omenti

40,000 apples on a table and an iPhone 7 plus

Imagine you wanted to power an iPhone or MacBook with apples.  You might drop the fruit from some height onto a generator that would stop the accelerating apple and turn it's kinetic energy into electricity -- sort of like a turbine does in a hydroelectric.  While not exactly practical, you could make it work and it's a nice way to think about power and energy.  

 

A joule one of many units of energy.  You tend to pick something appropriate for the task at hand and this turns out to be convenient for falling fruit among other things.  It's defined as the work done by a a force of one newton over a distance of a meter.  In the case of dropping something near the surface of the Earth this is just the product of the mass of the object being dropped, the acceleration due to Earth's gravitational pull and how far the object falls:  mgh.  If  the apple falls from a table (about 0.7 meters high),  a medium-size apple (145 grams or a bit over five ounces)  has one joule of potential energy turn into one joule of kinetic energy as it strikes the floor - or your generator.  

 

An iPhone 7 Plus has a 11 watt-hour battery.  A watt-hour is another unit of energy.  Here's how it works.  (Understand this and you're doing better than many online tech editors and writers).  Power is the rate at which energy is converted from one form to another - the kinetic energy of a falling apple into electricity for example.  A common unit is the watt.  A watt-second of energy can supply a watt of power for a second and is the same thing as one joule.  Supply a watt for an hour and you get 3600 joules or a watt-hour. So the iPhone battery can store 39,600 joules or 39.6 kilojoules( kJ).  There's nothing special about a watt-hour requiring an hour ..  it's just an amount of energy.  It could be 600 watts for 6 seconds.  (Normally I would stick with joules or watt-seconds, but I'll use both to stress their equivalence.)  A good analogy is your gas tank.  It may hold 20 gallons, but your accelerator determines the rate at which it is used,   Energy is an amount, power is a rate.  

 

Back to the task at hand.  An iPhone in normal use needs about a watt ..  run a video and you might need three watts.  Dropping apples takes an apple per second to supply a watt - a joule per second.   This gets inconvenient in a hurry.  An average of about 3600 apples falling from the table per hour rising to as high as 10,000 an hour when you're watching a video. You give the apples energy by picking them up from the floor and placing them on the table .. doing so each gains a joule of potential energy which converts into a joule of kinetic energy when they fall.

 

The laptop's power requirement is about six times that of the phone ..  six apples per second.  And it's worse than that as the generator is not going to be one hundred percent efficient.  Not to mention your body is only about 20% efficient picking up apples from the floor and putting them on a table.  It would take orchards. Or perhaps you could install a three story 10 meter  tower and run a 2,400 kg (nearly 5,280 pounds - a very large SUV) weight to the top.  That'd power your MacBook Pro for ten hours too...

 

It seems pretty stupid, but this is how the cheapest and one of the most practical forms of large scale energy storage works.  Pumped hydro is done in certain geographies where you can pump water up hill to a reservoir  when you have extra power and let it run back down to spin a generator when you need extra power.  The round trip efficiency can be as high as 80 percent - even higher if it rains (then you're just adding solar power).  The problem is you need a lot of water and a big drop to make it practical.  For a 100 meter drop the energy density is 980 joules per kilogram which works out to about 0.27 watt-hours per kilogram.¹

 

The pumped hydro facility - arguably the largest battery in the world - is the Bath County Pumped Storage Station. It can supply about 3,000 megawatts of power - about the same as three nuclear reactors.  The US has about an eighth of he world's total pumped water capacity of 168 gigawatts of power (updated - thanks David).  It's  much cheaper than other large scale forms of storage. Lithium-ion batteries would cost at least a hundred times as much.  Unfortunately there aren't many practical natural sites.  

 

For smaller applications you need much higher power densities.  Consider electro-chemical storage - electric batteries .. 

 

alkaline AAA non-rechargeable   118 Wh/kg    

alkaline C non-rechargeable         147 Wh/kg       

Li-ion 18650 rechargeable²             180 - 280 Wh/kg

 

An improvement, but what if your body ran on electricity?   You need about 100 watts of power on average around the clock.  That'd be about 10 kilograms of lithium-ion batteries for your daily energy supply. Not exactly practical. Fortunately life figured out how to use a much denser form of energy storage - the making and breaking of carbon-based chemical bonds.  

 

plain M&Ms     5,700 Wh/kg

beef hot dog      3,350 Wh/kg

 

People are often surprised when they learn a hot dog packs about three times energy of a similar sized stick of dynamite (1,150 Wh/kg).  Dynamite doesn't have a particularly high energy density, but it can develop a lot of power.  It's trick is the ability to undergo extremely fast combustion .. so fast the result is an explosion.  Too much power can be bad for your health.

 

Further up the hydrocarbon energy density scale are the oils..  vegetable oil has roughly the same energy density as petroleum based fuels.  All of these are really stored solar energy thanks to photosynthesis.

 

To get a sense of scale there are any number of games you can play.  A single plain M&M has about 3.5 nutritional calories of energy - about 14.7 kJ or 15,000 apples falling from the table.  Convert them to electricity at 100 percent efficiency and you could run your iPhone for ten hours.  This is one of the reasons why tiny fuel cells for electronic devices crop up every now and again.  So far they haven't been very practical.

 

Say you're an Olympic female volleyball player.  Blocking at the net you might jump high enough to raise you center of gravity by about 0.7 meters -- maybe a bit more. If your mass is 70kg you need a bit under 500 joules to get there.³  But the human body is only about 20 percent efficient for this kind of jumping, so you need more like 2500 joules (or watt-seconds).  The single M&M should be good for about six jumps.  By comparison a triple AAA alkaline battery stores about 5,000 watt-seconds - three AAA cells is about an M&M.  

 

A diversion, but one that's fun to think about, is what would sports be like on different bodies in the solar system.  The simple way is to just consider the effect of gravity, but that's not terribly interesting.  Balls interact with the air, so imagine a large open room with air at the equivalent of sea level.   The acceleration of gravity on the moon is about a sixth that of Earth so balls wouldn't drop as rapidly.  They'd go further, but how far would depend on air resistance.  Volleyballs have a lot of surface area and won't go as far as you might expect.  Putting spin on them, the Magnus effect is already important in volleyball,  would seem more dramatic than on Earth.  On very small bodies like asteroids and small moons you have the specter  of golf balls going into orbit (although the orbits wouldn't be very stable) - perhaps not the ideal spectator sport. There's also this matter of friction - something rather central to anyone who moves.  Most sports would require new rules to be interesting and practical.  Picking a sport or two you like and thinking about rules for Mars, the Moon or some other place is a nice form of daydreaming.   Or invent something new.  In both cases senses, reaction times, game play and beauty are involved.  How would things like balls, court or field size, net heights, etc change?  (computer simulations and real time visualizations are useful) Would your rules allow interesting competition?  Would it be fun to watch?  In the process maybe you'll develop a deeper insight for Earth-bound sport.  

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¹ Joules/kg is usually called energy density and watt-hrs/kilogram is specific energy.  Those historical conventions that can be confusing. 

² 18650 cells are a very common form factor.  The different energy densities represent different chemistries.  Picking a chemistry depends on the task at hand and they all involve tradeoffs.  Chemistries appropriate for cars tend to be on the lower end of the scale.

³ There's quite a bit more going on besides just raising your center of gravity, but the major component of work is the vertical jump. 

 

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Recipe Corner

 

Dairy-free "creamy" soups

 

The trick is to get the vegetable to stock ratio right, add some starch and and blend well.  I use about five cups of good veggie stock to two pounds (one kilogram) of veggies.

 

Cut the veggies into small bits for quick cooking. Start with an onion, a couple of leeks and a couple of cloves of garlic.  Sweat them in olive oil with salt until they soften. Add the starring veggies and sweat.  Add the stock, boil and then simmer.  Simmer 'til the veggies easily pierce with a fork.  Then use a blender or a stick blender to make the soup smooth.  Then finish with salt and pepper, lemon etc...

 

The big trick is the veggie to stock ratio and practice.

 

 

 

directional unfocusing

Because I could not stop for Death,
He kindly stopped for me;
The carriage held but just ourselves
And Immortality.

We slowly drove, he knew no haste,
And I had put away
My labor, and my leisure too,
For his civility.

We passed the school where children played,
Their lessons scarcely done;
We passed the fields of gazing grain,
We passed the setting sun.


We paused before a house that seemed
A swelling of the ground;
The roof was scarcely visible,
The cornice but a mound.

Since then 'tis centuries; but each
Feels shorter than the day
I first surmised the horses' heads
Were toward eternity.

 

My tenth grade English teacher pointed out that The Chariot and many other Emily Dickinson lyric poems can be sung to the tune of  The Yellow Rose of Texas. (I think it was Ms Svobodny -- Jeri?  I can't remember)  Of course the thing to do during study hall was to go to the library and find other poems and sing them in your head.  Try it with the Marine Corp Hymn, Ghost Riders in the Sky, the Wasbash Cannonball and probably many more.  I didn't think about it for years until I found myself chatting with a poet who brought it up.  She had been to a writing camp where a practice called Halloweening was used.

 

I'm getting ahead of myself.

 

This morning the director of a small technology company in Cambridge, England wrote thanking me for an earlier post on creativity asking if I could write a bit more.  Here goes..

 

First read my old post making sparks - it's short.

 

Neuroscientists talk about the Default Mode Network - think about it as an active set of connections that operates when you're not focused. An unfocused network.  It turns out to be quiet active and is often the part of the brain that makes the unusual connections found in creative thinking.  Learning how to engage and control it is a trick many creative people use is to engage this part of the brain.  

 

Some of this may be wired in, but the brain can be very plastic and adaptable. I'm reasonably convinced some of this can be learned and this is where the fun comes in.  You want to turn off some of the orderly task-focused work the industrial revolution gave us  and bring in some play and certain types of day dreaming.  Setting aside some time for your own thoughts is important as is getting away from multitasking.  Finding instant "answers" without having to think (wikipedia and Google) have been shown to be counterproductive if creativity is the goal. The dominated group think that comes with most brainstorming is kills creativity.  You get the idea...  structure tends to be bad if used throughout the day.

 

What appears to be good is letting your mind wander after having worked hard on something.  Do something very different to shift focus. Often repetitive "mindless" tasks work..  Einstein played scales on his violin, Feynman learned to draw and a dozen other things, a friend with a Nobel Prize knits and plays with Legos.¹  It should go without saying that you need to be deeply immersed in your main task for this to be useful.

Some find adding a bit of unpredictability important.   This works for me.  I draw (poorly) a bit every morning with the subject being whatever comes to mind when I'm brushing my teeth.  It all gets thrown away, but it's an important part of my toolkit.  I also take walks in the woods and try to avoid the same path and taking time to notice something new each time.  Stay away from the phone unless you have a creative friend to take a share the walk. Walking in a city I'll pretend I'm a slalom skier and find a path around other pedestrians.  

 

Jheri is coming into her own as a designer and clears her mind with fast bike trips through the streets of Copenhagen and Paris picking out a color from a magazine page and then turning in some direction when she sees it and moving until she sees the next color.  She's dangerously fast with hair flying out behind her trying to catch up.  She sometimes takes walks with colored lenses in her glasses  or wears some comfortable flat shoes that add about four inches.  Different visual perspectives divert and unfocus her mind.

 

Other tricks ..  if you're at a lecture you tend to retain more if you doodle rather than take notes.  Your friend is a piece of paper or a Field Notes book and a nice pen or pencil.  The class notes of prominent thinkers often turn out to be wild doodles with a few key words here and there. 

 

Halloweening.  The poet decided to try to get into Emily Dickinson's mind as much as possible.  She's not a lyric poet, so it was not exactly easy.  She wore white and stayed in the same rooms for a week not going outside communicating with others with a few physical letters as she wrote poetry trying for Dickinson's style..  She said it gave her a great breakthrough unrelated to Dickinson or herself - a different way of seeing the world.  Picasso's salon - la bande à Picasso - was very interested in geometry - specifically non-Euclidian geometry.  They studied Poincaré's  La Science et l'hypothèse and Picasso found inspiration and started into sketching the mathematical abstractions as well he could.   He tried to think like Poincare ... halloweening.  I suspect method actors are great at this. 

 

There is evidence physical play of the rough and tumble variety is important. And, for some, it's inverse.  Last Spring I found myself talking to a volleyball coach at Stanford.  He thought one of the reasons why some of his players were creative in their sport came from the fact they were actively engaged in mentally challenging majors.  Sport can be mentally challenging - it's just that math or biochemistry is challenging in a different way and can grant the gift of thinking differently.  We ended up having a fantastic talk about creativity in sport.

 

Find someone who is very different from you and smarter in many ways.  Hopefully you can bring  something to the table for them.  Playful conversation can fuel creative thinking.  This is where HR is critically important in any company that needs to be creative.  Sadly I see a lot of failure given what seems to be an increasing tendency to hyperfocus on THE task.

 

I'll end with a comment on thinking differently.  There is a tendency to conform to certain modes of thinking.   I've been told my hodgepodge of technique is unusual, but it works for me.  I certainly wouldn't suggest anyone else try it, but rather recommend they find their own.

 

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¹ I was lucky enough to have been around Feynman a bit.  People characterized his problem solving style as

1. write down a problem
2. think 
3. write down the answer

His thought pattern was just different from everyone else.  He played a lot and with considerable delight.  His mind seemed to be in a chaotic state between focus and play.  Listening to him you came away with the impression that physics was really easy.  Later you'd try and crash.,  His ability to distort reality made Steve Jobs look like an amateur.

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Recipe Corner

 

Peach-Peppermint ice cream (you can figure out the flavor name as Ben & Jerry's is unlikely to)

 

First make a simple peppermint ice cream.  I've made this one during the holiday season for years.

 

Ingredients

 

° 1 cup white sugar

° 2 cups heavy cream

° 2 cups half and half cream

° 1 tbl vanilla extract

° pinch of salt

° 1/4 c of good crushed peppermint candies  use 1/2 cup if just peppermint, but we're modifying it (I didn't say this was remotely healthy)

 

 

Technique

 

° hand whisk the creams, sugar, vanilla and salt until fully mixed

° refrigerate for a couple of hours

° churn-freeze 'til thick ... folks like Karrie may want to use the LN₂ technique:-)

° mix in the peppermint 

 

now go for ImPeachMint...

° swirl in 1/4 c chilled peach syrup - I use Torani 

° serve liberal portions

  

 

 

drawing lines of sound

Sound is an ornery beast.  Even serious people use different definitions.  To a physical scientist it's a vibration that moves through a solid, liquid or gas as a mechanical compression ..  moving regions of alternation compression and expansion.  To a psychologist or neurologist it's the result of processing the brain does after it detects the mechanical compressions - what you hear in your mind and neatly answering the question about trees falling in the woods without anyone around.

 

What we hear covers a range of wavelengths ranging from about 15 meters to 1.5 centimeters -  a factor of a thousand.  Visible light's range is less than two.  Sound waves are relatively slow in the air - about 340 meters per second.  The speed depends on temperature and, to a lessor extent, pressure and humidity.  Sound waves to be unfocused, bouncing off some things and getting absorbed and attenuated by others.  Our brains have evolved to make sense of all of this although sometimes we want better control.

 

If you're listening to live music the positions of the instruments and design of the hall can make enormous differences.  Even where you sit.  Acoustic engineers attempt to make the experience good over as much of the hall as they can, but have to deal with different audience sizes, the dynamics of the music and size of the ensemble, and even the clothes worn by the audience.  Some halls are better suited for certain types of music and some regions just sound better.

 

Movie theaters are a problem.  The same problem you have with music plus it has to synchronize with the film everywhere.  Not easy as the difference in distance to different speakers can sensed.  Some people can detect sounds that aren't synchronized to within ten milliseconds ...  a wave traveling ten feet more or less than one from another speaker for example.  Blockbuster movies - the ones that tend to make the most money - often have sudden percussive blasts of sound.  We are very sensitive to slight differences in timing for such sounds.  It would be great to be able to provide a good experience at every seat.  Wouldn't it be great if you could aim sound?

 

It turns out you can... and it started with a Canadian inventor around 1900.

 

Reginald Fesseden is one of those names you keep running into during the early days of radio. He noticed that if you take two slightly different frequencies and run them through something called a mixer they "beat" ..  You get a new frequency that is equal to the difference of the original frequencies.¹  He discovered this in electrical circuits, but the same thing happens in sound waves in the air.  You may have heard this beating if you've tune a musical instrument against a mechanical or electronic tuning fork.  Fessenden's discovery revolutionized radio and is still used.   In the sixties people realized you might be able use it to aim some types of sound.

 

Very high frequency sounds don't spread as much lower frequencies.  Even speech requires a wide range of frequencies.  Depending on the frequency of the sound how much the sound waves spread varies.  Generally the higher the frequency, the lower the spread.

 

The trick is to use ultrahigh frequencies - sound waves that would disturb bats and dogs. You use frequencies that differ by a frequency that you want to create.   Say your desired sound is a 440 A (440 Hertz or cycles per second)  and one of your ultrasonic frequencies is 100,000 Hz you beat the 100,000 Hz signal against one at 100,440.  In practice there is an array of ultrasonic transducers - the fancypants term for speakers - and with a few tricks you can create a "beam" that you can point.  If the beam strikes someone's ear, they'll  hear the 440 A, but someone just outside the path will hear nothing.   Generally you can get a beam about two feet wide at twenty feet.  

 

Clever, but there are a few problems that have kept it confined to very specialized uses - art installations for example.²  So I was curious when I heard about the Impossible Run:

 

It's encouraging and even heartwarming - send a couple of "lines" of sound down a track as a guideway.  The video is slick - a design company that did the work - but the idea isn't terribly flexible.  On the other hand it makes you to think a bit about what navigation for the partly sighted and fully blind could be like.

 

The sound beam approach is similar to the early days of aviation where directional radio stations spread out like a grid across the country beaming a pair signals in four directions.  The signal pair are at a slight angle.  One was the A in Morse Code  - dit dah, and the other N - dah dit.  The pilot tuned a radio receiver and, if you were flying directly towards the tower,  you'd hear a blur .. a more or less constant tone.  Veer to one side or the other and an A or a N would begin to appear.   This later became something much more flexible (VOR) that allowed you to use 360 different directions and then the shift to inertial guidance and finally GPS systems.  

 

So what about the partly sighted person?  The problem strikes home as my wife Sukie is nearly blind in one eye and has no peripheral vision.  She bumps into things and things bump into her.  Unlike a runner on an empty straight track or an airplane in flight, she has to worry about objects, often moving objects, in close proximity.  At least she still has some vision.  The problem is even worse for totally blind people.

 

I've built a few things, but building something smart enough to be trustworthy and making a useful interface is a serious problem.  I was inspired by the few blind people who have taught themselves how to echolocate (no kidding - this really works!).   For Sukie and other partly sighted person  personal LIDAR is probably the best emerging technology.  This is about the level for the amateur experimenter.  For the totally blind person you probably want centimeter accuracy navigation with LIDAR for object avoidance.  Preferably without realtime network connections!

 

Right now some hardware from Nvidia would work .. the problem is it would take several hundred watts of power.³  Expect a lot of progress.

 

I'm particularly curious about what might happen a new iPhone generations down the road with AirPods providing a sonic augmented reality interface.   I've done some thinking and a bit of simple prototyping to work out some ideas, but it is one of those things that will happen in a couple of years as some technology curves cross.   Perhaps hats come back into fashion.

 

Geordi La Forge indeed

 

In the near term I wouldn't be surprised to see movie theaters begin to provide sound through smartphone earbuds, but some sounds are not "heard" through the ears.  Some low frequency and loud sounds are detected as pressures on the skin and mixed in with the other signals in the brain to form the soundscape around us. Then again sophisticated earbuds and computation may add  augmented reality to the movie or home video experience.

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¹ Actually you get two.  If the original frequencies are f₁ and f₂ you get f₁ - f₂ and f₁ + f₂.  In practice you only use one. The new frequencies are called heterodynes.

² There is quite a history of trying to solve problems with this approach.  Sometimes it is called a sound laser, but the term is inaccurate and that's something else entirely.  It may be one of those hammers that keeps looking for the right problem.

³ Light Detection and Ranging.  A rotating pulsing laser beam measures range.  These are common on autonomous vehicles. 

 

teaching and using critical thinking

So frustrating!  

 

I was reading the transcript of an interview of the chief environmental officer of one of America's largest companies.  Their efforts appeared to be real rather than the normal corporate environmental green washing so many use.  Then she spoke about energy, but used units of power (watts)  rather than energy (watt-hours) .  Three times and a huge difference.   It may have just been a misspeak, but it stuck with me.  I frequently see science and engineering mistakes all the time in major newspapers ..  many might be simple editing errors.   There's a simple technique  that only takes high school science to understand what's going on.  It is a  quick way to do a bit of high level critical thinking.

 

Dimensional analysis involves looking at the dimensions of a quantity.  Velocity is the distance that can be traveled in some unit of time - or length divided by time (miles per hour): L/t.  Acceleration is the rate of change of velocity or velocity/time: L/t² . Area has the dimensions of length times length: L².  Volume is the cube: L³.  Force is mass times acceleration: m*L/t².  Energy is: m*L²/t² and so on.  

 

You can use this for simple tasks like changing units   60 minutes/hour * 60 seconds/minute = 3600 seconds/hour.¹   It can be a powerful way to quickly check an answer.  If you do a calculation and come up with E = mc³ you instantly know it's wrong as the units of energy are mL²/t² and not mL³/t³.  Mistakes like this or calling energy power cause you suspect the article in the New York Times or the Wall Street Journal.  Was it a bad writer or bad editor - or was it garbage in the first place?

 

In physics you do a lot of conjecture building.  A lot of this involves simple models to get rough answers.  The trick is to be correct enough to get a sense that it's a path worth looking into or just trashing.  It's also a very powerful way to estimate an answer when the physics involved is complex and you don't have enough information.   A few years ago I did a quick calculation to determine the energy cost of having a coxswain in competitive rowing.  [warning: Follow the link if you're curious about the power of the approach and are comfortable with high school level algebra and physics.  It starts after a bit of Olympic history.] I was able to quickly find a useful relationship between number of rowers and boat speed.  It surprised me at first, but fits with Olympic records.  From there you can  estimate the speed penalty of the coxswain as a dead weight.  Doing it properly would involve serious fluid dynamics and/or experimental measurements.²  Once you have the estimate you can do another simple calculation to estimate the energy cost of fighting the wiggle waggle of an un-coxed boat at the oars.  (the cox has other advantages, but that gets into human physiology and psychology).

 

Techniques like this are the tools of curiosity.  Being curious about something is the basis ...  this line of thought came while watching some rowing on the Olympics and being led to an obvious question -- why is there a cox in some events?   Then other questions present themselves and you follow. 

 

 It isn't difficult to teach thinking like this. Rather than the standard path of math courses - they're mostly aimed at 19^th and 20^th century tasks anyway -  I'd like to see some shortened or even eliminated and replaced by a statistics and probability course.  Logic and numeracy could come in almost anywhere.  Perhaps through multiple paths - science, history, computing skills and even art and sports.  All of this comes under the banner of critical thinking .. something everyone aspires to and most avoid as it causes too much questioning of the standard order.  

 

One of my favorite teachers in high school was a history teacher - Mr Wolff.  A master teacher, he taught a course in comparative religion and held an after-school philosophy group for interested students (that's where I first encountered and came to love Kierkegaard).  Somewhat after my time he was put on probation by the school board for putting religions on equal footing .. specifically for not teaching Christianity as the true religion. It wasn't proper for students to decide on their own one way or the other.  So much for critical thinking in the day.  

 

I'm not a trained educator and can't claim to know much about technique.  I do have a few ideas for information literacy as do many others.  It's time to experiment and see what works.  We're up against computational filters and conscious and unconscious biases of those who build them and the code underneath and a blizzard of purposely misleading highly targeted (some would say weaponized) information.  Creating unbiased information is extremely difficult - that's the hardest part of doing science.  Approaching the task like a scientist - being critical at all steps - is something that can be taught at simple levels.  Perhaps more important is recognizing that most information systems are built with such robustness and teacher the end user how to sort out what is fishy.  A subject for long discussion and perhaps a serious of posts on them and some critical ideas about STEM education.  

 

I'll end with part of a talk Richard Feynman gave in 1966 on the difference between knowing the name for something (how K12 history and science are usually taught)  and beginning to understand it.

 

So we went alone for our walk in the woods. But mothers were very powerful in those day's as they are now, and they convinced the other fathers that they had to take their own sons out for walks in the woods. So all fathers took all sons out for walks in the woods one Sunday afternoon. The next day, Monday, we were playing in the fields and this boy said to me, "See that bird standing on the stump there? What's the name of it?"

I said, "I haven't got the slightest idea."
He said, 'It’s a brown-throated thrush. Your father doesn't teach you much about science."

I smiled to myself, because my father had already taught me that [the name] doesn't tell me anything about the bird. He taught me "See that bird? It's a brown-throated thrush, but in Germany it's called a halsenflugel, and in Chinese they call it a chung ling and even if you know all those names for it, you still know nothing about the bird--you only know something about people; what they call that bird. Now that thrush sings, and teaches its young to fly, and flies so many miles away during the summer across the country, and nobody knows how it finds its way," and so forth. There is a difference between the name of the thing and what goes on.

The result of this is that I cannot remember anybody's name, and when people discuss physics with me they often are exasperated when they say "the Fitz-Cronin effect," and I ask "What is the effect?" and I can't remember the name.

I would like to say a word or two--may I interrupt my little tale--about words and definitions, because it is necessary to learn the words.

...

There is a first grade science book which, in the first lesson of the first grade, begins in an unfortunate manner to teach science, because it starts off an the wrong idea of what science is. There is a picture of a dog--a windable toy dog--and a hand comes to the winder, and then the dog is able to move. Under the last picture, it says "What makes it move?" Later on, there is a picture of a real dog and the question, "What makes it move?" Then there is a picture of a motorbike and the question, "What makes it move?" and so on.

I thought at first they were getting ready to tell what science was going to be about-- physics, biology, chemistry--but that wasn't it. The answer was in the teacher's edition of the book: the answer I was trying to learn is that "energy makes it move."

Now, energy is a very subtle concept. It is very, very difficult to get right. What I meant is that it is not easy to understand energy well enough to use it right, so that you can deduce something correctly using the energy idea--it is beyond the first grade. It would be equally well to say that "God makes it move," or "spirit makes it move," or "movability makes it move." (In fact, one could equally well say "energy makes it stop.")

Look at it this way: that’s only the definition of energy; it should be reversed. We might say when something can move that it has energy in it, but not what makes it move is energy. This is a very subtle difference. It's the same with this inertia proposition.

Perhaps I can make the difference a little clearer this way: If you ask a child what makes the toy dog move, you should think about what an ordinary human being would answer. The answer is that you wound up the spring; it tries to unwind and pushes the gear around.

What a good way to begin a science course! Take apart the toy; see how it works. See the cleverness of the gears; see the ratchets. Learn something about the toy, the way the toy is put together, the ingenuity of people devising the ratchets and other things. That's good. The question is fine. The answer is a little unfortunate, because what they were trying to do is teach a definition of what is energy. But nothing whatever is learned.

Suppose a student would say, "I don't think energy makes it move." Where does the discussion go from there?

I finally figured out a way to test whether you have taught an idea or you have only taught a definition.

Test it this way: you say, "Without using the new word which you have just learned, try to rephrase what you have just learned in your own language." Without using the word "energy," tell me what you know now about the dog's motion." You cannot. So you learned nothing about science. That may be all right. You may not want to learn something about science right away. You have to learn definitions. But for the very first lesson, is that not possibly destructive?

...

So much more to talk about...

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¹ As an exercise convince yourself that if you express a gallon as a volume, miles per gallon can be expressed in terms of  inverse acres.

² With a bit of other information I performed a simple calculation for the astonishing two hour marathon attempt and believe it would have been about 2:02 without car pacing - there is a serious aerodynamic advantage.  Record attempts should not allow pacing - or at least they should indicate where it is used and print and estimate of the advantage.  

Nike, of course, has a more accurate estimate of the advantage's size.  But simple calculations combined with some quick experiments may be enough to suggest pacing shouldn't be allowed if the record is to be considered pure.

 

compost heaps and ten minutes

 

And at the end he'll blow your minds and it won't be computer science.

 

Thanks.  Nothing like being put on the spot.  I was giving a visiting lecture in a friend's class the other day when he did this to me.  

 

The lecture was going to be fun.  Last year we had talked about the value of deeply understanding failure.  Failure analysis is key to the game of science and experiments are designed in a way that it can be understand and quantified.   I brought up Pixar's post mortem process and he complained this has become rare in software engineering.  Usually the pressure to patch or rewrite is so great that the process can be a bit blind.  We agreed it   would be interesting to teach an updated version of one of my favorite classes  - Engineering Disasters of the 20^th Century.  He took it seriously and created a class -  Engineering Disasters of the 21^st Century - so far...   The end of the course had a few sessions with guest lectures on looming disasters of the 2020s.  

 

 I'm not a particularly fast thinker and I don't multitask well (as it happens no one does).  I finished the the chat  thinking maybe I could just sneak out and find lunch.  No such luck - about three quarters of them stayed put. I had to come up with something.   I decided to talk about a realization that startled me as a teenager.  It still inspires wonder.   That's the rest of the post:

 

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Neutrons are radioactive.  In a bit over ten minutes a bag of factory fresh neutrons will decay into three particles - a proton, an electron and a neutrino (specifically an electron anti-neutrino) by a process called beta minus decay.  Since neutrons make up more than half your mass this should be approximately alarming.  

 

In the twenties people knew about protons and electrons.  A theoretical particle called the neutron was conceived to help explain why the proton and electron didn't crash together.  It wasn't very satisfying and  swept too much under the rug.  Then, in the early 30s, neutrons were discovered and they didn't act like the models that had been proposed.  New physics was necessary.

 

The neutron has a bit more mass than a proton - about a tenth of a percent more.  A free-range neutron has enough energy to decay.  But consider a neutron deep inside an atom. Now it's tightly bound to the nucleus and you need a good deal energy to pull it out.  Enter E = mc². Einstein showed us the total energy of a particle is proportional to mass.  So the mass of a bound neutron is lower than its free-range cousin.   In this case just low enough that it can no longer decay into a proton.  Stable beyond hydrogen are possible. 

 

If not for this small difference and mass-energy equivalence, anything more complicated than hydrogen would decay quickly.  The universe would be entirely different.  No people, no planets, no stars ...  not an interesting place.    

 

It still amazes me.   The stability of a bound neutron is a necessary condition for a non-trivial universe.

 

Up until this time there were just two known forces in Nature:  gravity and electromagnetism.  Beta decay didn't fit and turned out to involve a third force known as the weak force.¹   

 

You've probably heard that nuclear fusion in the Sun turns hydrogen into helium.  The process has a bit of complexity, but for the Sun the major reaction has three main parts.  The first part of the reaction involves the weak force with another type of beta decay - beta plus decay where a proton is turned into a neutron plus a positron (positive charged version of an electron) and an electron neutrino.  The weakness of the force means the process proceeds slowly.    Very slowly - the mean time in the Sun's core in about a billion years.

 

Most of the Sun's fusion takes place inside the core - out to  20% or so of the Sun's radius.  At this distance the density of the Sun is about forty times higher than water and the temperature is way high - about ten million degrees Kelvin (or Centigrade for that matter:-)  Less than that and very little fusion takes place.

 

The power density - watts per cubic meter - is surprisingly low at this distance - about ten watts per cubic meter.  If you move towards to the center few percent of radius where most of the fusion takes place, the power density rises to about 275 watts per cubic meter.   This is surprisingly low!  The average human has a metabolic power density of about 1200 watts per cubic meter.  The core of the Sun is about the same as an average compost heap -- or a lizard.  Sort of  an issue if you want to build a fusion reactor.  You need temperatures and pressures much higher than in the core of the Sun and different reactions to get reasonable power densities

 

We're really lucky .. in fits and starts it took about four and a half billion years  from the time the Earth formed to get to us.  That requires a mostly constant output  slow burning star and we've got one.  Its power density isn't much, but there's a boatload of Sun, so we get enough energy to run the film of life that covers our little blue dot. 

 

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¹ a fourth force is the strong force - it's about a million times stronger than the weak force and holds protons and neutrons together.  Getting into any detail gets into the weeds quickly. 

 

of secondary importance

Perhaps something useful..  a quick cheat sheet on the care and feeding of the rechargeable batteries in your devices.

 

For historical reasons rechargeables are known as secondary batteries and one non-rechargeables are primaries.  We may complain about constantly having to charge everything, but you'd have to spend a few bucks a day to power your smartphone on primary batteries ..  you'd end up sending the bunny about as much money as you send Apple or Samsung.

 

I'm not going into any depth on the various battery families and where they're appropriate. Lithium-ion refers to a very broad category with hundreds of types of batteries, while nickel-cadmium, nickel-metal hydride and lead-acid are much more specific terms.  I'm only going to talk about lithium-ion and lead-acid as they're the most common types most of us use daily.   

 

lithium-ion tips

 

Don't swing the charge too much if you can avoid it.  The innards of the battery expand and contract during charge and discharge  by as much as ten percent.  This results in cracking that lowers storage capacity  Most smartphone and laptop batteries are rated to retain at least 80% of their original capacity after about 500 charge/discharge cycles.  This generally assumes a usage pattern where you rarely completely charge the battery and rarely discharge it to under 20 or 30%.    If you try to stop charging around 80% and never drop below 30%, you should be able to double the battery's service life.  Conversely dropping to under 10% capacity most of the time followed by fully charging can drop the service life to 100 cycles or less.

The best rate to charge a lithium-ion battery depends on its state of charge and varies throughout the charging period, battery history, and a few other things.  Fortunately you don't have to worry about this any more as most name-brand phones and laptops have smart chargers that measure and sometimes even chat with the batteries.  Stay away from third-party chargers.  Not only are you likely to shorten battery life, some have proven to be serious fire hazards.  

Temperature is important.  Below about 40°F capacity drops dramatically.  Fortunately there isn't any damage unless they get really cold.   Heat is another matter.   Anything over about 95°F (35°C) will begin to cause permanent damage.  Not much at first -- constantly keep your phone in your pocket against your body and you may see a 20 or 30 percent drop in cycle life - but a few hours at 110°F (43°C) can kill a battery.   You don't need to live in Phoenix to get to this type of temperature in the Summer - just leave your device in your car on a sunny day.  If you're spending time in hot weather and carry your phone in a bag, it makes sense to put it near a cold pack.  Note that warranties do not cover batteries for excursions beyond rated temperatures and some devices track that.

And if you have to store your device for a long period - a month or more - store it in a cool place (below room temperature if possible, but not in the 'fridge) with a half charge.

so ...

don't overcharge

don't swing them too much

keep them cool - I tell people to treat handle like good chocolate (except don't eat them)

use the charger recommended by the device's manufacturer

 

lead-acid tips 

 

This  is the battery under the hood of almost every car with an internal combustion engine.

Keep them charged.  Your car usually does a good job when the engine is running.  Some of the discharged materialis transformed to a new state from which it can't be recharged. There is a  failure mechanism known as sulfation where some of the discharged material is transformed to a material that can't be recharged.   This takes place slowly over the life of a battery, but can be accelerated to a matter of hours if you allow the battery to fully discharge.   I remember my father accidentally leaving the lights on during the day only to come out to a dead battery eight hours later.  There is a small discharge that runs some of your car's resting electronics, but it isn't a major drain.

If you're away from your car for more than two weeks you should have someone start it up and run the engine for at least fifteen minutes.  If it is a few months you should follow instructions for long term storage (this also applies to other parts of the car).  When I'm away for extended periods I disconnect the battery to halt the small drain from the car's electronics. 

 In the cold weather it is much more difficult to start a car - the oil is more viscous and the starter may take so much energy that abnormally large amounts of sulfation take place.  Also the amount of power a battery can deliver drops.  Keeping a car above freezing for starting can make a big difference.  In cold Northern climates it is common to keep the oil warm by heating the engine block with a 1000 to 3000 watt heating element.  My father called this approach his "poor man's garage".

If you're really careful with the charging cycles and temperature a lead-acid battery can easily go 30 years.  This isn't possible in the more compromised environment your car has to live with.  Figure on replacing the battery in warm climates every six years and every five to six in colder regions.  If you manage to completely drain the battery - even if it is new - just replacing it makes sense.

 

Batteries are getting better, but other than cost it is a slow game.  Don't expect dramatic improvements in the next five years at a minimum.