Thursday Thirteen #40

1. One second is measured by the light emitted from an atom of Caesium (CS-133), the frequency of the light is 9,192,631,770 hertz (Hz = cycles/second), which means when that many oscillations of the light particle have taken place one second has passed.

2. The kilogram is the only unit of measurement that is still determined by a single physical standard. Originally it was defined as the weight of one litre of pure water at regular conditions (pressure, temperature etc), but that was problematic in practice so a kilogram is considered to be equal to the international prototype of the kilogram, which is made from an alloy of platinum and iridium. It’s cylindrical in shape, 39mm high and 39mm in diameter and is kept at the International Bureau of Weights and Measures near Paris.

3. From 1889 to 1960 a bar made of an alloy of platinum and iridium was the International Prototype Metre. These days it’s measured by the distance traveled by light in a vacuum, it is presumed that the speed of light in a vacuum remains at 299,792,458 metres per second.

4. Avogadro’s Number can be used to determine the number of atoms or molecules in something. It’s 6.022×10²³/mole. A mole is just a term used to describe an arbitrary amount, so if I have one mole of carbon weighing 12.01 grams (which is the atomic weight of carbon) then I have 6.022×10²³ (or 602 200 000 000 000 000 000 000) carbon atoms.

5. The freezing point of Ethanol is -114 degrees celcius. That’s low! I was curious what it was because we keep Ethanol in a -20 freezer and it doesn’t freeze, I didn’t expect it to be that low!

6. A spirit level, that various kinds of tradesmen use is so called because it contains a coloured spirit. It usually contains ethanol so it doesn’t freeze in cold weather.

7. Why is lieutenant pronounced ‘leftenant’ in England and supposedly Australia? There is no other word (that I can think of) that makes that sound with those vowels. I can see how a language foreign to me such as Gaelic or Welsh would make a sound but why should we say it like that?

8. There are some vitamins (A, D, E and K) that are fat soluble. That means that if you’re trying to lose weight quickly by taking pills that prevent absorption of fat in your digestive system, you could cause other problems. Those vitamins won’t be absorbed, which means that you’ll get less calcium intake (whose process is assisted by Vitamin D); you may get a dry throat, mouth, nose and lungs (if lacking Vitamin A); and if you get a cut you don’t want to be lacking too much Vitamin K as it helps blood to clot. [Don’t go crazy taking vitamins because I told you these were good, your body stores them and gets enough from your diet, unless you eat no fat at all. I wonder if Jack Sprat had rickets…]

9. The phrase “Shoot the puppy” is similar in meaning to “Bite the bullet”. It means to do something that you’ve been putting off or didn’t really want to do.

10. Cows can’t actually digest grass on their own. They have symbiotic organisms (bacteria etc) in their gut that help them to break stuff down.

11. Possums, when they are born don’t have the digestive organisms that they need in their gut, so when they’re young they eat their parents poo.

12. I discovered yesterday that Command/Apple+right on a Mac is the equivalent for “end” on a standard keyboard and Command+left is the same as “home”. Handy to know 🙂

13. Irrational numbers are numbers that can't be expressed as a fraction (e.g. 1/1, 1/2, 3/4, 28/50). They have decimal expansions that don't terminate and that don’t become periodic (i.e. they don’t repeat like 1/3 = 0.33333…). There are infinitely more irrational numbers than rational numbers.

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