Saturday, April 22, 2017

Word-thinking, Science Marches, Engineering, and my abs hurt.

🎵 Science! Ooo! What is it good for? Aah! Absolutely everything. 🎵

"If I drop a large ball bearing from a five meter height, how fast will it be going when it hits the ground? Approximately is fine."

This is a trivial Physics question, made simpler by the choice of numbers. Using $g=10$ $m/s^2$ as an approximation and ignoring other forces on the ball bearing (because they're relatively small), the time for the drop is one second ($5 = g/2 \times t^2$; solving yields $t=1$) and in one second the bearing accelerates to $ 1 \times g$, or 10 m/s.

Most people, including those who have had enough Physics in their formal schooling to know the above relationships, can't really answer questions like this. I've speculated that it's a mix of innumeracy (ignorance), acalculia (inability), and numerophobia (attitude).

It's also a reason why so many people believe that being word-thinkers over technical matters is acceptable. It's not. For a technological society to work, technical matters must be dealt in technical terms, and that almost always implies numbers-thinking.

Sadly, one sees the word-thinkers, or at least word-thinking, invading technical domains.



Many words about "science" but not one about scientific matters


There are several "Marches for Science" around the US today. Because there are some political undertones to some of the elements of these marches, a number of people who oppose the political side of those elements has made a lot of pronouncements about science.

(It's almost guaranteed that these people making pronouncements couldn't answer the question above, or do a mass calculation for the stoichiometric combustion of 2,4-dimethylpentane in pure oxygen.)

Politics aside, and that's a big aside, these people who are so concerned about the hijacking of science by political forces make a big deal of how the word "science" means a bunch of things, scientody, scidolatry, scientage, and other made up words, and then keep on harping about how the "dialectic" of this versus the "rhetoric" of that and so on and so forth.

Word-thinkers. Talking about science. The mirth potential is endless.

And as I read these (with my core muscles sore from yesterday's squat workout making belly laughs extremely painful), all that keeps going over in my mind is "can you explain the function of the Golgi apparatus?" or "what's the difference between alpha and beta decay?" Perhaps you wouldn't sound so ridiculous talking about "scientody vs scientage" if you could explain the macroscopic effects of the differences between a body-centered cubic crystal structure and a face-centered cubic crystal structure.

It's just ab-crampingly funny to read comments on how science works and how is should be interpreted by people who think that evolution and vaccines are conspiracies by the ruling elites to keep the sheeple under control, all data and evidence be damned. To read lofty words of advice on research methodologies by people who can't tell a burette from an Erlenmeyer flask.

As one might imagine, many of these word-thinkers about science are creationists, so it's without a drop of self-awareness that they talk about the sheeple "accepting authority" of scientists regarding the nature of reality.

Of course, most people don't simply accept the authority of scientists blindly; most people, at least people who think for a moment, recognize the incredible advances in quality of life brought on by science and technology (and the one that actually makes stuff, engineering).

While creationists accept the authority of, no, not God, they don't get their ideology from God (at least not without a large dose of LSD, Ayahuasca, or Psilocybin 'rooms -- and that's not God talking, that's the brain malfunctioning). They accept the authority of religious leaders, who have proven themselves a lot less than scientists and engineers.

As I said, not a drop of self-awareness.






Don't abracadabra with technical words, please

(This is an adaptation of a post on the EEVBlog forum.)

I pains me to see engineers use words as if they were incantations rather than technical concepts that have precise meanings.*

A little context: there was a discussion of a water-harvester device using a composite, MOF-81; there's a Science News article presenting it here and the actual peer-reviewed Science paper is here.

Some people complained that the paper itself is behind a paywall; I'm a member of the AAAS, so I can see it fine, but there are ways to read it without paying, the simplest one being through the proxy server of a public library. (Many libraries, including college libraries that carry Science online, have open proxies for their patrons and students to access online databases remotely; some of these proxies require no authentication or geographic validation.)

A few commenters in the forum were disparaging the research, using words like "thermodynamics" or "enthalpy of evaporation" without taking a minute to do some calculations. And no, you don't need to read the Science paper or solve the heat equation to avoid wrong statements.

The point of contention is the 3 liters of water per kg of MOF-81 per day. So, how much energy are we talking about and how big a surface to dissipate it?

The enthalpy of evaporation for water is 2.3 MJ/l and because it's so high you can pretty much ignore the energy of temperature change within the gas or liquid phases; only the phase change matters to a first approximation.

3 liters $\times$ 2.3 MJ/l = 6.9 MJ - per day, therefore (divide by 24*3600) 80 W of power.

(At this point most engineers should realize that there's no problem; 80 W from a large-ish metal surface in open ambient air will almost surely be peanuts. A human being radiates about 100-200 W depending on the level of activity, or at least that's the number used for HVAC dimensioning when I was in college, back in the Pliocene.)

How big an area are we talking about? Again, even without reading the paper we can do some basic calculations, assuming planar geometry for the MOF-81 deposition.

If the MOF-81 were as dense as lead, 11.34 kg/l, a thin(ish)-film deposition over the base material, say 1/25 mm, would lead to 2.2 $m^2$ of area, or a square about 1.5 m on the side. To dissipate 80 W. Piece of cake.

But since the MOF-81 is much less dense than lead and is deposited to maximize porosity (that's how the MOF-81 works, it's all physics, no chemistry), it's more like styrofoam, and the area would be around 24 $m^2$, which makes the "enthalpy of evaporation problem" a non-starter. (It was already a non-starter with 80 W in 2.2 $m^2$, but the 24 $m^2$ is closer to reality.)

(The actual geometry of the deposition is more complex, highly non-planar, making use of a copper foam that is infused with the MOF-81 powder, all on a copper substrate, but to know that you'd need the actual paper. Which you can easily read online using a library proxy.)

We are engineers; let's not act like muggles and resort to lobbing words around as if technical terms were incantations. If it's an engineering word, there are probably numbers hiding behind it somewhere. Get those numbers.

You shall know the numbers, and the numbers shall set you free.

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 * Of course, not all forum denizens are engineers; trolls make themselves obvious by nitpicking on details that engineers would assume and by responding to math with word-thinking and cherry-picking.