Schneier on Security

Clive Robinson • June 9, 2022 1:22 AM

@ Godel,

Blaim a tired mind… Doing odd hours yet again and sleeping twice a day. Back half a lifetime ago when I was a keen sporting sailor it was not a problem, these days…

As for units that sound like “mils” it’s perhaps the most context sensitive shortening there is (basically 1/1000th of XXX).

You have millimeters or 1/1000th of a meter and you will hear builders and carpenters say 1200mil meaning “four foot”. But just to confuse there are also thousandths of an inch ~1/4mm called mils and still used in the electronics industry causing confusion especially amongst software developers…

Then there one or two others in electronics such as reactive component values. Mils is often used as a shorthand for inductance, even occasionaly capacitance though “mike” and “puf” are more normal. Then there is milli-Siemens and a few other device parameters. Yes there is even milli-Hertz found used for measuring mechanical wave vibration frequency components in various geological sciences.

Then there is even air preasure in millibars, which gets shortened by some such –as those working with the atmosphere and Drs– to “mils”…

However things are not all they might seem… 1 atmosphere supports approx 30 inches / 0.75m of mercury, so whilst it is easy to make a measuring device using a U shaped glass tube –manometer– it’s actually not very precise… This is due to amongst other things hight, weather, temprature, local gravity and even phase of the moon and how good your eye sight is when measuring the meniscus… So we have Pascals defined under SI as one newton per square meter, and one hectopascal as one millibar. Only millibars are not always millibars, it depends on “the guage type and it’s datum / refrence point. Drs for instance still use mercury manometers so your “blood preasure” realy can be dependent on “which way the wind blows” 😉

Clive Robinson • June 9, 2022 11:44 AM

@ Bob Paddock, ALL,

Re : is it any wonder people get confused?

Remember the “English units” are often US / American and not the “Imperial units” which are UK / British… the “Continentals” having given up not just LSD but much else for the sake of Revolutionary French Finger Counting because some little bloke got insistent 😉

From memory the US liquids are based on the Elizabethan “wine gallon” the UK on what became the “beer gallon”.

But personally I go back to the very roots of science and blaim the chickens 😉

Let me explain, why they are the very devil in disguise and quite innocently caused science and industrialisation to happen (the third bad move after walking out of the oceans, and comming down from the trees)…

A chickens egg was the standard “kitchen measure” which eventually became both volume and then “weight” on a balance scale in a cup or small bowl[1]. From which most other kitchen measures were derived. But recipies are “the earliest published science experiments” and are ratio based not measure based, something most do not realise or why.

To make a balance measure you would have two small bowls hanging on either end of your measure balance stick, that you would “adjust dry” / “center for” the balance point.

So a recipe and method,

1) Put four unbroken eggs (appx 245g) in one bowl and add sugar to other bowl to balance. Tip the sugar into the mixing bowl.

2) Add flour to Balance eggs, then tip flour onto paper/plate.

3) Add fat (butter/oil) to balance, against the eggs and add to mixing bowl. Mix sugar and fat to make a smooth “cream”.

4) Mix in some flour and one egg, cream untill smooth.

5) repeat 4 untill all eggs and all flour mixed in.

6) If required add “full fat” milk to loosen the mix.

7) Put in two “8 inch” oven pans and cook in moderate oven.

8) when cooked and cooled make more butter cream to hold two together add more butter cream or icing to top add decoration serve in 12 slices with three large pots of tea (6pints).

And enjoy. No measures involved just ratios by balance.

When “small” helping mum so you got the mixing bowl to clean with your finger, tounge or more usually both ment you “learnt about ratios” before you ever did about measures of weight or mass or density (if you ever did).

As our world naturally works by ratios not absolute measures, you can also see why modern kids have trouble with mathmatics, where ratios make sense but absolutes rarely do except as multiplication / division constants[2].

The fact we teach things the wrong way around is why it takes so long for some children to learn. Give them cylinders and string and show them how to find a cylinder with twice or half the diameter of another teaches their “senses” a valuble lesson. If the cylinders are all made of the same material say wood and are the same length a simple “balance” teaches their senses another lesson (first area then volume). Then using an adjustable or graduated balance, you can teach them about “scales” then introduce the next logical step “rulers” / “measures” and introduce multiplication and division and “normalisation” for “percentages” then the concept of “powers”. Using squares and cubes and similar blocks alows for basic measurment and the notion of geometry and the likes of square roots etc.

Oh and explianing “equals” or the “=” symbol from “balance” is almost painless. Likewise the concept of “zero” which took mankind a few thousand years to grasp after they had learned how to “write” (the Italians AKA Romans never did get the hang of zero or negative it’s why their maths was so dificult, but they grocked ratios and geometry without problem)…

[1] As some know “white smiths”, “shoe makers” and druggists / “apothecaries” needing “small units” used the likes of Barleycorns (1/3 inch) and poppy seeds (1/12 inch) and similar “grains” for weight (7000 wheat grains being one medieval pound). Hence “Troy” and “apothecaries” “avoir de pois” “goods of weight” measures.

[2] Remember Y = K + (C x X) is actualy a “two line aproximation” to a power curve. Which is why in cooking meat in an oven you say,

“20mins per pound plus one for the oven.”

Importantly this is after the oven has come to temprature not before. Another mistake people make, so can end up with under cooked food, that can be quite harmfull to them.

Clive Robinson • June 10, 2022 6:16 AM

@ SpaceLifeForm, Godel, ALL,

As to determining the direction, well, that methodology is classified.

But quite simple to do.

One simple system requires only three “vent pipes” in an aproximate triangle. Comparing the “phase of the waves in the bowl” with a little mathmatics gives you direction and velocity.

I can think of several other systems, but that’s the easiest one to understand.

Oh fun fact you might know about the ancient Chinese earthquake detectors that gave direction by the use of multiple dragons mouths around the bowl. Well they also had directional wind whistles esentially a vertical pipe with a “bottle top” type resonator / whistle in it. The top of the whistle had a directional cowl.

Now… If you made the same, but with the cowl being rotated by a mechanism where the instantanious direction was known the amplitude of the whistle would be a sinusoid and have a phase difference with respect to the instabtanious position of the cowl…

Oh and quite a few experienced sailboat sailers can hear the speed and direction of the wind almost subconciously by the sounds it makes in the rigging when moored at the dock. Thus they know when the weather is “on the turn” and if it is worth / safe to venture forth.

Clive Robinson • June 10, 2022 9:07 PM

@ SpaceLifeForm, fib,

It is not rocket science, you just need to go outside, pay attention, smell the air, and watch the clouds.

Or listen to their bones[1], but seriously with so many people looking at their smart phones, do they ever look up and see the clouds, let alone watch them…

As you are aware my childhood would be considered strange these days with helping in the kitchen and garden to “bottle” vegtables, make vinegar to make pickles and make jams fruit cheeses and cordials. Then there was shoot / slaughter and prepare pigeons and chickens, chop up pigs heads and trotters and rendering down to get lard and boil out gelatine for making jellies but also seal in potted meat. To preserve the seasonal excecess to store in the pantry to be used in the rest of the year. As well as killing grey squirles to get the bounty on their tails. Normal stuff for children prior and during WWII but my parents even though on upper midle class salaries, were frugal and prepared. So the power and energy supply strikes of the early 1970’s and reading by candle light reflected by tin foil and focused through a bottle of water were just things you did and the likes of hay box cooking of hearty stews etc and waking in the morning to find ice on the inside of the windows “normal”.

Now people who do this are given stange names like “preppers” as though they are strange weirdo more dangerous than “pot-head-hippies” and taffeta weaving “back-to-the-soil” hedge witches.

And this change for the worst has taken less than half a century…

[1] It is treated as a folk lore or myth by those that do not suffer from “weather bones” all that realy tells you is that they have probably not had a serious broken bone in their life. I can assure you, having had many broken bones in my time, including the almost unheard of in living people full fracture at the point of the lower jaw that they do definately ache with changes in the weather. The broken toes and fingers from sporting injuries “dull ache”, and the broken collar bone “hot aches” as for the lower jaw, people talk about having their teeth set on edge, imagine if you can your teeth feeling like they are trying to do an “ice-cream brain freeze” in very slow motion.