On April 3rd, 2018 we learned about

Strangely slow galaxy attributed to missing dark matter

Some missing dark matter may help confirm that this invisible substance exists. Dark matter is as-of-yet theoretical form of matter that doesn’t interact with light as we know it, making it invisible or dark to our various probes and sensors studying the universe. It does seem to interact with gravity like other matter does though, and so most of our ideas about it come from watching how normal objects move and react to the pull of something that’s otherwise undetectable. Of course, since as much as 80 percent of the mass of the universe is actually dark, studying what is does and doesn’t do isn’t easy.

Luckily, dark matter doesn’t seem to be equally distributed. Galaxy NGC 1052–DF2, a cluster of stars 65 million light-years away from Earth, may lack dark matter entirely. NGC 1052–DF2 looks pretty normal at any given moment, but the over time the motion of some bundles of stars, called globular clusters, has turned out to be too slow. For the amount of mass we can see, the galaxy should have around 60 billion times our own Sun’s mass in dark matter. The total mass of normal and dark matter would then require the globular clusters to move much faster than they’ve been observed. The orbital speeds that have been seen only make sense if there’s no dark matter there at all.

How could the dark matter be missing?

This is weird, to say the least. Galaxies are thought to form around the gravitational well created by clumps of dark matter, so this finding raises questions about how NGC 1052–DF2 ever came together in the first place. One possibility is that the dark matter has been stolen by some of its neighbors. Some galaxies have been found with extra dark matter, and so there’s a chance that NGC 1052–DF2 lost its invisible mass to the stronger gravitational pull of another galaxy.

The last option is that there was never dark matter in NGC 1052–DF2, or anywhere else for that matter. Some researchers suggest that the best way to make sense of the movement of large galaxies is with modified Newtonian dynamics, or MOND. In this model, the physics we’re used to just aren’t correct on the scale of a galaxy, and thus need adjusting so that they make sense with what we’ve observed. However, the weird speeds of NGC 1052–DF2 are strengthening doubts about MOND, since even modified dynamics should be consistent in every galaxy. It’s then easier to imagine one weird galaxy missing its dark matter than figuring out some other caveat to explain why the math behind MOND would need further adjustments in just this case.

Source: Dark matter is MIA in this strange galaxy by Emily Conover, Science News

On February 22nd, 2018 we learned about

New timeline means that Europe’s earliest painters were Neanderthals, not humans

When the cave of Altamira was first discovered in Spain in 1880, it sparked a controversy over the capabilities of primitive humans. The caves had been essentially sealed for tens of thousands of years, and yet were covered in remarkably sophisticated paintings of people, animals and abstract shapes. Some people found it unthinkable that this kind work could have been accomplished by primitive humans, leading some skeptics to claim the paintings were a hoax. An recent examination of the nearby La Pasiega caves is proving those nay-sayers were half-right, but not for reasons they’d be happy to hear. New research has confirmed that the paintings were not made by early humans, because they must have been created by even earlier Neanderthals instead, 64,000 years ago.

Dated by decay

The paintings in La Pasiega, as well as similar caves found in Maltravieso and Ardales, were originally dated based on the decay of carbon 14 atoms. By measuring the amount of carbon-14 isotopes still found in organic matter and comparing that to the known rate of decay, or half-life, of these atoms, researchers can estimate how old an object is. This method is fairly reliable in some scenarios, but it does have its limitations. In this case, a significant issue is that after 50,000 years, so much carbon-14 has decayed that its hard to detect the remaining isotope in any given sample. Since the La Pasiega paintings are now known to be at least 64,000 years old, it’s easy to see how the previous attempts to arrive at an age ran into problems.

This latest investigation then dated the cave paintings using uranium-thorium dating. Rather than sample the paint directly, this method looks at the amount of uranium and thorium found in the carbonate that has built up over time at a given location. The amount of each product of the uranium’s radioactive decay can then provide an age for that speck of carbonate, which therefore provides the latest possible age of whatever the carbonate is sitting on. So by dating the carbonate that’s naturally accumulated on the paint, we now have a more credible age for the creation of the cave’s artwork.

Advanced cultural capabilities

The technique to date the cave paintings is obviously less surprising than the new estimated age of the paintings themselves. We’re confident that humans didn’t arrive in Spain, or any of Europe, before 40,000 years ago. So with these paintings firmly predating the arrival of Homo sapiens, it seems that our species’ only role in this artwork was discovering it. The only other candidates for their creation are Neanderthals, a species of hominid that seems more sophisticated with every new archaeological discovery we make.

This is a big jump in our understanding of Neanderthals’ cognition and culture. The steps required to develop paint as a tool, pick a location to paint, then represent images of the natural and abstract world represent a variety of achievements. Most importantly, recording images for their symbolic, rather than practical, value shows that Neanderthals were able to transmit their culture in a way we had previously thought to be the invention of humans.

This isn’t to say that humans weren’t culturally innovative. Artifacts estimated to be 70,000-years-old have been found in Africa, showing that Homo sapiens has long been a creative species as well. However, the Spanish cave paintings show that Neanderthals weren’t trailing far behind our species in their development. Researchers now want to investigate other European cave paintings in case they were made by Neanderthal hands as well.

My five-year-old asked: How did they make their paints?

The caves were only painted in reds and blacks. The black was from charcoal, most likely retrieved from a fire, and the red was made of pigments like ochre. The painters probably started by crushing the minerals into a fine powder, then moistening them with water or oil to make them spreadable on the stone walls of the cave.

Source: Neanderthals were artistic like modern humans, study indicates by Andrew White, Phys.org

On February 21st, 2018 we learned about

Tsunamis may soon be detected with a single hydrophone and a decent amount of math

Tsunamis aren’t subtle, but they do still manage to be surprising. They’re created by earthquakes under the sea, sometimes so far from a coast that people will have no idea any seismic activity occurred. Then, once the surge of water reaches a shoreline, anyone there has very little time to react and escape the area. As we get better at monitoring the ocean floor for earthquakes, these events are becoming slightly easier to predict, but the sea floor is so vast that it’s not the most practical endeavor. However, new research is suggesting that the key to catching tsunamis earlier may come down to listening to the sea, and acoustic gravity waves in particular, in just the right way.

Massive amounts of movement

When an earthquake occurs in the ocean, there’s obviously a lot of shaking and vibrating going on. In addition to massive amounts of displaced water, a quake will send out acoustic gravity waves (AGWs) in every direction. These waves are a bit like a hybrid of sound waves moving laterally through the air, and the gravity-sensitive waves you see shaping fluids like the average waves near a beach. This has made AGWs tricky to study and model, since they don’t follow the exact patterns we see in more common wave activity. One trait that has stood out, however, is that an AGW can move through the ocean at the speed of sound across huge distances. Because of their impressive sizes and speeds, researchers have long hoped that they could be detected well in advance of a tsunami’s arrival, buying people more time to get to safety.

The difficulty hasn’t been detecting the AGWs, but making sense of them. Fortunately, scientists from the University of Cardiff are now suggesting that this kind of analysis is not only possible, but practical even with only a single hydrophone sensor in the ocean to detect the wave. The distinct shape and speed of any AGW should reveal various aspects about the earthquake that created them. With more information in the system, such as details about the suspected fault location, researchers state that the tsunami’s amplitude and potential impact on a shoreline can be predicted. Once compiled, these data could then be used to trigger tsunami alarms in the tsunami’s path, giving people crucial time to find safety.

Heard through single hydrophone

On a basic level, this is similar to the tsunami alarms we have today. Devices known as dart buoys are anchored at sea, and can then detect unusual pressure changes in the water below them. This works if the buoys are in the tsunami’s path, which then requires that they’re located in all the right locations at all the right times. Measuring AGWs, however, don’t require that kind of specific placement. Because AGWs expand in multiple directions from an earthquake’s epicenter, hydrophones in any direction could detect clues about the formation of a tsunami. This then leads to a much more practical system for early warnings, increasing the chances that an alarm will reach people with enough time to get away from the water.

Source: Could underwater sound waves be the key to early tsunami warnings? by Cardiff University, Science Daily

On January 15th, 2018 we learned about

Sifting through the causes, concepts and misconceptions of quicksand

Despite growing up in tame suburban landscape of sidewalks and lawns, my kids are very concerned about how to deal with quicksand. I can only assume that repeated viewings of Wreck It Ralph and The Force Awakens (no Princess Bride yet) have helped build up the mystery of watery sand, particularly since fiction usually portrays it as something perilous that can capture a hero without warning. Of course, having seen DuckTales and G.I. Joe, I know that my kids’ concerns are unfounded, and that we’ll never run into quicksand near our home. Or so I thought.

Sources of soupy sand

Well, I was right about the general composition of quicksand. It’s any loose, grainy soil with a large concentration of water in it to turn it into a fluid. One of the most common places to run into quicksand is at the beach when water rushes into loose sand. Sand that’s only moist is likely to clump together, but with enough water flowing through the sand, each grain will separate and basically roll around independently of each other. The resulting soup can then look like solid ground from above, but has a consistency just a bit thicker than water when you step into it. While quicksand in nature is going to involve water, Mark Rober has a great demonstration of how sand can behave like a fluid using air as well.

Now, not every puddle turns into quicksand, obviously, mainly because the water needs to flow in a way that helps separate the grains of sand or soil. A great way to break up clumped soil turns out to be vibrations from earthquakes, and tremblors are a major cause of quicksand in all kinds of environments. Quake-produced quicksand is actually a significant safety hazard, not so much for people suddenly in need of conveniently placed vines, but for buildings that partially sink into the ground, stressing or warping their structural integrity. As such, researching the exact combinations of vibrations, soil composition and water flow has been the subject of research looking to predict which locations are most likely to suddenly turn to soup when the ground shakes.

Saving yourself from sinking

Aside from our next trip to the beach, the intersection of quakes and quicksand adds sudden legitimacy to my kids’ concerns about sinking into the soil. We don’t live especially close to a marsh or lake, but earthquakes aren’t uncommon in the Bay Area. Unless a water pipe bursts at just the right spot, it still seems unlikely that we’ll run into quicksand nearby, but there aren’t many conveniently placed vines to grab hold of if we did. Despite what cartoons and movies have taught us, that’s probably ok, since most quicksand isn’t likely to swallow you up in the first place.

While drowning in fluidized soil can happen, most instances of quicksand in nature aren’t that deep, so you aren’t likely to be fully submerged in order to drown. You might get stuck though, and trying to lift your legs straight up to take a step would be very difficult. Your best option is to try to lean back and spread your arms, letting buoyancy help lift you up. Small movements of your legs will help loosen them, but sharp vertical yanks aren’t going to be practical. This isn’t to say that people don’t die after getting stuck in quicksand, but some of those cases are due to other factors, like rising water levels, than the quicksand on its own.

Source: How Quicksand Works by Kevin Bonsor, How Stuff Works

On January 14th, 2018 we learned about

Stands of trees can function as shields against some seismic vibrations

A well-placed tree can do wonders for your home. It can provide shade that lowers your cooling bill, increase property values, and lower stress levels, absorb carbon dioxide, prevent erosion, etc. Researchers are now realizing that a properly-arranged group of trees may even be able to help your home survive an earthquake, based on the same principles that are being used to develop invisibility cloaks.

Rerouting seismic waves

That may sound like some sort of science fiction word salad, but the ideas behind it have been tested in controlled conditions. Lots of work is being done with metamaterials, which can control how light, as electromagnetic energy, interacts with their surface. Instead of reflecting off an object, light can be bent and routed around an object, like water flowing around a rock in a stream. This allows an object to effectively become invisible, as a viewer ends up seeing whatever is behind the cloaked object as if it weren’t there.

When it comes to trees and earthquakes, the trees act like a metamaterial, and the vibrations in the ground act like light, moving around a space without hitting it directly. Researchers first tested this idea by making a grid of posts in the ground, then pumping sound waves through the ground, since an actual earthquake isn’t terribly practical to plan around. As the vibrations moved through the dirt, they would interact with the posts in one of two ways: Smaller posts would shake in response to the incoming wave, dissipating much of its energy straight down. Large posts could vibrate in a way that actually reflected the wave back in the opposite direction. The combination of different sizes of posts, or better yet, trees, could then stop a seismic vibration from reaching a nearby structure at full strength.

Practical earthquake protection?

So how practical is “arboreal shielding” at this point? No tests have been conducted with actual trees and buildings yet, mainly because of the logistics involved. More simulations are being done to better understand optimal spacing and sizing for the trees involved, as the heights of the trees is an important factor in just how well they’ll reroute incoming seismic vibrations. Early simulations have used trees arranged in a grid, but ideally models will be developed that can account for more naturalistic distribution of tree growth, in case this concept is beneficial for more than the most carefully controlled green spaces. Additionally, researchers are finding that it’s easier to block horizontal pulses of energy, such as those found in Love waves, than tremors that also move vertically, as in Rayleigh waves.

Nonetheless, the potential benefits would be very significant. For a 10-story building, a 30- to 50-foot tree could make a huge difference. These trees could be planted around buildings that can’t use traditional seismic reinforcements, such as historical structures and monuments. Even if the trees couldn’t completely protect a structure, they could reduce the amount of protection that would be needed in the building itself, potentially cutting engineering costs, and adding all that shade, erosion control, green space, etc.

My third-grader asked: Wouldn’t wooden buildings work just as well?

Aside from the structural limitations wood creates when compared to concrete and steel, the wood itself isn’t the key ingredient in this seismic shielding. An early test actually replaced the trees or posts with holes in the ground, as the key was their size and placement in the ground. As long as those were properly calibrated to divert vibrations that might match the resonant frequency of the building, no lumber was necessary.

Source: How forests could limit earthquake damage to buildings by Edwin Cartlidge, Physics World

On December 31st, 2017 we learned about

Using sound to assess the size, and quality, of bubbles in sparkling wines

Sorry sommeliers, but the best way to assess a sparkling wine’s quality may involve anyone’s sense of taste or smell. When judging a specific lot of wine, the most objective measurement turns out to be the sound of the wine, or more specifically, the sound of the bubbles inside. The most desirable bubbles are tiny, which not only tickle the tongue but also resonate at a different frequencies of sound than larger bubbles, not unlike a smaller bell versus a large one. So rather than rely on people’s mouths to test a vintage’s quality, vineyards may start employing hydrophones to make sure every batch of champagne and sparkling wine is up to snuff.

You’d be forgiven if you’ve never put a glass to your own ear to listen to a glass of sparkling wine before taking a sip. Detecting the exact nuances of each batch of bubbles was surprisingly tricky for researchers as well, even with years of experience recording other sounds underwater. Early tests using standard hydrophones, or underwater microphones, were impeded by the bubbles themselves. As the carbonation would rise through a glass, the bubbles would stick and cover the outer surface of the hydrophone, significantly altering the data it could collect. A smaller, more specialized hydrophone had to be used to compensate for the bubble build-up, meaning your ear really doesn’t stand a chance at picking up the level of detail necessary to asses sparkling wine or champagne.

Tips for tinier bubbles

With some iteration, researchers were able to identify the sounds of optimally tiny bubbles, which should help vineyards more accurately judge the quality of their product. While improved quality control should be good for vineyards, this research also revealed information that can be put to use by those of us who don’t have a piezoelectric transducer-based hydrophone at home. While trying to get consistent measurements of the bubble’s resonance, researchers found that the shape and material of the wine’s container greatly influenced the size of the bubbles produced. Champagne flutes help the carbonation produce smaller, consistent bubbles, just as you’d hope. On the other end of the spectrum, a flat-bottomed Styrofoam cup did just the opposite, making for bulkier bubbles, robbing the wine of its potential.

Once you have some delightfully tiny effervescence in a proper champagne flute, the best way to prolong the carbonation is by keeping your bottle and glass consistently cold. A separate investigation into preserving carbonation in open bottles of sparkling wine looked at stoppers, spoon handles and more, and found the best way to keep the bubbles coming was to never let a bottle warm up after it had been opened. So if you have the equipment to really check your next glass of bubbly, make sure your glass, and hydrophone, are properly chilled.

Source: Pop the bubbly and hear the quality by Acoustical Society of America, EurekAlert!

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