On July 19th, 2018 we learned about

Even with extra atmospheric carbon dioxide, plant-eating dinosaurs probably didn’t struggle with nutritional deficiencies

If a mouthful of meat has more calories than the same volume of veggies, how could the world’s biggest dinosaurs manage as herbivores? Between having relatively small mouths and a diet we presume to be based around green, leafy material, it’s hard to imagine how a 33-ton Apatosaurus could find time to do anything but eat in order to power its enormous body. To further complicate things, scientists have long believed that the higher concentration of carbon dioxide (CO2) in the Mesozoic atmosphere would have encouraged plant growth but left them with less nutritional value. Unless these animals had some amazing metabolic trick unheard of in any of their living bird and reptile relatives, the simplest explanation would be for some of these assumptions to be… wrong.

Approximating the Mesozoic atmosphere

As one of the key building blocks of plant life on Earth, CO2 availability does make a difference in how plants grow. Since it’s hard to pull nutritional data from fossilized wood or leaf impressions, scientists conducted an experiment, growing various plants in different atmospheric conditions. The plants were all picked as approximations of the species that lived millions of years ago, and included things like dawn redwoods, monkey puzzle conifers, ginkgo, ferns and horsetails. Naturally, these plants have likely changed to adapt to modern conditions on Earth in the last 65 – 250 million years, but they could hopefully offer a sense of how CO2 would affect their nutrient levels.

Growing a tree or fern in 400 to 2,000 parts per million concentrations of CO2 is only step one though. To figure out how much one of these high-carbon plants might benefit a hungry dinosaur, researchers had to next come up with a fake digestive tract, which they created by fermenting the plants in cattle rumen fluid for 72 hours. By capturing the various byproducts of this process, this technique is used to figure out how easily digestible food is for livestock, and thus could give us a sense of how easy or tough any particular plant was to extract nutrients from. Chewing and other processing strategies like gastroliths weren’t really included in the ‘simulation,’ although since different species of dinosaur ate differently, that seems like a fair omission.

Everything a growing dinosaur needs

In the end, researchers found that the extra CO2 didn’t reduce the nutritional value of these plants as much as had been previously assumed. A 33-ton sauropod was calculated to have only needed 242 pounds of monkey puzzle leaves grown in the CO2-rich Triassic air. That’s certainly a lot of food, but since it’s at the low-end for an African elephant’s daily intake, it would have certainly been possible. If that weren’t good news enough for large herbivores, researchers also found that some plants showed no loss of nutrition at all. A dinosaur eating horsetails grown at three-times modern CO2 levels would only need 112 pounds of food a day, assuming they really liked horsetails.

The overall takeaway is that herbivorous dinosaurs likely had a more nutritious salad bar than we’d ever thought. The gap between these nutrition values and earlier estimates suggest that ancient flora could have fed 20 percent more herbivores than anyone thought, possibly requiring reconsideration of dinosaur population density in general. As exciting as more giant sauropods and hadrosaurs may sound, not every animal would have benefited from these CO2-soaked leaves. Herbivorous insects rely a lot on nitrogen in the plants they eat, which was one of the few nutrients that was definitely reduced in the experimental plants. It’s too early to say at this point, but it’s possible that insect populations suffered in the way we had previously assumed dinosaurs did.

Source: The real palaeo diet: the nutritional value of dinosaur food by Susannah Lydon, The Guardian

On July 19th, 2018 we learned about

Without climate control, heat waves take a measurable toll on our cognitive abilities

On the hottest days of summer, I generally just feel like giving up. By later afternoon, temperatures in my older building easily surpass whatever’s happening outside, a factor compounded by the outdated myth that “nobody needs an air conditioner in northern California.” The net effect is a feeling of tired fogginess, making concentration on just about any task rather difficult. While this may sound like a lot of whining (it is!) scientists have actually been able to quantify the cognitive hit inflicted by seasonal spikes in heat, pointing out that they take a measurable toll on all of us.

Testing the effects of living in high temperatures

Unusually high temperatures associated with heat waves have long been known to be detrimental to human health, although most research on heat has focused on cases when it’s literally a danger to people’s lives. To investigate cognitive issues possibly experienced by everyone, researchers purposely skipped at-risk populations like infants and the elderly, working only with healthy college students. In theory, any issue that would affect a 22-year-old would probably be an issue for 30- and 40-year-olds as well. The only other criteria that mattered was whether or not each student had air-conditioning in the dormitory where they lived.

Every day of the study, test participants were asked to take a few cognitive tests when they woke up in the morning. The tests included tasks like quickly reading the names of colors with letters displayed in conflicting hues, which is a long-standing way to asses how well someone can filter relevant information in a hurry. They were also asked to do some math and memory tests, giving researchers a range of performance metrics to compare. To make sure environmental conditions were also comparable, test subjects’ rooms were outfitted with temperature, carbon dioxide, humidity and noise sensors. Physical activity and sleep were also tracked with a wearable device.

Extra time and additional errors

After five days of normal temperatures, there was a spike in the area’s heat index. Almost immediately, students living without air conditioning started showing a decrease in cognitive performance. They took 13.4 percent longer in deciphering the color words, and also had 13.3 percent more errors in their math tests. Even after the heatwave broke and the outside world returned to normal, much of that heat was retained indoors, extending the impact of overheated students’ low scores.

Anyone who has lived through unusually hot days won’t be surprised by this, but anecdotally hot homes don’t help science diagnose health problems shape policy. By measuring the significant impact heat has one people’s ability to handle cognitive tasks, this study reveals that rising global temperatures may be causing more immediate and widespread problems than people realized. It’s practical to demand air conditioning for every hot home on the planet, but we may need to further prioritize heat-shedding designs in future construction, plus look for ways to mitigate possible problems caused by people too hot to think clearly.

Source: Extreme heat and reduced cognitive performance in adults in non-air-conditioned buildings by Harvard T.H. Chan School of Public Health, Medical Xpress

On July 18th, 2018 we learned about

Study of spiderwebs finds how to stay sticky when a surface is wet

Don’t tell the kids, but they might need fewer band-aids in the near future. As exciting as getting a colorful adhesive bandage for a scrape or cut may be, getting a second bandage after a bath is even better, because you get more trucks or robots without the need for another injury. Because of the way glues interact with water, bath time has generally ensured that no bandage would survive a full day, but that may soon change if scientists can learn to reproduce some key properties of spider silk.

Sticking to water instead of a surface

The root of the problem with glues and paints on wet surfaces is interfacial water. This water gets between the adhesive and it’s intended target, then ruins any bonds that were in effect by essentially taking their place. In the case of a bandage, this means that the adhesive ends up bonding with the water that was next to the skin, instead of the skin itself.

Loose band-aids or peeling paint is one thing, but creatures like spiders really can’t tolerate having their webs come unstuck whenever things get humid. Since plenty of spiders manage to keep webs stuck to moist leaves with enough strength to catch struggling prey, researchers started looking at the exact chemistry to see what their secret was. Their search eventually came to focus on three types of ingredients— two glycoproteins, a batch of low molecular mass organic and inorganic compounds (LMMCs) and interestingly, water itself.

Working with water instead of against it

On their own, each of these ingredients wasn’t anything terribly unique. Glycoproteins are used as a source of stickiness by a variety of organisms, from algae to sea stars to ivy. The trick was how each ingredient complimented the others. Researchers found that the LMMCs worked to make the glycoproteins stick better, mainly by absorbing water and moving it away from the target surface. So rather than become completely hydrophobic and try avoid water at all costs, spider silk stays sticky by absorbing water and just moving it away from points of contact with other surfaces. With further development, researchers hope to apply this lesson to the design of adhesives we depend on, even if it means that a water proof band-aid will actually need to be water-absorbent.

Source: Research on spider glue resolves sticky problem by Lisa Craig, Phys.org

On July 18th, 2018 we learned about

Engineers’ brief attempts to speed up trains with airplane engines

When I first read my kids the story of “Thomas and the Jet Engine,” I treated it as nothing more than fan service for kids. Sure, the idea of their favorite train being temporarily boosted across the tracks by a jet engine was fun, but clearly ridiculous. And of course, I was wrong. Not only have there been real attempts to build trains powered like aircraft, but working prototypes powered by jet aircraft have been built in multiple countries. These experimental trains were designed to join the speed of air travel with the hauling capacity of trains, although none of them ever went into regular, if speedy, service.

Pushed and pulled by propellers

The very first attempt at a plane/train hybrid was the railplane. George Bennie created a vertically oriented track that was intended to be built above existing railways, saving space and simplifying logistics. At the front and back of the pill-shaped vehicle, electric motors drove large propellers so that the railplane could ‘fly’ down the track without worrying about actual flight. The test track was too short to confirm it, but Bennie estimated that the railplane could have traveled as fast as 120 miles-per-hour, beating even today’s travel times. Unfortunately, Bennie couldn’t get enough funding to continue developing his prop-propelled train, leaving us only with advertisements and some footage of the prototype.

Jet-powered propulsion

With airplanes shifting to jet engines in the 1950s, trains in the 1960s had some catching up to do. By 1966, multiple parties were looking to either retrofit or design jet-powered trains from scratch. In France, Jean Bertin started work on the Aérotrain, which was designed to hover on an air-cushion atop an elevated track. The hovering was intended to reduce friction, making it easier for the Aérotrain’s single jet engine to propel the train down the track. Multiple rounds of prototypes were developed, including an 80-passenger train that could reach 155 miles-per-hour under the power of two jet-engines. Like the railplane before it, the Aérotrain was eventually abandoned in 1977 due to funding problems, although you can still find sections of test track France and near Pueblo, Colorado.

In the United States, turbojet train development looked a bit more like a retrofit. Don Wetzel led an effort to make trains faster and cheaper, which translated to front-mounted jet engines on an otherwise traditional-looking commuter train. Early iterations used recycled General Electric jet engines, purchased from the Air Force. Like the Aérotrain, Wetzel’s jet-powered trains never progressed past test tracks and prototypes, although they did manage to hit an impressive 183 miles-per-hour before the project was shut down.

Even if commuters never got to enjoy jet-engine speeds on the rails, these efforts caught the attention of engineers in the Soviet Union. With long-distance travel served by rail, plus a Cold War competitive spirit, the Speed Wagon Laboratory started work on their own jet-train in the late 60s as well. Target speeds ranged from 155 to a theoretical 223 miles-per-hour, but the project was dropped in the 1970s, partially thanks to the expenses associated with all the jet fuel those speeds would require.

Rounding things out, Japan had their own attempt at jet-powered trains, starting around 1968. Engineer Hisanojo Ozawa offered a few twists on the “common” jet-train design, aiming for a train with three jet engines that ran on rollers instead of traditional, flanged train tracks. The project didn’t seem to progress past a working scale-model, although that model predicted speeds up to 733 miles-per-hour.

Floating but not based on flight

Like Thomas the Tank Engine’s accidental sprint across the Island of Sodor, the age of jet-powered trains was short-lived. Fuel and other expenses made this form of propulsion less attractive, and so high-speed train designs have moved on to other design concepts, mostly. While not explicitly modeled after air travel, maglev trains do hover over the ground to reduce friction, allowing them to reach speeds of up to 249 miles-per-hour. The form of propulsion is different, but the basic premise of track-based transportation still appears to be one of our most practical ways to cross long distances.

Source: Turbojet train, Wikipedia

On July 17th, 2018 we learned about

Cleaner shrimp communicate with their client fish via a set of specific visual signals

Cleaner shrimp have been found to stake a lot of their survival on their eyesight, which is impressive because their eyesight is terrible. Tiny crustaceans like Ancylomenes pedersoni were long thought to depend on their sense of smell to figure when they were safe to go out and forage, but new experimental data suggests that they get by with visual cues alone. It might help that these cues are somewhat interactive, and so the source of the shrimp’s food helps inform them when it’s time to eat, or when they might be eaten themselves.

A. pedersoni forage on the parasites and debris found on the gills, scales and even in the mouths of predatory fish in coral reefs. Blue tangs, parrotfish and snappers that could happily gobble up the shrimp themselves have learned that A. pedersoni provide bigger benefits if left to their work, and thus make a point to cooperate with the crustaceans’ foraging. Cleaning sessions start when a shrimp waves its white antennae in the water, signalling that it is ‘open for business’ to nearby fish. The fish then indicate their intent by darkening their body color as they approach, letting the shrimp know that they’re there to be serviced instead of posing a threat. Both parties stick to the script quite consistently, leading to successful partnerships over 80 percent of the time.

Which signals are sufficient?

To pin down exactly which signals mattered, researchers showed captive shrimp a variety of images on a tablet computer outside their aquarium. Thanks to the shrimps’ poor eyesight, these images didn’t need to closely resemble fish as long as they followed the expected protocol of a potential cleaning client. So as long as a collection of circles and triangles wiggled and then darkened, the shrimp were happy to go to work, wiggling their antennae and even attempting to hop on top of the the imaginary fish outside the tank. It may not seem like the shrimp were being especially discerning in their response, but it does prove that they’re looking for visual signals from cooperative fish instead of olfactory or auditory signals.

As a final step, researchers modeled the visual perception of both fish and A. pedersoni using a simulator. Software called AcuityView confirmed that the shrimp can’t make out shapes or colors clearly, which is probably why fish who want to be cleaned need to announce themselves with a light-to-dark color change. The fish, on the other hand, have slightly better vision, and can likely spot a shrimp’s waving antennae from a few feet away in the reef’s shallow water. So on both sides of this partnership, visual signals alone are coordinating how these two species manage their cooperative behavior.


My kindergartner said: Oh, it’s like the guys waving signs at the car wash. A shrimp car wash!

Source: When cozying up with would-be predators, cleaner shrimp follow a dependable script by Duke University, EurekAlert!

On July 17th, 2018 we learned about

Making sense the inconsistencies of cars’ mud flaps

Kids are supposed to ask why the sky is blue, what happened to the dinosaurs, and maybe where babies come from. My five-year-old, apparently content in his knowledge of such things, has instead been wanting to know more about mud flaps on cars. What are they for? Do they help a car drive faster somehow? The thing that was really bothering him though, was if mudflaps are useful, why aren’t they part of every car and truck on the road?

Mudflaps have probably been conceived a number of different times throughout automotive history, but Oscar Glenn March of Jones, Oklahoma is generally credited with inventing the products we know today. Unlike the side-mounted “anti-splashers” patented by William Rothman in 1922, March’s flaps were built and put into immediate use. March worked in the motor pool on Tinker Air Force Base during World War II, and realized that they needed a way to protect sensitive radar equipment from mud and rocks when it was hauled on flatbed trucks. The flaps were originally made of canvas which has since been replaced by rubbers and plastics, although March’s original bracket-mounting design is still in use today.

How functional are rubber flaps?

In addition to keeping your radar equipment clean, mud flaps can also protect the vehicle they’re mounted on. In areas with lots of rain, snow, salted roads and of course, dirt and mud, the right mud flaps can help prevent dirt and rocks from damaging the paint on fenders right behind a car’s wheel well. Beyond one’s own car, mud flaps can also help cut down on how much dust and water your vehicle will spray on anyone around you, which is part of the reason they’re legally required on trucks in many states. These vehicles’ higher frames and larger wheels makes them prime candidates to launch more rocks and water at other drivers, and so properly-sized mudflaps trap those materials before they cause trouble.

Of course, not every car today has mudflaps, which raises the raises questions about how valuable they really are. A piece of heavy rubber can’t be that expensive, so why don’t all cars come equipped with mud flaps by default? Many modern cars do have some extra plastic molded behind their wheels, but why not use the flexible flaps trucks are required to use? This is a trickier question to answer, as there’s no single authority declaring that mud flaps be excluded from modern car designs. Sometimes there are concerns over improperly mounted mud flaps, which require holes be drilled in a car’s body that can end up leading to rust damage. Other people argue that the flaps cause a small amount of aerodynamic drag, making them slightly less efficient to drive with. Finally, there’s the issue of aesthetics— some people think they look great on their cars, while others think they’re simply eyesores that will get bent up against speed bumps. There may not be a single “right” answer to this, although that won’t stop some people from asking questions.

Source: Who Invented the Mud Flap?, Fruehauf Trailer Historical Society

On July 16th, 2018 we learned about

Spawning salmon found to indirectly influence the number of berry plants grown from seeds in bear scat

If you’re trying to grow more berries in your yard, you might want to check on the local salmon population. Fish might not seem like the most intuitive component of a healthy cloud or blueberry crop (ok, maybe salmonberries…) but researchers have put together a food chain that shows how everything from salmon to rodents helps plant life in places like southeastern Alaska. It all starts to make more sense when you consider the keystone ingredient in berry production, which is bear poop. Obviously.

While freshwater fish do end up eating food that doesn’t live in the water, the salmon are simply an attractive but imperfect food source in this ecosystem. As they migrate upstream to spawn the fish are famously snatched up by brown and black black bears attempting to fatten up for the winter. While the salmon the are not the only component of a bear’s diet, their population density does greatly influence how many bears can be supported in a specific area. If there are more fish to be eaten, more bears can gather to start eating the next link in this food chain, the berries.

Bear scat with berry seeds

Berries have long been a critical component of bears’ pre-hibernation diets. The sweet fruits offer a lot of nutritional and caloric value for a bear, but they also carry seeds that other organisms depend on. Those seeds generally pass through a bear’s digestive tract unscathed, turning the bear’s poop into a concentrated collection of rodent-ready berry seeds. Detailed observations, including motion-sensitive cameras tracking activity around bear droppings, found that a single poop carried enough seeds to feed a deer mouse for 91 days. Various species of mouse seem to be aware of these bear-processed buffets, and individual animals would often visit scat multiple times a day to get as many seeds as possible.

Because the bears create such a rich concentration of seeds in a single poo, many rodents will try to “scatter-hoard” excess seeds in the surrounding territory, burying them in various locations for safe keeping. Just like squirrels attempting to hide acorns over a wide range, some of these seeds are forgotten by the mice and voles that buried them, greatly increasing the odds that a new plant will germinate. So while it might seem like the bear poop could act as a potential fertilizer for a new berry plant, the unintentional gardening of rodents is what really helps more plants take root.

Many individual steps of this process may not seem surprising, but the whole chain of dependencies may change how conservation efforts are organized. There are many reasons to try to preserve any one of the species involved in this process, but a good understanding of how they interact demonstrates how complex and interdependent an ecosystem can really be, from fish to seeds saved from scat.

Source: Berry-gorging bears disperse seeds through scat and feed small mammals by Chris Branam, Phys.org

On July 16th, 2018 we learned about

Mowing grass in varying degrees of moderation to promote plants, landscaping or pollinators

According to my kindergartner, the lawnmower was “amazing.” The shiny red tractor appeared to have an air-conditioned cab, three wheels and as my son put it, “two cutters” for the grass. It easily made short work of the city park we were visiting, presumably leading to the reopening of a field that had been temporarily closed to the public to allow the grass to recover from the beating it took during Fourth of July festivities. This raised a question for my son though— why was it bad for people to walk on the grass that this amazing machine was now chopping with it’s impressive “cutters?”

Lopping off portions of leaves

To make sense of how grass withstands regular trimmings, it helps to note how grass is structured. The flat ‘blades’ we like to feel under our bare feet are leaves the grow out of a smaller stem just above the plant’s roots. Like the leaves on a tree, losing some percentage of these leaves isn’t as dangerous as damage to the stem. Unlike leaves on tree, grasses have evolved to regrow the cropped portion of a leaf, ensuring that the effects of a modest mowing are only temporary. This likely evolved to help grasses survive visits from grazing herbivores, helping keep the grass and the nibbling animal happy as long as the plant’s stem isn’t trampled.

Mowing for more density

Humans are generally less concerned with grazing on our lawns these days, but there are still plenty of thoughts on how to properly manage grass growth cycles. If one’s goal is to maintain an even, densely-packed lawn, it’s recommended that you trim grass every week. This is to keep any single blades of grass from overshadowing their neighbors, leading to uneven growth overall. There’s also a risk of overcompensating after a lawn has grown taller than desired, as removing more than a third of the grasses’ height at once is more likely to stress the plants.

Pausing for more pollinators

On the other hand, most of us don’t play golf and don’t necessarily need the dense, homogeneous botanical carpet of a putting green. If that’s an option, allowing a lawn to have a bit more time between trims can promote the growth pollinator-friendly flowers like clover and dandelions. Even if you’re not interested in saving time, mower fuel or making tea from your yard’s yellow flowers, allowing some flowering plants to bloom in your lawn may make a big difference to a variety of bees. In a study by University of Massachusetts Amherst and the U.S. Forest Service, honeybees, bumblebees, carpenter bees, leafcutters, masons and sweat bees were all observed taking advantage of suburban lawns, but only if the lawns were mowed on a less aggressive schedule.

This doesn’t mean you need (or should) give up on mowing your lawn altogether. Some lawns in the study were only mowed on three-week cycles, but they didn’t seem to be any better than their two-week counterparts. The cause for this diminished return wasn’t immediately clear, but researchers suspect that three-week-old grass may be tall enough to hide some of these flowers, and thus didn’t provide much of a boost to pollinators.

Source: Why 'lazy' lawn mowers are heroes for bees by Russell McLendon, Mother Nature Network

On July 12th, 2018 we learned about

Ingentia prima offers an alternate model for how dinosaurs could be so big

Being gigantic is obviously awesome, but that doesn’t mean it’s easy. Juggling growth rates, heat retention, reproduction and stuffing one’s face full of calories have long seemed like a difficult challenge for evolution. While there have been some wrong turns, paleontologists have been putting together the pieces of history’s largest dinosaurs, hoping to build a sort of anatomical formula for how to prosper as a huge animal. Many of those key traits seemed to have gotten their start 180 million years ago in the Jurassic period, when long-necked sauropods like Vulcanodon started paving the way for eventual giants like Brachiosaurus and Argentinasaurus. Of course, science is all about revisions, and a newly discovered dinosaur out of Argentina is making researchers rethink what was needed to be big, right down to when being big became a thing in the first place.

An earlier start for being big

Ingentia prima was a 32-foot-long herbivore that lived 215 million years ago, in the Triassic period. Since most of the early dinosaurs of this period were closer to the size of large dogs and turkeys, the fact that this creature likely grew up to 11 tons in that time period wasn’t really expected. Yes, there would have been a transition from smaller dinosaurs to the larger herbivores of the Jurassic, but I. prima predated those species enough that it’s not actually a direct relative of the sauropods that came later. This means that however specialized a long neck and barrel-shaped body may seem, scaling that anatomy up to ridiculous sizes was advantageous enough that evolution did it at least twice.

Different ways to develop limbs

That’s not to say that I. prima was a perfect predecessor of the sauropod cousins that would come later. Features that were thought to have been critical to these dinosaurs’ evolution apparently…wasn’t. For example, many large sauropods had straight, column-shaped legs that likely helped support the animals’ immense weight, even at the cost of mobility. These legs may have helped some later sauropods like Argentinasaurus reach their truly mind-boggling sizes, but I. prima apparently handled 10 tons of mass with relatively crouched knees and elbows.

In addition to a different posture, the growth of I. prima’s bones was different as well. The bone structure of most sauropods indicates that they grew at a regular, even pace. In contrast to this, I. prima may have handled its bulk by growing in quick fits and spurts. Cross-sections of the I. prima’s bones show that it’s bone growth looked a lot like tree rings in seasonal conditions, increasing immensely at certain times while being relatively static at others.

Shared air sacs in the spine

All this analysis of I. prima’s skeleton did find that the dinosaur did share one size-strategy with it’s Jurassic cousins, which is the inclusion of air sacs in its spine. Similar to the air sacs found in modern bird skeletons, these carefully located voids would have lightened the weight of vertebrae without sacrificing structural integrity while also helping with respiration and possibly temperature control. The fact that this trait later evolved again in large sauropods indicates that, unlike thick, even legs, taking a load off one’s back may have truly been a crucial piece of how these animals grew to such enormous sizes.

Source: Discovery of 'First Giant' Dinosaur Is a Huge Evolutionary Finding by Laura Geggel, Live Science

On July 12th, 2018 we learned about

Looking for light in Antarctic ice has revealed a source of otherwise untraceable cosmic particles

Around four billion light years away, just to the left of the constellation Orion, an active galactic nucleus is blasting ultrahigh-energy cosmic rays and neutrinos right at us. This jet of particles and energy is the by-product of that galaxy’s central black hole shredding and consuming captured objects. As intense as such a stream of energy may be, this particular nucleus, named TXS 0506+056, appears even brighter than usual because it’s aimed straight at Earth, qualifying it as a blazar. The weird part of all this is that even though astronomers have long been able to detect the energy from this blazar across all bands of the electromagnetic spectrum, we’ve only just been able to trace the stream of particles it sends out for the first time.

Tracking the paths of particles

The two types of particles blasting out of TXS 0506+056 are cosmic rays and high-energy neutrinos, and both carry their own challenges for detection. The cosmic rays are mostly super-charged protons, which are known to be flying all around the universe. They can and do collide with other particles which makes their detection a bit easier, but because they are positively charged particles, their paths get bent and reshaped by every magnetic field they fly through. As such, even when you detect a cosmic ray, it’s nearly impossible to know where it came from on.

Neutrinos can help solve that problem, but not without creating challenges of their own. These tiny particles are sort of a neutral version of a proton, generally created when protons have been smashed and accelerated in the same conditions that would create cosmic rays. As their name implies, they are electromagnetically neutral and thus can fly through the cosmos without interacting with magnetic fields. This means that if they’re detected, you can count on them to have been moving in a straight line, creating a traceable path back to their source. However, detecting them is very difficult, because they’re so small, fast and neutral that they can fly through objects without interacting with anything. To really try to figure out where in space these super-fast particles, scientists had to build a very specialized detector in the ice of Antarctica.

Illumination in the ice

The IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station has turned a cubic kilometer of ice into the world’s best neutrino detector. Over 5,000 light sensors have been embedded in the ice in a grid formation. When a neutrino does happen to collide with atoms in the clear ice, it releases a cone of blue light that the detectors can then measure. By measuring which detectors see the brightest light, the original trajectory of the neutrino can be pieced together. After checking to eliminate collisions from slower neutrinos created by comic rays hitting Earth’s atmosphere, coordination begins with astronomers around the world to verify the high-energy neutrino’s suspected point of origin.

On September 22, 2017, a collision was detected in the ice that had the signature of galaxy-crossing, high-energy neutrino. An alert was then sent out to various telescopes around the world as quickly as possible so that they could look for any cosmic activity that could explain the neutrino’s trajectory. NASA’s orbiting Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov Telescope, or MAGIC, converged on the aforementioned TXS 0506+056 blazar. Researchers then looked at data from previous years to see if this trajectory was part of a possible pattern, and were able to find more instances of neutrino and gamma ray activity that also shared that point of origin. More data is obviously desired to really confirm these findings, but right now this all strongly suggests that we finally traced a high-energy neutrino back to its source.

A whole new way to know what’s in space

The idea that a blazar like TXS 0506+056 could pump out neutrinos and cosmic rays isn’t a shock. The energy necessary to get a neutrino and comic ray to be traveling close to the speed of light isn’t easy to come by, and something as violent as a blazar or galaxy collision would fit the bill. Learning more about such an object is obviously exciting, but the real significance of this detection is how it opens up a new way to study space and astrophysics. For the most part, everything we know about the universe outside our solar system has depended on measuring some portion of the electromagnetic spectrum, from radio waves to light to gamma rays. That energy can’t always be found though, and so tracking neutrinos gives us a whole new way to collect data on the universe. Coupled with the recent detection of gravity waves, scientists are comparing this so-called ‘multi-messenger’ detection to suddenly developing a new sensory organ in your body. We’ve long been able to see into space, but now we’ve gained a new way to touch it as well.


My fourth-grader asked: So if a neutrino can go through big objects without hitting them, can they pass through a black hole?

As the IceCube detector demonstrates, neutrinos can hit other atoms, but their speed, size and lack of charge helps them avoid doing so most of the time. None of those things offer a way to avoid the bent space-time of a black hole though, which can famously capture light which moves faster and has less mass than a neutrino. So while a black hole can help produce neutrinos and spray them into space, none of those neutrinos would be going anywhere if they’re aimed at the black hole itself.

Source: More than century-old riddle resolved—a blazar is a source of high-energy neutrinos by University of Wisconsin-Madison, Phys.org