Fabian R Lischka bio photo

Fabian R Lischka

Buenos Aires, Moers, Karlsruhe, Warwick, London, Palo Alto, Hong Kong; Goldman, Credit Suisse, HackerSchool, metric system, The Economist.

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I just want to explain why I am a big fan of SI units (the metric system), and the ISO date format.

First, the metric system. It is so simple and elegant. Consider some examples: If an airplane has a glide ratio of 1:10, it can glide 10 metres for 1 metre of altitude loss. Now, I am 1.5 km high, and I have an engine failure. How far can I glide? Well, 1.5 x 10 = 15 km. Ok, I can reach that airport, time to go through the checklists. Or that's what it were if the metric system were used. In reality, it is 4500 ft high. So, how far can it glide? Well, 4500 x 10 ft = 45000 ft, that's easy enough, but distances are in nautical miles, so that's 45000 divided by, what, let me try and remember, err, it's about 6070 ft per nautical mile, so that's 45000 by 6076, so that's about 450 by 6.076 or about, let me think, err, 7.5 plus minus a few percent, except by this time I've already lost some 500 feet altitude and now it's only, err, wait, about 6.5 nautical miles. 

Note, by the way, that there is a straightforward way to convert between nautical miles and kilometres, namely: 100 km = 54 NM. Why? Because the metre was chosen such that the distance from pole to equator is 10000 km (that's why the circumference of the earth is about 40 Mm (megametres)). On the other hand, a nautical mile corresponds to one arc minute of latitude. But there are 60 minutes per degree, and 90 degrees in a right angle, and from the equator to the pole is just a right angle, i.e. 90 degrees, or 90 x 60 = 5400 arc minutes. Thus, 10000 km = 5400 NM. In practice, this is approximate, because the earth is not quite round.

Next, suppose I want to buy a cheap orange juice. I have one bottle with 2 litres, one with 250 ml, and another with 1.5 litres. I can convert the 250 ml into litres: It's 250 / 1000 = 0.25. Now that was hard. Now I just divide the respective prices by the respective volume (2, 0.25, 1.5), and can choose the cheapest one. Except if I'm in the US. (According to wikipedia, the only 3 countries in the world that do not officially use the metric system are the US, Liberia, and Myanmar. I haven't been to Liberia, and in Myanmar I got fresh juice, not bottled, and given that the country is going through a phase of positive development, I am sure they'll switch to the metric system before long). So, in the US, one bottle will have a half gallon, the other one 3 pints, the next one 10 ounces, and the next one 2 quarts. How to determine which one is cheapest? I have no idea, and I don't really care. Maybe that's why they do it. 

Let's look at energy consumption of humans vs cars. An average human eats about 10 MJ (mega Joule) a day, that's 10 000 kJ in one day or 86400 seconds, so let's just call it about 0.1 kJ  = 100 J (more or less) per second. Now, a Joule per second is just a Watt, so we humans burn around 100 Watt. That's about as much as a bright light bulb. A car, on the other hand, has about 100 kW, so uses in the vicinity of thousand times as much as a human. Try to reach that conclusion using calories and horse power.

As for dates, my preferred date format is YYYY-MM-DD, eg 2013-02-20. It has several advantages:

  • it is unambiguous. 2013-02-20 means 20th February 2013. What does 06/07/08 mean? The DD/MM/YY and MM/DD/YY date formats are particularly reprehensible to me, due to this ambiguity. Why continue to use them? (I have missed meetings, because an international organisation thought it wise to send invitations to a meeting in London on "3/4/2001", which took place in March, not April, when I had filed it.)
  • alphabetical order coincides with chronological order. If I name my files "Bank Statement 2012-02-20", "Bank Statement 2012-01-21" etc., and then sort them by name, they are also sorted by date. If I name them "Bank Statement 20 Feb 2012", or "Bank Statement 20.02.2012", and then sort them by name, they will not be sorted by date, but in some mess.
  • it is in line with the way we write time: in 19:15:00, we have the largest unit (hours) first, then the middle unit (minutes), then the smallest unit (seconds). If we were to write time the US way, we'd write 15:00:19 (or, given that it's the US, 15/00/7p), while the continental European way would be 00.15.19. How much nicer to write 2013-02-20 19:15:00 (note how that this way, alphabetical order coincides with chronological order even including time, because we progress from biggest to smallest unit (assuming of course that you use the 24h clock))!

This gets to my last point: How civilised is the 24h clock! A day starts at 00:00:00, progresses via 00:00:01, later 11:59:59, 12:00:00, 12:00:01, and 23:59:59 to end at 24:00:00, which is also the 00:00:00 of the next day. (Ignore leap seconds for now). No messing with am and pm, and in particular no messing with the question whether noon is 12 am or pm. And if there is a deadline for midnight of the 10th February, it is 2012-02-10 24:00h. Done. No ambiguity with the question as to what day it is, or whether it's noon or midnight. A flight could depart on 2012-02-11 00:00h, at the same time as the deadline. In the US, your deadline would probably be shortened by a minute to 2/10/12 11:59p, robbing you of a valuable minute to finish things, while your flight would be delayed a whole minute to the exceedingly ugly 2/11/12 12:01a.

Note that the YYYY-MM-DD format is also the international standard (as highlighted by the wonderful xkcd).

To conclude, I have nothing against necessary compromise, and can understand evil that benefits at least someone. But unnecessary, useless, and ugly evil, such as "2/11/12 12:01a"? How revolting.