The World’s Longest Pedestrain Suspension Bridge Is A Terrifying Path Through A Swiss Valley (Amazing Places / Adventure)

Bravery isn’t quantifiable, but we think it can be pretty accurately measured in just one glance at the Charles Kuonen Suspension Bridge. As of its August 2017 opening, this structure is the longest pedestrian suspension bridge on the planet. It’s beautiful, impressive, and vertigo-inducing. Would you cross?

You’ll find the bridge in Randa, Switzerland, and it looks like something out of a fairy tale. The bridge, opened in August 2017, cuts through the picturesque Swiss Alps at a dizzying height of 282 feet (86 meters) above ground at its highest point. That’s the height of 16 giraffes stacked one on top of the other.

The path is so thin (25.5 inches/65 centimeters) and long (1,620 feet/494 meters), it barely looks physically possible. Apparently, it’s sound, but we aren’t exactly racing to go test that out …

Engineers from Swissrope and Lauber cableways built this record-breaking bridge in just 10 short weeks. With its completion, it’s now the longest suspension bridge in the world, surpassing the glass-bottomed bridge across the Zhangjiajie Canyon in Hunan province, completed in 2016. One look at the Swiss pathway begs the question: WHY?! Before this walkway was erected, a different path connected the two sides of the valley, but it was damaged by rock falls. The height of the new bridge may seem unnecessary, but it keeps the path out of the rocky danger zone.

Maintaining a bridge here is quite the gift to hikers, who would otherwise have to hike four hours to get to and from the towns of Zermatt and Grächen. With the Charles Kuonen Suspension Bridge, the trek is now 10 minutes — if you’ve got the guts, anyway. If you don’t want to look down while traversing the Swiss Alps valley via this bridge, just look around you. The Matterhorn, Weisshorn, and the Bernese Alps are visible in the distance: a view that might just be worth the acrophobic terror.

References: (1) (2) (3)

A Major Breakthrough: We Now Have A Solution For Preventing Corrosive Buildup In Nuclear Systems (Material Science / Chemistry / Physics / Engineering)

If you are an engineer, you must be very well aware of CRUD, yeah its a metallic oxide particles in the nuclear energy world, which build up directly on reactor fuel rods, impeding the plant’s ability to generate heat. These foulants cost the nuclear energy industry millions of dollars annually.

This issue has vexed the nuclear energy industry since its start in the 1960s, and scientists have only found ways to mitigate, but not cure, CRUD buildup. But that may be about to change.

The recent paper of authors describes about their work, which offers a novel approach to design fouling-resistant materials for use in nuclear reactors and other large-scale energy systems.

The team’s research goes beyond theory and lays out specific design principles for anti-foulant materials.

Short and his students built a flow loop (a way of recreating reactor conditions without radiation), and conducted a series of experiments to see which materials encouraged, and which discouraged, the growth of CRUD.

Researchers have floated a host of surface forces as candidates for causing the stickiness behind CRUD: hydrogen bonding, magnetism, electrostatic charges. But through experimentation and computational analysis, Short and his team began to suspect an overlooked contender: van der Waals forces. Discovered by 19th-century Dutch physicist Johannes Diderik van der Waals, these are weak electric forces that account for some of the attraction of molecules to each other in liquid, solids, and gases.

Then came a major breakthrough: Carlson recalled a 50-year-old equation developed by Russian physicist Evgeny Lifshitz that he had come across during a review of materials science literature.

If you dont know about Lifshitz’s theory let me tell you, it describes the magnitude of van der Waals forces according to electron vibrations, where electrons in different materials vibrate at different frequencies and at different amplitudes, such as the stuff floating in coolant water, and fuel rod materials. His math tells us if the solid materials have the same electronic vibrations as water, nothing will stick to them.

And that’s what short and his team thought.. What if cladding, the outer layer of fuel rods, could be coated with a material that matched the electronic frequency spectrum of coolant water, yeah, then these particles would slip right past the fuel rod.

The researchers got to work demonstrating that van der Waals was the single most important surface force behind the stickiness of CRUD. In search of a simple and uniform way of calculating materials’ molecular frequencies, they seized on the refractive light index—a measure of the amount light bends as it passes through a material. Shining calibrated LED light on material samples, they created a map of the optical properties of nuclear fuel and cladding materials. This enabled them to rate materials on a stickiness scale. Materials sharing the same optical properties, according to the Lifshitz theory, would prove slippery to each other, while those far apart on the refractive light scale would stick together.

Fig: Multi-foulant materials used by short and his team. Amorphous 2% fluorine-doped tin oxide, crystalline SiO2, CaF2, and Na3AlF6, which all nearly match the refractive index spectrum of water, successfully resisted adhesion of six diverse foulant materials in aqueous AFM measurements.

By the end of their studies, as the paper describes, Short’s team had not only come up with a design principle for multi-foulant materials but a group of candidate coatings whose optical properties made them a good (slippery) match for coolant fluids. But in actual experiments, some of their coatings didn’t work. Yeah, it wasn’t enough to get the refractive index. Materials need to be hard, resistant to radiation, hydrogen, and corrosion, and capable of being fabricated at large scale.

Additional trials, including time in the harsh environment of MIT’s Nuclear Reactor Laboratory, have yielded a few coating materials that meet most of these tough criteria. The final step is determining if these materials can stop CRUD from growing in a real reactor. It is a test with a start date expected next year, at an Exelon commercial nuclear plant.

References: Cigdem Toparli et al. Multi-Foulant-Resistant Material Design by Matching Coating-Fluid Optical Properties, Langmuir (2020). DOI: 10.1021/acs.langmuir.9b03903 link:

Black Silicon Photodiodes Reached Above 130% Efficiency (Physics)

Garin and colleagues have developed a black silicon photodiodes that has reached above 130% efficiency. Thus, for the first time, a photovoltaic device has exceeded the 100% limit, which has earlier been considered as the theoretical maximum for external quantum efficiency.

Fig: UV-light triggers electron multiplication in nanostructures. Credit: Wisa Forbom

The independent measurements were carried out by the German National Metrology Institute, Physikalisch-Technische Bundesanstalt (PTB), which is known to provide the most accurate and reliable measurement services in Europe.

The external quantum efficiency of a device is 100% when one incoming photon generates one electron to the external circuit. 130% efficiency means that one incoming photon generates approximately 1.3 electrons.

The researchers found out that the origin of the exceptionally high external quantum efficiency lies in the charge-carrier multiplication process inside silicon nanostructures that is triggered by high-energy photons. The phenomenon has not been observed earlier in actual devices since the presence of electrical and optical losses has reduced the number of collected electrons.

In practice, the record efficiency means that the performance of any device that is utilizing light detection can be drastically improved. Light detection is already used widely in our everyday life, for example, in cars, mobile phones, smartwatches and medical devices.

References: M. Garin, J. Heinonen, L. Werner, T. P. Pasanen, V. Vähänissi, A. Haarahiltunen, M. Juntunen, and H. Savin, “Black silicon photodiodes achieve external quantum efficiency above 130%”, Phys. Rev. Lett., 2020. DOI: link:

We Now Know How Radioactive Uranium Spread Uncontrolled In The Environment (Material Science)

Scientists at EPFL’s Environmental Microbiology Laboratory (EML) have recently made an important discovery about uranium that could have major implications for soil and groundwater remediation as well as radioactive waste management.

Fig: Conceptual model of U(VI) reduction by magnetite. Magnetite particles are indicated in black and uranium species in blue. The reaction starts with rapid adsorption of aqueous U(VI) species onto the magnetite surface. Adsorbed U(VI) is reduced to U(V) and U(IV) species. While U(V) remains on the magnetite surface, U(IV) precipitates out as uraninite nanoparticles that self-assemble into nanowires structures anchored to the magnetite surface.
Nanowires continue to grow while reduction proceeds. Eventually, crystal growth and coalescence lead to the collapse of nanowires into UO2 nanoclusters in which nanoparticles display a preferred orientation.

They studied the properties of uranium as it occurs naturally in the environment, and made significant breakthroughs in understanding how it goes from one oxidation state to the other, transitioning from a water-soluble compound to a stable mineral.

At the +6 oxidation state, uranium is mostly soluble and can therefore spread uncontrolled in the environment. But at the +4 oxidation state, it is less soluble and less mobile. In their research authors were able to pinpoint the nanoscale mechanisms of interaction between uranium and particles of magnetite, a magnetic iron oxide, to transition from one oxidation state to the other. They showed the persistence of Uranium at the +5 oxidation state, which is usually considered metastable.

Fig: Scanning transmission electron micrographs of U-magnetite samples

Most interestingly, the scientists also identified a molecular phenomenon that occurs during the transformation from the +6 to the +4 oxidation state: they discovered the formation of novel nanowires composed of very small nanoparticles (~1-2 nm) that assembled spontaneously into chains. These chains eventually collapse as individual nanoparticles grow larger.

The scientists were able to view the nanowires—which have a diameter of just 2–5 nm, or 100,000 times thinner than a human hair—thanks to the electron microscopes at EPFL’s Interdisciplinary Center for Electron Microscopy (CIME). The evidence of this transient U nanowire structure could improve understanding of how radioactive compounds spread in the subsurface at contaminated sites.

References: Zezhen Pan et al. Nanoscale mechanism of UO2 formation through uranium reduction by magnetite, Nature Communications (2020). DOI: 10.1038/s41467-020-17795-0 link:

Researchers Developed A New Kind Of Superelastic Alloy With A Nearly Limitless Superelastic Window (Metallurgy / Material Science)

Xia and colleagues has developed a new kind of superelastic alloy with a nearly limitless superelastic window. In their paper, the group describes the new alloy’s properties and possible uses for it. Another study carried out by Paulo La Roca and Marcos Sade outlined the state of bendable alloys and the work done by the team in Japan.

Fig: Mechanical properties of Fe-Mn-Al-Cr-Ni shape memory alloy system. Credit: Science (2020). DOI: 10.1126/science.abc1590

Most metals in everyday use can bend somewhat and to get them to return to their original shape generally requires force. Superelastic alloys (also known as metals with shape memory) can be bent with up to 20 percent deformations and will return to their original shape automatically. La Roca and Sade note that superelasticity in metals can be explained by the presence of stress-induced martensitic transformations. But there is a caveat for such alloys—they can only rebound back to their original shape when they are in a certain range of temperatures: their superelastic window.

Unfortunately, most such windows are quite small, limiting the use of superelastic metals in practical applications. Scientists would like to discover alloys that can be used in wider temperature variations for use in applications such as space science (because of the temperature extremes). In this new effort, the researchers have found just such an alloy—one with a nearly limitless superelastic window. During testing, its superelastic window was found to be 10 to 473 K (-263 C° to 200 C°), making it applicable in virtually all natural settings. The researchers note that the alloy was also found to have very low thermal expansion.

The team created the alloy by adding chromium to a Fe-Mn-Al-Ni alloy. In so doing, they also showed that entropy change is controllable using this approach. The entropy change for the new alloy was tested to be very near zero. The researchers also note that the alloy is tunable by varying the amount of chromium, which highlights the fact that the team actually created a host of superelastic “invar” alloys.

References: (1) J. Xia el al., “Iron-based superelastic alloys with near-constant critical stress temperature dependence,” Science (2020). … 1126/science.abc1590 link: (2) Paulo La Roca, Marcos Sade, “Designing a wider superelastic window”, Science, 14 Aug 2020 pp. 773-774 link:

Humans Used To Sleep In Beds 200000 Years Before (Archeology)

Researchers in South Africa’s Border Cave, a well-known archeological site perched on a cliff between eSwatini (Swaziland) and KwaZulu-Natal in South Africa, have found evidence that people have been using grass bedding to create comfortable areas for sleeping and working on at least 200,000 years ago.

These beds, consisting of sheaves of grass of the broad-leafed Panicoideae subfamily were placed near the back of the cave on ash layers. The layers of ash was used to protect the people against crawling insects while sleeping. Today, the bedding layers are visually ephemeral traces of silicified grass, but they can be identified using high magnification and chemical characterisation.

Several cultures have used ash as an insect repellent because insects cannot easily move through fine powder. Ash blocks insects’ breathing and biting apparatus, and eventually dehydrates them. Tarchonanthus (camphor bush) remains were identified on the top of the grass from the oldest bedding in the cave. This plant is still used to deter insects in rural parts of East Africa.

Modern hunter-gatherer camps have fires as focal points; people regularly sleep alongside them and perform domestic tasks in social contexts. People at Border Cave also lit fires regularly, as seen by stacked fireplaces throughout the sequence dated between about 200,000 and 38,000 years ago.

Although hunter-gatherers tend to be mobile and seldom stay in one place for more than a few weeks, cleansing camps had the potential to extend potential occupancy.

References: Fire and grass-bedding construction 200 thousand years ago at Border Cave, South Africa. Science, 2020. DOI: 10.1126/science.abc7239 link:

According To This Quantum Theory, You’re Immortal (Quantum)

The laws of the quantum world are so bizarre that if you follow them to their logical conclusions, you get some very strange results. That’s why quantum physics is so full of thought experiments. You may have heard of Schrödinger’s cat, for example: If you put a cat in a box with a vial of poison that has a 50/50 chance of killing the cat, the cat is both alive and dead — in a superposition of states, you might say — until you open the box. Well, try the quantum suicide thought experiment on for size: In that scenario, you’re the cat — except you never die.

The quantum suicide thought experiment was first posed by Max Tegmark in 1997, and it goes something like this: Imagine a gun is hooked up to a machine that measures the spin of a quantum particle every time the trigger is pulled. If the particle is measured as spinning clockwise, the gun will fire; if it’s spinning counter-clockwise, it won’t. A man points the gun at a sandbag and pulls the trigger 10 times. The gun goes off seemingly at random: “bang-click-bang-bang-bang-click-click-bang-click-click.” Then, the man points the gun at his own head and attempts to pull the trigger 10 more times. What does he hear? “Click-click-click-click-click-click-click-click-click-click.” He could keep on pulling the trigger for eternity, and the gun would never fire. How is that possible?

Now let’s go back in time to the first moment he pointed the gun at his head. He pulls the trigger, and the gun fires. The man is dead. How can that happen when we already know the gun never fired? It’s because every time he pulls the trigger, the universe splits into separate timelines: one where the gun fired, one where it didn’t. When he was shooting the sandbag, he existed in the timelines created by that series of bangs and clicks. But when he aimed the gun at himself, the only timelines he could exist in were the ones where he survived — and thus, the ones where the gun didn’t go off.

This way of thinking is known as the many-worlds interpretation of quantum physics, which says that our reality is just one in an infinite web of infinite timelines. It’s controversial but cool to think about nonetheless. With the many-worlds interpretation, every time you do anything, you cause a split in the universe. You’re reading these words, but there’s another timeline where you closed the article. You got out of bed at a certain time this morning, but there’s another timeline where you slept later. You chose one career, but there’s another timeline where you chose something wildly different. In each case, all you know is the timeline you’re in.

In his 1994 paper, Max Tegmark pointed out an ironic twist to the many-worlds interpretation, which he calls the MWI: “Many physicists would undoubtedly rejoice if an omniscient genie appeared at their death bed, and as a reward for life-long curiosity granted them the answer to a physics question of their choice. But would they be as happy if the genie forbade them from telling anybody else? Perhaps the greatest irony of quantum mechanics is that if the MWI is correct, then the situation is quite analogous if once you feel ready to die, you repeatedly attempt quantum suicide: you will experimentally convince yourself that the MWI is correct, but you can never convince anyone else!”

References: (1) (2) (3)

What Is Quantum Entanglement? What Will Happen If You Put Third Particle In The Mix? (Quantum)

Quantum entanglement is one of the delightfully bizarre phenomena that underpins quantum mechanics. The basic idea behind it is that two particles can be linked to each other—that is, affect each other’s quantum states — over any distance, even if that distance is the diameter of the universe. What’s more, the effect happens instantaneously, but without going faster than the speed of light. How? Just let us help you wrap your head around it.

What this means in practical terms (if anything about quantum mechanics can be considered practical, that is) is that if we know something about one particle, we know something about its entangled mate. But it’s weirder than that. Say you have a pair of gloves. If you know that one glove is right-handed, you automatically know that the other is left-handed, even if it’s billions of light years away. But with entangled particles, the act of measuring one particle actually changes the state of the other. It’s as if both gloves were in a superposition of right- and left-handedness—that is, both right- and left-handed at the same time—and only when you observed one did it become right-handed, thereby making the other become left-handed that very instant. That is, even if you check both gloves at the same microsecond from opposite sides of the universe, one becomes right-handed and the other becomes left-handed. That’s why Albert Einstein called quantum entanglement “spooky action at a distance.”

But wouldn’t this break the universal speed limit known as the speed of light? No, and here’s why: the information isn’t “sent” in an instant, the way you might send an email. The relationship between the particles already exists from the time the particles first interacted and became entangled. As Frank Wilczek writes in Quanta Magazine, “in all known cases the correlations between an [entangled] pair must be imprinted when its members are close together, though of course they can survive subsequent separation, as though they had memories.” The particles are “sending” information without sending anything at all. If you think that sounds like a fantastic way to create a supercomputer, you’re onto something—it’s precisely why quantum computing has such a huge potential.

This gets much more complicated, as you might expect. For example, the concept of “complementarity” says, in essence, that particles have certain complementary properties that can’t be known at the same time. One quantum physics example of complementary properties are position and momentum, but in our glove example, let’s say it’s handedness and color. A glove can be either right- or left-handed, and black or brown. Complementarity says that if you know one glove is right-handed, you can’t know what color it is; and if you know what color it is, you can’t know which hand it goes on.

Albert Einstein, Boris Podolsky, and Nathan Rosen discovered that something strange happens with the complementarity of entangled particles. If you measure both gloves for handedness, you’ll find that one is right and one is left. Likewise, if you measure both for color, you may find that both are brown. But if you measure one for color, and the other for handedness, there’s no match—a brown glove’s mate is equally likely to be right or left handed.

When you put a third particle in the mix, things get even stranger. Let’s say Mike likes brown, left-handed gloves and Steve likes black, right-handed gloves. If you take a whole lot of gloves, and measure two entangled gloves for color and one — also entangled — for handedness over and over and over, exactly none or two results are Mike’s. But if you measure three entangled gloves for handedness, one or three results are Mike’s. So are there an even or odd number of Mike’s gloves? The question makes no sense, because in quantum physics, systems like that don’t have definite properties — if they did, it wouldn’t matter whether or not you measured the gloves. That’s the mind-bending essence of quantum mechanics.

References: (1) (2) (3)

This Quantum Theory Says Reality Requires An Observer (Quantum)

The traditional view of quantum physics says that very tiny particles exist in many states at once until an observer measures them, which makes them choose just one state. But according to a tantalizing and incredibly controversial interpretation, nothing actually exists in many states at once — the observer just isn’t sure which state it’s in. Once he makes a measurement, then he knows. Conceived by quantum theorist Christopher Fuchs, this observer-centric view of quantum mechanics is called Quantum Bayesianism, or QBism for short.

If you think about the quantum world as a deck of cards, the traditional (Copenhagen) interpretation would go like this: When the dealer puts a card face down, that card is simultaneously all 52 cards at once. In traditional quantum mechanics, that’s a concept known as superposition, and the mathematical formula that describes all of those states is called a wavefunction. Only when you pick that card up and look at it does it “choose” its identity, also known as “collapsing the wavefunction”.

Likewise, if all the cards are dealt so that you know that only the ace of spades and the queen of hearts remain, and you are dealt the ace of spades, that changes the state of the remaining card so it becomes the queen of hearts. That relationship where the state of one card changes the state of the other is a concept called entanglement.

Here’s how QBism sees that same card game. When the dealer puts a card face down, a player knows that the card has a 1 in 52 chance of being any one of the cards in the deck; a 1 in 4 chance of being any one of the suits, and a 1 in 2 chance of being red or black. According to QBism, that’s all a wavefunction: a description of probabilities. When he turns the card over, instead of the card “choosing” to be, say, the ace of spades, the player just updates his knowledge: That card now has a 100 percent chance of being the ace of spades. The wavefunction is updated, not collapsed. Likewise, when only two face-down cards are left on the table, each simply has a 1 in 2 chance of being either card — they’re only related by probability, not some spooky quantum phenomenon. According to QBism, quantum mechanics is just probabilities of reality, not reality itself.

Because that’s actually how cards work, this simplified version of QBism sounds pretty airtight. But QBism takes a unique view of probability: It’s more a description of an observer’s uncertainty than the chances that one thing is actually correct. That’s why the main objection to QBism is that it’s all about subjective personal experience, so it seems to say that reality only exists in the mind of the observer, and two different people can have two different realities. Science is objective, critics say. Reality is reality, whether there’s an observer or not.

But, as N. David Mermin writes in Nature, this accusation is unfair: “Although I cannot enter your mind to experience your own private perceptions, you can affect my perceptions through language. When I converse with you or read your books and articles in Nature, I plausibly conclude that you are a perceiving being rather like myself, and infer features of your experience. This is how we can arrive at a common understanding of our external worlds, in spite of the privacy of our individual experiences.”

QBism does raise questions of its own, though. If quantum mechanics doesn’t describe an external reality, what does? As Fuchs tells it, that may be the wrong question. “Usually we think of the universe as this rigid thing that can’t be changed,” he told Quanta Magazine. “Instead, methodologically we should assume just the opposite: that the universe is before us so that we can shape it, that it can be changed, and that it will push back on us. We’ll understand our limits by noticing how much it pushes back on us.”

References: (1) (2)

Eternal in Knowledge, Eternal in Contents..