Question of the Week

Jan 082017
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According to media reports, the Italian neurosurgeon Dr. Sergio Canavero will attempt the first transplant of a human head (cephalosomatic anastomosis) in the end of 2017.[1] Valery Spiridonow is volunteering for this project since he suffers from spinal muscular atrophy (SMA) and believes the surgery will offer a chance to escape from this fatal disease.[2]

Similar experiments have already been performed more or less successfully on animals. In some cases, the animals survived but they remained paraplegic and their cardiovascular and respiratory systems had to be supported. Also they did not survive quite long after the surgery.[3,4] In fact, many experts are strongly doubting the success of this highly expensive transplant too.

Head Transplant : Fact or Fiction ?

Head Transplant : Fact or Fiction ?

Even if it might become a 100 % success, there remain a lot of serious questions:
– Will the patient (the head) be mentally and emotionally the same person as before?
– Will the brain be able to cope with a completely strange body and vice-versa?

Of course, Spiridonow will first have to find a donor for the body. He needs the body of a physically healthy man suffering from cerebral death and the consent of his relatives. Spiridonow’s new body will have the genome of the donor, so what are the legal consequences for any offspring regardless of whether they were conceived before or after the transplant?

So once again we are confronted with the problem of how far mankind can go to explore the possibilities of science and consider ethics at the same time. I think we should be excited and enthusiastic for the outcome of this dramatic surgery if it is going to happen anyway.

— Tatjana Daenzer

Read more:
[3] Canavero, Surg Neurol Int. 2013, 4, 335.
[4] Canavero, Surg Neurol Int. 2015, 6, 18.

Nov 162016
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Touchscreens are getting more and more important for modern media. The most striking advantage of this technology is the combination of intuitive in- and out-put devices, which allow the user to directly interact with the system and vice-versa. But how does such a screen work, which types are available, and why do certain type of touchscreens react to fingers, but not to a normal pen? These questions we will answer in this week’s featured question.

How a resistive screen works?

How a resistive screen works?

One of the first touchscreen technologies (that is still in use nowadays) is the so-called resistive screen. This specific screen type is composed of two conductive, relatively transparent layers (usually indium-tin-oxide (ITO)), which are held separated at a small distance by spacer dots. To the bottom layer, a small voltage is alternatingly applied in x- and y-direction, while the top layer connects to the second half of the circuit. They are capped by a stiff, but bendable layer and directly sit on the actual display. Touching the screen with a little bit of pressure bends the conductive layer on top and closes the circuit. The resulting currents along the x- and y-circuits can be measured and provide information about where the circuits are closed. The idea is that the longer the current path , the higher becomes the electrical resistance. This technology is still commonly found in cheaper devices and in devices meant to be operated with gloves and can yield high accuracy. However, due to the mechanical deformation the screen has a finite lifetime.

How a capacitive screen works?

How a capacitive screen works?

The second, and probably most common, technology is used in “projected capacitive screens”. Those screens are composed of two grids, rotated at 90° to each other, of very fine conductive wires (usually ITO deposited on glass) with spacers in between. In contrast to the resistive screens, they do not form a continuous layer. Instead, the ITO grids create a large amount of crossings, which act like little capacitors whose capacity changes whenever a conductive or dielectric object (like a finger) approaches the grid. A digital controller measures now the capacity of all grid points one by one and if a certain deviation from the saved standard value is reached, a touch is registered. This technology allows multi-touch applications since all grid-points are measured separately and the image quality is enhanced due to the lower amount of ITO between the user’s eye and the actual display. However, these touchscreens need specific materials to be able to detect a signal and barely work with thick gloves or normal pens due to the fact that the capacity does not change if a standard insulator (like plastic) is brought close to it.

There are far more types of touchscreens based on, e.g. infrared light, inductive coils, sound and the piezoelectric effect. However, the two types, mentioned here, are the most commonly found ones nowadays. In the future, there might exist even more sophisticated types of human-interface-devices (HIDs), but at the current time, touchscreens still are one of the most successful HIDs and were able to widely repress the simple push-buttons.

–Kai Litzius

Further reading:

Nov 062016
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There have been already two Questions of the Week about the weather: “Can we control the weather?” ( by Nicola Reusch and “Is accurate weather forecast possible?” ( by myself. Today, I do not want to go into detail about the meteorological work, but demonstrate a mathematical theorem by the means of weather.

You certainly heard about antipodes, i.e. points that lie on diametrically opposite sides on the earth’s surface. If you’d like to have a look where your antipode is at the moment, check refs. [1] and [2]. Now, these two parts of the earth are the farthest apart from each other as you can get, while staying on the ground; with the exemption that they are a little closer, when you are at sea level on both ends than they are when you are on top of Mount Everest on one side. Think about how different the climatic conditions must be between those two antipodal points. What if I told you that at any moment there are at least two antipodal points on earth’s surface which share the same temperature and air pressure. Would you believe me?

No? So too what I thought at first. But let me reveal that it’s true. Take a look at Fig. 1(left). There you see the two antipodes A and B. If we measure the temperature of both points and they are identical, fine, we did our job. But most likely this won’t happen. If we move from the original point A to point B on any path while keeping A and B antipodal points (Fig. 1, middle), the temperatures of the two points will swap (Fig. 1, right). Therefore, there must be at least one set of antipodal points, where the temperature of A and B is identical, since swapping would be impossible otherwise.

Fig. 1: Two antipodal points A and B (left), antipodal paths from A to B (middle), and swapped points A and B (right).

Fig. 1: Two antipodal points A and B (left), antipodal paths from A to B (middle), and swapped points A and B (right).

Since swapping will occur on one set of points on a given antipodal path, you can imagine a line separating hemisphere A from hemisphere B on which any pair of antipodes will have equal temperature (Fig. 2). If we check air pressure on one set of antipodal points, we most likely won’t find matching values. But we can also be certain that both values will swap, if we move from one point to the other, while staying on the equal temperature path from Fig. 2.

Fig. 2: Antipodal points on earth’s surface with equal temperature.

Fig. 2: Antipodal points on earth’s surface with equal temperature.

Therefore, we must find one pair of antipodes with equal temperature and equal air pressure on earth’s surface at any given moment. Fascinating, isn’t it? This is called the Borsuk-Ulam Theorem.[3] It is a mathematical theorem which remarkably illustrates that results which seem impossible can in fact be true, if you keep investigating in a scientific manner.

–Andreas Neidlinger


Oct 092016
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What is the most useful invention of humans? Sure, most people will answer this question with “The Wheel!” Indeed, today almost any machine runs with some kind of wheel. But do we know whom to thank for this gift? Let’s take a little journey back through time.

Rewind to our greatest invention.

Rewind to our greatest invention.

Of course there was a time before the wheel, around 5000 BC. People used slides and logs of timber to transport goods. During the Bronze Age (ca. 3500 BC), wheels of clay and of wood were being attached to carts. Records of those first wheels are found in different cultures of the same age. For a long time, it was believed that the Sumerians from Mesopotamia were the inventors of the wheel. But new findings prove that other cultures from Western and Eastern Europe of the same age built something similar. The main difference of those earliest constructions were in the suspension – some were rotating with the axis, some were rotating around it.

Over the ages, this technology spread all over the world. The wheels became lighter and more stable. The development of trade, technology and (even) warfare, is due to the wheel. The wheel has made it possible for us to wonder at all the modern engineering marvels.

Still it is unlikely to identify a group of people – not to mention a single person – as the inventors of the wheel. To imagine what fortune one would amass today from such an invention…

– Tatjana Daenzer

Read more:

Oct 032016
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The story of music and human cognition is intricate and intertwined from the beginning. Since close to fifty millennia, music has remained an integral part of being human.[1]

Music has always aroused feelings of rapture and desire, even though it is intangible. And now science has unlocked the mechanism. As the reward center in the brain gets primed with the anticipation of listening to familiar music, there is a flood of dopamine, the “happiness” neurotransmitter.[2] Things can get discordant too. If one listens to unpleasant music, there is a reduced production of serotonin, our mood-regulator.[3]

Music for peace of mind.

Music for peace of mind.

It is quite natural to ask, if the audience is experiencing euphoria, what is the artist feeling ? Well, scientists have looked into that aspect as well.

The brains of musicians light up like a celebration of fireworks when they play.[4] The left and right hemispheres enter in a harmonious exercise when an artist performs on their musical instrument.

But can music improve how we interact with life ? And the answer is a resounding “YES”.

Learning an instrument with structured and disciplined practice, has an array of benefits.[5] It can enable us to find more creative solutions to problems in social as well as academic settings. Playing music makes for a greater neural plasticity in the brain which can better help with retrieving and indexing information – in short, a better functioning memory.

Even though we know what neurotransmitters are responsible and the neural pathways they seem to take in the brain when we hear music, still there is so much more that we do not know. For instance, the auditory cortex is still quite unknown to us in its organization and functions. Only recently, there was a discovery of two separate populations of neurons, sensitive to how we process music and human speech, different from ambient sound in the environment.[6] Though, it is still a question of speculation – are we born with it or is it developed through experience.

Four hundred years have passed since William Congreve remarked, “Musick has Charms to sooth a savage Breast”. Music, has indeed, displayed the ability to heal. It has shown promise to improve the lives of those affected with schizophrenia.[7] As music also helps in better connecting our episodic memory, it can have a positive influence in individuals suffering from Alzheimer’s or PTSD.

So let’s tune in to some nectar for the brain and turn those frowns upside down.

– Soham Roy

[2] Salimpoor, VN et al. Nature Neuroscience, 14, 257–262 (2011).
[3] Evers, S et al. Eur Arch Psychiatry Clin Neurosci., 250, 144–7 (2000).
[5] Miendlarzewska, EA et al. Front Neurosci., 7, 1–18 (2013).
[6] Norman-Haignere, S et al. Neuron, 88, 1281–1296 (2015).
[7] Talwar, N et al. BJP, 189, 405–409 (2006).

Aug 162016
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You certainly know the game little kids play where they have a cube, a sphere and a pyramid, and they have to put them through holes of the corresponding shape. In the beginning, this might be difficult, but it becomes quite easy and dull after some time. Now, it is simple for most people, but how difficult is the same task for blind people? i.e., Can people who have been blind for their entire life and are familiar with different shapes by their tactile sense, recognize the same shapes when they gain the ability to “see”?

This question, referred to as the Molyneux Problem, was first asked by William Molyneux, an Irish philosopher and politician, in 1688.[1] Of course, answers that could verify this question were not easy to find in the 17th century due to the impossibility of highly complex surgeries at that time. Nevertheless, a lot of discussions arose about the co-operation between our senses. For instance: Is the eye able to understand the geometry of objects or is the visual recognition just possible by a learned collaboration with the tactile sense?[2] Or the other way around: How do blind people understand shape; how do they “look” for them?

Just recently, in 2011, five children, who were born blind, became able to see after surgery at the ages between 8 and 17. They were familiar with several shapes by examining them with their hands. Interestingly, they were not able to relate this tactile information with the visual input from these objects, but they learned to connect both senses quite fast.[3] However, discussions are still not at an end, to unequivocally explain the outcomes.

The Molyneux Problem once again shows that even simple questions can result in long-lasting discussions and unexpected outcomes. Never stop asking questions and dig through the JUnQ to find the hidden treasures!

— Andreas Neidlinger

[1] W. Molyneux: Letter to John Locke, 7 July 1688, in: The Correspondence of John Locke (9 vols.), E.S. de Beer (ed.), Oxford: Clarendon Press, 1978, vol. 3, no. 1064.
[2] S. Pasewalk: „Die fuenffingrige Hand“: Die Bedeutung der sinnlichen Wahrnehmung beim spaeten Rilke, De Gruyter; Auflage: 1., 2002, pp. 106.
[3] R. Held, Y. Ostrovsky, B. de Gelder, T. Gandhi, S. Ganesh, U. Mathur, P. Sinha, Nat. Neurosci. 2011, 14, 551–553.

Aug 072016
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Lying on the grass and looking into a sparkling star-filled summer sky. Can there possibly be anything more beautiful? But it also makes me think about how small we really are and are we truly alone in the universe. This question has bothered humans since the beginning of our existence.

In the observable universe, there are at least 100 billion galaxies containing 100-1000 billion stars each. Not to mention the gigantic number of existing planets surrounding those stars including trillions of habitable ones. Consequently, there must be plenty of opportunities for alien life to develop.

But is the contact with extraterrestrial life really that likely? It has to be mentioned, that a huge number of existing galaxies are completely out of reach because of the expansion of the universe. Only the ones being part of our local group come into consideration for a theoretical alien contact. Anyways, if life had developed only on 1% of all planets in habitable zones in the Milky Way, there would be millions of planets inhabited by aliens. Since life on earth emerged rather late compared to the age of the Milky Way, potential super-intelligent and technologically advanced aliens would have had much time to build powerful space ships and to make a trip to our blue planet. In fact, if those guys would have been able to build generation space ships, they could colonize the Milky Way in a few million years. And that is not a long time when we think that life on earth exists since 4 billion years and the fact that other planets might have had developed life long before earth did. So if only one of those theoretical alien races would have developed into a super-technological civilization, shouldn’t we know by now?

So where are all the aliens? Why did they not contact or – in a bad scenario – attack us so far? This lack of proof for aliens despite its apparently high probability is called the Fermi Paradox, named after the physicist Enrico Fermi.

There are different scenarios which can resolve the Fermi Paradox and some of them are quite amusing and imaginative. Here is a small selection:
1. In spite of the apparent high probability, we are alone in the universe. We might always have been and always will be. The condition for the emergence of life could be much harder and complicated than we assume.
2. There were intelligent aliens long before humans came into existence. They could have gone extinct before someone on earth ever thought about extraterrestrial life at all. Indeed, we do not know everything concerning different thresholds life has to overcome in order to survive. We might just be lucky that we do not yet have encountered one really tough barrier, like the dinosaurs obviously did. Or maybe at some point, every sophisticated culture will destroy itself by inventing a highly destructive super-weapon.
3. Our extraterrestrial friends want to observe us in order to do psychological studies or maybe we are just part of some “galactic zoo” for aliens. They also might just wait until we are a threat to them and then kill us. This has also been a topic in various science fiction books.
4. Life forms from outer space are already among us and we do not notice.
5. The aliens are simply not interested in having communication or imperialistic wars with anyone else and stay peacefully and happy on their home planet.
6. The universe is full of extraterrestrial signals but we are not advanced enough to detect them.

Maybe there will be a day in the future when we get a more definite answer to the Fermi Paradox. Let’s just hope it will be a salubrious one!

– Jennifer Heidrich

Read and watch more:
— M. H. Hart: Explanation for the Absence of Extraterrestrials on Earth. Quarterly Journal of the Royal Astronomical Society. 1975, 16, 128.
— A. Frank and W.T. Sullivan: A New Empirical Constraint on the Prevalence of Technological Species in the Universe. Astrobiology. 2016, 16, 359.
The Fermi Paradox — Where Are All The Aliens? (1/2)
Drake’s Equation – A Deep Dive | Answers With Joe

Jul 242016
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If you ever wander about the barren lands of southern Africa, like the scarcely vegetated Namib desert in Namibia, you will most certainly stumble across a fascinating malformation of the soil called fairy circles. They are circle shaped bare patches of dry ground with a diameter of several meters enclosed by taller grass at the edge, compared to the steppe landscape of the surroundings.

Fairy circles in the Namib Naukluft Park, Namibia. (© Heike D?nzer)

Fairy circles in the Namib Naukluft Park, Namibia. (© Heike Daenzer)

Their origin has long been a cause of intense discussions. The earliest interpretation of their appearance may come from the Himba people, who share the legend that the circles are the footprints left behind by their ancestor Mukuru. Other stories tell of aliens, dragons or fairies.[1] On the other hand though, science suggests toxic gases or residues from already dead plants, radioactive elements or insects to be the origin of the features.[2] Lots of investigation have been made in the last decades to prove each theory but no one could come to a substantial and indisputable conclusion. Since no toxic or radioactive substances were found in the soil of the fairy circles, they must arise from something else.[2]

Supported by satellite images, Dr W. Tschinkel, from the Florida State University, was able to offer proof that the circles are not permanent. They grow and develop and after a lifespan of 41 years on average, they “die”.[3]

Cramer et al. used an empirical model considering various biological, chemical and weather factors to predict the appearance of fairy circles. They conclude that circle formation must be the result of plant organization and competition for nutrients since the plants at the periphery of the circles are more lush than the plants farther away.[4]

A very vivid explanation comes from N. Juergens who examined the termite population of fairy circles. The sand termite Psammotermes allocerus, their nest and tunnels were the only similarity found in 100 % of the investigated circles and even in young circles. Apparently they feed on plant roots and keep large areas free of water accumulating vegetation which causes also a higher water content in the ground centered beneath the circle.[5]

Only a few years ago, fairy circles were found in Pilbara, Australia similar to those in Africa. Getzin et al. doubt the dependence of the pattern formation from termites or ants since many circles didn’t host any of these insects. They blame pattern-creating plants in water-limited environments, such as in a desert, to be responsible.[6]

– Tatjana Daenzer

Read more:
[2] van Rooyen, J. Arid Environ., 2004, 57, 467–485
[3] Tschinkel, PLOS ONE, 2012, 7, 1–17
[4] Cramer, PLOS ONE, 2013, 8, 1–12
[5] Juergens, Science, 2013, 339, 1618–1622
[6] Getzin, PNAS, 2016, 113, 3551–3556

Jul 032016
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We all know what the color ‘black’ is. If I ask anyone, I will get different responses. From the familiar blackboard in the classroom to the ubiquitous asphalt of the roads. Some might recall, with fondness, it as the color of the little dress on their high-school prom date. Others might be more correct, and remind me that “true” black is the absence of any reflected light. And point me towards the nearest black hole (at the center of the milky way or on the Sagittarius arm of it, depending on what one believes [1]).

Is it Black or is it Grey ?

Is it Black or is it Gray ?

Even then, when I show the above graphic, all (including me) will be unequivocal in declaring the colors to be shades of black. Although those are hues of gray. Such befuddlement ails us all. As Dr. Stephen Westland, professor of color science and technology at Leeds University, is right in saying, “Unless you are looking at a black hole, nobody has actually seen something which has no light.” [2]

Given our feeble attempts at defining and rendering ‘Black’, it becomes quite a challenge to explain Vantablack – the blackest material known [3, 4], where Vanta is an acronym for Vertically Aligned Nano Tube Arrays. Although, NASA might argue that their super-black deserves that title [5]. It is easy to visualize Vantablack as a forest of carbon nano tubes. The tubes are stacked in a vertical orientation, with the length of the individual tubes being much much larger than their diameter.

Vantablack (downloaded from

Vantablack (downloaded from

Yet, that still doesn’t explain why it is the ‘blackest’ of blacks and could rewrite and replace all previous conceptions of black [6]. When light hits the Vantablack surface, it gets trapped in between the carbon nano tubes. The photons undergo a lot of collisions with the walls of these tubes. They lose their energies as heat to the walls and the tiniest amount is reflected back as light, all of 0.035 % [2, 7].

Such properties make it very exciting as future prospects. From manufacturing telescope coatings, where even the tiniest speck of scattered light can seriously affect its contrast and resolving power. To the defense and stealth sectors, who find the material extremely fascinating [7].

Yet, it is still baffling to answer how does it feel to see the blackest material known. We understand a surface by its depth or its topological features. These features change reflectance. But for Vantablack, even when it is crumpled up, it defies perception. “You expect to see the hills and all you can see … it’s like black, like a hole, like there’s nothing there. It just looks so strange”, as Surrey Nanosystems CTO Ben Jensen puts it [2].

Vantablack is the darkest material we have that is as close to perceiving what a black hole would look like. This might be a bit disconcerting for us in the future, expecting to see textures but being greeted with an abyss. “And if you gaze long into an abyss, the abyss also gazes into you.”

-Soham Roy

[4] E. Theocharous et al., Optics Express 2014, 22, 7290-7307.

Jun 122016
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Modern aviation is one of the most important and possibly, also the safest when it comes to transportation and travel. As a result of the increasing need for fast and reliable transfer of resources, airplanes have become increasingly complex and nowadays only a relatively small number of people know how they are operated.

Figure 1: Landing of a modern aircraft.(downloaded from

Figure 1: Landing of a modern aircraft.(downloaded from

In this Question of the Week, we want to focus on one particular detail of aviation: The landing. A typical airplane approaches the airstrip with a speed of around 270 km/h and has to decelerate within a very short time to guarantee a safe landing. So how do you brake an airplane?

To answer this question, we first have to think about how braking works in the case of any wheel-based vehicle. In a nutshell, the braking process always exerts a torque upon the wheels which then use friction with the ground to lose kinetic energy. Friction, however, is massively dependent on the weight that rests on the wheels. In case of landing an airplane, the aerodynamic lift basically nullifies the weight of the plane and therefore makes braking while using the wheels extremely inefficient. As a result, the plane needs other ways to slow down until the aerodynamic lift and speed is sufficiently reduced. In modern aviation, this is done by two different braking systems: The Spoilers and the Reversers, that both are usually operated by a computer, which tries to reach a constant deceleration of convenient magnitude (about 0.17 – 0.3 g).


Figure 2 : Spoilers on an aircraft. (downloaded from

As soon as the wheels get in contact with the ground, the Spoilers (Figure 2) are fully activated. These are flaps located on the back-end of the wings and can significantly reduce the aerodynamic lift as well as increase the drag. These flaps are extremely important for the braking process because without them the friction of the wheels is not sufficient for efficient braking. Basically, wheel brakes and Spoilers together can already be sufficient for slowing down an airplane.


Figure 3 : Reversers on an aircraft. (downloaded from

However, to reduce the amount of stress the wheel brakes have to withstand, there is an additional system: The Reversers (Figure 3). These are mechanisms located at the engines that can be activated to redirect the engine’s exhaust forward, rather than backwards (commonly referred to as thrust reversal). All three systems together can be used by a computer to reach an extremely smooth braking process without putting too much stress on the single components.

As a result, the landing process by itself is extremely complex and depends on many factors. Most of them can be controlled by a computer, however, in case of any unforeseen circumstances, the pilots have to be prepared to take over and land the airplane manually. This (and many other factors) makes the training of pilots one of the most demanding educational processes of our time.

– Kai Litzius

Further reading: