - the pale blue dot. 

 

Exploration of the planets of the outer solar system was the prime mission. The fly-bys were smashing successes, but the two spacecraft kept working.  Instrumentation was primitive by today's standards and optimized for conditions expected around Jupiter and Saturn, but it was possible to track the solar wind and a few other things.  

 

In 2004 Voyager 1 crossed the boundary of the heliosphere - a huge region surrounding the Sun inflated by the solar wind.  There was celebration as something made by humans had crossed into interplanetary space 94 times as far from the Sun as we are.  There was a shock in 2007 as Voyager 2 traveling in a different direction, crossed the boundary about ten percent closer to us.  The nature of the boundary was also different. It was, and is, a time of delight as so many new questions and hypotheses formed.

 

I'll skip the details, but there are two protective regions that deflect charged particles that help make life as we know it possible on Earth.  The smallest and most important is a comet-shaped region around the Earth generated by our planet's magnetic field.  This magnetosphere deflects charged particles streaming at us from the Sun as well as some cosmic rays from deep space.  Without it much of our atmosphere would have blown away and radiation levels would be high on the Earth's surface.  

 

The much larger heliosphere defects cosmic rays from outer space.   We've learned that the Sun has been traveling through a dust cloud known as the local interstellar cloud for about 60,000 years.  We're currently at an edge and soon we'll be on the outside (this may have already happened!) Then we travel for about 2,000 years before entering another dust cloud called the G cloud.  Depending on its density the heliosphere may shrink.  Cosmic ray fluxes would increase and that raises an interesting set of questions.  

 

[speculation alert]  Between two and three million years ago some crust samples show a lot of Iron-60.  The isotope does not occur naturally on Earth - rather it's the product of supernova explosions.  We may have spent time passing through a cloud laden with the "ash" of these huge explosions.  The heliosphere would have shielded us from charged particle radiation levels that would have done a number on life on Earth, but some would have made it through.  Who knows - perhaps this had an impact on evolution? In any event there are a huge number of questions.

 

A number of fantastic missions to the outer solar system on the drawing board - missions that may find the first extraterestial life.  I probably won't be around to learn about the findings, but am an enthusiastic supporter.  One of the most interesting is a follow-on to the Voyagers - probes that dip their toes into interstellar space. A study project is underway in the US and the Chinese are talking about a mission.  Details on the US proposal are amazing.  It's modern day cathedral building with details that must work forty and fifty years out when most of the designers are probably gone and the world will probably be a different place.  Thinking about it makes the hair on your back stand up. 

 

In addition to the scientific and engineering challenges, there's also a management challenge.  How do you form a cohesive team of experts who will have to excite and train new people along the way?  These projects tend to be small and the loss of one expert can be a disaster.  A great book that covers the New Horizons mission to Pluto and beyond shows how it can be done:  Chasing New Horizons by Alan Stern and David Grimspoon.

 

 

couplings and friction

a quick minipost

 

Beginning physics students learn about simple coupled systems.  Things like pendulums with a weak spring between them and the like.  Next you look at somewhat more complex systems like a group of pendulums.  Put them on a solid surface and start them in different oscillations and they do their pendulum thing unaffected by their neighbors.  Now add a little communication by putting them on a floor that can transmit a bit of vibration, something interesting happens.

 

The coupling of systems is common in nature covering a very wide range of complexity inducing our brain.  Many of these systems are mathematically fascinating.  Turn up the amount of coupling and they behave as you might expect - at least to a point.  Then, as the comments of the system impose themselves on each other,  there's a dramatic change.  Sometimes these are good from our point of view and sometimes they're disasters.  The point of inflection is often marked by a perturbation - lightning strikes, hurricanes, pandemics, big lies.   The couplings are too strong to allow for anything but a change to a new state.

 

One feature of our society is an increased coupling of systems.  Social media and other targeted messaging, GPS, the Internet of Things, globalization, just in time everything, religion, democracy....  More systems are being connected and the amount of communication is increasing at a terrific rate. These couplings are often introduced to decrease cost and the "friction" parts of the system have with each other.   Many are  too complex to understand well, but the basic math of over coupled systems is clear - these systems can be very unstable. 

 

Building alternate pathways and redundancy into these systems is an answer, but that costs money and clever design.  Another alternative is reducing the coupling of certain important subsystems.  It's something I find myself paying more careful attention to.  Highly coupled or low-friction systems are usually brittle at some point.  I dislike the term "black swan" as real black swans (the bird) are not uncommon in nature.  But we continue to build serious and increasingly effective black swam bait...

 

 

 

31 is the new 35

Andrew Revkin and I had a brief exchange about the power of labels.  Both of us object to the phrase "climate emergency."  Even though it is an emergency that could escalate into an existential threat, people don't respond to labeling longer term threats as emergencies.  I've been suggesting we've entered an adaptation epoch.  Andrew, a much better communicator, is still searching.

 

The past two or three years have taught us short term temperature excursions can be dramatic.  Last year the Pacific Northwest recorded previously unheard of temperatures -  the highest in the area in at least 7,000 years and probably much longer.  This Spring it was South Asia.  Last week record heat came to England and parts of Europe.  These events are probably going to be more common and time goes on and greenhouse gas levels continue increasing. 

 

Wet bulb readings of 35°C (95°F at 100% humidity)  have long been considered unsurvivable.  A person in good physical shape would probably die in a few hours. Such events are extremely rare. Until the past decade they've only been recorded a few times and then only for an hour or so.  They're increasing in frequency and length - mostly in the Indian subcontinent.  Finding cooler spaces for people is a matter of life and death.  

 

It's become clear the 35° number was something of a guess.  Recent careful work shows it's more like 31° for young people in good physical shape.   Older and compromised people have lower limits.  The Tokyo Olympics had periods with wet-bulb temperatures in the upper twenties. Athletic performance during these periods was certainly compromised (I saw it happen to a friend). 

 

What can be done?  Cities suffer from heat island effects.  All of the asphalt and concrete increases the local daytime temperature and holds them at higher levels at night. (hot nights may be harder on the body than hot days).  Air conditioning helps, but it costs money and a power grid that not everyone has access to.  Reducing the amount of asphalt and concrete while planting trees can make a big difference.  It's a great justification for reducing the number of cars and roadways in cities (green spaces are a key motivating reason for the dramatic change currently underway in Paris).  Unfortunately green spaces are usually linked to wealth.  In many places racism and redlining have produced some of the worst heat islands.

 

There are other tricks that are easily implemented.  White paint  on roofs can make a difference. Paint that holds up to temperature and monsoons for the better part of a decade isn't cheap, but is becoming more popular.  In Western countries more reflective shingles are appearing. Some of these look fairly normal, but are highly reflective in the infrared and can make a difference in cooling bills. 

 

And you can send some of the excess heat directly to space.  

 

If you're in a very dry area go outside on a clear night and look up.  Feel the cooling on your face.  Now hold a piece of cardboard between your face and the stars.  You'll notice a warmer feeling.  Remove the cardboard and your face gets cooler. 

 

Your body glows - you've undoubtedly seen infrared photos and videos of people.  We radiate photons at a variety of wavelengths, but it peaks around 9.5 microns - about twenty times longer than visible light.  The  atmosphere is transparent to visible light and also from 8 to 13 microns.  Photons from our bodies can radiate to space.   Deep space is really cold (a bit over 2° above absolute zero) so your face is radiating some of it's heat directly to space - enough that you can feel the cooling.

 

Clever material engineering has produced materials that are good at absorbing the heat around them and then radiating it into space. It's enough to reduce cooling requirements - at least in places with very dry atmospheres.  There's still work lowering costs and making the surfaces last longer, but it's something else to try.

 

Back to the idea of an adaptation epoch. Many things will need to be tried and efforts will stretch for generations.  There's enormous opportunity.  It's both sad and dangerous there's so much 19^th century political inertia, but I'm optimistic more clever people, organizations and governments will finally emerge.  As a species we don't have a choice if we want to survive.

 

just two things..

minipost

Recently I gave a talk to an audience of non-scientists.  During the question and answer section some asked "what's something important you'd leave us with?"

 

Everything you see is in the past.  Light travels about a foot in a billionth of a second, so if you look at your feet, light takes five or six billionths of a second to make it to your eyes.  You see your feet five or six billionths of a second in the past.  The moon you see is one and a quarter seconds in the past, and the Sun about eight and a third minutes.   The Andromeda galaxy, the farthest you can see without aid, about two and a half million years in the past.

 

I was going to point out it's more complex as it takes a few tenths of a second for your brain to register the image and the whole notion of "present" is imprecise, but that would muddy things.

 

Next someone asked for another useful piece of energy.  

 

About a horsepower of solar energy falls on an average sized umbrella on a very clear day with the Sun directly overhead. 

 

 

 

oh my gosh!

I knew they'd be amazing, but seeing the full resolution images from the James Webb Space Telescope this morning was one of the best moments I've had in awhile.   These represent about five days of observing time as the science run gets underway.  The telescope has enough fuel to execute it's figure-eightish "orbit" around the Earth-Sun L2 Lagrange point for about twenty years, so much more is to come.  Also - no technology currently exists for a repair mission, but the telescope has a refueling point just in case...

 

NASA has a page with the small versions of the five released images and some high level commentary here.  For the full effect you want to go to the full images section and look at the full size png images (over 100 MB each) and spend some time taking it in.  (note: astrophysics types are even more blown away by the spectrums!)

 

The deep field image shows a number of galaxies and they manage to show up in the background of some of the closer images.  One hundred years ago it was generally thought the Universe was static and there was just one galaxy.  That changed towards the end of the 1920s and the scale of the known universe grew along with i's age and the fact it was physically expanded.  Now the age is known to be about 13.8 billion years old.   The JWST can take us back to a few hundred million years from the beginning (we have other ways of seeing the point where light leaves the Hot Big Bang about 380,000 years from the beginning, but that's long before stars started forming.)  

 

Some of these galaxies have a trillion stars.  Our own Milky Way is between 200 and 400 billion stars.  The lower limit on the number of galaxies in the observable universe is about 200 billion - but that's ridiculously conservative.. a more realistic estimate is two trillion galaxies, but that's also conservative.  And then there's this issue of the observable universe.  Much of it can't be see due to the finite speed of light.  Some reasonable estimates put a lower limit of at least 200,000 times the volume of our observable universe. 

 

How much life has come into existence? How much has evolved to the point where civilizations can exist?  How many civilizations extinguish themselves and how many survive?  What is the range of life.

 

So many questions...

 

Wonder is an amazing engine.  We build these telescopes because kids looked up at the sky and imagined what it might be with their crayons.  They get a spark and their curiosity takes them to a place where their dreams are turned into telescopes, accelerators and microscopes.  And kids will see the images today and pull out their own crayons...

 

 

expectation dislocation

a quick minipost

I was listening to a  training technique discussion sports scientist Ross Tucker was having with a Royal Marines Green Beret.  Royal Marine training consists of a lot of what you might expect and adds a few areas you might not.  Expectation dislocation is considered one of the most important.   How do you psychologically and tactically deal with unexpected change?  How do you train people to handle it?

 

In science dislocation of expectations are considered a good thing, although they can be extremely frustrating at the time.  The overlooked, doing something stupid, being on the wrong track, the holy grail of unexpected discovery, and things mostly out of your control like equipment failures.  These things tend to play out more slowly than the battlefield or in sports.  Early in your career you make a lot of the stupid mistakes, find yourself on the wrong track and tend to overlook the obvious.  You learn with experience, but curveballs aren't uncommon and sometimes there's the taste of discovery.  

 

Sport offers dramatic examples.  I've had conversations with Sarah about preparing for and recognizing these dislocations in her sport.  How do you manage the psychological implications when you're trying to be "in the moment" at the same time?  Covid and the postponement of the Olympics had a huge impact on her.  But there are smaller examples.  Here's one of the most striking ones:

 

Sarah and Melissa face April and Alix in a semifinal in Cagliari.  Both teams are amazing - arguably the best in the world.   It's night with a chilly heavy rain.  At the 6:30 mark in the video Melissa goes down with a seriously dislocated shoulder.  After a doctor looks at it and a physical therapist re-locates it, she decides to go on - playing with one good arm.  The Canadians need to figure out local tactics and find a strategy as they go along. They only have their shared experience and all to brief moments of communication.  At one point a very fast spike targets Melissa's injured arm.  Something lights up in Sarah and she goes into her beast mode.  They win and go on to the gold medal match.  Unfortunately Melissa's arm isn't in great shape the next day and  they only take silver.

 

It's widely applicable.  Your car breaks down on a trip, a bad medical diagnosis ... any number of things ranging from very bad to very good.   How do you handle them in your life or your line of work?  How do you prepare yourself for these events?  These moments that can probe what we're made of.

 

that energy thing

Patent reading is something I avoid as recreation.  They're written in a humorless formal style that's perhaps a shade more entertaining than Vogon poetry.   Sometimes you have to go through them trying to sort out the claims and their feasibility.  I generally translate them into images and numbers I can understand in the process of plowing through.  It was during that process that my jaw dropped.  Someone had successfully patented something that was clearly impossible.  It violated the underlying physics - the patent office usually catches these mistakes early on.  Someone had already spent a fair amount of change. At least I could alert my client.

 

The patent was trying to harvest waste energy.  That's all and good - more of it should be done, but it claimed to be more efficient that was possible.  

 

A good deal of engineering is concerned with efficiency.  The story of the steam portion of the Industrial Revolution amounted to increasing the efficiency of extracting energy from fossil fuels.  Steam engines are a case in point.  There was a huge need for them pumping water from mines and the early engines made an impact even though they were extremely expensive to run. James Watt and others came up with clever hacks and improvements continued for over two centuries. (The chart shows how much energy can be extracted from a kilogram of coal.  The highest level corresponds to an efficiency in the mid forty percent region)

 

There are many forms of energy... heat, light, motion, electric, chemical, nuclear, gravitational , and so on. These are usually grouped into two types when considering how work is done:  kinetic and potential.   In general something happens when energy moves from one form to another.   But what is energy?  The dictionary and some high school science texts say it's the capacity to do work.   OK .. so what's work?   Dictionaries often say it's a measure of energy transfer when an object is moved.    Nothing like circular arguments, eh?  During the 19th century the definition was a point of contention in physics, but before going into that consider a roller coaster.

 

Roller coasters are great ways to explain the transfers between kinetic and potential energy.  If there wasn't any friction or wind resistance you could start a car off at the highest peak and it would move around the track coming back to where it started.  Gravitational potential energy would turn into kinetic energy as the car dropped and the kinetic energy would turn back into potential energy as it went uphill.  Of course there is friction from the wheels against the track and air resistance. The wheels, axle bearings and track heat up, pieces vibrate, air swirls and sound is generated.  If you add all of these up you can account for the total energy of the system.  You might even be able to harvest some of these, but in general that's a difficult task.

 

Much has been and is being done on recovering lost energy.  Regenerative braking in electric cars, using waste heat from power plants to heat buildings (combined heat and power), etc.  Unfortunately there are limits to how much can be recovered.  As the waste heat is closer in temperature to its surroundings, the less efficient extraction will be.  This was a fatal error in the patent I looked at.  It assumed air temperature was much colder than it really is. 

 

Back to a definition of energy.  Emmy Noether showed that for every conserved quantity in physics there's a corresponding symmetry and visa versa.     Noether's theorem is central to physics.  It's one of those things that makes you gasp when you first realize how it works.  Among other things it shows time invariant processes are those that conserve energy.  If you fall off a building at noon or two o'clock the result will be the same.  Falling under the influence of gravity doesn't depend on time and energy is conserved. Unfortunately really diving in requires some serious math.   You can get an idea of what's going one from this non-mathematical discussion by a physics grad student.  So if you're curious and remember some high school physics:

 

In the meantime note that we waste an incredible amount of energy.  Not only are we staring down the barrel of global warming, but paying for energy is expensive by itself.  There's a lot of low-hanging fruit out there.  The problem is often getting people to imagine.

 

personal social media usage experimentation

minipost

 

A few years ago I found myself spending far too much time on Twitter .. generally an hour to an hour and a half a day.  Time I didn't have.   For a month I went cold turkey, but was frustrated as there were a few people I only interacted with on Twitter and, following about 50 people in one of my fields was a good way to learn about new discoveries and papers.  I decided to limit my time, aiming for a half hour a day in two or three sessions. One would be devoted to hunting for new papers and the rest of the time would be the water cooler.   It's been mostly successful - I'll admit to hours of serious doom scrolling around the January 2021 coup attempt, but generally I'm under my thirty minute a day limit.  (I also have one day a week when I try to cut Internet access completely).

 

With that background I was fascinated to come across a report on some real-world experimentation by a group of about sixty college undergrads - a group known for heavy social media use.   Matt Salganik taught Sociology 204: Social Networks at Princeton last Fall.  He posted a report on Princeton's Center for Information Technology Policy's Freedom to Tinker blog:  

 

Improving Your Relationship with Social Media May Call for a Targeted Approach

 

From the introduction:

 

What students did:

Our class had about 60 students, from a variety of years and majors, and like most Princeton students, many of them were heavy users of several social media platforms. Each of them designed their own treatment and selected an outcome of interest. For example, some students were interested in improving their sleep and others were interested in wasting less time. In addition to these student-specific outcomes, we also had all students track two common outcomes that have been studied by other researchers: subjective well-being and time use changes.

This process of self-experimentation is a bit different from what social scientists normally do. Typically, researchers standardize the treatment, randomly assign treatments to participants, and collect data so that we can compare across participants and treatment groups. In our class, however, each participant was a researcher and designed a unique treatment for themself. Even though this is not standard for research, self-experimentation can be a good way to learn. The treatments students developed fell into three main groups:

Targeted limitation (about 45%). Students in this group restricted – but did not eliminate – their social media use. For example, students in this group did things like stopping TikTok use after 8pm and avoiding the Instagram feed (but still using Instagram for messaging).

Targeted increase (about 15%). In class, we learned about some research that suggests people who use social media actively—rather than passively scrolling—see an improvement in their well-being. So some students committed to increasing their active engagement with social media. For example, students in this group did things like posting 3 times per day on Instagram or direct-messaging at least 3 friends.

Elimination (about 40%). Students in this group eliminated their social media use altogether on one or more apps. Students who designed these treatments did things like delete Instagram or TikTok from their phone, and some actively replaced their social media use with another activity they valued such as reading the news or spending time with friends.

 

It's worth reading and non-technical.  It also offers some advice and techniques in the assignments section if you want to try learning about  your own usage.  It seems clear that there's a broad spectrum of positive and negative use patterns. 

 

repairability

My Dad was a Ford man.  More specifically the Ford Falcon.  It was a simple compact car with a 170 cubic inch displacement straight six coupled to a three speed manual transmission.  It scored on the high end of the Mobil fuel economy test - about 19 miles per gallon when the average sedan was in the 12 to 14 range.   But what he really liked about it was how repairable it was.  Not only was it simple to work on, but most of his friends had cars with the same engine and transmission.  If something needed fixing we could usually do it ourselves using tools borrowed from one of his friends.  For more serious repairs there were specialized tools from Strobel's A to Z Rental, garages or (shudder) the Ford dealer.

 

The simplicity of cars of the day was balanced by crude manufacturing tolerances.  Pistons fit so poorly in the cylinders that the first 500 or 1000 miles were done with great care using an abrasive oil to polish the parts into shape.  It made a big difference in gas mileage and extending the life of the engine past 50,000 miles.  

 

The dual gas shocks of the 70s opened the market for better cars that used higher precision design and manufacturing processes.  That and the beginnings of cars that crumpled to absorb energy in crashes made simple repair much more difficult.  The amateur mechanic had largely vanished by the 80s.

 

Clothing and shoes were expensive back then.  Quality construction and repairability were important considerations while shopping.  Tailors and dress makers were common.  The same was true for appliances.  Vacuum cleaners, toasters and anything electronic could be repaired at home or the local repair shop. 

 

There are exceptions today .. Jheri makes her own clothing or buys high quality pieces with the intention of buying very little as she hopes each piece will last at least a decade.  She's abandoned fashion and has created a style very much her own.  I suspect some of you - Om for example - have a similar philosophy.    But while it can be done in clothing, it's next to impossible when electronics are involved.

 

By the time I was fourteen I had three or four black and white TVs.  None of them worked - watching TV wasn't interesting.  The tubes, capacitors, transformers, switches and so on..  now those were useful!  I designed and built a few radios and a stereo amplifier.   It was straightforward and the experience taught me a lot about electronics.  Now I look in a computer, TV or radio and see only massive integration.  It's still possible to build things, but design is much more difficult. Learning about circuit elements is probably better done with computer simulations.   

 

The right to repair movement has grown in recent years.  I welcome  it for some products, but given the tight integration of hardware and software  I worry it may not be as generally attractive as proponents claim.  

 

Smartphones are a case in point. Apple is infamous for discouraging third party repair.  You can order a kit from Ifixit to replace a screen, battery and some other parts.  It can work well if you have a bit of experience and Ifitit is upfront with the degree of difficultly. You lack the tools and technique to take apart, replace and reassemble the device to design specifications.  

 

My personal results are mixed.  I easily replaced the battery (twice!) on my first day, first generation iPod.  The battery and screen on my out of warranty iPhone 5 was a different matter.   After five hours of frustration I was left with an operating phone, but the case was fitting tightly and whatever waterproofness was gone.   The misaligned case also interfered with the physical buttons on the side.  I did get another year and a half from the phone though.   It could be worse.  I know someone who replaced the battery on an Android phone with an inexpensive battery from Amazon.  The phone got very hot during charging and caught on fire when he took it apart to pull the battery out.  It filled his place with acrid smoke, but fortunately only destroyed the phone and wastebasket

 

Apple is afraid of regulation so they offer repair kits for some of their devices.   The Verge documented a battery replacement.  You get a huge repair kit with a large hold on your credit card until Apple gets the kit back.  The process probably works well if you're skilled at working with small electronic devices, but this isn't for everyone. Given the cost of shipping I suspect Apple's losing money, but they're also trying to make a point of what it takes to do a high quality repair.  Of course a third party repair shop could buy the tools and perform quality repairs and I suspect that will happen.  Lower quality shops abound, but your phone or laptop may be a bit wonky afterwards.

 

We need to understand what's repairable, what's sort of repairable, and what's not.  Easy to repair smartphones have been offered but they're generally expensive and lacking in features.  I suspect smartphones, laptops and smartwatches are probably moving to a subscription model anyway.  Clothing and some appliances could made for longer lifetimes and repairability.  Then again convincing consumers and companies to move away from a consumption model is a huge, but very important, challenge. 

 

I've mentioned clothing, but should follow-up with other product areas where design for long life, repairability and upgrading is important. It's generally expensive, but in the long run can have advantages.  You may live in an example.

 

 

digging in a bit deeper

He would see something familiar in a cloud, the habit of a tree,  or a splatter of mud and use it as inspiration for one of his stories.  Lloyd loved stories.  Growing up, his would make up new stories to tell each other twice a month and, as an adult, he continued the tradition with his own family and the neighborhood kids.  I was one one of those kids. 

 

One night both of our families were camped near Two Medicine Lake on a spectacularly clear and dark June night.  The mountains cut pitch black outlines into the starry sky with new stars bursting into view as the Earth rotated. So many stars were visible it was difficult to find some of the constellations so Lloyd made up some of his own and started into his storytelling.  But two constellations survived - the Big and Little Dippers.  They were so well known to everyone that it was difficult seeing something else.   My contribution to the evening was pointing out some dark patches in the Milky Way. Like the mountains that seemed to be eating the sky and one looked like a galloping horse - enough to launch Lloyd on one of his ten minute excursions into fantasy.

 

Pareidolia is something familiar in otherwise unrelated objects.  It's seeing the face on the Moon or a bunny rabbit in a cloud.  It's a type of apophenia - our tendency to look for patterns in information.  Sometimes the patterns are there, often they're not.  The trick is to take a critical empirical look at the underlying information.  Exactly what is it? How was it measured and what steps were used to interpret it?  (this is where machine learning can fail  .. it's not just bad data sets).

 

Let's go back to the constellations - Ursa Major, the Big Dipper, in particular. Early on we learn that, with the help of culture, we're just finding familiar patterns as we connect the dots.  Stars are usually at different distances and brightnesses.  We're giving up the third dimension.  Nothing to see here .. or is there?

 

For years I considered the constellations to be nothing more than useful human constructions for finding one's way around the sky.  Ursa Major turns out to be special when you dig a bit deeper.  If you ignore Alkaid, the end of the handle, and Dubhe, the furthest point on the bucket, the remaining stars are all just a bit more than 80 light-years from Earth.   They also have the same proper motion - they're moving in the same direction at about the same speed.  Use a telescope and look at the distance and proper motion of dimmer stars you find over fifty that make up a physical cluster.  Spectroscopically they're very similar.  It looks like they were formed from the same dense cloud of gas about a half billion years ago - just after the Cambrian explosion on Earth.  With the exception of Alkaid and Dubhe they've moved in a slowly expanding formation and will continue along their way for some time 

 

And for years I thought the grouping must be nothing more than a human construct. A more critical look exposes a richer story.