Questions of the Week

Why do raw and cooked eggs rotate differently?
Put a raw egg on a flat table, and give it a good spin with two fingers. The egg spins, however, rather slowly because the liquid inside poorly exchanges momentum with the outside shell. Thus, when you spin the egg by applying force to the shell, most of the inside resists the motion and the friction forces between the inside (immobile) and the shell (mobile) will be slowing down the egg’s speed. But if you consider a cooked egg, proteins contained inside the egg are now forming a solid phase that is tightly joint to the shell. In that case, there are no friction forces in the “egg system” and […]
How normal glass can be (nearly) indestructible – The secret of the Prince Rupert’s Drop
Ordinary glass as it is used for windows can exhibit exceptional behaviors and even shred a riffle bullet to pieces, furthermore it can help to make car windows safer and to understand the inner processes in volcanos. Key to all these fascinating properties are the so-called Prince Rupert’s Drops. These structures are solidified drops of glass, which are produced by letting a drop of molten glass fall into a bucket of water. The sudden shock caused by the massive temperature drop on the surface of the glass basically locks in the outer shape of the drop, preserving main body and tail. (Fig. 1) [1,2,3]. This object has now very unique […]
Why Does Alcohol Burn in Wounds ?
Have you ever wondered why rubbing alcohol, i.e. isopropyl alcohol, which is used to disinfect cuts burns so much when applied to the wound? As my mother always said: “As long as it burns, it helps”. This didn’t help me much as a kid, anyway. But why does it burn in the first place? Do you feel the bacteria die? Do some of your cells get killed, too, and you feel that? In fact, neither is true. Interestingly, the pain you feel is due to a heat reaction. But wait, doesn’t alcohol usually give you a cool sensation when applied to the skin? True, but when the alcohol is able […]
Will It Ever Be Possible To Successfully Transplant Heads ?
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 […]
How does a touchscreen work ?
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. 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 […]

C215 – A Parisian Street Artist Focused on Stencil Graffiti

Current Issue, Issue 1, Mar 2017, News and Commentaries, Vol. 7 Add comments

Apr 152017

“I try to interact with context, so I place in the streets elements and characters that belong especially to the streets. I like to show things and people that society aims at keeping hidden: homeless people, smokers, street kids, bench lovers for example” – C215

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