Sunday, July 17, 2016

Fun with numbers while walking

Walk in San Francisco, July 16, 2016

Yesterday I went for a walk in San Francisco. To pass the time and keep my mind off the Pokemon Go players making pedestrian traffic in Golden Gate Park hazardous, I decided to do a few approximate calculations about jet engines.

Let's say a jet engine used as a gas generator produces 22 000Lbs (= 10 000 kgf or 100 000 Newton, approximately) of thrust at a nozzle velocity of 720 km/h. How much air is it moving?

To generate thrust, a mass $m$ of air is accelerated from zero to 720 km/h (200 m/s) per second. The thrust is given by $F= ma$, so the flow, or mass/second, is 100 000/200 or 500kg/s. Since air density is about 1g/l at ground level, we need 500 cubic meters of air to go through the engine per second. That's the volume of a large room (20 by 10 meters surface, 2.5 meters ceiling) per second.

Just for fun, how much power is the engine generating? Considering only the kinetic energy imparted to the air (per second, since we're interested in power), we have $1/2 \times 500 \times (200)^2$, or 10  MW. Of course, since the air is very hot, some more power could be recovered using heat exchangers on the power turbine exhaust gases.

Since a gas generator has an efficiency of around 1/3, this turbine will need about 30 megajoule of chemical energy per second entering the combustors, or about one liter of jet fuel every 1.2 seconds. (Looked up jet fuel energy density on my phone while walking --- ain’t living in the future grand? In the past I'd have to look that up in Perry's or Marks'.)

Yes, the numbers are very rough approximations; that's what you do when walking around. I also picked numbers that would be easy to divide in my head. Remember, I had to avoid Pokemon Go players who kept moving in unpredictable patterns in my path:

Walk in San Francisco, July 16, 2016

Edited (about 30 minutes after posting): During my walk I incorrectly computed the power as 1 MW instead of 10 MW, basically because keeping a lot of zeros in your head while avoiding the Pokemaniacs is difficult. The original post used that value; while rereading it after posting, I realized my order-of magnitude error and corrected it and the fuel calculation.

Sunday, July 10, 2016

Two lessons from a simple puzzle

Suppose you're given a set of fifteen integers for a puzzle:

$A = \{ 1, 3, 7, 11, 19, 23, 35, 37, 41, 43, 57, 59, 61, 67, 71\}.$

The puzzle is to add six of these numbers to make up $101$.

Take a moment to try to solve it.

Ready to proceed?

Before we get to the puzzle, one of the people along the chain that brought me this puzzle said that there were "hundreds of combinations."

True. There are indeed fifty "hundred combinations" (plus five), since $\left(15 \atop 6\right) = 5005$.

Apparently a number of children and adults had been searching for the solution and someone thought that writing a search program would be a good idea; they didn't know how to do it, though, since none of them were programmers. Personally, I'd do it in Prolog, since tree searches are so easy to program in it.


Except that all the numbers in $A$ are odd, as is $101$. And a sum of six odd numbers is necessarily an even number. The problem has no solution.
PROOF: Each number we pick, $n_i \in A$, is odd so it can be written as $n_i = 2 \times k_i +1$ for $k_i$ integer; adding six of them yields 
$2\times (k_1 + k_2 + k_3+ k_4+ k_5+ k_6) + 6$, 
which is even for any $k_i$.
Some of the adults involved were primary school teachers. Who teach basic arithmetic. And apparently not one of them abstracted from the numbers long enough to see that the problem was impossible. I'm told some of them didn't want to believe there was no solution.

So, here are two lessons from this simple puzzle:

1. Understanding beats blind search.

2. Statements of "impossible" require a proof.

Tuesday, July 5, 2016

This Week In Smart

Internet atheist Sargon of Akkad presents a regular feature, titled "This Week In Stupid." Entertaining as though it can be to watch, it always leaves me a little uneasy, and not because of any particular topic.

It's the mindset, common to many i-atheists and "I effing love science" types, described in the post The Sky Is Blue Therefore No Vodka on Transatlantic Flights: atheism (or "love" of science) as mockery of others. Sometimes with some reason, sometimes based on pointing and sputtering.

(Quick, "lovers" of science: do you dilute concentrated sulfuric acid by adding the acid to the water or the water to the acid? Hint: one yields diluted sulfuric acid, the other yields chemical burns.)

As a counter to that mindset, here are a few things that showcase smarts, not stupidity. Just some things I watched or read that I liked and think they are good examples of what knowledge, work, intelligence, and drive can achieve. Plus, big machines.

The Juno probe has now been inserted in orbit around Jupiter.

Mythbuster Adam Savage applies Science! to an important problem: how to best sear meat.

Crazy Australian Dave Jones (EEVblog) discusses the effects of radiation on electronics in space.

China completed the largest radiotelescope in the world (via WSJ).

A new crew will be going to the International Space Station tomorrow, on a Soyuz capsule. Coverage will probably be available at Spaceflightnow.

A statistical analysis of the data processing used on fMRI data raises questions about a lot of results in neuroscience-adjacent fields (neuroeconomics, neuropsychology, neurofinance, neuromarketing -- no not joking, etc).

Dr. Don Lincoln of Fermilab (your tax dollars at work) explains quantum "color."


1. Quite a few smart people I know are still stumped by this puzzle (yes, there's a solution):
You're NOT at the North Pole. You walk 1 km South, 1 km West, 1 km North and find yourself where you started. Where are you?
2. Some of the little ones in my family have quickly solved this 6-queen puzzle (in Portuguese for my niece, whose name, as some might infer, is Mariana):

Puzzle das seis Marianas

(Place six Marianas in the six-by-six board in such a way that each line, column, and diagonal has only one Mariana.) Pass it along to little ones you know, maybe it'll help make them careful thinkers

Gratuitous big machine video of this week:

Yes, I understand that it's much more popular to mock people and discuss events than to bring up ideas and focus on the positive advances being made; but since I don't rely on the internet for money (ironic, given what I really do for a living) I don't need to pander to that audience.

Pasta la vista.

Thursday, June 30, 2016

Some thoughts on exercise

(Based on a twitterhea that started after I came back from the gym today. I'm still recuperating from a long trip and a upper respiratory infection from the return flight.)

Strength training

If I could only do one strength exercise, that would be the deadlift, possibly with a trapezoid ("hex") bar. Interestingly, if I could only do two exercises, those would be squat & pulldown, so there's no nesting of the exercise sets. Actually the topology becomes ever more complex: three exercises would be squat, pulldown, incl. press; four exercises would be squat, pulldown, flat bench press, military ("shoulder") press. Past that, the topology becomes more workable, with five exercises adding back the deadlift and six adding horizontal row.

An alternative nesting, recognizing the importance of deadlifts:

(Yes, military "shoulder" press ahead of [flat] bench press; much more useful for life, plus pecs get worked on pulldowns.)

In reality, I do all six exercises (and a few more strength exercises) in a standard three-split powerlifting program (Monday: squat; Wednesday: bench; Friday: deadlift).

I seldom do any biceps or triceps work, as I find the upper arm gets enough exercise from the compound movements. Once a month or so, if I'm not too tired on a bench press day I might do three sets of standing curls superset with three sets of rope press-downs; but seldom more than once a month, and my arms aren't exactly skinny.

Accessory work

(Understood as accessory beyond the accessory work for the powerlifting lifts.)

Core: a lot of people worry about having "six-pack" abs; I train the core for strength, because it's a big deal in stabilizing movement and maintaining spinal health. I do a variety of exercises for the abs, obliques, and transverses, all under load. Unlike most gym-goers I understand that what makes for pretty six-packs is lack of fat, while what makes for good spine stability is strong muscles.

Specific posterior chain exercises: yes, the deadlift works the posterior chain, no kidding. But since standing up straight is somewhat important, I do a lot of other exercises targeting parts of the posterior chain beyond the glutes, particularly the various spinal extensors.

Neck (yes, I know it's in the posterior chain, at least the extensors): hey it's no big deal; it just HOLDS THE HEAD. Maybe gymbros could cut two or three of the hundred sets of standing curls they do per workout to strengthen the muscles that HOLD THEIR HEADS. Then again, perhaps they understand that there's nothing valuable there. Extension (with load), rotation, flexion (with load), plus careful mobilization.

Wrist: bodybuilders do do some wrist work, as their forearms are visible outside of a t-shirt, but they do it for show. I do wrist work because it protects the movement of the hands, which is kind of important for life. Wrist curls, reverse wrist curls, internal and external rotation with load.

Grip: I have a gripper, I use it. Short of a Hammer Strength grip machine (few gyms have those and even fewer the MedX equivalent), best thing for developing grip strength. No point in having upper body strength if the grip can't hold the load (bodybuilding bros say "strength? it's all about size, bro"), like having a very powerful engine in a car with bad tyres.

Rotator cuff: another area that needs to be protected against damage; I do a variety of low load movements of all the rotations of the rotator cuff, then train the two main movements (rotate forward, rotate backward) with standard strength training programming.


I'm a big fan of sled pushing and heavy farmer's walks, but mostly I end up doing treadmill intervals, hill sprints, or stairway sprints as that's what's available. I've tried to do farmer's walks with heavy dumbbells in commercial gyms, but unless the gym is almost empty, it's futile and garners strange looks from the know-nothings that mostly populate those gyms.*

In the past I have run mid-to-long distance, but that was in an age of ignorance. Quite a lot of information has come to light about the superiority (not equivalence, superiority) of high-intensity interval training over long low-intensity "cardio" for conditioning purposes.

Thinking about functional value of this conditioning training, it really matches real-life needs more than any long low-intensity training: usually if there's any running to be done (for example), it's a short burst of high speed.

I do a number of other activities that look like exercise but aren't:

Rowing is a hobby and I prefer to do it on the water. It's a very calming activity, considering how it's basically 15 to 20 explosive movements per minute. Even on a Concept II, the movement is very calming. It's basically yoga --- at 15-20 explosive movements per minute. If I'm doing it on a machine, I might listen to audiobooks: multitasking of the kind that works, unlike multitasking attention.**

Walking is what I do to clear my mind. I like to take long walks to think; it's an habit I cultivate that most people abhor (thinking, not walking; ok, most people abhor walking as well, but mostly they avoid, abjure, and detest having to think). When I say "long" I mean 25-50km long. This has led to some complaints from friends whose idea of long is "ten minutes" rather than "fifteen hours."

Working, reading, studying, watching lectures or other educational videos on "cardio" machines, typically the elliptical, treadmill, or stationary cycle. Since I have a gym in my building, and these machines tend to be available during my work hours, I can simply translate "sitting" into "slow moving" and get some advantageous oxygenation during the intellectual work. I don't count these as exercise because they don't get anywhere near the level of intensity that would create the need for the body to adapt, i.e. to gain any new capabilities.


A lot of strength athletes pay lip service to mobility, but not more than that. I did that too when I was young and foolish.

Now in my early middle age (ahem...), I find that the ability to reach and stretch is kind of important so I've been spending more and more time making sure that I get as much range of motion as possible, both in the gym (before and after working out) and several times a week outside of the gym.

And an inexplicable phenomenon...

Something that happens at some commercial gyms has been puzzling me: I finish my workout (warm-up, strength training, accessory work, mobility) and do a short cool-down on a treadmill or elliptical, walking slowly... and get the evil eye from the people on the machines next to me.

I can't explain it; I've surmised that these people's entire workout is 20-30 minutes of slow walking (sometimes slower than my own cool-down) on these machines, while I do my 15-20 minutes at the end of 90-120 minutes or more of moving metal (sometimes, a lot of metal), so there may be some divergence of the minds there.

Oh, on an unrelated note, I tend to switch the TV in front on my machine to FoodTV or the Travel network (if there's a food show on it) during the cool-down; I like food and food shows. I notice that no one else seems to be watching that channel, although they all appear to like food a whole lot.


-- -- -- --

* Also, farmer's walks with dumbbells are dangerous: while it's difficult to get your feet under a standard farmer's walk rig without doing it on purpose, it's a law of Physics that a dropped dumbbell will always hit your foot edge on. Check it.

** I end up doing a lot of rowing on machines because going to the Berkeley Lagoon is a schlep and then I have to pay a rental fee for a shell (I'm not a member of the rowing club). Since I have my own Concept IIc at home, I tend to use that.

The 15-20 strokes/minute rhythm is because I'm short but with a heavy torso (long torso to begin with, and powerlifting muscles weigh a lot), so I need a very slow return not to lose speed on the water due to my own inertia.

(I could row much faster on a machine, of course, but that would create bad habits for the water. On a related note, the way most gym goers – especially those who do something that rhymes with Fosscrit – row on the machines is hilarious: on the water they wouldn't move at all.)

Friday, June 17, 2016

More fun with people who "love" science

"How many Joule in a kilowatt-hour?"

This is not a trick question. It's a trivially simple question, that requires a middle-school undestanding of science. Yet, someone whom I'll call Igor (for Ignorant Grandstanding Oblivious Rabble-rouser):

a) Had no idea what I was talking about;

b) Didn't think there was any relation between my question and Igor's topic of "energy";

c) Didn't realize that Igor's ignorance of basic units of energy undermined Igor's credibility as a source of information on "energy"; and

d) Wasn't deterred from continuing a long Jeremiad about the "good" types of "energy" and the "bad" types of energy.

(One Watt equals one Joule per second, so one kWh is 3.6 million Joule. I knew this before I was 10, since I was a science geek even then, but it's taught in middle school where I come from.)

Having worked in education for a while (on and off), I've seen many cases where people don't learn, forget what they learned, and forget that there's something to be learned. But Igor is different.

Igor thinks that learning is unnecessary, because Igor already knows. Igor knows because... well, because all Igor's life, Igor was never contradicted as long as Igor's words fit the prevailing narrative. Igor's self-esteem ballooned like a spinaker in strong wind, and never deflated. Igor's education avoided science, where Igor might occasionally be wrong, so Igor never learned the most important lesson:

Reality always wins in the end.

Sunday, May 22, 2016

Nerds/geeks as an example of aggregation problem - A rant.

Aggregation problems come from the loss of information and detail from data reduction procedures. It applies to classifications of humans as well. The problem, that is.

Hi. My name is José, and I'm a geek.*

The classification of someone as a nerd/geek (used interchangeably throughout this post) has been on my mind recently. For clarity, I mean the old-style STEM-geek, not the new-agey "anything"-geek like food-geek or exercise-geek.

Here are a few things that get put under geekdom:

1. Playing video games

2. Reading comic books. I mean, graphic novels.

3. Watching science fiction television shows and movies.

(Huh, these read as "basic entertainment," with a notable lack of physicality. So far I score basically a zero. I watch some SciFi television and movies, but as a fraction of my [already minimal] media consumption, they are negligible.)

4. Reading science fiction books.

5. Solving logic puzzles.

6. Learning STEM for ludic purposes (as opposed to for school)

7. Watching science and engineering documentaries (including YouTube).

(Well, now I'm batting 1.000 on these last four.)

8. Applying math, engineering, and science to everyday problems.

9. Having a home lab, building mechanical, electrical, or electronic devices, programming computers (no, not just "using" computers), basically being an amateur scientist or engineer.

10. Choosing a career in STEM.

(Again, 1.000 in the last three.)

My point here is that 1--3, the most popular "geek" activities, represent a choice of entertainment that is mostly non-physical but has minimal intellectual involvement (SPARE ME YOUR BELLYACHING, GAMERS, I HAVE READ MOLECULAR BIOLOGY OF THE GENE FOR FUN, COMPARE THAT WITH YOUR PEW-PEW-BOOM), 4--7 represent more intellectually challenging choices of entertainment, and 8--10 are essentially having the mindset that leads to a career in STEM.

So, what's the point, really? Bragging?


There's a lot of buzz around the "rise of nerds" or some such idea, basically that because of the importance of technology and the enrichment of some entrepreneurial nerds, society is moving towards a more accepting attitude towards nerds.

That might be true, but the evidence I see for this is almost always from the rise of activities in the 1--3 points above. And that isn't what makes for a real societal change (except in the undesirable consequences of having young people who avoid physical exertion, something that I never did, mens sana in corpore sano and all that...)

People who really like machines (like I do), will easily spend hours watching Chris Boden "autopsy" equipment (someone give Mr. Boden a sandwich or twenty, please):

People who really like the science in "science fiction" will argue about different parts of the movies than audience members who are there for the spectacle or for the back story of the characters:

(If I were ill-tempered, I'd invite readers to compare those reviews, by an actual engineer who works in space exploration, with the generic comments by a science popularizer that plays a scientist in the media but who's an administrator in a museum in NYC. Just for comparison, before Carl Sagan became a popularizer with Cosmos, he had a long list of academic publications. Unlike this popularizer, who made a fool of himself trying to fill Sagan's shoes. But I won't name him, because that would be mean.)

Hardcore nerds might even spend some quality time with a textbook or two, learning new stuff in their middle-age, or taking in a lecture from a little technical school in Massachusetts, free!

I'm not saying that one thing is better than another, just that they're different. That science books that appeal to "mass market geeks" (1--3) are going to focus on different matters (events, people) than science books for the "hardcore geeks" (the STEM, the logic), but with this confusion between the first (and larger) group and the second (smaller but more dedicated) group, many popularization channels for STEM are becoming more like mass entertainment and losing their focus.

(Ranting? You bet. On top of my full-time quant job, I agreed to teach an MBA class, and even though I'm no longer an academic I still get refereeing requests; so I'm tired, I'm over-caffeinated, I'm fed up with people who "love science" like they "loved Armani" in the 1990s, and people who think that a biography of a physicist is a science book. And don't get me started on the people who try to crowbar the Arts into STEM to create STEAM, a steaming pile of... but I digress.)

It's nice that geeks are more accepted by society in general, but it's important to feed the hunger for knowledge of the "hardcore geeks" not just pander to the "mass market geeks."

(Seriously, I've worked about 70 hours since last Monday and now there's an unpaid referee report that I have to write. I'd much rather watch a few more equipment autopsies.)

-- -- -- --
* Also a powerlifter, so watch your mouth. :-)

Saturday, May 21, 2016

Groups who facilitate or benefit from technological illiteracy

Technological illiteracy isn’t a random occurrence; without starting conspiracy theories, there are quite a few identifiable groups of people who participate in and benefit from this state of affairs. Just off the top of my head:

“True believers” really think that if they concentrate enough on the whiteness and maleness of Isaac Newton they won’t die when they fall off a cliff, as long as they self-identify as something other than white and male. Well, maybe not gravity, but there are true believers in a variety of nonsense who think that just because something is virtuous (say Solar Power), it must be immune from the laws of Physics and Economics.

“Dunning-Krugers” consider that anything that isn’t their part of the job, like say engineering and manufacturing, is a trivial point that can be solved in an afternoon, while their part, say choosing the color for the packaging, is a key success factor and must be the most important part of the project. (See: Fontus Water Bottle.)

“People who love science” (as long as they don’t have to learn any) are always looking for ways to virtue signal their love of science, so anything technological which allows them to pretend they’re at the forefront of technology will be eagerly embraced. More so if the right celebrities, especially sciencey celebrities, are behind it. (See: Solar Roadways.)

“Geek-haters” did poorly in science and math class, and they hate the people who actually understand STEM, so when they see a popular product that only geeks complain about they take the opportunity to attack those who did well in STEM. In other words, they see these nonsense products as opportunities for creating friction between the geeks and the general population. (See: Triton Artificial Gills.)

“Early Outs” understand that the product is made of vaporware, hype, and fraud, but they also know that before that’s exposed their share of the company will be sold to the next level of investors so they’ll make a fortune and have no liability, as they will have all sorts of CYA written into the bylaws of the company. (See: Solyndra.)

“Banksters” know how to pass any losses they might have from buying later into the company to their clients or to taxpayers, so they don’t care about the long-term feasibility of any company as long as they get their fees and carry-over trade gains. (See: Dot-com bubble of 2000.)

Probably a few more. Certainly “patient enemies of our nations” would be a possibility, but that would be conspiratorial now…

[Based on a comment I made on this post by Dystopian Science Fiction author Davis Aurini (author of As I Walk These Broken Roads).]