Question of the Week

Aug 242015
 
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I am sure you all spend some time at the beach when you were a kid. And I am also sure that your started digging holes in the sand when you were there. Or maybe you did something like that in your backyard. Anyhow, have you ever wondered how deep you would be able to dig? If you maybe could dig through the whole world? And if yes, why hasn’t anyone done this, yet?
Russian scientists tried this out for real between 1970 and 1994. They dug a hole, the Kola Superdeep Borehole, which got 12.2 km deep in the end.[1] Only being about one third of the thickness of the earth’s mantle, this is even deeper than the deepest point on earth, the Mariana Trench southeast of Japan, which is “only” 11.0 km deep. So why did they stop, when they already bested the Mariana Trench? Well, it just became too hot. The temperature in these depths is around 180 °C and this was obviously too much for the drilling equipment. So they just sealed up the hole and left it.
Is the story over here? No! Just recently the so called 2012 MoHole to the Mantle Project was started. It supposedly costs about one billion dollars. They adventurous plan: starting to dig at the bottom of the Mariana Trench, so the mantle to dig through would be thinner already in the beginning.[2] There weren’t any news after 2012. So, if the project was stopped, I cannot tell, but maybe the diggers just need to collect some courage (and more money).

Andreas Neidlinger

References:
[1] http://www.iflscience.com/environment/deepest-hole-world (last access 23.08.2015)
[2] http://science.howstuffworks.com/environmental/earth/geophysics/dig-hole-to-earths-mantle.htm (last access 23.08.2015)

Jul 092015
 
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Almost one year ago Facebook and Apple announced that they will cover the cost of egg freezing for their female employees [1]. Egg freezing is seen as a way to improve the success of a potential future in-vitro fertilization (IVF) procedure by using an egg that is years, even decades, younger than the mother. However, this approach is based on a not yet solid assumption: That a woman’s eggs are produced during fetal development and, as direct consequence, gain in age (and loose in fertility) with the woman that carries them [2, 3]. The age of first-time parents is rising in our time, which entails growth of the IVF industry that seeks to ensure fertility of women that are rather at the end of their reproductive age [4].

What if IVF could be circumvented by letting the body generate new eggs? This process would require appropriate stem cells that are able to divide. Whether such cells exist is still a matter of debate. In 2005 the group of Jonathan L. Tilly identified bone marrow transplantation as source for stem cells that restore fertility in sterilized mice [5]. The same group claimed to have identified actively dividing germ cells in the ovaries of reproductive age women, that were capable to develop into eggs [6].

The hoped-for natural substitute of IVF seemed found at last, but was soon challenged by Zhang et al., who could disprove the existence of dividing stem cell precurors in mice [7]. In fact another paper confirmed that mouse oogenesis originates from cells that are already formed at birth [8]. Thus the debate remains open, with some scientists claiming that “absence of evidence is not evidence of absence” [9]. Current evidence arguing for or against non-renewable ovary stores in mammals is reviewed in [10].

Felix Spenkuch

Read more:

[1] http://fortune.com/2014/10/16/fertility/ (called at 8.07.2015)
[2] S. Zuckerman (1951) The number of oocytes in the mature ovary. Recent Prog. Horm. Res. 6, 63-108.
[3] S. Zuckerman, T. G. Baker (1977) The development of the ovary and the process of oogenesis. The Ovary, Academic Press, New York, 41-67.
[4] http://time.com/money/2955345/high-tech-baby-making-is-fueling-a-market-boom/ (called at 8.07.2015)
[5] J. Johnson et al. (2005) Oocyte Gerneration in Adult Mammalian Ovaries by Putative Germ Cells in Bone Marow and Peripheral Blood. Cell. 122, 303-315.
[6] Y. A. R. White et al. (2012) Oocyte formation in mitotically active germ cells purified from ovaries of reproductive-age women. Nature Medicine, 18, 413-421.
[7] Zhang et al. (2012) Experimental evidence showing that no mitotically active female germline progenitors exits in postnatal mopuse ovaries. Proc Natl Acad Sci USA, 109, 12580-12858.
[8] Lei Lie and A. C. Spradling (2013) Female mice lack adult germ-line stem cells but sustain oogenesis using stable primordial follicles. Proc Natl Acad Sci USA, 8585-8590.
[9] D. Bhatiya et a. (2013) Ovarian stem cells: absence of evidence is not evidence of absence. J Ovarian Res, 6:65.
[10] C. B. Hanna, J. D. Hennebold (2014) Fertility and Sterility, 101, 20-30.

May 262015
 
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The Younger Dryas Event (YDE) is a climatological phenomenon that happened roughly 13,000 years ago. In a span of a few years, the temperature in Western Europe and North America dropped sharply and stayed low for over a millennium. The effect was more diffuse in northern America and less pronounced in the southern hemisphere.
Nonetheless, the YDE is associated with the mass extinction of large mammals in North America. At this time, humans had already spread around the globe and started civilizations. One of these civilizations was the so called Clovis culture that also vanished during the YDE. It is entirely possible that the extinctions coinciding with the YDE are not due to climatological changes, but rather human overkill [1]. The decline in mammal population in turn led to the decline of the Clovis. But as life is complicated, the activity of humans likely conspired with the changing climate to cause the extinction and the downfall of the Clovis.
In contrast to our current civilization, the people 13,000 years ago did not have the means to affect such dramatic climatic changes (going far beyond even our current level of climate change).

The question now is: what caused the YDE in the first place? A widely held belief is that the melting of the North American ice caps disrupted the thermohaline circulation (the ocean circulation that nowadays brings warm water from the Gulf of Mexico to Western Europe), by dumping large quantities of fresh water into the north Atlantic. In 2007 Firestone et al. proposed an interesting trigger for the melting of the ice caps [2]: An impact of an asteroid, or rather the explosion of an asteroid in the atmosphere. This would have been much stronger version of the 2013 Chelyabinsk meteor. Support for this hypothesis comes from the presence of nanodiamonds in the geological layers associated with the YDE. The only other strata where these diamonds are present is the K-T boundary that marks the global extinction event that killed the dinosaurs [3].

The impact hypothesis is however hotly debated [4]. Many of the original markers used to determine that an impact took place have later been discredited, as it turned out they can also be produced by earthly phenomena, e.g. volcanism. The markers left over on the other hand could not be consistently reproduced by other research groups. One problem is that different groups include different kinds of nanodiamonds in their analysis or use different calibration scales for the dating of samples. The uncertainty in the dating is often several hundreds of years so that it is not clear if potential impact markers have been deposited at the same time or in independent events. Additionally the uncertainty in the age of the samples makes it hard to pin them to the relatively narrow time frame for the beginning of the YDE. The impact event might thus have happened significantly before or after the onset of the YDE, or it might not have happened at all. After all new climate models suggest that the melting of the North American ice sheets could have occurred without a specific trigger such as the proposed impact.

So where are we left if the impact is not necessary to explain the behavior of the climate and the evidence for an impact is disputed? There is certainly the possibility that an impact took place without changing the climate, but the main question seems to be if the impact ever occurred.

Stephan Koehler

Read more:
[1] Samdom et al., Proceedings of the Royal Society B 281, 20133254 (2014).
[2] Firestone et al., PNAS 104(41), 16016-16021 (2007).
[3] Kinzie et al., Journal of Geology 122(5), 475-505 (2014).
[4] van Hoesel et al., Quaternary Science Reviews 83, 95-114 (2014).

May 122015
 
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Have you ever felt vertigo after a ride on a merry-go-round? Why can we feel this acceleration so intensively, while we do not notice at all that our very world does rotate around itself and rotate around the sun the entire time? This seems odd, considering that the Earth is travelling around the sun with a speed of approx. 30 km/s[1], while a merry-go-round is comparably slow with 8 m/s (see below).

First of all: What is “vertigo”? It is the perception of a (mock-)motion of oneself against the environment. Responsible for such cognition is the vestibular system which is able to recognise acceleration. In the labyrinth of this organ in the inner ear tiny hair is arranged in two planes: horizontal and vertical. It is embedded in a heavy matrix, which remains as it is in case of linear acceleration. Thus the hair experiences deflection and it comes to a sensory stimulus.

Rotatory acceleration is also recognized by sensory hair, which arranged in semi-circular canals which are filled with lymphatic fluid. If it comes to a rotation, this fluid remains (due to inertia) in contrast to the cranial bone. Thus the sensory hair is deflected and again we have a sensory stimulus.

So, now as we know about that, we need to clarify how the movement of the Earth is affecting us. The Earth carries out two kinds of movement: It rotates around the sun and around itself. If we assume a speed of 30 km/s (which is quite fast) and 365 days as a time period the Earth needs to travel around the sun, we can calculate an acceleration of approx. 1 mm/s2, which is very small, in deed. (For this calculation we neglect the fact that the speed is fluctuating.)

For the rotation of the Earth around itself we assume a perimeter of 40000 km. Since the rotation of the Earth around itself takes one entire day we have a speed of approx. 0.5 m/s and an acceleration of 5 μm/s2, respectively. This figure is even smaller than the one we calculated for the travel around the sun.

If we assume a merry-go-round with a diameter of 15 m and a velocity of 30 km/h the acceleration which the body experiences is 1.5 m/s2. This value is much higher than the acceleration of the Earth that is resulting from the travel around the sun and the rotation around itself.

I don’t know if I considered all effects that are somehow important to answer the question why we do not feel dizzy on our planet. But I think if one keeps in mind that it is not the speed but the acceleration that causes dizziness, the answer that I can give sounds reasonable.

Katharina Stockhofe

Read more:

[1] http://www.sternenhimmel-aktuell.de/Erde_Geschwindigkeit.htm

Apr 272015
 
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Covade syndrome can be defined as a psychosomatic phenomenon with little or no recognized physiological basis that affects male partners mainly during the first and third trimester of pregnancy and disappears early after the birth of the children. Determining the incidence rates of couvade syndrome has been problematic, as rates as low as 11% or as high as 97% have been reported which is in part attributed to a “Macho” culture in which men do not admit to symptoms to not appear weak. Also socio-demographic factors have been a matter of debate, as studies have reported a greater occurrence of the syndrome in men under 30, men over 30 and highly educated or working class men by different studies respectively. The matter is further complicated by the fact that different studies focused on different symptoms, physiological and psychological.

Infant holding fathers hand byClarence Goss (downloaded from https://upload.wikimedia.org/wikipedia/commons/a/a1/Got_You_Daddy.jpg)

Infant holding fathers hand by Clarence Goss (downloaded from https://upload.wikimedia.org/wikipedia/commons/a/a1/Got_You_Daddy.jpg)

Psychoanalytic, psychosocial as well as paternal theories have been put forward to explain the origins of Couvade syndrome. From psychoanalytic theories comes the idea that the man is envious of the ability of the woman to conceive children. The unconscious need to experience the woman’s pregnancy then manifests in psychosomatic pregnancy symptoms. Another view argues that the man fears to lose his partner to the baby and this might reactivate old sibling rivalry for the love of the mother. Psychosocial theories point out that men are often marginalized during pregnancy and birth, which might adversely affect the father’s health. Another theory postulates, that the pregnancy symptoms help the man prepare for his new father role in reinforcing the reality of the pregnancy. Paternal theories suggest that the emotional closeness to the unborn child is the cause of couvade syndrome. However, studies investigating the connection between couvade syndrome and either the involvement of the father in the pregnancy or anxiety levels in fathers have not shown clear results.

Physiological mechanisms underlying the syndrome might be connected to hormones, as men reporting Couvade symptoms showed higher prolactin and lower cortisol and testosterone levels.

But human males don’t seem to be the only ones experiencing pregnancy symptoms. Males in two species of monkeys (common marmosets and cotton-top tamarins), who are monogamous and caretakers of children gain up to 20% of their body weight during the pregnancy of their partners. While it is thought that the extra weight prepares the fathers for exhausting sleepless nights or carrying small children, it is not yet understood how the monkeys manage to gain weight.

Although numerous studies on how, where and why Couvade syndrome occurs, there is still not much we really know. Many of the studies are contradictory and the syndrome seems to be hard to pin down. We know that we are dealing with psychosomatic symptoms occurring during pregnancy, but for a deeper understanding, studies with large sample sizes investigating a multitude of physiological as well as psychological factors are needed.

— David Huesmann

Read more:

Brennan A, Ayers S, Ahmed H, Marshall-Lucette S. A critical review of the Couvade syndrome: The pregnant male. Journal of Reproductive and Infant Psychology, 2007, 25, 173 – 189

Ziegler TE, Prudom SL, Schultz-Darken NJ, Kurian AV, Snowdon CT. Pregnancy weight gain: marmoset and tamarin dads show it too. Biology Letters, 2006, 2, 181-183.

http://theconversation.com/couvade-syndrome-why-some-men-develop-signs-of-pregnancy-31881

http://www.spektrum.de/news/wenn-maenner-schwanger-werden/1316542

Mar 242015
 
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He chuckled. ‘That old line. You’re reading the wrong newspaper!’[1]

The statement “You read the wrong newspaper!” is an exclamation of exasperation and pity. When was the first time this statement was recorded in print or in any other medium? In which language was it stated? By whom? And why?

The first time I heard someone say “You Read the Wrong Newspaper” – in Dutch – must have been in the early nineteen-seventies. This was more an exclamation of exasperation and pity than a simple statement of fact. It was said because the speaker felt exasperation and pity for the reader of a liberal-conservative newspaper.[2] Later I heard and read the same phrase many more times. Mostly in the same unmistakably condescending way. The phrase was always deliberately used as a rhetorical device: a debate-stopper. Recently, in an ironic or a dialectic twist of history, I heard the same phrase spoken, this time by a liberal-conservative speaker to someone who ostensibly challenged his opinions and ‘facts’.[3] First I thought ‘The Times They Are a-Changin‘ once again, then I started wondering: from where does this phrase actually originate? When was it first recorded? In which language? By whom? And why?

Thus the Open Question became: Who First Said or Wrote: “You Read the Wrong Newspaper”?

Firstly, I conducted a quantitative Google search in three languages (English, German, Dutch). The results of the Google search (Germany, 20 December 2014, between 11:15 and 11:20 CET) are thus:

phrasing number of Google hits
“you read the wrong newspaper” 3,460
“you read a wrong newspaper” 0
“you’re reading the wrong newspaper” 796
“you’re reading a wrong newspaper” 7
“you are reading the wrong newspaper” 261
“you are reading a wrong newspaper” 0
“Sie lesen die falsche Zeitung 44
“Sie lesen eine falsche Zeitung” 0
“du liest die falsche Zeitung” 834
“du liest eine falsche Zeitung” 0
“U leest de verkeerde krant” 6
“U leest een verkeerde krant” 0
“je leest de verkeerde krant” 102
“je leest een verkeerde krant” 0

 

In all three languages the versions with the definite article (“the”, “die”, “de”) are more frequent than the versions with the indefinite article (“a”, “eine”, “een”) . Most of the time the version with the definite article is the only versions. In both German and Dutch the informal versions (“du”, “je”) are more popular than the formal versions (“Sie”, “U”). Apart from the very basic quantitative results the Google search did not provide qualitative data that could answer any of the four questions (where, when, by whom and why).

When it became apparent that the Google search had not yielded any answers, I consulted two relevant professors in Germany (University of Bamberg; Technical University of Dortmund) and one in the Netherlands (University of Groningen). I also contacted the Internationales Zeitungsmuseum in Aachen (Aix-La-Chapelle). Only the Dutch professor replied and he frankly admitted that, although he, too, had heard the phrase often been uttered, he did not know from where it originates.

Finally, as a last desperate measure, I contacted Dr Garson O’Toole of Quote Investigator and put the question to him. I have not received his answer yet.

The phrase “You read the wrong newspaper” may be connected with the Marxist term ‘false consciousness’. This term was introduced – in print – by Friedrich Engels.[5] Even though it was never clearly defined it meant something like “the material, ideological and institutional processes in capitalist society [that] mislead members of the proletariat”.[6] In the end it boils down to the idea that someone who does not share your opinions has as false consciousness. The idea is as old as mankind but the phrasing was new and sounded more scientific and with more revolutionary engagement than the flippantly relativistic ‘Well, that is what you think’. The relation between the phrase and the term may be via the German adjective ‘falsch’: “falsches Bewustsein” (false consciousness), “falsche Ideologie” (false ideology), and “Sie lesen die falsche Zeitung” (you read the wrong newspaper). If this were true that would mean that the origin of the phrase lies in the German language and probably in Germany itself.

320px-2003_newsagent_England_1205519685

 

 

 

 

 

 

 

Spot the ‘wrong’newspaper.[7]

This preliminary search did yield no answer. Thus the question: ‘Who First Said or Wrote: “You Read the Wrong Newspaper”?’ remains very much open.

Wolter Seuntjens
Dutch Academy of ’Pataphysics, Amsterdam

Notes and references:
[1] Sophie King, The Supper Club. London: Hodder & Stoughton, 2008, p. 414.
[2] This label – liberal-conservative – for what it is worth.
[3] At 12:35 of https://www.youtube.com/watch?v=9MHmsb17TH4 (last access 20.12.2014)
[4] http://quoteinvestigator.com/ (last access 20.12.2014)
[5] http://www.marxists.org/archive/marx/works/1893/letters/93_07_14.htm (last access 20.12.2014)
[6] http://en.wikipedia.org/wiki/False_consciousness (last access 20.12.2014)
[7] “2003 newsagent England 1205519685” by Dan Brady from Newcastle upon Tyne, UK – Toppling of Saddam – newspapers. Licensed under CC BY 2.0 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:2003_newsagent_England_1205519685.jpg#mediaviewer/File:2003_newsagent_England_1205519685.jpg (last access 20.12.2014)

Mar 162015
 
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Have you ever wondered why most people can tell which color they see but they most likely cannot label a note they hear without having a reference note? The second ability is known as absolute pitch (AP) or perfect pitch and is rather rare in Europe and North America. Only one of 10000 people possess this ability, e.g. some popular musicians such as Mozart. [1]

There already has been considerable interest and research about where AP stems from but it still is an unanswered question. By searching the internet you will find several websites telling you that they can teach you to get AP. But from a scientific perspective it is not proven that this is possible: Only one study has shown that a learning process of about 60 hours led to some kind of success. [2] This seems much of an effort compared to the essentially unconscious learning of AP in childhood.

There are basically three different explanations for the genesis of AP:

  • training makes it possible (this is what the websites mentioned above will tell you)
  • genes are responsible
  • learning is feasible but only if you start at a young age

The genetic origin of AP is supported by the fact that young children already possess it and that it is more likely to have AP if there are other family members with AP. Of course in the latter case it is possible that young children get “trained” by these family members and do not just have it in their genes. But in fact there is some scientific evidence that a specific part of the genome could – at least partly – be the reason. [3]

There are also reports about the benefit of an early start of musical training. Another distinctive feature is the linkage to the acquisition of speech in infancy. There are differences between speakers of nontone languages like English and tone languages, e.g. Mandarin or Vietnamese. Tone language speakers seem to have an advantage, which is possible due to some kind of training effect in tone languages: The meaning of some words changes if you use another pitch. So children that are speakers of a nontone language have to learn more about pitches when they start musical training.

Up to now we can only speculate that the right composition of these requirements could be the clue to gain AP.

If you want to test yourself, you should have a look at http://www.absolutepitchstudy.com/index.html.

 

Nicola Reusch

References:

[1] Deutsch, D. Absolute pitch. In D. Deutsch (Ed.). The psychology of music, 3rd Edition, 2013, 141-182, San Diego: Elsevier.

[2] Brady, P. T. Fixed scale mechanism of absolute pitch. Journal of the Acoustical Society of America, 1970, 48, 883-887.

[3] Elizabeth Theusch, Analabha Basu, Jane Gitschier, Genome-wide Study of Families with Absolute Pitch Reveals Linkage to 8q24.21 and Locus Heterogeneity, The American Journal of Human Genetics 85, 112–119, 2009.

Mar 112015
 
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A lot of people do have a cold at the moment. Most likely it is because of the chilly temperatures we have been experiencing the last few weeks. Or isn’t it? I have been watching it, while walking around in the streets, going on some bus or train, or even at the dinner table. Everywhere they are present: Smartphones! I myself own such a fine piece of 21st century electronics and do not want to miss it. But what I have been wondering about is: Will people who use their smartphones very intensely become sick more regularly?

What comes to mind in the beginning is the filthy screen. Just grab it out of your pocket or pick it up off the table and take a look at it. I bet you, it is not stainless. So basically what you do is, using it with dirty hands, hopefully wash them at some time, but do you also clean your phone? NO! And directly after sanitizing your hands, you touch it again, getting germs and whatnot directly back on your fingers, which will soon after, believe me, touch your face. Or think about it differently: When walking around, does it happen to you? All around you, people who look slightly down on their screens while crossing roads, doing grocery shopping, or walking their dog. They must bump into other people more frequently than the open-eyed pedestrian. Does that mean they are “attacked” by more germs because of their numerous contacts to each and every sick person than more careful people? Do they get sick more often?

Well, I cannot really answer this question, since I wasn’t able to find any study on this – must be a great View on Life for JUnQ for that matter. I could just find some tricks on how your smartphone can survive cold weather.[1] And some article from Sueddeutsche Zeitung from 2012 where they tell you about developers planning to bring out an app which allows you, after snotting on your phone, to detect which kind of cold you have.[2] I am so looking forward to everybody smearing their sputum on their smartphones! Anyhow, since our civilization hasn’t broken down, yet, I think we’re more or less off the hook. Maybe even the opposite is the case. I mean, your immune system has to be trained and might even develop allergies if not subjected to enough “real” enemies. So, do smartphone users, due to their increased exposure to germs, become more healthy and resistant? I can neither answer this question. Maybe they have more traffic accidents? So many open questions…

Andreas Neidlinger

References:

[1] http://edition.cnn.com/2013/12/13/tech/mobile/cold-weather-phones/ (last access on 04.03.2015)

[2] http://www.sueddeutsche.de/gesundheit/technik-fuer-die-erkaeltungszeit-dem-smartphone-was-husten-1.1265829 (last access on 04.03.2015)

Mar 022015
 
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An increase in obesity in the population is one of the problems many industrialized nations face today. Along with rising levels of obesity come many other health concerns such as heart disease that are frequent causes of death. Often the rise in obesity is attributed to the sedentary lifestyle many people in the afflicted societies have adopted. Fewer people have physically demanding jobs or exercise on a regular basis while the access to food high in calories has become easy and cheap.
But obesity does not just afflict adults, but children as well. Interestingly children younger than five years of age have a slightly lower chance of being overweight than they did twenty years ago. This changes as they get older and with eight years the rate of overweight children has nearly doubled compared to the past. The sharp increase in weight happens right around the time when children start school. So what is it about this time in their life that leads to the increase in weight?

– Stephan Koehler

Read More:
S. Hoffmann, R. Ulrich, P. Simon: “Refined Analysis of the Critical Age Ranges of Childhood Overweight: Implications for Primary Prevention”, Obesity, 012

Feb 182015
 
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DIN

Logo “Deutsches Institut für Normung” (downloaded from https://upload.wikimedia.org/wikipedia/commons/4/4c/DIN-Logo.svg).

All over the world, Germans are known to be very order-loving and well-organized people. Even if this might not be true for everyone, there is a standard for almost everything in Germany. At the moment, there are about 32,500 DIN standards and the number is ever growing.[3] We all know our DIN A4 notebooks from school and we know that a sheet of DIN A4 paper will fit into most printers. We also know that when we buy screws with the right thread standard, we will be able to put together anything without problems. But standards are not only limited to physical things, there is a plethora of other cases where standards are important, which are non-physical as for example the DIN 1505 which regulates title details in documents.[1]
So what else is there to know about DIN norms? DIN stands for “Deutsches Institut für Normung”, which means “German Institute for Standardization” and was already founded in 1917 in Berlin as “Standardization Committee of German Industry”.[2] Despite what many may think, DIN norms are not obligatory and are only to be understood as guidelines. Nevertheless, they can influence jurisprudence even if they are not laws in the common sense. As soon as they are cited in contracts, laws or regulations, they become binding.
So what is it that we Germans like so much about DIN standards? Well, a very simple explanation would be that it makes life a lot easier most of the time. In addition, DIN standards contribute with roughly 17 billion Euros[3] to Germany’s gross domestic product, because they remove trade restrictions and the proverbial quality of German workmanship (“Deutsche Wertarbeit”) has helped build the good reputation of Germany after the two world wars. Something “Made in Germany” stands for something with high quality and value. Also, the world known bavarian purity law (“Reinheitsgebot”) concerning the production of beer in Germany established in 1516 fits into this context. But do we really like DIN standards so much because they make life easier or because we simply like making them? To strengthen the latter: there is even a DIN norm for the term “norm”: DIN EN 45020.[3]

— Kristina Klinker

Read more:
[1] http://de.wikipedia.org/wiki/DIN-Norm
[2] http://www.din.de/cmd;jsessionid=JRRFPOOXMEZ6ZMPMSXPTUMG3.3?level=tpl-bereich&menuid=47391&languageid=de&cmsareaid=47391
[3] http://www.planet-wissen.de/politik_geschichte/wirtschaft_und_finanzen/normen/index.jsp
[4] http://www.faz.net/aktuell/wissen/din-normen-die-ordnung-der-dinge-11925078.html
[5] http://www.arbeitsratgeber.com/die-din-normen-standards-fuer-die-wirtschaft/