On October 12th, 2017 we learned about

Materials and methods that can make a building a bit more fire-proof

With wildfires destroying over 3,500 structures across northern California in the last week, it’s understandable that my kids are feeling concerned about the safety of our own home. Aside from the smoke, we’re well out of harms way, but that hasn’t stopped some age-appropriate brainstorming about fire safety. Maybe force-fields would help? How about everyone using their garden hoses to spray the fires? Why can’t houses just be fire-proof?

Fire-proof, in the 3rd-grade understanding of the term, probably isn’t possible, but houses can be made to be very fire-resistant. Depending on the materials and design of a building, it may be able to withstand up to four hours of intense flames, and even then structural problems might come up before the whole thing actually burns. Basically, the key is to build in materials that can absorb and withstand heat while remaining chemically inert— ie., not actually combusting themselves. From that perspective, the wood frames that hold up so many American homes are sort of a terrible idea, as the wood will both burn and transmit heat to other parts of the structure. Moving away from the idea of a rustic log cabin, we should really all be living in homes made of concrete.

Preventing conflagration with concrete

Concrete frames and walls provide a number of advantages over wood. The limestone, clay and gypsum that go into concrete are very stable, and thus unlikely to react with oxygen and heat during a fire. Instead, a concrete slab can absorb a lot of heat, trapping some of it in internal pockets and pores. This can help isolate the heat from a fire, as well as insulate the building from unpleasant hot and cold temperatures in less dire circumstances. If you want to maximize the impact of your concrete walls, you probably want to install them as insulated concrete forms (ICFs), which are modular systems to further compartmentalize your concrete slabs, keeping the buildup of heat from a fire as isolated as possible.

If a building isn’t concrete, there are other options to up its fire-resistance. Bricks, having been created in kilns, hold up to heat quite well. In a fire, they can absorb heat without being damaged, with the point of failure usually being the mortar that holds a wall together. Gypsum board used in drywall can absorb a fair amount of heat without burning as well, with Type X gypsum boards being packed with calcium sulfate and water vapor inside. When exposed to fire, the water vapor can help suck up a lot of heat before the gypsum has to get cooked too much, all of which will hopefully provide time for the fire to be dealt with. On the outside of your building, common stucco usually has cement, sand and lime as ingredients, which again are inert enough to absorb heat without burning themselves.

Bad and best practices

Even with concrete or brick walls, many buildings still have weaknesses that can make them susceptible to fires. Vinyl siding and framing around windows melts pretty easily, exposing any wood framing underneath. Single pane windows that get broken allow both heat and oxygen to pass into or out of a burning building. If the source of flames is from an external wildfire, roofs are often a point of combustion. Loose shingles or semi-open tile work, can provide openings burning embers to get into a house’s attic. Overhangs are another place where fire-resistant materials are likely to be joined to more combustible wood, exposing the roof to danger even if the walls are otherwise unscathed.

So what should my kids’ theoretical fire-proof house look like then? Starting with the yard, no trees or brush should be too close to the house itself. Instead of a wooden deck, a stone or concrete patio would act as a firebreak, protecting the concrete walls. Tempered glass windows, or maybe glass bricks with an internal wire matrix to avoid cracking, would be further protected by roll-down metal fire doors that could deploy automatically in response to extreme heat. A steeply pitched roof would encourage burning embers to fall to the ground, rather than sitting and burning on the building. Internal walls would be brick or concrete, maybe with gypsum boards if you needed a softer material for some surfaces. It might start to feel a little bit like a fortress, as long as no lava (“Or asteroids!” “Or monsters!”) show up, it should be one of the cozier places to be after a wildfire.

Source: Why is concrete fire resistant? by Colleen Cancio, How Stuff Works

On October 10th, 2017 we learned about

Baryons confirmed to constitute a considerable portion of the universes’ invisible material

We call it outer space, but that really paints the wrong picture of just how much stuff is really out there. Yes, the distances between objects are usually bigger than we can truly comprehend. Sure, there’s a lot of cosmic territory that look empty, neither reflecting or emitting any kind of detectable energy, from light to heat. However, the movement of the things we can see indicates that there’s a lot more matter in the universe, even it’s not directly visible. Researchers have long trusted that gravity hasn’t been fooling us, and now two teams have finally found some of that imperceptible stuff that scattered throughout space.

Deciphering the dark

When we look out at the universe with our eyes, telescopes, microwave detectors and more, we really only see about 20 percent of what we know must be out there. The 80 percent that we can’t directly observe is referred to as dark matter, since it never shows up as a source of light or other energy when we look. However, the behavior of planets and stars would only make sense if they were being influenced by the gravity of a lot unseen material. As confident as astrophysicists are about the gravitational forces that should be shaping the universe, it’s always good to try to validate one’s models, even if it’s just to confirm what was mostly already known.

Cranking up the contrast

In this case, two teams of researchers have independently imaged clouds of tiny particles called baryons. Baryons are smaller than a proton, consisting of only three quarks. That size reduces their chances of interacting with something like visible light, which is part of why we don’t see the huge swaths of them floating around space. To make things even trickier, they’re distributed in diffuse clouds between galaxies, making whatever traces they’d leave on their surroundings even harder to detect.

To make these baryon clouds more obvious, both teams used a technique which essentially upped the contrast on our readings of two galaxies that had been observed by the Planck satellite in 2015. Both groups overlaid the observed data on itself over a quarter-million times, making the clustered baryons more obvious to detection, although even then they weren’t directly visible. Instead, researchers had to rely on the Sunyaev-Zel’dovich effect, which is when light from the big bang itself is scattered by passing hot gas. So in the end, the teams were only able to see strands of scattered light connecting two galaxies, but that was enough to confirm the presence of otherwise invisible matter.

This doesn’t solve all of our dark matter mysteries, but it does account for a significant chunk of what was otherwise unconfirmed sources of gravity. There are hypothesis about what other kinds of particles are helping fill the cosmic void, but for now it’s nice knowing that we’ve been on the right track with our understanding of gravity so far, and that only half the universe’s mass can’t be explained. Yet.

Source: Half the universe’s missing matter has just been finally found by Leah Crane, New Scientist

On September 13th, 2017 we learned about

Fiber-optics under Stanford can feel every car tire and footstep

Every moment has repercussions, a fact my neighbors are no doubt acutely aware of on Saturday mornings when the kids wake up. Every step, thumb and bump not only hits the floor (or wall, or… ceiling), but transmits energy through those materials, much of which we end up noticing as sound. Thankfully, many of these vibrations are either too faint or the wrong frequency to be detected by our ears, but that doesn’t mean they’re not there. In fact, if you really wanted to, it turns out that it’s possible to detect and decipher almost every vibration a person’s movement might make— right down to individual footsteps along a busy sidewalk.

Wired for sound

This kind of listening is already underway at Stanford University in a project called the Big Glass Microphone. Three miles of fiber-optic cables have been laid in a loop under part of the campus, originally to investigate seismic activity. Seismographs around the world already rely on vibrations being transmitted through the ground in order to sense and triangulate activity like earthquakes, but the fiber-optics have proven to be especially sensitive. Like more traditional seismographs, the fiber-optics can measure small changes in electrical current as it’s mechanically perturbed by vibrations, but the scale of the vibrations detected provide previously unknown resolution in those readings.

As a foot steps on the ground, a relatively small, low-frequency vibration is transmitted through the sidewalk and dirt. This then hits the fiber-optic cable, which at the length of a hair is small enough to stretch slightly as the vibration passes through. With light running through the cable, these fluctuations are measured, and in most applications, thrown out as background noise that would muddy data on earthquakes or explosions. In this case, engineers are looking the other way, seeing how well they can track footsteps and cars, possibly even identifying the source of those sounds by unique vibration “signatures.”

Uses for more electronic ears

This effectively means that any material that can house a fiber-optic cable could conceivably serve as a mechanical sensor for nearby activity. In the case of a sidewalk or road, it could track the movement of people or specific cars driving by. In a building, vibrations could reveal what floor people are on to trigger changes in lighting and heating, or detect when a pipe is leaking in the wall. Or just track you even more than your phone already does.

The fact that this kind of system isn’t terribly difficult to set up is seen as both a good and a bad thing, depending on how it’s applied. It could be a relatively cheap way to get better data on how traffic operates, or to make buildings more efficient. However, any system that can track people without their knowing it is certainly open to abuse, and so many of the questions surrounding the project are now about when it should be used, rather than just if it could work.

Source: Is the ground beneath the Stanford campus listening to you? by Yasemin Saplakoglu, The Mercury News

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