On August 21st, 2017 we learned about

Thin, smooth bark makes Madrone tree trunks seem cool to the touch

I may need to start petting trees more often. I’ve long known of trees that had particular colors and smells in their leaves and trunks, but I only learned in the last week that some trees hold surprises for your finger tips to discover. The tree in question was a Pacific Madrone (Arbutus menziesii), and was actually hard to miss thanks to its striking red bark peeling off the trunk. The surprise was that the tree was cool to the touch, which is why it’s sometimes called the “refrigerator tree.”

For something cool to the touch, Madrone trees need lots of sunshine to thrive. If conditions are right, they can grow to be nearly 100 feet tall, but at smaller sizes Madrone trees can be mistaken for some of their red-barked relatives, like the Manzanita (Arctostaphylos). Both plants’ eye catching bark grows thin and smooth, but this trait is especially striking in mid-summer when Madrone tree bark starts to peel off the trunk. At that point, a quick touch makes it hard to ignore how much cooler these trees are than the surrounding environment.

Cold or just conductive?

Except that they’re not really cooler. The trees’ temperature is likely the same as any of the other similarly-sized plants that grow near them, just like a paper book is the same temperature as a metal keys sitting in the same room. With sufficient time, the temperatures equalize, but when we touch the metal, or the Madrone trunk, it feels colder. This is because heat is more easily transferred to certain materials than others, and when heat from our hand is conducted away we perceive it as colder. Now, a Madrone tree obviously isn’t metal, but that thin, smooth bark isn’t as good an insulator as the rough, corky bark that you find on most trees. Your hand is able to come into more contact with the smooth surface, and the sap and fluids flowing inside the trunk can then wick your body heat away.

Even if refrigerator trees aren’t actually colder, their unusual bark obviously still stands out from that of their neighbors in the forest. The thin, peeling bark that exposes the trunk may have originally evolved as a form of defense. By shedding the outer layer of bark, the tree can dump any fungi, mosses, lichens or other parasites that tried taking up residence on the red wood. The red itself is likely another form of defense, as the tannins that make up that coloration would be bitter and possibly toxic to animals that might want to munch on the tree, not unlike the colorful bark found on rainbow eucalyptus. It’s good that the peeling is helpful to these plants, because now that they know about these chilled trees, it’s going to be hard to keep my kids’ hands off them.

Source: The Refrigerator Tree by Steve, Nature Outside

On August 17th, 2017 we learned about

Eclipse experiments designed to exploit the Moon’s shadow as it slides across the Earth

Monday’s solar eclipse will be exciting, strange, and possibly cause all kinds of tumult and chaos, which is pretty impressive considering it’s technically just a big shadow sweeping across the Earth. For all of the hype and hoopla, the upcoming total eclipse does offer some unusual opportunities for actual scientific research. Researchers have many experiments planned for the Moon’s shadow, many of which don’t even relate to the Moon itself. Instead, they’re looking at the Earth, Mars, Mercury and the composition of the Sun.

Earth’s atmosphere

One of the larger-scale studies planned for the eclipse will look at how a lack of sunlight changes the Earth’s ionosphere. This layer of atmosphere is normally bombarded with ions from the Sun, protecting those of us on the surface of the planet while also setting off the colorful auroras we call the Northern and Southern Lights. During the eclipse, the Moon will be intercepting those ions, and so volunteers will be measuring how this brief drop in activity affects radio wave transmissions through an unusually calm ionosphere.

Mimicking Mars

Another experiment planned for Monday involves releasing 50 high-altitude balloons into the Moon’s shadow so that we can see how a few moments in the stratosphere affects bacteria. Alongside each balloon is a metal plate swabbed with Paenibacillus xerothermodurans bacteria, which are noted for their incredible durability in harsh environments. Since it’s hard to ensure spacecraft are completely sterile before they arrive at another planet, researchers want to see how these bacteria might hold up in tough environments. The stratosphere’s thinner air, low temperatures and higher radiation levels are already a good proxy for other worlds, but during the eclipse these attributes will all be shifted to a point that closely resembles the surface of Mars. So once the balloons are recovered, researchers will get a chance to see how P. xerothermodurans might hold up on the Red Planet.

Measuring Mercury

Looking a bit deeper into space, there are plans to take advantage of the blocked sunlight to get a better look at the planet Mercury. Mercury’s proximity to the Sun makes it hard to measure, as the light and radiation levels are somewhat overwhelming for most instruments. So when the Moon makes things a bit darker, scientists plan to measure the changes in temperature around Mercury from special airplanes fitted with sensors. These planes will fly in the path of totality, or where the Moon completely blocks the Sun, in order to have more than the two minutes and 40 seconds anyone on the ground could hope for. They’ll also be flying at high altitudes to help bypass distortion that might be introduced by the Earth’s atmosphere.

Studying the Sun

Finally, at least one study will be looking at the Sun itself, which seems appropriate considering the nature of this event. Actually, scientists will be gathering data on the Sun’s corona— the wispy outer layers of plasma that will be visible during totality. As with the study of Mercury, instruments mounted on special aircraft flying at over 470 miles per hour will collect data for around six minutes to try to figure out how the Sun’s outer layers are composed, and why they’re hotter than the inner layers of the Sun. Previous measurements have found that the outer layers of the sun are hotter than most models would expect, and researchers how that this new data will help explain how that’s possible.

And of course, if anything is inclusive, we can all try again during the next total eclipse, which is only three years away if you can make the trip to Chile.



Source: Solar Eclipse-Chasing Jets Aim to Solve Mystery of Sun's Corona by Tom Metcalfe, Live Science

On July 17th, 2017 we learned about

The mathematical model that describes how body size sets top speeds

If video games have taught me anything, it’s that bigger characters hit harder, but move slower. This always felt pretty intuitive, to the point where giant characters in fantasy stories are depicted as moving in slow motion compared to human-sized folks. The thing is, movement is tied to our muscle strength, and that strength is (at least partially) due to muscle size, which would suggest that bigger creatures should move faster, not slower. Nobody’s seen an elephant run at 373 miles per hour though, so it looks like reality is siding with video games here, and we finally have the math to prove it.

Fighting physics and fatigue

Myriam Hirt, a zoologist from the German Center for Integrative Biodiversity Research, came up a formula to predict how size influences speed. The first factor is the animal’s mass, which not only dictates the amount of muscle available, but also the amount of inertia that animal has to overcome to start moving. So a large elephant may have some impressively large muscles, but it takes a lot more work to get those legs moving. This is different from weight, which is the influence of gravity on the body’s mass. If you moved an elephant to the Moon, it would weigh less, but still have a lot of inertia since the size of its body didn’t change. The upside of this is that if you did get an elephant moving that fast, it’d be remarkably difficult to then get all that mass to stop.

The second factor is the animal’s anaerobic metabolism, which explains why an elephant isn’t about to do that extra work to break into a swift sprint. Most of the time, a body relies on aerobic metabolism, which uses oxygen to provide energy to your cells, and is used in longer, lower-intensity activities like a long walk. For a quick burst of energy, like sprinting at top speed, muscles use anaerobic metabolism, which burns sugars like glucose directly. This allows for fast twitch activity in muscles, but produces byproducts like lactic acid, putting a cap on long muscles can work this hard. Taken together, the fastest elephants have only been observed hitting 25 miles per hour.

Mutual maximums

In the case of our charging elephant, overcoming the inertia of its mass requires too much anaerobic activity to work. The animal’s large muscles may give it a lot of strength and endurance, but not enough to rocket forward like a cheetah. In fact, across animals moving on land, sea and the air, the same size ratios held true 90 percent of the time. Like a bell curve, small bodies have little inertia to overcome, but lack the muscle to give them much power. Large bodies are too big to get moving before the muscles start to burn out. The sweet spot to maximize speed and size is then in the middle, around the size of a cheetah. Cheetahs have other adaptations that make their bodies even more efficient sprinters, like their super-flexible spines, but the size still matters. A double-sized cheetah wouldn’t be nearly as energy efficient and would like be unable to reach the same 74-mile-per-hour speeds.

This formula does more than confirm the speeds of animals we’re all familiar with. Thanks to it’s high accuracy, it can help us estimate the speed of animals we can’t observe, like dinosaurs. We’re estimating body mass in extinct animals as well, but baring other adaptions to improve performance, it’s fair to assume that a Velociraptor could have run at 34 miles per hour, in contrast to a much bulkier Tyrannosaurus would have only hit 17 miles per hour. Big bodies can provide a lot of power, but physics requires that they also take a lot of work to move around.

Source: Why the Biggest Animals Aren't the Fastest by Stephanie Pappas, Live Science

On July 3rd, 2017 we learned about

The factors that shift the sound of fireworks from deafening to delightful

For as much as he enjoys making noise himself, my four-year-old is not a fan of loud noises. The Fourth of July is a stressful holiday, since he like the dazzling colors of fireworks but is very sensitive to the booming explosions created by a professional show. As much as we try to reassure him that there’s nothing to be worried about, he’s not entirely off-base to be worried about the volume levels of large fireworks— the World Health Organization (WHO) recommends that kids not be exposed to sounds more than 120 decibels (dB) to avoid hearing damage. Depending on how they’re made, some fireworks might be as loud as 150 dB, so how can we take our kids to see, and hear, these explosions in the sky each year?

How bad is that boom?

To make sense of this, it’s good to know what’s happening when you hear a loud ‘boom’ in the sky. When a firework shell explodes, the heated particles and gases expand outwards with immense force, slamming into the air molecules already in the sky. The exploded particles push the air outwards, compressing those molecules into a pressure wave moving faster than the speed of sound. That blast wave continues expanding in all directions at once. This is important, because it means that the initial energy of the explosion is being spread out more and more the further outwards it travels. If you’re a reasonable distance away, you’ll only be hit by a portion of the initial explosion’s energy, rather than the whole thing. So a firework that explodes at 140 dB will only reach you at 93 dB if you’re 200 feet away. Most professional fireworks explode at higher altitudes than that, reducing the amount of energy that ever gets to your ear.

This can still be a significant amount of energy though. If you’ve watched a professional fireworks display you’ve probably felt at least a bit of pressure on your body as the wave of knocked air particles slams into you. This may have felt more or less intense depending on the state of that air before the explosion. Humidity helps carry sound, and pockets of cold air below warm air carries blast waves better as well. Back-to-back explosions don’t actually boost each other’s power, but the repeated sounds are perceived as louder to our ears.

In addition to distance from the explosions, timing is important too. Brief exposure to loud sounds isn’t nearly the problem long exposures are. Even if you did hear a 120 dB explosion, your hearing would most likely bounce back to normal, while spending eight hours listening to 87 dB noise could leave you with permanent hearing loss. This isn’t to say that listening to explosions is necessarily pleasant for your ears, as you might experience short-term hearing loss after really loud sounds, but that chances are the firework show won’t last long enough to really be reason for concern.

Deafening by design

The last element to consider is that not all fireworks are created equal. Most professional shows are only punctuated by loud booms and crackles, partially to avoid overwhelming the audience with a wall of indistinct noise that wouldn’t be fun. The loud fireworks are known as salutes, and they actually boom by design. Just as pyrotechnicians use knowledge of chemistry, physics and geometry to create cool colors and patterns in the air, they can also choose to make a particular shell noisier or quieter. For some people, the booming noise is actually a priority, and they work to create louder, more concussive blast waves. The pinnacle of this design theory is the Gabe Morte, or “dead head,” which actually skips the pretty lights altogether to focus on entirely on the size of the sound. Obviously, my four-year-old will be passing on anything following the “thump junkie” school of thought, but hopefully he’ll be able to enjoy the quieter shows most of us enjoy on the Fourth of July… from a reasonable distance.

Source: How Loud Are Different Fireworks? by Kris Zambo, Dynamite Fireworks

On July 2nd, 2017 we learned about

Protecting artwork for posterity when it’s made from materials prone to dilapidation and putrefaction

In the last week, I’ve had the pleasure of going to an art museum with eight- and four-year-olds, once at the four-year-old’s request. They especially enjoyed the modern and contemporary pieces that felt more open-ended in how they could be interpreted (protip: kids like Nick Cave.) The biggest concern for our visits was reminding everyone that these objects, even the stuffed animals sewn into a suit composed largely of fishing bobs, weren’t there for us to touch. In order for people two thousand years in the future to be able to see these new pieces the way we were able to see an Egyptian sarcophagus, we all needed to do our part to keep things as pristine as possible. This challenge extends beyond kids’ fingers though, as non-traditional materials used in contemporary art are posing huge challenges for art curators.

Replace and repair

Synthetic items like fishing bobs and stuffed animals seem like the should be easy to preserve. Plastics famously take ages to break down, but manufactured goods don’t always hold up the way you expect. A plastic bob might get cracked during transport, or lost as some of the knitted yarn that holds it breaks down. The question then becomes how to repair the piece— if the original item can no longer be purchased, do you find a substitute? How much change can a piece of art accommodate before it’s no longer the same creation? This has been an issue in some art purposely built from manufactured goods, like florescent tube lights in installations by Dan Flavin. In that case, Flavin knew the lights couldn’t be replaced forever, forcing the piece to change over time.

Responding to rot

Some materials turn sculptures or paintings into what amount to performances. Food has been incorporated into art for thousands of years, but when that food isn’t just presented as an image, things can get messy. Dieter Roth embraced this in his biodegradable art, covering photos in cheese to see how they’d change over time. Jim Victor and Marie Pelton sculpt butter in refrigerated cases, knowing that each piece has a short lifespan from the start. When the eventual decomposition isn’t intentional though, art conservationists have a bigger problem. Janine Antoni has made a few copies of a piece called Lick and Lather, each consisting of self-portrait busts made of chocolate and soap. Over time, chocolate pushes some fatty lipids to the surface, adding white, chalky texture to the otherwise brown surface. The soap versions actually prove to be more difficult to preserve, and curators have worked with Antoni reformulate the exact soap formula so that future replacements can hopefully survive the test of time a bit longer.

Recuse from the light

Of course, even traditional materials need special care to hold up over time. While the effects of heat and humidity might be more obvious, even light can damage an oil painting. Ultraviolet light can damage pigments in paint, breaking up specific molecules that end up changing the painting’s colors. Museums therefore do their best to avoid bright light on paintings, but even darkness can cause changes. Linseed oils used to make the oil paint more malleable tend to darken and yellow in darkness, although that particular change is eventually self-correcting after a painting is exposed to light again.

All these changes mean that a lot of planning, thought and even physics and chemistry are needed to keep art objects in good shape over long periods of time. Collectors are now having art appraised not just for their vision and value, but also for how durable the piece may be. In some cases, the solution is to plan ahead and build replacement parts with an original piece, but other times the answer seem to be accepting that change is inevitable. Even if something doesn’t end up looking like the artist originally intended, there’s still a good chance it will be valued and appreciated for generations to come— just ask those Greek sculptors who might barely recognize their own work now that the paint and arms have fallen off.

Source: How Do You Conserve Art Made of Bologna, or Bubble Gum, or Soap? by Jacoba Urist, The Atlantic

On June 29th, 2017 we learned about

Frozen waffles and a flaming, melted plate teach us about toasters and microwaves

“Mommy! Daddy! There’s a fire!”

This is not how you want to start your day, but it wasn’t completely surprising when we heard it at 6:30 Tuesday morning. After all, just the night before we’d told our eight-year-old that if she wanted to cook a frozen waffle she was allowed to use the toaster. We told her where the waffles were and how long to cook them for. We reminded her to be careful with the hot toaster, and to get help if there was any sign of a fire. She was, therefore, just doing exactly as we told her.

The problem was what we hadn’t told her: Plastic plates can go in the microwave, but not the toaster.

The fire was contained, although at the coast of one Ikea plastic plate (dishwasher, microwave, but not toaster safe!) and the toaster itself. The plate’s flames were actually rather persistent, requiring some effort to be fully extinguished. Our daughter wasn’t actually too phased by all this— she just wanted to know why a plate could be used in one metal cooking box, but not the other?

Warmed from the inside by water

A plastic plate can survive your microwave because microwave ovens heat water, not plates. A magnetron behind the oven’s buttons generates microwaves that are then piped into the main compartment where your food is. Those microwaves are a lot like high-energy radio waves, but with shorter wavelengths. The wavelength is important, because it can affect what the microwaves will be blocked by, interact with, etc. In this case, the wavelengths are just below five inches long, and they’re kept contained by the metal shielding along the sides of the oven, bouncing around like light bouncing off a mirror.

When the microwaves hit your food, they primarily interact with water molecules your food contains. It will cause those molecules to vibrate in place, and some of that activity creates friction between molecules. As with other cases of friction in the world, that friction converts the initial source of energy into heat, and warming your food. In a way, the water molecules are doing the actual heating here, and so drier food (or plates) don’t get warmed very much, while water-filled items like pie filling can become scaldingly hot very quickly.

Cooking with heated air and coils

A toaster oven heats food through convection. Electric coils are pumped full of energy so that some of that energy can start heating the air in the oven. Warmer air rises, triggering a bit of circulation to eventually give you a very hot pocket of air in your metal box. All ovens heat food through convection heating, but some ovens (and even our replacement toaster) now bill themselves as “Convection Ovens.” These ovens include a fan to circulate hot air faster, making the warming process a bit faster, although sometimes drying out food more in the process.

Just as hot coils give away heat to the cooler air in the oven, hot air transfers heat into your cool food. Under ideal conditions, the temperatures would eventually equalize, and no heat would need to be transferred further. However, since the heat is being transferred from the outside in, thicker pieces of food need to wait for the outer layers to warm up before the insides warm up. The upside is that this “outside-in” heating can give you crunchy crusts and crispy skins in a way that a microwave will never do.

What pans go where?

Circling back to my daughter’s confusion over plates, plastic can go in a microwave, but only a few plastics can survive an oven. Because the plate doesn’t get heated as much as the food in a microwave, its temperature isn’t likely get hot enough to melt or ignite.  Metal is a big problem though, because it can reflect microwaves back at your magnetron and damage it, or build up an imbalanced electrical charge that results in dramatic sparking and arcing. That can damage the shielding of your microwave, allowing it to “leak” microwaves when you use it. Those microwaves can then harm body parts that have a hard time shedding heat, like your eyeballs.

In a convection oven, metal’s just fine. It can easily conduct heat from the air to your food, presumably without hitting its melting point. For aluminium, that’s 660° Fahrenheit, and 1200° Fahrenheit for a cast iron pan, both temperatures that would probably make a mess of your meal. Since common plastics like ABS can get squishy at 88° Fahrenheit, and ignite at 416° Fahrenheit, it’s makes sense that my daughter’s plate couldn’t handle the toaster. From here on out, hopefully the toaster will only have to deal with waffles.

Source: Microwave ovens by Chris Woodford, Explain That Stuff

On June 20th, 2017 we learned about

How Marcia Huit could start to see through solid objects

Sciencing the Sisters Eight!

It takes a long time for her sisters to understand what’s going on with Marcia Huit in book five of The Sisters Eight. Her behavior becomes rather erratic, and after a fair amount of confusion she reveals that she’s stressed because she can see and hear everything. Unlike the animal kingdom’s top listeners, like the greater wax moth that can hear a wide range of sounds we can barely imagine, Marcia is just very sensitive to every sound, even those originating a great distance away. However, the weirdest thing is that this seven-year-old can also see through objects, looking straight through buildings as if they were glass.

Our vision depends on the fact that light in the visible spectrum is absorbed or reflected by objects around us. A blue ball will absorb most frequencies of light, but the light with a 475 nanometer wavelength will bounce back, and when it hits the correct cone cell in our eye, it sends a signal that our brain will interpret as “blue.” However, there’s a lot of energy out there that can’t be seen by our eyes, from gamma rays with tiny wavelengths to radio waves with huge wavelengths. These frequencies don’t get absorbed and detected by our eyes, usually passing right through us without any interaction. As a result, they’re essentially invisible to us.

Looking at light we can’t see

The fact that these frequencies of light pass through us is a clue though, since they usually pass through other materials as well, at least to a point. Radio waves, for instance, can pass through the walls of a house pretty well, although if you’ve ever lost cell reception in the middle of a building, you’ve noticed that they do get blocked when a material is at least as thick as the signal’s wavelength, which can range from four inches to 62 miles long. If any of these waves were actually reflected, they could conceivably be detected bouncing back, and be used to build an image like our eyes and brains process stimuli from the visible spectrum.

Researchers at MIT have been working on using radio waves as an alternative to visible light for a while. They’ve built antennas that can emit high-powered radio waves, and then try to catch enough of those waves that might bounce back to build a picture. By carefully interpreting what wavelengths get reflected first by a wall, and then by objects beyond the wall, they can essentially see through that wall to know what’s happening inside a building. The catch for Marcia is that the technology to do this isn’t small— the first models of these sensors were around eight feet long, designed to be mounted on a truck, not inside an eyeball.

Other strategies for seeing

Radio waves aren’t the only thing to penetrate common materials, but other portions of the electromagnetic spectrum present their own issues. Gamma waves have very short wavelengths and can pass between molecules in objects, including the molecules that you might want to see. They do interact at times, but not reliably enough to form pictures of anything that’s not at least as dense as lead. To add another tool to Marcia’s visual toolbox, there’s also a chance she is making use of less traditional detection methods, like electrons passing through matter and back in a process called quantum tunneling. Right now, this requires elaborate equipment with carefully arranged lasers and detectors, but an electron’s return trip through other matter could conceivably be used to create an image of what’s behind a wall.

In the end, none of these fully account for Marcia’s enhanced vision on their own. However, if her visual receptors could somehow make use of a wider range of the electromagnetic spectrum, some of those wavelengths would be able to provide information about objects behind other objects. By blending and filtering which range the spectrum she focused on, she might be able to see through walls bother near and far, although how she makes her eyeballs collect all those wavelengths remains to be seen.

Source: Seeing through walls by Emily Finn, MIT News

On June 19th, 2017 we learned about

How Jackie Huit blurred the air around her to beat a train to the big city

Sciencing the Sisters Eight!

In the fourth book of The Sisters Eight, Jackie Huit finds herself left behind at a train station while her sisters head off to the city. Fortunately, her newfound power lets her move at inhuman speeds, and she’s able to not only catch up to the departed train, but even overtake it along the way. From the window of the train, Jackie’s sisters see her as a sort of blue, blurred dervish, and they don’t even realize it’s their sibling racing by. Jackie arrives at the station barely breaking a sweat, clearly pushing what’s possible for bipedal motion as we know it.

What steps produce speed

We’re never told how fast Jackie actually travels, but we can make a few estimates. The commuter train is likely to be moving around 30 to 50 miles-per-hour, and since Jackie passes the train, she must be moving faster than that. However, for being a blue blur, she’s still moving slow enough that she takes a few moments to pass the other girls’ window. The relative speed gap between Jackie and the train probably shouldn’t be enough to cause a blur like that— even without checking the math, our eyes don’t have trouble seeing a car passing us quickly on the highway, and so a runner would need to be which suggests that the blur is coming from some other kind of movement. Maybe Jackie is passing the train at an impressive 70 miles per hour, but the blurring is because she’s moving her arms and legs extremely quickly? That might explain things, except that if she’s flailing her limbs that much, she’s probably running very badly.

World champion sprinter Usain Bolt has been studied to see what parts of his movement enables his record breaking speeds. While it would seem like you’d want to pump your legs more frequently to move faster, scrambling your legs like some kind of Looney Tunes cartoon, and possibly Jackie Huit, isn’t really that useful. Analysis of Bolt’s movement found that the trick is actually to hit the ground harder with each step, pushing down with between four to five times their own body weight with each step. However, all that effort still couldn’t crack even 30 miles per hour, largely because of wind resistance. It’s been calculated that as much as 92% of Bolt’s work goes into fighting drag, not working to achieve motion.

Path of least resistance

There’s no obvious way for a human, even one smaller than Usain Bolt like Jackie Huit, to beat that kind of drag while they’re running in Earth’s atmosphere then. However, what if that weird blurring wasn’t motion blur, but actually a vapor cone. When an object like a jet approaches the speed of sound in the sky, around 770 miles per hour, the sound waves moving through the air begin to pile up in front of the plane, as they can’t move away any faster than the plane is flying. This ends up creating a low pressure zone right behind this leading sound wave that lowers air pressure, sometimes enough to form a cone-shaped cloud around the aircraft. Planes can often push through that cone and continue fighting the air ahead of them, breaking the sound barrier in the process.

Jackie, on the other hand, might be hiding behind this pressure wave on purpose. Perhaps the key to her running is actually that she can reduce the air pressure in front of her body without needing to reach the speed of sound. The lower air pressure would then let her move more freely, keep her cool for a longer run, and make a cloud of water droplets that would distort her image to anyone on the train, assuming there was just enough air pressure to continue breathing. Since humans can’t endure a full-tilt sprint for more than a minute at a time without risking exhaustion, running in this low-resistance bubble would let Jackie work less, and fall back on humans’ special adaptations for long-distance running.

Source: Physics of running fast: Scientists model 'extraordinary' performance of Bolt by Institute of Physics, Science Daily

On June 19th, 2017 we learned about

How Georgia Huit could bend light to become invisible

Sciencing the Sisters Eight!

In Geogia’s Greatness, then seven-year-old Georgia Huit discovers that if she wiggles her nose, she can become invisible for as long as she’d like. As with her older sisters Annie and Durinida’s powers, this invisibility gets the Huit girls out of a few tight spots, but is never explained beyond the nose wiggling. So how possible is invisibility, and how close are we to having it in the real world?

Bending light around a body

Even though invisibility has been a part of fantasy and science fiction for a long time, it is something scientists are working on right now. Since we see objects after light is reflected off their surfaces into our eyes, the common approach has been to make sure that light never gets to us. Rather than attempt to make objects completely, perfectly transparent, researchers are trying to bend light around objects. That way, the light that actually makes it to your eye will have originated behind the invisible object, rather than come off the object itself. You’ll get an “unobstructed” picture of what’s behind the object, as if it weren’t blocking your view of it’s surroundings.

This hasn’t exactly been achieved yet though. Right now, engineers are researching what are called metamaterials that can bend specific frequencies of light around objects. One approach involves embedding a lattice of 10,000 gold rings, called resonators, into one square centimeter of silk. Each ring has a second ring inside it, and they’re all arranged to closer together than the wavelength of the light that is being targeted for manipulation. Most experiments are based around microwaves instead of visible light, because the wavelengths are longer and it’s just easier to arrange, but scientists are confident that the system could be adjusted to target a the visible spectrum. It’s been theorized that running electricity through the resonators could add some flexibility to the system, allowing one set of resonators to be adjusted to bend different frequencies of light.

If this were somehow the explanation for Georgia’s invisibility, it would probably mean that her pores (and clothing?) were somehow growing tiny resonators all over her body. Her nose wiggling would then be the moment that she pushes an electrical charge through the resonators so that they get tuned to the visible spectrum, at which point light that would hit and reflect off of her would instead be bent around her body, continuing along it’s original course as if she weren’t there.

Traveling instantly through space-time

To spoil The Sisters Eight just a bit further, Georgia discovers that she has a second ability in the final book, The Final Battle …For Now. Her cousin explains that when invisible, she can also teleport to whatever location she’s thinking about, presumably instantaneously. That timing is important though, because dematerializing a body and rebuilding it elsewhere in a single instant has a lot of problems with physics. Georgia’s mass shouldn’t be able to move that fast through space. Even if a new copy of her is being created elsewhere, a human body is so enormously complex, it would be an absurd amount of information to somehow transmit to a new location.

A better bet would be that Georgia is somehow just moving to a new location through a sort of cosmic shortcut. Part of Einstein’s theory of relativity allows for things called wormholes, which are like portals that connect one spot in space-time to another, even if it’s very far away. While wormholes have been described mathematically, the closest we’ve come to seeing them involves masking a magnetic object in a special chamber. To human senses, a magnetic rod was pushed through a special sphere and came out the other side. From a magnetic perspective, the magnetic field of the rod actually vanished, reappearing on the other end as if it had teleported. It’s a far cry from a little girl appearing on the other side of the house, but perhaps Georgia’s gift allows her to create her own space-tunneling wormholes at will, appearing wherever she wants.

Or maybe she just runs to a new spot while invisible, making everyone think she teleported. Physics would be good with that explanation as well.

Source: Inside the Lab Where Invisibility Cloaks Are Made by Philip Ball, The Atlantic

On May 29th, 2017 we learned about

Stressed metals can sprout circuit-shorting “whiskers”

In humans, acute stress has been linked to hair loss. In metals like tin and zinc, the opposite is true, as stressed bits of metal can sprout wispy, hair-like structures commonly known as metal whiskers. Before any stressed, balding folks feel jealous of these growths, they’re actually worse than any hair loss you’ve experienced, because these whiskers can cause everything from equipment failures to fires, often in delicate electronics or equipment.

Unlike your hairs which are discrete structures assembled by special cells in your skin, metal whiskers are simply outgrowths of the same metal the larger object is made of. They’re basically a function of the metal’s crystal structure being bent and warped in new ways, with single rods of metal being extruded from the surface of the object. These whiskers don’t branch, and generally start growing at a perpendicular angle to the objects surface, although once they get going they can start clumping and bunching into a tangled rat’s nest that would be a challenge for any hair brush.

Hazardous hairiness

Many metals seem to be capable of growing metal whiskers. copper, cadmium, silver, gold, zinc and even alloys have been found to grow whiskers, although the biggest problem is tin. Tin seems to be relatively whisker-prone, which is a problem because tin is often used in soldering electronic circuits. The whiskers can end up making new connections in electronic devices that can cause short circuits, a phenomenon that has crippled computer networks, pacemakers, a nuclear reactor and even satellites. Even more dramatically, thin whiskers conducting a current can heat up enough to combust, leading to fires in computer banks. In some cases, particularly tiny bits of metal were found to have become airborne, drifting through the air until settling between other components, causing short circuits where whiskers weren’t even growing in the first place.

Engineers have yet to isolate a single reason for a piece of metal to fuzz itself up. Various stresses on the metal, from mechanical stress to stresses induced by diffusion of different metals have been linked to whisker growth, and so effective preventative measures aren’t always obvious. Lead used to help block the formation of metal whiskers, but it’s now banned from use in consumer electronics out of concern for human health. One of the more popular options now is conformal coatings, which basically coat your object in a protective sheath that is strong enough to stop whiskers from growing out of the metal before they get started.

Source: Metal whiskers – It’s like hair, on metals. And it’s a huge problem. by Umair Hussaini, Technobyte