omenti

a solar puzzle, 16 inch guns, and home repair

It looked awfully painful, but the burns didn't seem to bother him that much.  Ray plopped his tray down and the table and listened to catch the drift of of the lunchtime conversation.  Brookhaven was a wonderful place at the time.  Some of the best scientists in the world worked there and many were great at spending time with grad students and postdocs.

 

Ray Davis was already something of a legend in the late 70s.  He came to BNL in the early 50s to work on big problems.  Eventually he came to work on one that was fundamental - what are the mechanisms that power stars.  

 

Most of the energy on Earth originated in the Sun.  Your lunch today was probably sunlight that left reached our planet in the past year.  The gasoline in your car is older solar energy that has been stored for tens of millions of years.  The core mechanism that produces this sunlight turns out to be fascinating.  In the eighth grade you probably learned it is through nuclear fusion and in high school physics you may have done a simple mass to energy calculation.  The real mechanism turns out to be a tad more complicated that hydrogen fusing to helium.  There are several steps, but it can be roughly expressed as 

 

Four protons (hydrogen nuclei) are burned to a single helium nucleus, two positrons (positive electrons), two electron neutrinos and some energy.  The four hydrogens are a bit heavier than the helium nucleus and the positrons.  The mass difference is transformed into its energy equivalent and carried off in the form of a high energy photon called a gamma ray.  That energy eventually makes its way out of the Sun and radiates into space mostly in the form of visible light.  A tiny bit of what leaves the sun - about a ten billionth - makes its way to the Earth.  

 

Ray had a neat way to verify part of this - he could measure the number of neutrinos that left the Sun.

 

Hold up your thumb to the Sun.  Every second tens of billions of solar neutrinos zip through it.  They fill the space around us.  How hard can it be to measure them?

 

This turns out to be extremely tricky business requiring enormous care in experimental design and analysis.  Neutrinos were thought to be massless at the time and they interacted weakly with the forms of matter we're familiar with.  A solar neutrino striking the earth has a one in a thousand billion chance of interacting with anything.  Hold up your thumb and you would wait a century or so for anything to happen.

 

Ray's group used a 100,000 gallon tank of perchloroethylene - simple cleaning fluid which is chlorine rich).  It was buried almost a mile underground in an abandoned mine in South Dakota to act as shielding from other particle reactions.  If an electron neutrino with enough energy strikes a Chlorine atom, Argon-37 and an electron are produced.¹  

 

Every day about ten billion billion neutrinos would pass through Ray's tank and about two would react.

 

Every few weeks the tank was flushed and the Argon-37 was trapped in a charcoal filter and returned to BNL.  Ray happened to have access to a gun barrel from a 16 inch WWII battleship.  It was cut into a convenient eight foot, eight ton section that happened to make a dandy shield for low level radiation detection.²

 

Ray was very patient and very careful

 

The experiment went on for years and years - Ray and his group were seeing only about a third of what was expected.  Either the experiment or theory were wrong.  In cases like this you try to figure out just what went wrong, but the experiment was solid and the theory was very predictive and had become accepted.  Everyone knew Ray was missing something.

 

It turns out theory was wrong - or more correctly incomplete.  Twenty years later it was discovered neutrinos had a tiny mass.  They weren't pure electron neutrinos, but rather an admixture of states.  They would start out as electron neutrinos and during the journey to the Earth some would oscillate to the other state that was undetectable by Ray's apparatus.  

 

Oh - Ray's burns.  They were from a home repair incident.  They happened all the time.  He would do ordinary tasks to relax and think about other things.  There were times when his mind, which was working away at something, would shift to the problem and the real world would bang into him.  This certainly wasn't the only time and I'm afraid it happens to me more than I'd care to admit.

 

Last week I was walking down a street just before dawn.  It was amazingly beautiful with a thin cloud bank forming a few feet about the ground.  It wasn't more than ten feet thick.  I felt my mind wandering and suddenly I knew how to work a problem that  I had abandoned a month before.  I find putting problems aside that require creative energy to be extremely effective - assuming you have the raw material of richly diverse experiences and connections floating about.  

 

Recently Jean mentioned she sees a few levels of the process and has relied on scheduling her offline creativity.  Mine isn't that polished, but I require spaces where I'm not focused on current problems if I want to be creative.  Thankfully my parents allowed me a great deal of freedom. Had I been scheduled to the point where I didn't have the freedom to be bored it is possible I would have been locked out of fields I love.

 

Neuroscience notes that creative bouts tend to occur when our heavily organizing frontal lobes lose a bit of control and free association in other parts of the brain lights up.  Being able to partly shut down the frontal lobes may be the key to creative thought, but you wouldn't want it to take place all the time.  A fascinating hypothesis that is currently being investigated is known as transient hypofrontality.  Some people are very good at it.  When very creative people are interviewed they all seem to have tricks to put themselves into this state where they can be highly creative.  There are lots of techniques including meditation, home repair, taking long walks in nature, alcohol (more than a few writers) and other drugs, and so on.⁴  You find what works for you.  I share walks in nature with Beethoven and Einstein although I'm not in their league.  Sketching is also very effective for me along with getting lost in music.  Whatever works and I'm far from an expert.   Creativity is much much deeper and richer than this, but it is a fascinating idea and these practices are very common in some groups.

 

There is something else that is beautiful about transient hypofrontality. Neuroanatomists note the wires that connect up different regions of our brain are myelinating as we develop. It peaks in our frontal lobes in our early 40s, and then begins to unwind and demyelinate, starting at the front of the brain and working backwards.³ Our frontal lobes become poorly at conducting signals, so our ability to move the connection processes to other areas of our brain may increase after the age of 45 or so.  Perhaps we can become more richly creative with age  - also if you are creative, it may stick around longer than some other processes.  I caution this is only a hypothesis at this point, but it may explain a lot and some of the initial experiments are promising.

 

In 2002 Ray Davis shared a baptism with Swedish holy water with two other physicists.  A richly deserved reward.

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¹ Nuclear physics involves alchemy - one element can be transmuted to another.  It turns out the detailed process that goes on in the Sun has a branch that produced neutrinos from the decay of Boron-8.  Those are the only neutrinos in the Brookhaven experiment with enough energy to convert Chlorine to Argon)

² Argon-37 is radioactive and has a half life of a bit more than a month.

³ Think of myelin as the insulation that shields our neural wiring.  It allows signals to transmit quickly and efficiently.  

⁴ Seymour Cray dug tunnels and built a boat every year.  The boats were burned at the end of the Summer to give reason to build a new one.  Of course finishing a boat was not the point of the work.

 

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Recipe corner

 

A simple avocado salad based on a recipe by Mark Bittman

 

Avocado Salad with Ginger Dressing.

 

Ingredients

 

° 85g rice vinegar

° 50g white granulated sugar

° 2 tbl minced peeled fresh ginger

° 2 avocados pitted peeled and seeded

° 75g chopped roaseted peanuts

° cilantro sprigs

 

Technique

 

° Put vinegar, sugar, pinch of salt, and 2 tbl water into a small pan over medium heat  Cook until the sugar dissolves

° add ginger and continue cooking until the dressing thickens - about 5 or 6 minuts.

° Remove from heat cool and cover.  Let it chill at refrigerator temperatures at least an hour.

° Place a few cilantro sprigs on salad plates and overlap avocado sliceon top.  Drizzle wit the ginger dressing and garnish with peanuts and a bit of a finishing salt if you like.

 

blowing in the wind

While computational models have made big strides there is a large gap between model predictions and the real world.  If you are serious about how something interacts with the air moving by it you need access to a wind tunnel.  This gets interesting with athletics.  At the highest levels in cycling wind tunnels are used, but only sparingly as wind tunnel time is hard to come by.  It was interesting that one of the big three bicycle makes recently opened a private wind tunnel to sort out bicycle aerodynamics.  

 

I'd much rather see focus on the real issues of increasing bicycle commuting, but the fact is that much of the upscale market in the US is built on the bike as an expensive toy and exercise machine.  Competition in making racing bikes is fierce and I expect the other major makes - especially Trek - to build their own facilities in the near future.  

 

Of course I'm assuming they will have people who know how to properly design the experiments and analyze the information.  It makes me think about the current big data explosion.  Some will do great things, but getting there isn't easy and requires very careful design and the right people.  Just going out and hiring "data scientists" and "data vis" people won't work and may even be counterproductive.

 

Any time you are dealing with data (I would say information) analysis, it is important to know what it is, where it came from, how noisy it is, and possibly many other things.  You have to know about the manipulations and filters it passes through.  Are your questions   for the data set?  How biased is your analysis?

 

Look up at the night sky and constellations pop out.  Constellations are artificial and offer no physical meaning.  In fact they led to early counterproductive models of the cosmos and some people still attach meaning to them.

 

Humans are naturals at apophenia - we have evolved to easily find artificial patterns in information.  We find it in scientific, engineering, financial, weather and most other forms of data.  We can and do make serious mistakes.  Hunting for patterns in large data sets can be enormous fun, but it can be very misleading - as the Danes would say: there are owls in the marsh....  A deep tool and domain knowledge is essential.  Given how many misuse spreadsheets and simple statistics, I'm not universally optimistic. But others will be very good at avoiding the pitfalls.

 

There are ways to guard against mistakes.  Science is built on these procedures, but there are those who see big data as the shiny new thing.

 

I was interested in measuring how efficient a human could be on an average bike.  There are a lot of numbers, but they vary dramatically.  Using a numeric model and a digital wind tunnel we are talking about serious big data.  For fun one can get time in a low speed wind tunnel.  There is much more going on than in the digital model, but a bit of clever design means we are not recording that many numbers.  With some care we can understand what is going on throughout the experiment - something that isn't as easy with the digital model.

 

The opportunity presented itself and I was able to record a nice round number - From an earlier post a friend on a commuter style bike can exceed the equivalent of 1,000 miles per gallon.  a few details:

 

Looking at someone in good physical condition riding in an upright position with no external wind on a very non-aerodynamic bike.  At 22.5 kilometers per hour (14 mph) she needs about 80.6 kilojoules to cruise along for a kilometer.  This works out to about 31 nutritional calories per mile.  She is burning something like 434 calories over her basic needs to cycle for an hour.

It is interesting to calculate the power she is getting from the metabolism of her food at this steady pace.  In an hour she requires about 1814 kilojoules of energy, so dividing by the seconds in an hour we get a bit more than 500 watts. Not all this food energy is being converted into useful mechanical work.  It turns out many of the muscle movements we make have efficiencies around twenty percent.  Colleen happens to be a trained athlete with wonderfully smooth motions and is a bit over twenty percent efficient on a bike.  She is delivering about 100 watts of power to the pedals and most of that (about 95%) is making it to the rear tire.  

Imagine a car that gets 30 miles per gallon.  A bit of arithmetic shows 30 mpg of gasoline is about 2750 kilojoules per kilometer.  The car uses a bit more than 34 times the energy Colleen does to travel the same distance.  Of course she is only carrying around a bike and a car has to carry a lot of weight besides the driver.

She is close to 1025 miles per gallon - if  fueled by a gasoline near equivalent like a vegetable oil.  That doesn’t work for her so you can figure out what she gets on a gallon of Ben & Jerry’s if you like. 

 

There are a lot of ways to come to different numbers and not everyone has the access to a wind tunnel and the metabolic measurements that an Olympic program uses.  If the information is found it is necessary to know something about it.  There are a lot of specialized conditions that go into this little number.  One can ask many other interesting questions and learn even more, but I only show the rather flashy economy number.  

 

In the end just doing it was much more efficient that building a model and using computational fluid dynamics.  If I was asking a more isolated question - perhaps a design question - the model may have been the way to go.  A bit of experience goes a long way.

 

My worry is that many decisions come down to needing a simple and clearly stated result.  The culture of those who describe the information and those who act on it may be so different that the analysis is worthless or even dangerous.   Domain knowledge is critical.  Even Nate Silver gets silly when he is away from politics and sports.

 

You have to be careful and critical - doubt and curiosity are very important tools as is playfulness.  Science is lucky.  There is an absolute right that can be independently tested using multiple approaches.  Along the way there are many wrong descriptions, but over time they are stripped away and a clearer picture emerges

 

There isn't any magic in it.  Big data will be great for some organizations, and others will get results that lead them down mistaken paths (ask Mitt Romney).  How an organization builds this into their culture is critical.   It should also be stressed that some organizations that have a good understanding of their domain using conventional techniques may find this counterproductive.  Other companies may find it much more useful to continue to build more conventional techniques to understand their customers and operations - Trader Joe's comes to mind.

 

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Recipe corner

 

I've been seriously occupied for the past few weeks and did very little in the way of interesting cooking.  So here is a fundamental technique I use all the time - brazing and glazing vegetables.  It is very useful to master this one:-)

 

° Cut some firm vegetables (I love this with sweet potatoes, it doesn't work well with produce that isn't firm) into roughly equal sized pieces so they cook at similar rates.  Put them in a pan with a lid that fits well and is just big enough to hold them in a single layer.

° Add enough water to cover the bottom of the pan along with a little olive oil or butter.  Add any seasonings that need cooking - garlic or shallots for example.

° Place the pan over a medium heat, cover and stir every few minutes to see if the veggies are getting tender.  You can add a bit of water if needed.

° When they are getting tender, remove the cover and crank up the heat to high. Stir constantly and wait for the water to evaporate and the veggies to start to turn brown - this many only take a couple of minutes.

° Add whatever spices you need.  Salt, pepper, some chopped herbs etc.  It often helps to add just a bit of acid - a squeeze of a lemon or a tbl of vinegar.  

° serve