2019-06-21 (Midsommarafton)

Today, I learned that:

Today is the brightest day of the year on the Northern hemisphere, it is the day of the Summer solstice. You may remember that I already wrote about it briefly three years ago, on 2016-03-20, but here are some more interesting facts:

1. Summer solstice

The Summer solstice is the day of the year when one of the Earth’s hemispheres is located as close to the sun as possible. On the Northern hemisphere it happens around June 21 and on the Southern hemisphere around December 21. As a consequence, this is also the longest day of the year, considering the time from sun rise to sun set. But it also means that on the opposite hemisphere, it is the shortest day of the year. Read reference # 1 below for more information about the solstice.

So, which is the difference in duration of daylight in a particular place, if we compare those two dates? Well, the closer you live to the North Pole or the South Pole, the bigger the difference in time. You have probably heard about the expression “Midnight sun”, which is a phenomenon observed by those who live within the Arctic circle. As an example, in Kiruna, the northernmost city in Sweden, this year its habitants are lucky to have days with 24 h daylight from May 28 all through to July 16, a total of 50 days! But at the time around the December equinox, it is of course the opposite. From December 11, 2019 to January 1, 2020, during a total of 22 whole days, the Sun does not appear above the horizon not even a single minute!

And the closer one lives to the Equator, the less difference in time between the longest and the shortest day of the year. As an example, in Manaus, the capital of the Brazilian state of Amazônia, located 2 degrees South of the Equator, the difference is only 22 minutes, and in Macapá, the capital of the Brazilian state of Amapá, located exactly on the Equator, every day in 2019 is 12 h 7 min long. In my town Paranavaí, located slightly North of the tropic of the Capricorn, thus within the tropics, today is only 10 h 43 min long, whereas on December 21 it will be 13 h 34 min, a difference of 2 h 51 min. Reference #2 below has a link to a site that gives such information for any place on Earth, well worth studying.

2. UTC #1

And speaking about time, maybe you have noticed that the old abbreviation GMT (which stands for Greenwich Mean Time) is more often these days exchanged to UTC, how come?

I believe it is a matter of jealousy. Although the time settings for the globe are maintained within a zero meridian passing through the Greenwich observatory in UK, why should the British people have the privilege also to the name? So instead, UTC was introduced. Now, what does UTC stands for, exactly?

The fact is that it is a fabricated “abbreviation” involving English and French. Some centuries ago, the French had their own zero meridian for time, passing through Paris, but they had to succumb to Greenwich in that sense. So, as a compromise, they managed to enforce the denomination UTC. In English it would be similar to “Coordinated Universal Time” (CUT), and in French “Temps Universel Coordonné” (TUC), so UTC is not a bad compromise. Reference #3 has the whole story about it.

3. UTC #2

While I was doing research about UTC #1, I remembered that UTC is also the (real) abbreviation of a technical university in France, where I studied in the 1970s. I already wrote something about it on 2017-11-11, but here comes more. This UTC means Université de Technologie de Compiègne. It is a technical university belonging to the French state, created in 1972, and since 2012 it makes part of the group of Sorbonne Universities. It has a reputation of being more integrated into the society, with frequent trainee periods in the French industry, as well as many interchange programs with other international universities, than the traditional theoretical French technical universities, e.g. École Polytechnique.

I studied there between September, 1978 and June, 1979, exactly 40 years ago. During that year happened an interesting fact, a group of students from China came to study at our university. It was a sensation at that time, because China was extremely closed to external activities. This photo shows the Chinese students, taken in February, 1979. They have since kept the contact and met year after year and update themselves. See also reference # 4 below. At the bottom of that page you can also find the complete magazine edition of April 2019, both in French and English.

The group of Chinese pioneers who studied engineering at Université de Technologie de Compiègne, France. This picture was taken in February 1979, when they has just arrived at the university.

4. ISS flies over Paranavaí

The sensation today here in my home town was the passing of the international space station (ISS). I had heard about it before, that it would be possible to see it with the naked eye, but never had the chance to actually see it. See also reference #5 with the announcement.

Update on 2019-07-12

Today we had a chance of viewing the ISS even better and for longer. And it did not hurt at all that the moon was eager to also play a vital part of the scene, being half way between the crescent and full moon phases. See the photo below. Reference #6, which tells the ISS passing date and time for any location on the earth, said the following about this event:

A photo of the international space station en route passing over Paranavaí, PR, Brazil. The ISS is the small dot you can see up in the left corner, appearing together with an almost full moon. This photo was taken on 2019-07-12 at 19.25 local time.

That’s what I learned in school !

Refs.:

1: Solstice

2: Kiruna, Sweden — Sunrise, Sunset, and Daylength, June 2019

3: Coordinated Universal Time

4: Des étudiants chinois à l’UTC depuis 40 ans

5: Estação Espacial poderá ser vista novamente no céu de Paranavaí

6: 10-day predictions for satellites of special interest

*: What did you learn in school today ?

2016-02-21 (Sunday)

Today, I learned once more that:

One of the most abstract things in our world is also something that we rely on the most. I am thinking about the so-called fourth dimension, time. Due to the earth’s rotation around its own axis, the world has been divided into 24 time zones, with the meridian that crosses the Greenwich observatory in England used as a starting point for the division, and thus establishing Greenwich Mean Time (GMT), nowadays mostly named Coordinated Universal Time (UTC).

Due to its subcontinental size, Brazil has four different time zones, which are related to the official Brazilian time in the Federal capital of Brasília. The following times apply as standard times:

  • Brasília time – 2 h (UTC-5 h): State of Acre, and the Southwestern part of the state of Amazonas. The proportion of people living here is only 0,5 % of the country’s whole population (a little more than 1 million people). This time zone covers only about 6% of the Brazilian territory (although it is about the size of France).
  • Brasília time – 1 h (UTC-4 h): States of Mato Grosso, Mato Grosso do Sul, Rondônia, Roraima, and the rest (main part) of Amazonas. 5% of the country’s population live here (about 11 million people). The area is big, 34% of the land area of Brazil (thus larger than Argentina).
  • Brasília time, BRT (UTC-3 h): Federal District (which includes Brasília); and also the states in the Southeast Region ( Espírito Santo, Minas Gerais, Rio de Janeiro, and São Paulo); the South Region ( Paraná, Rio Grande do Sul Santa Catarina, and Rio Grande do Sul); and the Northeast Region ( Alagoas, Bahia, Ceará, Maranhão, Paraíba, Pernambuco, Piauí, Rio Grande do Norte, and Sergipe) as well as the states of Amapá, Goiás, Pará, and Tocantins. Almost 94% of the whole Brazilian population live in this time zone, which also covers about 60% of the country’s land area.
  • Brasília time + 1 h (UTC-2 h): A few small offshore Atlantic islands, namely Fernando de Noronha, with 2,837 inhabitants and 0,0014% of Brazil’s population, an the non-populated islands of Trindade, Martim Vaz, Rocas Atoll, and Saint Peter and Saint Paul Archipelago.

The reason I am mentioning this today is that yesterday at midnight in Brasília, some of the states mentioned above, namely the Federal District and the 10 Southernmost states (Rio Grande do Sul, Santa Catarina, Paraná, Mato Grosso do Sul, São Paulo, Rio de Janeiro, Espírito Santo, Minas Gerais, Goiás, and Mato Grosso) ended the period of Daylight Savings Time (DST), also called Summer Time, that had been valid since October 18, 2015. The population in those areas account for 64 % of the total Brazilian population.

DST was used in Brazil for the first time in 1931, but from then on there was no consistency in when it was applied. It was only in 1985 that DST was instituted and followed on a regular, annual base, normally between the third Sunday of October and the third Sunday of February the subsequent year. However, Carnival and general elections have influenced on different start and end dates on some occasions.

One interesting observation that can be made is that the change always happens around midnight Brasília time, which creates a big confusion about which day it is at a given time. To me, the European rule of making the change at 02:00 / 03:00 seems much more logical.

However, there are people that oppose to the use of DST. As an example, there are currently three different propositions in the Brazilian Congress that want to forbid the use of DST. One of those propositions was written by congress man Valdir Colatto from Santa Catarina. Here are his arguments:

  • An institute of cardiology performed scientific tests about how DST affects the people, and they found an increase in health problems, from hypertension to diabetes, sometimes also depression.
  • During DST, the children learn less in school, because they have to wake up earlier.
  • He normally needs to wake up at 04:30 on Monday mornings, so that he can take a plane from his home town, Chapecó, to Brasília an hour later. During DST, he has to wake up at 03:30 solar time, an hour earlier due to a decree from the President of the Republic.
  • He responds to the official argument, that the use of DST saves energy, that nobody notes that difference in their electricity bill.
  • According to him, a survey performed on the internet resulted in that 80 % of those that responded to the survey said that they were against the use of DST.

 

Solution to Riddle # 1 (Two blind men), posted on 2016-02-19

When the socks are sold in the store, they are also grouped together in pairs. Thus, it is easy to grab one pair, separate the socks and place one each in each of the two men’s bags. Continue doing so, and eventually you will have two blue socks, two red socks, two pink socks, two green socks, and two orange socks in each bag.

I have already told this riddle to many people, but only one person could ever solve it, and it took only 15 seconds! This is a tribute to my good old friend, the chemist John Snyder, one of the most intelligent people I know!

The riddle was first proposed by Kim Nasmyth, Professor of Biochemistry at the University of Oxford, to explain how chromosomes divide in cell division, see reference # 3 below.

Riddle # 2 (The pill roulette)

You suffer from a temporary disease, which you have to treat by taking one pill every day during seven days. So the pharmacist took your order and gave you the pills. You are just about to take the first pill, when you receive a telephone call from the pharmacy.

You are informed, that the attendent mistakingly gave you eight pills, the seven you need and also an eighth one, that has the same appearance as the other. But it is poisonous and furthermore it weighs a little bit more than each of the other seven, undetectable by assessing it in your hand, but sufficient to be determined by a precision scale.

Luckily, you are in a laboratory which has such a scale, an old analogue weighing scale with two pans for high precision weight measurement. The problem is that you will only be able to perform two measurements, after which the scales will not work any more.
Here is a drawing of the scales you can use:

two-pan-balance-scale

A two-pan balance scale to be used in riddle # 2

So how do you solve this riddle, to identify and discard the poisonous pill, with only two comparative measurements? A solution to this riddle will be published next Saturday, 2016-02-27. The first person that comes across the correct solution and sends it to medieborgaren@sjson.com will receive an honorary mention.

… That’s what I learned in school !

Refs.:

1: Time in Brazil

2: Horário de verão acaba à meia-noite deste sábado

3: How chromosomes split in cell division

+: What did you learn in school today ?