Question of the Week

Feb 152016
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Tinnitus – the non-stopping auditive experience – is a well-known malady. Patients with tinnitus hear sounds even though no source of this acoustic impression is present; at least not outside of the brain.[1] The source of the sound is in fact inside the brain, which is proven by several observations. Firstly, patients whose acoustic nerves have been severed still “hear” the sound. And secondly, the acoustic sensation is independent of the position of the ears. Both facts do not comply with regular sounds. Furthermore, EEG analysis showed that neuronal activity is altered in tinnitus patients.[2]

In the current Question of the Week, however, I do not want to focus on tinnitus, but on another similar phenomenon: The Hum. First mentioned in the 60s of the previous century, the hum has been detected around the world.[3] But what is this hum? People who complain about it “hear” a low-frequency humming sound similar to a diesel engine or a turbine without any physical source.[4] But what is the difference compared to regular tinnitus? It displays some dissimilar properties like varying volumes depending on the location of the patient and modulation, e.g. it is not perceived as a single tone but more as a vibrato like sound.[5]

So if it is not tinnitus, what is the reason for the hum? There are a variety of speculations. Most of them assign the hum to electromagnetic fields emitted by modern technology like mobile telephones of sending masts as well as Wi-Fi networks. But this cannot be the (only) case, since the hum was already described before these technologies existed. Until now, no unambiguous explanation for the hum exists, but it is mainly described in high-technology societies like Europe or Northern America.[6] This however might just be accounted to limited data from other countries of the world. In fact, the hum is still an unsolved question and it remains unclear if it indeed has an origin which waits for its detection or if it is just the imagination of the patients.

– Andreas Neidlinger

[2] I. Adamchic, B. Langguth, C. Hauptmann, P. A. Tass, Front. Neurosci. 2014, 8, 284.

Feb 082016
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The Voynich manuscript is probably one of the most prominent and mysterious examples of a document of yet undeciphered content. It is named after Wilfrid Michael Voynich who discovered and acquired it in 1912. The origin of the manuscript most likely lies in the 15th century as suggested by radio carbon analysis, but neither its authorship nor the complete ownership history can be recovered. The first known possessor was Jakub Horcicky de Tepenec, a 17th century bohemian chemist, pharmacist and physician at the court of Emperor Rudolf II. After several intermediate owners – amongst others, the Jesuit College and the already mentioned Wilfrid Michael Voynich – the manuscript today is in the possession of Yale University’s Beinecke Rare Book and Manuscript Library.

The Voynich manuscript is written in none of any familiar languages, containing an unidentified writing system with unkown letters and a huge amount of mysterious illustrations, such as drawings of obscure plants or bathing women. Derived from the arrangement of these illustrations, it is usually divided into a herbal, an astronomical, a biological, a cosmological, a pharmaceutical and a recipe section.

Fig. 1: An illustration from the herbal section of the Voynich manuscript.[4]Fig. 1: An illustration from the herbal section of the Voynich manuscript.[4]

Despite many attempts, the Voynich Manuscript has never been deciphered and its content is still left to speculation. Nevertheless, many theories about its origin and meaning have been proposed. Some suggest that the artificial language is based on actual Latin or German, alienated by several encryption steps. Others point out that the variation of letters shows similarities to Semitic languages. The number of hypothesized authors include Roger Bacon, a 13th century Franciscan friar and polymath, Antonio Averlino, a 15th century North Italian architect, Raphael Sobiehrd-Mnishovsky, a 17th century Bohemian writer and many more – even Voynich himself, Leonardo da Vinci or aliens!

In the last decades of Voynich research, some scientists suggested that the whole manuscript is an elaborate hoax without any real meaning. For example, in a study published in Cryptologia, the Austrian physicist Andreas Schinner suggested that the order of words within the manuscript is of unnatural regularity.[1] Yet, an obvious argument against the hoax theory is that the manuscript is too complex and required too sophisticated work to just be a fraud.

A more recent study published by the physicists Marcelo Montemurro and Damian Zanette in PLoS One also points to the non-hoax direction.[2] It involves an analysis of the long-range word distribution in the manuscript using methods from information theory. In contrast to the earlier study of Andreas Schinner, Montemurro and Zanette found out that the word distribution is not homogeneous, but similar to natural languages in showing certain patterns and clustering. For instance, specific clusters of words can only be found in specific sections of the text. Moreover, word frequency obeys Zipf’s law, another hint that the writing system is based on a natural language.

In 2014, Stephen Bax, professor of applied linguistics at the University of Bedfordshire, proposed a translation of 10 words of the manuscript by applying a “bottom-up” approach like the one already used for decoding of the Egyptian hieroglyphs.[3] More specifically, he compared several of the Voynich manuscript’s illustrations of plants and stars with drawings in other European and Middle Eastern medieval manuscripts to identify them with their names and put these names into association with proper nouns within the text. In this way, he for instance, was able to find the alleged word for the constellation Taurus.

Still, it remains to be elucidated if Stephen Bax’ approach will eventually lead to a meaningful translation of the Voynich manuscript and if its secrets will ever be revealed.

– Philipp Heller

[1] A. Schinner, “The Voynich Manuscript: Evidence of the Hoax Hypothesis”, Cryptologia, vol. 31, no. 2, pp. 95–107, Mar. 2007.
[2] M. A. Montemurro and D. H. Zanette, “Keywords and Co-Occurrence Patterns in the Voynich Manuscript: An Information-Theoretic Analysis.”, PLoS One, vol. 8, no. 6, p. e66344, Jan. 2013.
[3] S. Bax, “A proposed partial decoding of the Voynich script”, Version 1, Jan. 2014

Jan 312016
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As we all learned in our childhood, solid rocks belong to the abiotic environment and cannot move by their own selves. They have no will of their own and besides, no locomotor system.

The rocks in Racetrack Playa, located in the Death Valley National Park in south-west USA – a hostile place of annual heat records (the hottest temperature on earth since recording was measured in the Death Valley in July 1913 and came to 56.7°C)[1] – however seem to overrule this fundamental law of biology.

The name Racetrack Playa is no accident: over decades, tens to hundreds of rocks have been found with tracks behind them as if they were slowly sliding leaving grooves in the dusty soil (left picture). The tracks are often parallel and run in the same direction looking as if the rocks were participating in a slow-motion race (right picture).


Rock with a distinct track (left)[2] and aerial image of rocks moving in the same direction (right)[3].

This phenomenon was first discovered in 1948 and started versatile speculations about its origin. Some of the rocks weigh more than a hundred kilos, so help by humans is only possible with heavy equipment but no such traces can be found around them. Mud and even slime-producing algae as well as the weather were considered.[4]

Wind in conjunction with ice floes, as the most possible critical factors for rock movement, were supposed for years but no direct observation was made since studying in person is not recommended due to the temperatures and the restricted access in the Death Valley. But during the winter of 2013/2014, the group of Richard D. Norris and James M. Norris was able to monitor the motion using GPS in combination with information from weather stations.[5] Several rocks were provided with GPS transmitters and the area was observed by time lapse photography. Between November and February most of the Playa was covered by a shallow rainwater pool which froze at night-time. During sunny and windy days the ice melted partly and the rocks were driven on their ice sheets by the wind and running water. On this occasion, they pushed the mud beneath them aside forming long flat furrows. Some rocks only glided a few meters, some travelled up to 66 m and some shared an ice sheet which produced parallel lines. Under some rocks, the ice was already crushed so they showed no movement at all. At the end of February, the temperatures rose, the water evaporated and the spurs were exposed. Norris’ results prove that freezing temperatures for the formation of ice sheets and wind forces of 3-5 m/s are necessary for a rock movement of 2-5 m/min whereas the velocity is also dependent on the individual texture of the stone’s surface and weight.[5]

This is an excellent example of a long unexplained phenomenon that finally found elucidation by rigorous research. Do such allegedly mysterious occurrences lose their charm by an objective, scientific clarification like this? No! On the contrary, they show how complex and versatile the interactions of nature’s mechanisms are even by such a peculiar phenomenon as the wind-driven “wandering” rocks in the desert.

– Tatjana Daenzer

Read more:
[2] “Runningrock2” by Tahoenathan – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons –
[3] “Racetrack playa 2013-12-20” by Richard D. Norris, James M. Norris, Ralph D. Lorenz, Jib Ray, Brian Jackson. Licensed under CC BY 1.0 via Wikimedia Commons –
[4] R. P. Sharp, D. L. Carey, J. B. Reid, P. J. Polissar, M. L. Williams, Geol. Soc. Am. 1996, 765–767.
[5] R. D. Norris, J. M. Norris, R. D. Lorenz, J. Ray, B. Jackson, PLoS One 2014, 9, 1–11.

Jan 242016
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“Many will swoon when they do look on blood.” (Shakespeare, As You Like It, Act IV, Scene III)

Some people know this phenomenon only from movies, TV shows or books. Others from relatives, friends or even themselves: The terrible weak feeling of fainting that is triggered by the sight of a large amount (or sometimes even just single drops) of blood. Such people are, in most cases, not suitable for donating blood, not to mention, work in emergency rooms in hospitals.

But where does this strong reaction come from? Is it even good for anything?

First of all, we are talking of the so called blood phobia, also known as hemophobia. It is part of a whole group of blood-injection-injury phobias (BII), as categorized by the Diagnostic and Statistical Manual of Mental Disorders (DSM) [1].

The general consensus behind the cause of exaggerated blood phobia, which results in vasovagal responses, is that they originate from the psychological traits of an individual rather than from their genetic heritage. It seems, for example, sometimes to be caused by childhood traumata [2]. On the other hand, twin studies suggest that there might also be certain genetic predispositions which are common for phobias in general [3].

Anyways, are there any explanations? Indeed, there are three more or less fascinating ideas that could hold the key:

(1) The danger theory: Seeing blood is an alarm signal. So when we start feeling weak, we automatically seek for a safe place to rest and/or hide. This would of course only make sense, if the process of fainting takes some time, allowing us to act.
(2) The “play dead” theory: During stone-age, some predators were not interested in paralyzed preys. They would actually wait for a person to flee, only to follow them. Good for the people with hemophobia during those ancient hunts!
(3) The self-healing theory: The blood pressure decreases during fainting. An injured person could thereby slow down the blood loss and instead support the blood coagulation.

Whatever the true origin might be, nowadays the fear of blood is nothing more than annoying. But luckily, as with any phobia, blood phobia can be cured [4].

-Jennifer Heidrich

[1] Lipsitz et al. (2002), The Journal of Nervous and Mental Disease 190(7): 471-478.
[2] Thyer et al. (1985), J. Clin. Psychol., 41: 451–459
[3] Kendler et al. (1992), Arch Gen Psychiatry; 49(4):273-281.
[4] Sanford, J. (2013), Stanford Medicine, Spring 13.

Jan 122016
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This might seem to be a very odd question at first, because we practically know everything about particles, atoms, molecules, and their sizes, right?
When we are in school, we learn that an atom is composed of a nucleus, which is very small in comparison to the atom itself and is surrounded by a “cloud of electrons”. This description implies already that we cannot be sure, where the electrons actually are; we describe this fact as electron densities, thus entailing that an atom does not have clearly defined edges. In theory, an electron can be found in any distance from the nucleus, but the probability decreases substantially when you go farther away. This is the case because of what we call wave-particle dualism.


Figure 1: Visualization of a Helium atom.(downloaded from

An electron behaves like a particle as we know from classical physics, but due to its very small size, an electron can also be described as a wave following the laws of quantum mechanics. Among other methods, people have used a type of scanning probe microscopy called atomic force microscopy (AFM) to determine actual radii of atoms. AFM relies on the detection of the interaction of a sample and a very sharp tip. It is a little bit as if a finger would profile an atomic surface. In contrast to optical microscopy methods, the resolution of AFM is not constrained by the optical diffraction limit, which makes the visualization of single atoms possible. But since this interaction between the tip and the sample atom depends on the respective electron clouds described by a certain wave function, it would not be fair to say that we know the definitive size of an atom.

– Kristina Klinker

Read more:
[1] F. J. Giessibl, Mater Today 2005, 8, 32–41.
[2] (last access 10.01.16).

Jan 042016
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In the history of mankind, the sky above us has always fascinated and inspired. Many investigations with different scientific questions have led to great progress towards better understanding of the universe and our Solar System. But many questions are still waiting to be answered – not only in the distant universe, but also in our direct neighborhood. One such question is about the origin of the Moon.

Astronomers have presented several hypothesis how the satellite of the Earth could have been formed. Most likely, the Moon has not been captured and is also not the result of a fission process [1]. Nowadays, most scientists agree on the giant impact hypothesis: Another celestial object named Theia collided with the proto-Earth about 4.5 billion years ago [2]. After the impact, matter in the orbit around our planet could have accumulated to form the Moon. Compared to other planet and satellite pairs, the Moon is peculiarly large. To explain the corresponding angular momentum, Theia must have been as large as Mars [3]. But this hypothesis does not explain all characteristics of the Moon. Whereas the density differs between the Earth and the Moon, the chemical composition, mainly investigated in terms of abundances of some element isotope ratios (e.g. oxygen, titanium or tungsten), is rather similar. This is odd, because most other objects in our Solar System show significant differences that represent their different origin in the Solar System. Therefore, the Moon’s chemical composition should resemble the one of Theia – at least for the assumed impact angle and velocity and mass ratios [3].

One possible solution: coincidence! The composition of proto-Earth and Theia as collision partners must have been similar. Earlier this was thought to be too unlikely, but new investigations and simulations show that there is a certain probability of about 20% for this incident to happen [1]. Subtle differences in isotope ratios may be the result of a late accretion following the impact [4,5]. But why this accretion led to the isotope ratios astronomers observe nowadays, still remains a riddle.

-Nicola Reusch

[1] A. Mastrobuono-Battisti, H. B. Perets, S. N. Raymond, A primordial origin for the compositional similarity between the Earth and the Moon, Nature 520 (2015), 212–215.
[2] R. M. Canup, E. Asphaug, Origin of the Moon in a giant impact near the end of the Earth’s formation, Nature 412 (2001), 708–712.
[3] R. M. Canup, Simulations of a late lunar-forming impact, Icarus 168 (2004), 433–456.
[4] M. Touboul, I. S. Puchtel, R. J. Walker, Tungsten isotopic evidence for disproportional late accretion to the Earth and Moon, Nature 520 (2015), 530–533.
[5] T. S. Kruijer, T. Kleine, M. Fischer-Goedde, P. Sprung, Lunar tungsten isotopic evidence for the late veneer, Nature, 520 (2015), 534–537.

Nov 292015
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Mainz sports an unusually busy sky given its close proximity to Frankfurt International Airport. And quite often, maybe even every few minutes during the day, one just has to look up and see airplanes zipping across. In their wake, these vehicles leave behind long and wispy trails. Trails, not unlike those, of boats against the turquoise of the ocean. But if one patiently keeps on watching, he/she will be able to make out these trails combining to form cirrus clouds.

These trails are the ejected exhaust crystallizing under a supercooled condition and forming ice. In other words, they are very aptly named as condensation trails or contrails for short. Subsequently, these clouds then act as a blanket and trap the heat radiating from the surface…an impromptu greenhouse effect…and just like a greenhouse they prevent the sun’s rays from reaching the surface also.

Contrails : Benign or Not ?

A 1999 report by the IPCC revealed an inconvenient truth – a 15 percent increase in global warming within the next 5 decades from aircraft carbon emissions [1]. Several international think-tanks including NASA over the last fifteen years have tried to promote zero-emission flights but results have not been commercially viable for long-haul flights yet. Still it remains one of the big challenges going forward [2]. So one must really take stock and think about where are we flying to.

Fortunately, not all is lost just yet. Researchers, after meticulously combing through 20 years of flight data over the busy North Atlantic flight route, have shown from calculations that even a small detour for long haul flights of around 100 km can lead to something quite unexpected [3]. Their predictions indicate it would not only reduce the formation of a serpentine mile long contrails which would trap more heat but also at no added cost to the environment compared to CO2 emissions from the jets themselves.

So yes, we may have 10 year old statistics stating the obvious misuse of our carbon footprint [4] but hey, those ethereal formations may yet have a silver lining.

– Soham Roy

[3] E.A. Irvine et al., “A simple framework for assessing the tradeoff between the climate impact of aviation carbon dioxide emissions and contrails for a single flight”, Environ. Res. Lett., 2014, 9, 064021.
[4] D.S. Lee et al., “International Emissions”, UNEP ‘Bridging the emissions gap’, 2011, 4, 40.

Nov 252015
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White Christmas, open air events without rain or in agriculture – the weather is important in many aspects of our daily life. From time to time, we would like to change it. But can we specifically influence it?
If we aim to control weather, we first have to understand the correlation between different weather phenomena. But, actually, weather forecasts only indicate a probability about how the weather will most likely be on the next day. These forecasts are based upon numerical simulations, because weather phenomena are the result of nonlinear dynamics. They cannot be described by analytic solutions, but rather have to be described by means of chaos theory.[1] The most prominent example is the so called “butterfly effect”: A small change in the initial conditions (e.g. the flapping of a butterfly’s wings) leads to a big difference in the outcome. In this case, the result is not a compulsory consequence – not to be mixed up with the snowball effect! But if forecasts are already difficult, can we succeed in controlling the weather?
For example, lightning rods are a tool to influence the weather. It also seems possible that silver iodide can be used for cloud seeding and, therefore, to induce rain or suppress hail. But scientific evidence is still missing.[2, 3] Several ideas to prevent hurricanes have been gathered in a documentary in 2007.[4] They include the removal of electrical charge by means of lasers or the cooling of the surface of the ocean with liquid nitrogen to deprive the heat energy of an oncoming hurricane.
In spite of several interesting applications, we are far away from controlling the weather. Mostly, we neither understand the complete outcome of such interventions, nor can we calculate them quantitatively. The future will show whether we can specifically influence the weather some day with all its chaotic effects.

-Nicola Reusch

[1] J. Slingo, T. Palmer, Uncertainty in weather and climate prediction, Philosophical transactions Series A, Mathematical, physical, and engineering sciences, 369, 2011.
[2] B. A. Silverman, A Critical Assessment of Hygroscopic Seeding of Convective Clouds for Rainfall Enhancement, Bull. Amer. Meteor. Soc., 84, 2003.
[3] Z. Levin, N. Halfon, P. Alpert, Reassessment of rain enhancement experiments and operations in Israel including synoptic considerations, Atmospheric Research, 97, 2010.

Sep 012015
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Among the building blocks of life there are molecules that behave like mirror images to one another. They are called enantiomers, which means that the atoms are connected in the same way, but in three dimensions they have another arrangement – just as the right hand differs from the left hand. To distinguish between two of such so-called chiral molecules we add L- or D- to their names. Though many properties of two enantiomers are similar, in biological systems they can show a rather different behavior. One example is the odor of carvone: one enantiomer smells like spearmint while the other one smells like caraway. [1] Furthermore, in nature we almost only find L-amino acids whilst sugars appear in their D-form – a phenomenon we call homochirality. [2]

Despite intensive research on this topic, we still do not know why nature chose to favor the corresponding configuration. There are several hypothesis on the origin of homochirality. Some state that it is a result of necessity, others explain it on a “by chance”-basis. In each case, an initially small excess of one enantiomer could have been amplified until only the D- or the L-form dominated.

One possibility is that asymmetric photochemistry led to an enantiomer enrichment in space that meteorites could have brought down to earth. Currently, the Rosetta mission investigates the question on enantiomer excesses on comets. [2] In some cases also the crystallization conditions can lead to a symmetry breaking. Furthermore, there is a really small energy difference due to parity violation (calculated to be on the order of 10-12 – 10-15 J/mol) between two enantiomers and by now we cannot exclude that this also could be the origin of homochirality. [2, 3]

Either way, to understand where homochirality stems from would also improve our knowledge of the origin of life itself.

Nicola Reusch

[1] Theodore J. Leitereg, Dante G. Guadagni, Jean. Harris, Thomas R. Mon, Roy., J. Agric. Food Chem., 1971, 19 (4), 785–787.
[2] Iuliia Myrgorodska, Cornelia Meinert, Zita Martins, Louis Le Sergeant d’Hendecourt, Uwe J. Meierhenrich, Angew. Chem., 2015, 127: 1420–1430.
[3] Martin Quack, Angew. Chem., 2012, 114: 4812–4825.

Aug 252015
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When you sleep, the brain subconsciously processes a lot of information gathered during the day. This is often reflected in the fact that we dream. But besides processing an overflow of information, the accumulation of cellular waste products in our brain is happening during sleep. A mis-accumulation of these metabolic by-products plays an important role in the development of neurodegenerative diseases. For example, the accumulation and aggregation of β-amyloid proteins is hypothesized to be one major cause for Alzheimer’s disease. Generally, the body has developed its ways to eliminate toxic metabolic by-products from the system. In other parts of the body than the brain, our lymphatic system is responsible for waste removal. Since it would be fatal if any compound were able to freely diffuse between the brain and the rest of the body, the blood-brain-barrier prevents the unhindered exchange very effectively. As a consequence, it is plausible that there must be a separate “garbage truck” exclusively for the brain. This system has been identified by a group of researchers in 2013 and called the glymphatic pathway.1 In very simple terms, regulated by an expansion and contraction of the brain’s extracellular space during sleep, solutes between the incoming fluid, called the cerebrospinal fluid and the interstitial lymphatic fluid in our brain are exchanged. In this way, metabolic waste is drained from the brain.

Interestingly, the same group of researchers found in a follow-up study in rats that body posture during sleep exhibits an effect on the clearance rate of metabolic waste.2 Using different techniques including dynamic-contrast-enhanced magnetic resonance imaging (MRI) and fluorescence spectroscopy, the researchers concluded that waste removal was more efficient in the lateral position (laying on the side) compared to the prone (laying on the stomach) or supine position (laying on the back).

These findings combined may first of all explain, why sleep is essential for our survival. Second, even if there may be no simple explanation why one body posture during sleep improves the glymphatic transport compared to others, this research certainly goes in the right direction concerning fully understanding the molecular causes for neurodegenerative diseases and, thus, maybe finding a way to prevent Alzheimer’s disease.

– Kristina Klinker

Read more:

1 M. Nedergaard, Science, 2013, 340, 1529–30.

2  H. Lee, L. Xie, M. Yu, H. Kang, T. Feng, R. Deane, J. Logan, M. Nedergaard and H. Benveniste, J Neurosci, 2015, 35, 11034–11044.