omenti

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.