Saturday, July 20, 2013

Devils Tower Prairie Dogs

A black-tailed prairie dog
One of the most-interesting and social rodents of North America can be found at Devils Tower National Monument: the black-tailed prairie dog. French Canadians called them prairie du chien, and later English-speaking explorers used the English translation.
   The prairie dog is actually a member of the squirrel family. They are excellent tunnelers and are aided by their small ears, short tail and powerful legs. Their tan coloring and black tail makes for excellent camouflage against the backdrop of their burrows.
   Their range has been drastically reduced over the last century due to loss of habitat and they are now mainly found on protected areas like Devils Tower National Monument or Badlands National Park in South Dakota.
   Prairie dogs live in densely populated areas called towns. Large towns are divided into wards which are separated by hills, roads, streams or patches of forest. Wards are further divided into coteries. A typical coterie contains one adult male, three or four adult females and several yearlings and juveniles. However, coteries can be as small as two or as large as 39 individuals. If there are two adult males in the same coterie, one is dominant over the other. The residents of each coterie protect their territory from intruders, including prairie dogs from other coteries in the town.
Devils Tower National Monument
   Prairie dogs use the excavated earth from their burrows to make mounds which serve as watch towers and make dikes to divert water from heavy rains. Prairie dogs repair the entrance to their burrows by pounding wet earth into place with their noses. A burrow contains several chambers including a listening post, a toilet and a multi-chambered living area. One chamber of the living area is usually built above the rest to serve as an underground lifeboat by trapping air when the burrow floods.
   Prairie dogs breed from late February until early April. 35 days after conception, four to six blind, hairless pups are born. The mother will actively protect the nest after the pups are born until they are weaned, about six weeks later.
   Prairie dogs are almost wholly vegetarian, although they will eat small insects on occasion. Tall plants are cut down both for food and to increase visibility, leaving only a thin covering of grass and other plants surrounding the burrow. The main source of water for prairie dogs comes from the moisture in the plants and roots they eat. Unlike some other prairie dogs, black-tailed prairie dogs do not truly hibernate and on warm winter days they can be seen actively foraging for vegetation.
   Many carnivores prey on prairie dogs, including coyote, fox, badgers, mink, bobcats, weasels, owls, hawks, eagles, and rattlesnakes.
   Prairie dogs communicate with each other through a variety of methods. When two individuals from the same coterie meet they exchange an identification kiss to show recognition and acceptance. A short, high-pitched warning bark is repeated several times along with a flicking of their tail when danger is sensed. When the town hears a warning bark, they will sit up to see what is causing the alarm. If the warning bark is faster and higher pitched it means a hawk or eagle has been spotted and they will run for the safety of their burrow. After the coast is clear, the prairie dog will throw its forefeet up and point its nose to the sky before coming down on all fours to signal that all is well. This call can also be used to warn prairie dogs not in the coterie that the territory is taken and to stay out.

Monday, May 20, 2013

The Northern Hawk Owl

The Northern Hawk Owl is adept at capturing rodents
under the snow due to their great hearing.

The Northern Hawk Owl is a non-migratory owl that resembles a hawk in behavior and appearance. During flight it looks similar to a Cooper's Hawk. It is one of the few owls that is primarily active during the day.
   Northern Hawk Owls are unevenly distributed throughout the boreal forest. They live mostly in open coniferous forests, or coniferous/deciduous mixed forests of Canada and Alaska, sometimes extending down to other northern states during winter or after a population explosion in their prey. They are also found across northern Eurasia, reaching Siberia at its eastern range. 
   Their prey includes small rodents (usually voles) snowshoe hares, red squirrels, and a variety of birds. During winter, they prefer to feed on ground-dwelling birds such as grouse and ptarmigans. The Northern Hawk Owl's fortune rises and falls with its prey. During prey population explosions, their numbers can swell to more than 50,000 breeding pairs, but if food is scarce, their numbers dwindle accordingly.
   The hunting strategy for the Northern Hawk Owl is to perch on a spruce tree in open forest and scan the immediate area for prey. If nothing is found, they move on to another location. When prey is spotted, the owl attacks by going from a horizontal position into a gliding dive. If the prey is further away, the bird will flap its wings a few times during the dive to make up the extra distance. This owl has superb hearing and can plunge into snow to capture rodents beneath the surface.
   The Northern Hawk Owl is one of the least studied birds in North America. They are hard to study because of a low, fluctuating population density and remote breeding locations. This lack of knowledge makes it nearly impossible to accurately estimate the population levels of this species.
   Northern Hawk Owl densities are estimated to be at most six pairs per 100 sq km. But because they live throughout the boreal forest, the North American population is thought to be quite large. In North America, over half of their breeding territory occurs in non-commercial boreal forests, so as long as nothing threatens this habitat, the species should be OK even though the populations seems to be declining. Improved monitoring should be a high priority so that we can be more confident in that assessment.

Monday, May 13, 2013

Centrifugal vs. Centripetal

I went to my daughter’s open house at school last Friday and afterwards we played a bit of tether ball before heading home. And while I’m not that great at tether ball, I can explain the forces involved in the game.

   Centrifugal force is what is often used to describe what happens to the ball as it rotates around the pole—it’s being pushed as far away from the pole as possible. But in actuality, centrifugal force is a fictitious force. The only force being applied to the ball, pulling it toward the center of rotation, is a centripetal or center-seeking force. There is nothing actually pulling the ball away from the string, what you have is just inertia as described by Newton in his First Law of Motion: An object at rest remains at rest unless acted upon by a force and an object in motion remains in motion—at a constant velocity—unless acted upon by a force. 
   Newton based his first law on the work of Galileo, who described what he called the Law of Inertia: “A body at rest remains at rest and a body in motion continues to move at constant velocity along a straight line unless acted upon by an external force.” Until Galileo, it was thought that one must exert a force in order to keep an object in motion. Galileo recognized that the reason moving bodies eventually come to rest is because of resistance forces such as friction. Without friction, bodies would continue to move at constant velocity. But I digress…
   So if you were to cut the rope as the ball is rotating what would happen? Some might think that the ball would fly away from the pole, but that’s not correct. The ball would actually move perpendicular to the pole, due to inertia. The centripetal force of the rope works against inertia by keeping the ball from travelling in a straight path. It is this constant struggle against inertia that makes it seem that the ball is trying to move away from the pole. What we call a centrifugal force is actually just the effect of inertia working against the centripetal force. Your welcome.

Monday, May 6, 2013

The Rose of Saturn

Recently, NASA release an incredible photo of Saturn’s north pole showing a massive spinning vortex of a storm they dubbed “The Rose”. This false-color image taken by the Cassini spacecraft shows the storm spanning a 2,000 km diameter which, by comparison, is 200 km wider than Hurricane Sandy. Maximum wind speeds of 530 km/h have been calculated—that is some hurricane!
   See how much you know about the ringed planet by answering these ten quiz questions, below. Good luck!

Monday, April 29, 2013


Asteroids have been making quite a few headlines as of late. Recently, we had NASA announcing its intentions to capture and asteroid robotically and bring it back for study by a manned expedition. The ten-year, $2.6 billion project would partner with private companies to capture a 500-ton, near-Earth asteroid that would be bagged, brought back, and placed in a gravitational parking lot known as the Earth-Moon lagrangian point (L2). There, a manned outpost could study it and set up a mining station to harvest its resources, especially its trapped water. Considering that it currently costs $10,000 per pound to haul water into orbit, mining it from an asteroid could save a billion dollars at current launch prices. Add to that the ability to use water to create rocket fuel by splitting it into its elemental components hydrogen and oxygen, it's no surprise that water is also called "space gold".
   On February 15, 2013, a meteor exploded over Russia’s Ural mountains in the Chelyabinsk region, injuring about a thousand people, as the shockwave blew out windows and rocked buildings. On that same day, there was a close flyby of asteroid 2012 DA14, which passed within about 27,000 km of Earth which is closer than the orbits of television and weather satellites that surround our planet. The two events were unrelated. 
Ceres, the largest asteroid
and also a dwarf planet.
   In the weeks after these events, there’s been a renewed call for creating an asteroid detection system. As it stands now, all anyone could do if we discovered a large asteroid headed toward New York City or some other large metropolitan area is “pray,” according to NASA chief Charles Bolden. We only know the whereabouts of about 10% of the estimated 10,000 city-killer asteroids. The Chelyabinsk asteroid is the largest to hit Earth since the 1908 Tunguska asteroid exploded over Siberia, leveling 80 million trees over an area of around 2,100 sq km.
   The asteroid belt lies between the orbits of Jupiter and Mars. Even though there are asteroids in other parts of the solar system, most are found here. About half the mass of the belt is contained in the four biggest asteroids: Ceres, Vesta, Pallas and Hygiea. These have average diameters of more than 400 km, while Ceres, which is also a dwarf planet, has a diameter of about 950 km. The remaining asteroids are thinly distributed and range all the way down in size to dust particles.
Vesta as imaged by the Dawn spacecraft.
   Asteroids are rocky. Because they come from the inner solar system, any ice would have been baked off by the sun long ago. Their orbits are fairly predictable, so with good observations, we can track down the big ones and determine if they’re threats.
   There are more objects beyond Neptune. The Kuiper Belt extends more than 100 times farther from the Sun than Earth. Beyond that is the Oort Cloud which extends 10,000 times farther from the Sun than Earth. These collections of small, icy bodies are remnants from the formation of the solar system. When their orbits are disturbed by other objects they can move into the inner solar system, becoming comets. As they come close to the sun that ice evaporates and creates the comet’s tail. They are less dense than asteroids, and tend to be moving faster by the time they reach the inner solar system. Some comets, like Halley’s comet which returns every 76 years, have predictable, periodic orbits.
   Knowing where an object comes from is a good indicator as to whether it is an asteroid or a comet. It’s not all black-and-white—objects from the outer solar system might be rocky and some asteroids do have some ice. But overall this is good way of thinking about them.

Sunday, April 21, 2013

The Wave

The Wave, Arizona

This incredible formation of Navajo Sandstone is stunning in its beauty. Formed during the Jurassic period about 190 million years ago, sand dunes compacted and hardened, with erosion forming the wavelike shapes in the structure over time. Everywhere you look, there are stunningly beautiful formations for hikers and photographer to enjoy. These famous undulating forms can only be reached by a rugged, pathless hike.
Characteristics of treads and risers cut 
into Navajo Sandstone at The Wave.
   The Wave is located near the Arizona/Utah border on the slopes of the Coyote Buttes. It consists of two intersecting troughs that have eroded into the sandstone. The troughs that make this formation have dimensions of about 19 x 36 meters and 2 x 16 meters. At first, infrequent runoff eroded these troughs along joints within the sandstone. After their formation, the drainage basin which fed water to these troughs shrank to the point where it no longer contributes to the erosion. Now the troughs are mostly eroded by wind which cuts characteristic erosional treads and risers into the sandstone along their steep walls. These treads and risers are oriented relative to the prevailing wind direction as it funnels through the troughs.
Cross-bedded Navajo Sandstone at The Wave.
   The Wave exposes large sets of cross-bedded sandstone which represent periodic changes in the prevailing winds during the Jurassic as huge sand dunes migrated across the desert. The thin ridges and ribs seen in The Wave are the result of the different erosion rates within the Navajo Sandstone. The sandstone is soft and fragile, so hikers needs to walk carefully to avoid damaging the small ridges.
   In places, The Wave exposes deformed layers within the Navajo Sandstone, created before the sand was turned to stone. This deformation likely represents dinosaur tracks and the fossil burrows of desert-dwelling insects.
The Wave is located near the Utah/Arizona border
between Kanab and Lake Powell.
   The Wave is located within the Paria Canyon-Vermilion Cliffs Wilderness and is administered by the Bureau of Land Management (BLM), part of the U.S. Department of the Interior. From Interstate I-15, it's about a 2-1/2 hour drive, passing through Kanab, Utah towards Lake Powell. If you want to visit The Wave, you will need to get a day-use permit. The BLM limits access to the North Coyote Buttes Wilderness to just twenty permits per day—ten in advance through an on-line lottery and ten by walk-in lottery at 9:00 am the day before one's intended hike, held at the visitor center in Kanab.

Monday, April 15, 2013

Salar de Uyuni

During the rainy season, Salar de Uyuni
becomes the world's largest mirror.

Salar de Uyuni is the world's largest salt flat at 10,600 square kilometers—about 100 times larger than the Bonneville Salt Flats in Utah. It is located in the Andes in southwest Bolivia at an elevation of 3,656 meters, making it the highest salt flats in the world. The salt flat was formed as a result of transformations between several prehistoric lakes. It is covered by a few meters of salt crust, which is extraordinarily flat. The crust serves as a source of salt and covers a pool of brine, which is exceptionally rich in lithium, of which it contains 50-70% of the world's reserves. 
Salar de Uyuni traditional salt harvest: salt is
scraped into small mounds to evaporate the water
for easier transportation.
   The salt flat is the remains of an ancient lake from about 40,000 years ago. Because it is surrounded by mountains, there is no drainage outlet and the salt collects on the lake bed as the water evaporates. The salt is scraped away from the surface by locals and piled up into mounds. This helps the water evaporate more quickly so the salt can be transported away. Salar de Uyuni contains about 10 billion tons of salt, and each year 25,000 tons are harvested by a cooperative of miners that share in the profits.
   The large area, clear skies and the exceptional flatness of the surface make Salar de Uyuni an ideal place to use to calibrate satellite altimeters. It is the major transportation route across the Bolivian Altiplano and is a major breeding ground for several species of pink flamingos. Salar de Uyuni is a climate transition zone, for towering clouds that form in the eastern part of the salt flat during the summer cannot penetrate beyond its drier western edges, near the Chilean border and the Atacama Desert.
   During the rainy season the water creates the world's largest mirror which must be seen to be believed. You can see the sky and clouds under your feet and feel like you're walking on them. Even though it is quite remote, many photographers and tourists take amazing photos at Salar de Uyuni.
   There is currently a political battle going on over the lithium resource that Salar de Uyuni hold. The Bolivian government is not willing to simply export the raw materials needed for the ubiquitous lithium-ion batteries used for electric vehicles, iPhones and other consumer electronics—they want to manufacture locally as well as protect the salt flats from damage. Bolivia is aiming to become the Saudi Arabia of lithium production and they are being courted by conglomerates such as Mitsubishi and Sumitomo who believe that the next wave of automobile batteries must come from Salar de Uyuni. Meanwhile, due to political uncertainty and poor relations with the Bolivian government, the U.S. is sitting on the sidelines.

Monday, April 1, 2013

The Passenger Pigeon

Martha, the last passenger pigeon before her death
in 1914 at the Cincinnati Zoo.

How the most abundant bird in North America went extinct is a story of mass slaughter on a scale even greater than that of the bison. It has been nearly a century since we lost the passenger pigeon, and it remains an example of nature's abundance and humanity's ability to exhaust it.
   Early Europeans in North America often commented on the vast numbers of blue and orange, long-tailed, graceful and fast pigeons in the country. One of the first Virginia settlers wrote "There are wild pigeons in winter beyond number or imagination, myself have seen three or four hours together flocks in the air, so thick that they shadowed the sky from us."
   As late as 1854, a New York resident wrote that "There would be days and days when the air was alive with them, hardly a break occurring in the flocks for half a day at a time. Flocks stretched as far as a person could see, one tier above another." Other reports describe flocks a mile wide flying overhead for four or five hours at a time during their migration to their breeding areas. The flocks were packed so thickly that 30 or 40 birds could be brought down with one shot and many were killed simply by hitting them with sticks as they flew over hilltops.
   Passenger pigeons bred in large colonies, with up to 100 nests in a single tree. Branches broke and whole trees collapsed by the sheer weight of roosting birds. Nesting colonies could cover many hundred of square kilometers of forest. Nests were made of small twigs loosely packed. Usually, one egg was laid and tended to by both parents up until about two weeks after it hatched. Then the chick would be abandoned, still unable to fly. The whole flock would leave, and the chicks would drop to the ground. After a few days, the chicks would begin to fly and take care of themselves.
   The best guess to the peak number of passenger pigeons in North America is about 5 billion individuals, or about the same amount as the total number of birds found today in the U.S. One reason the passenger pigeon existed in such large numbers was the lack of natural predators apart from eagles and hawks. They were, however, surprisingly vulnerable to humans. Their habit of nesting in vast colonies and migrating in huge flocks made them very easy to attack. The birds fed mainly on acorns, chestnuts and beech nuts in the woodlands of North America, so as these forests were steadily harvested, the passenger pigeon was left with shrinking habitat and food supplies. The Indians captured the pigeons in large nets and by the 1630s the settlers of New England were doing the same. The young squabs were considered a great delicacy and they were hunted for their feathers as well.

   For the first 200 years after the Europeans arrived, the number of pigeons did not decline much, but after 1830 the practice of using live pigeons for trap shooting began. One resident in Dubuque, Iowa, netted as many as 1,500 birds in one morning and sold them alive for ten cents each for trapshooting. The crippled birds were killed and sold by the barrel, which went for a dollar on the market in Chicago. About 250,000 a year were being killed this way by the 1870s.

   The population had been reduced by the 1850s but was still several billion strong. The real onslaught began with the onset of large-scale commercial hunting carried out by well-organized trappers and shippers in order to supply cities on the east coast with a cheap source of meat. It began once railways linked the Great Lakes area with New York in the early 1850s. With the coming of the telegraph, the locations of flocks could be determined, and the birds were relentlessly hunted. By 1855 300,000 pigeons a year were being sent to New York alone. The worst of the mass slaughter took place during the 1860s and 1870s. The scale of the operation was incredible, yet perfectly legal and very profitable. In 1869, Van Buren County, Michigan, sent 7,500,000 birds to the east. But by 1880, numbers had been severely reduced, and a total of "only" 500,000 birds were shipped east from Michigan.
   The last nesting birds were reported in the Great Lakes region in the 1890s and by 1900, they were all gone. Some remained in captivity, but it was just a matter of time. The last passenger pigeon, named Martha, died at the Cincinnati Zoo on September 1, 1914. Who could have dreamed that in such short order a species that was once the most numerous bird on Earth would be gone forever? John James Audubon wrote this about the passenger pigeon: "When an individual is seen gliding through the woods and close to the observer, it passes like a thought, and on trying to see it again, the eye searches in vain; the bird is gone." How many more species will some day only exist as stuffed specimens in museums?

Monday, March 18, 2013

Jurassic Park 4

Our best guess at what Deinonychus looked like.

Jurassic Park 4 is scheduled to hit theaters on June 13, 2014, so this might be a good time to have a little heart-to-heart discussion with Mr. Spielberg on a few technical details. It’s been 20 years now since Jurassic Park first came out in theaters and paleontologists have learned a great deal since then. 
   Even though the appearance and behavior of dinosaurs is largely speculation, there are a few things that could be updated. From preserved specimens showing quill knobs, we know that Velociraptor had feathers, probably colored black, white and rust brown. And based on their size, those dinosaurs should be called Deinonychus.
   Crichton’s central idea was that the amber which preserved the mosquito also preserved the dinosaur blood from contaminants and harm—a simple idea which made for a compelling story. But there are definitely issues with this. You can’t get dinosaur DNA from a dead mosquito trapped in amber. After sitting in a chunk of resin for millions of years there is going to be mixing of the mosquito’s DNA and the DNA of whatever it fed on and anything else trapped in the amber. Even if it could be done, there’s no way of knowing what kind of animal a mosquito had bitten. How many would Hammond have to go through before finding one that had actually bitten a dinosaur? Not to mention how would extinct plants get cloned since mosquitoes don’t eat plants.
A 70-million-year-old T. rex
fossil has yielded soft tissue.
   There’s a better way. One of the biggest developments in paleontological research in the last two decades has been the discovery of soft tissues preserved in fossil bone interiors. These bones come from the badlands, and are excavated using sterile field techniques and without protective polymers and glues to keep contaminants from entering the bone interiors. The fossils are then taken back to a lab where the mineral components are dissolved in baths. If the dinosaur bones were truly permineralized then the entire fossil would basically dissolve in solution. But that didn’t happen when the first lab tests of this kind were conducted back in the early 2000s. After the mineral components had dissolved away, there was spongy, squishy, soft stuff left over. Paleontologists had discovered bits of tissue, blood remnants and marrow from their samples. This was absolutely unheard of when Crichton wrote Jurassic Park. Even though it’s not yet possible to retrieve 70 million year old DNA, this method is much closer to reality than sucking out dinosaur blood from a fossilized mosquito. If you want a park with a triceratops in it, just head out to the Badlands, find some triceratops bones, and mine them for their soft tissues.
   The other big change for Jurassic Park would have to be the DNA gap-filling. No more frog DNA. They would need to use bird DNA, preferably a more primitive species like an emu or ostrich. There has been a lot of genetic work done on chickens lately, so chicken DNA might work as well because we know so much about it. In a movie, it would not be much of a stretch to say that we have control over the chicken genome, and thus could reduce it back to a stem state, where the combination of the dinosaur DNA with the trimmed chicken genome lets you build a dinosaur.
   Not only could you clone dinosaurs with the soft tissue story line, but marine dinosaurs, too. Giant ichthyosaurs, mosasaurs, plesiosaurs—there was plenty of scary stuff in the ancient seas. For the purpose of a movie, anything that’s fossilized could be fair game. There are plenty of big, scary extinct animals to choose from...

Monday, March 11, 2013

The Golden Tortoise Beetle

The Golden Tortoise Beetle (Charidotella sexpunctata)

The golden tortoise beetle is a common North American beetles that lives on and eats morning glory leaves. They can also be found on sweet potatoes which belong to the morning glory family. Both larvae and adults feed on foliage of which they make many small- to medium-sized irregular holes. Rarely are tortoise beetles numerous enough to be considered damaging to the host plants.
   In spring and summer, the beetle earns its name by turning the color of brilliant liquid gold. The color is produced by an optical illusion—the outer cuticle is transparent and reflects light through a layer of liquid over the next layer of cuticle. The beetles change color depending on the availability of the liquid layer which they control through microscopic valves under their shell. In the fall and winter, the beetles become less lustrous and are more orange and bronze often with black spots similar in appearance to ladybugs. If you try and add the beetle to an insect collection, it quickly turns dark brown as is dries, and looses its golden color. The beetle is most beautiful while alive.
   The larvae hatch out in late May and June and are just as interesting as the adults, but in a much different way. The young larvae are surrounded by many small protuberances giving them a spiny appearance. As the larvae molts, it keeps its old skin attached to a fork-like structure hinged to its rear end. The larvae will add its own feces to the old shell to create a type of shield which it can use for defense. When they are disturbed by another insect or predator, they flip the shield up in the direction of the disturbance. This "poo protector" is an unappetizing and effective deterrent against potential predators looking for a meal!

Monday, March 4, 2013

All Eyes on ISON

Comet C/2012 S1 (ISON) shares many of the same
characteristics as the Great Comet of 1680.

Be sure to keep tabs on comet C/2012 S1 (ISON), which is hurling toward a close approach with the sun this fall. Even though ISON is still a long way away, located just inside Jupiter’s orbit, it has already formed a tail of gas and dust stretching 90,000 km.
   This is thought to be the comet’s first pass into the inner solar system and promises to provide us with a spectacular show between November 2013 and January 2014 after it has its close encounter with the Sun.
   C/2012 S1 was discovered in September 2012 by two amateur astronomers using the International Scientific Optical Network in Russia, hence the nickname ISON has been adopted by the media.
   ISON has been recently observed by NASA’s Deep Impact spacecraft. Deep Impact, which was launched in January 2005, was originally used to study comet Tempel 1 by hitting the comet with a small metal probe then doing a close flyby to study the debris it kicked up. In 2010, Deep Impact flew past comet Hartley 2 and is now on its way to a January 2020 visit to a near-Earth asteroid that is large enough and close enough to us to be classified as a potentially hazardous object (PHO) by NASA.
   C/2012 S1 will be well placed for observers in the northern hemisphere during the last two weeks in December 2013. Some speculate that if it does not break up as it reaches perihelion it could become brighter than the moon at its peak, but many sungrazing comets do not survive the encounter. It has been calculated that as it nears the Sun it will reach a peak temperature or 2,700°C, hot enough to melt iron. 
   ISON’s orbital path is similar to that of the Great Comet of 1680, another sungrazer that is also known as Newton’s Comet because Isaac Newton used it to verify Kepler’s laws of planetary motion. Newton’s Comet was one of the brightest comets of the 17th century. It was noted for its extremely long tail and at its peak it was bright enough to be seen during the day. Time will tell if ISON will someday be known as the Great Comet of 2013.

Monday, February 18, 2013

The Oh-My-God Particle

One of the two Fly's Eye Cosmic Ray Detectors.

The Oh-My-God particle was an ultra-high-energy cosmic ray—most likely a proton—detected on October, 1991 in the skies over western Utah. Its observation by the University of Utah's Fly's Eye Cosmic Ray Detector was a shock to astrophysicists, who estimated its energy to be approximately 50 J. In other words, a subatomic particle with kinetic energy equal to that of a baseball traveling at about 90 kilometers per hour.
   The particle was traveling at almost the speed of light. Assuming it was a proton, its speed was only about 1.5 quadrillionth of a meter per second less than the speed of light. In other words, if it were in a race with a beam of light, the Oh-My-God particle would fall behind only one centimeter every 220,000 years.
   The energy of this particle is some 40 million times that of the highest energy protons that have been produced by the Large Hadron Collider. However, only a small part of this energy would be available for an interaction with another proton or neutron. Most of the energy would remain as kinetic energy. The effective energy available for such an interaction is still 50 times greater than the collision energy of the Large Hadron Collider.
   Applying special relativity to such a fast particle yields some incredible results. Time passes more slowly as velocity increases, and for anyone hypothetically travelling on the back of this particle time would nearly stop. For example, a trip to the Andromeda Galaxy, which is more than two million light years away, would have a perceived travel time of only three and a half minutes. Special relativity also tells us that there is a length contraction in the direction of motion. If the Earth were somehow able to match the speed of the Oh-My-God particle, it would pancake down to a thickness of less than four hundredths of a millimeter!
   The University of Utah experiment relied on two telescopes searching the sky for the characteristic flashes of ultraviolet light that are produced when a cosmic ray collides with a molecule in Earth’s atmosphere and creates a shower of secondary particles. The two telescopes were covered in photomultiplier tubes and looked like the compound eyes of a fly. By capturing almost all the light in the shower, they were able to make a good measurement of the particle’s energy.
   These ultra-high-energy cosmic rays are very rare. Since the first observation, only about fifteen similar events have been recorded to confirm the phenomenon. What cosmic process transforms an ordinary particle into an Oh-My-God particle? A supernova or supermassive black hole might explain it, but when astronomers followed the impact track back to its source they found nothing unusual in that direction.

Monday, February 11, 2013

The Water Bear

The tardigrade is also known as the water bear.

A polyextremophile is an organism that can survive many types of extreme environments. One of the most complex polyextremophiles is the tardigrade, which can live in just about every environment possible here on earth, plus some not on Earth (more on that later). Tardigrades are about a millimeter long when fully grown. They are short and plump with eight tubular legs, each with 4-8 bear-like claws. Given that they also move like a lumbering bear, tardigrades have earned the nickname water bear.
   Tardigrades typically live in marine, fresh water, or semiaquatic environments, but you can also find them in the mosses and lichens found in forested areas. As long as there is some water around, they can thrive. They feed on the fluids found in plant and animal cells. Their mouth is able to pierce the cell walls so that they can then suck out and ingest the inner parts of the cell. 
   Tardigrades can survive being completely desiccated for nearly 10 years as well as exposure to high levels of chemical toxins. They can survive extreme heat (150 °C) for a few minutes and extreme cold (-200 °C) for a few day. When exposed to extreme cold their body composition changes from 85% water to only 3% which keeps their body from being damaged by ice crystal formation. 
   The can survive extreme pressures far greater than that found at the Mariana trench. In 2007, tardigrades were sent into space on the Russian/EU satellite Foton-M3 for ten days. Even after being exposed to the vacuum of space for this long, most of the samples survived after being rehydrated back on Earth, some of which had also been fully exposed to the Sun’s radiation. Tardigrades were also sent into space on the final flight of Space Shuttle Endeavour where experiments showed that cosmic radiation and microgravity did not significantly affect their survival, confirming their usefulness in space research.
   You’re probably wondering just how these creatures could be so resilient. They rely on cryptobiosis—a state of suspended animation that they can enter in response to adverse environmental conditions where all metabolic processes stop. Their bodies dehydrate into a dense, mummified disc called a tun. They can remain in this state indefinitely until their environment becomes hospitable once again. When this happens, the tun plumps back up and the tardigrade return to its previous metabolic state.

Monday, February 4, 2013

Dangers of a Vacuum

The vacuum chamber that Jim LeBlanc was in
when his spacesuit lost all pressure.

Recently, a reader asked “What happens to the human body in a vacuum? For example, if an astronaut removed his space suit.”
   This reminds me of a scene from the movie 2001: A Space Odyssey. In the movie, HAL has figured out that Dave is planning to disconnect him when he returns to the ship, so he refuses to let Dave back in. Dave is forced to go in through the unpressurized emergency airlock, but there’s a problem: he doesn’t have his space helmet. 

  Terrifying, but Kubrick got the science right. Short-term exposure to the vacuum of space would not make your body explode or freeze solid as some movies have depicted. If you don’t try to hold your breath, exposure to space for about 15 seconds would cause no permanent injury. Holding your breath would be bad, though, because in a vacuum your lungs collect gas from your bloodstream and expands with the drop in pressure. Holding your breath would cause your lungs to overinflate and possibly rupture. This is similar to how scuba divers need to exhale when rising to the surface or risk damaging their lungs. 
   Temperature would not be an immediate problem because although space is very cold, a vacuum is a perfect insulator. You would only gradually radiate away your body heat. Exposure to direct sunlight would give you a sunburn. Your saliva and tears would quickly evaporate and you might have eardrum troubles.
   After about 15 seconds, oxygen-deprived blood from the lungs reaches the brain causing you to lose consciousness. 
   At such low pressures, your body fluids will boil away. Moist surfaces such as the eyes, mouth and airways experience this immediately. Fluids inside your body also start to vaporize. This happens rapidly in the lungs and under the skin. Bubbles of water vapor that form in the bloodstream will interrupt the circulation. This is called ebullism. No one knows how long the human body can withstand the vacuum of space—perhaps a couple of minutes. 
   In 1965, this actually happened to Jim LeBlanc while working at the NASA Manned Spacecraft Center (now called the Johnson Space Center). He was testing a space suit in their vacuum chamber when the tube that was pressurizing his suite came loose and his suit was almost completely depressurized within seconds. He stayed conscious for about 14 seconds and they began repressurizing the chamber right after he passed out. After regaining consciousness, he recalled that he could hear and feel the air leaking out of his suit, and the last thing he remembered was the saliva on his tongue starting to boil.

Tuesday, January 29, 2013

Violet Skies Are for the Birds

I love the XKCD webcomic, especially when it features a science-related theme. Comic number 1145 poses the question “Why isn’t the sky violet?” which I will attempt to answer this week. But first we need to understand why the sky is blue: it’s because of Rayleigh scattering.
   Rayleigh scattering (named after the British scientist Lord Rayleigh) occurs when sunlight passes through the atmosphere and is scattered by air molecules. The light from the sun is a mixture of all the colors of the rainbow, each with its own characteristic wavelength. Sir Isaac Newton demonstrated this nearly 350 years ago by using a prism to separate white light into its different spectral colors.
Rayleigh scattering: blue light is scattered
more strongly than red light as it passes
through the atmosphere and is why the sky
is blue during the day.
   The amount of scattering is inversely proportionate to the fourth power of the light’s wavelength. That means that the shorter-wavelength components of sunlight (blue and violet) are about ten times more strongly scattered than the longer-wavelength components at the red end of the visible spectrum. Rayleigh scattering is responsible for the blue color of the sky during the day and the orange color during sunrise and sunset. It’s also the reason that the sun itself is yellow when overhead and red at sunrise and sunset.
   Now back to the original question: since violet light has an even shorter wavelength than blue light, why does the sky appear blue instead of violet? 
   First, the sun produces a lot more blue light than violet light. The Sun’s spectral peak is in the green range and as the wavelength decreases from blue to violet there is a steep drop-off in intensity.

Solar emission intensity compared to human cone cell responsivity. Both are shown
as a function of wavelength.
   Second and more importantly, even though blue and violet both have short wavelengths, our eyes don’t see violet as well as blue. We have three types of color receptors in our retina, called cone cells. There are short-, medium- and long-wavelength cone cells that respond most strongly to blue, green and red light, respectively. Cone cells are stimulated in different proportions and our brain uses this information to construct the colors we see. Across the visible spectrum, it turns out that blue provides the maximum responsivity.
This image demonstrates how
yellow light can be perceived
as a mixture of red and green
light. Take a few step back from
the monitor to see the effect.
   Since the cone cells are sensitive over broad, overlapping ranges of wavelengths, many colors can be seen by mixing other colors. Take yellow for example. There’s a good reason why caution signs are yellow—yellow light lies right between green and red on the spectrum and causes a large response in both the medium- and long-wavelength cone cells. Regardless of whether you see pure yellow or a mixture of red and green, your eyes can’t tell the difference. When two colors can be created with different spectral distributions they are called metamers. In this same way, the sky’s combination of violet and blue triggers the same cone response as pure blue plus white light, which yields the pale blue color that we see.
   It’s no coincidence that we see things the way we do. Human evolution is shaped by our environment—the ability to separate the colors around us provides an evolutionary advantage. 
   Even though humans don’t see violet in the sky, some birds might because they have an extra type of cone cell that extends their color vision into the ultraviolet range. The male Blue Grosbeak appears mostly blue to humans but has plumage shifted to the UV range that he uses to his advantage during courtship. The Common Kestrel uses its UV-enhanced vision to find voles by following their scent trail which reflects UV light, making it visible to this clever hunter. So maybe violet skies are for the birds.

Monday, January 21, 2013

Big Brains

There’s probably no single event more significant in the history of human evolution than the harnessing of fire. Many species make and use tools, but only humans control fire. Fire provided early humans a means to protect themselves from predators. Fire provided humans with warmth and light, and expanded productivity into the night. Socializing around a campfire may have been an essential part of human development.
   Perhaps the biggest benefit of fire was for cooking. Cooking food provided better nutrition and made food safer to eat. Cooked meat was easier to digest because less energy was spent digesting the tougher proteins and connective tissues.
   Cooking plants that contained starches made the complex carbohydrates they contained more digestible so that more energy could be absorbed from them. The human digestive system has evolved after we started eating cooked foods: our teeth, jaws and digestive tract have all gotten smaller, allowing our developing brain to have a greater share of the food energy taken in. Eating cooked food helped provide the extra energy required to support a hunter-gatherer lifestyle.
   The earliest known evidence for the controlled use of fire comes in the form of ash and charred bone excavated from a South African cave that is known from previous digs to have been occupied by early man. These materials were found alongside stone tools in a layer dating back about a million years.
   Although modern humans are the only human species alive today, originating about 200,000 years ago, other human species once roamed the Earth, such as Homo erectus, which arose about 1.9 million years ago.
   Some anthropologists think that Homo erectus was cooking as far back as 1.9 million years ago and was the reason that they experienced major brain expansion at that time. Others think that brains got bigger just by the introduction of meat into their diets and that while there was the opportunistic use of natural fire, it was not until about 300,000 to 400,000 years ago that early humans fully mastered the use of fire.
   One thing is certain—our brains have tripled in size over that last two million years. But evolution doesn’t say anything about whether larger brains are good or bad, just that it happened. Author Kurt Vonnegut believes that our brains have over-evolved: “Our brains are much too large. We are much too busy. Our brains have proved to be terribly destructive.”
   Vonnegut explored this theory in his 1985 book Galapagos where our big brains have brought civilization to the brink of destruction. The last humans ironically survive because they get stranded and isolated on the Galapagos Islands made famous by Charles Darwin. They spend the next million years de-evolving.
   As evidence for his theory, Vonnegut says that big brains invented nuclear weapons and the Third Reich. Even Einstein noted that “He who joyfully marches to music rank and file, has already earned my contempt. He has been given a large brain by mistake, since for him the spinal cord would surely suffice,” indicating his belief that war is a huge step backwards in human evolution. And while I’m more optimistic, I didn’t witness the bombing of Dresden firsthand as did Vonnegut, nor did I have to flee my home and country out of fear for my life as did Einstein. Food for thought…

Monday, January 14, 2013

Dark Lightning

Artist’s conception of the Earth’s magnetic field (in pink)
funneling positrons (in yellow) and sending them to the Fermi
Gamma-ray Space Telescope where they were observed.

The Fermi Gamma-ray Space Telescope is an Earth-orbiting space observatory that is being used to perform high-energy gamma-ray astronomy. Launched in June of 2008, this telescope is probing the cosmos for gamma rays and high-energy events. And while it is finding many sources for these events, such as supernova explosions and distant, supermassive black holes from other galaxies, it has also found an unlikely source closer to home.
   In 2009, the telescope was hit by a stream of high-energy positrons—the antimatter version of electrons—coming from a thunderstorm on Earth. 100 trillion positrons had been funneled into a tight pulse by the Earth’s magnetic field and hurled straight to the observatory at nearly the speed of light. To put that number into perspective, it’s more than what hits the Earth’s atmosphere from all other cosmic sources combined. Somehow, antimatter had been produced in the clouds above Earth and the best theory we have to explain it is dark lightning.
   Earth-orbiting satellites have been observing terrestrial gamma ray flashes (TGFs) from thunderstorms as far back as 1994. And it is also known that gamma-rays at the right energy can produce electron-positron pairs.
   Normal lightning occurs when unbalanced electrostatic charges in the atmosphere trigger a massive discharge between a cloud and the ground or between two clouds. A light flash traces the path of the charged particles which heat the air to 30,000°C, nearly six times hotter than the surface of the Sun. 
Feynman diagram for a gamma ray photon
decaying into an electron-positron pair.
   Dark lighting may seem crazy, but there is mounting evidence that it’s real. Like ordinary lightning, dark lightning also tries to neutralize the unbalanced electric fields in a thunderstorm. Under the right conditions, the thunderstorm creates a powerful avalanche of electrons shooting away from Earth at nearly the speed of light. The electrons collide with air molecules in the atmosphere to produce gamma rays. Next, the gamma ray energy transforms into electron-positron particle pairs. Further collisions between these particles and other air molecules creates a repeating cycle—a self-generating, self-sustaining particle accelerator. Once the loop gets started, it can discharge the thundercloud as fast as lightning. And because the cascading electrons and positrons generate more gamma rays than visible light, the process is practically invisible to the human eye. 
   Researchers once thought the gamma ray flashes from thunderstorms were a weird by-product of ordinary lightning. Now many think it is dark lightning instead. The gamma ray burst monitor onboard the Fermi Gamma-ray Space Telescope is perfectly suited to record these flashes and new data processing techniques have improved the burst monitor’s performance. In mid-2010, a testing a mode was initiated which allows for the detection of faint gamma ray flashes that had previously gone undetected. Now Fermi should be able to catch nearly 1,000 flashes each year. With an abundance of new data, researches hope to gain new insights on the mysteries of dark lightning.

Monday, January 7, 2013

A Hundred Authors Against Einstein

The book “Hundert Autoren Gegen Einstein”
(A Hundred Authors Against Einstein) was
published in 1931.

The old adage “there is strength in numbers” is not always true, especially when it comes to science. Science is not advanced through polls or consensus. Observation and experimental evidence is what matters. Thankfully, being in the minority does not necessarily mean one is wrong.
   Case in point: The book Hundert Autoren Gegen Einstein (A Hundred Authors Against Einstein), a collection of various criticisms of Einstein’s theory of relativity. Published in 1931, it contains short essays from 28 authors, and published excerpts from 19 more. The balance was a list of 53 people who were also opposed to relativity for various reasons.
   The book was not a reaction against Einstein from the physics community—only one physicist had contributed. Nor was it supported by the younger generation—only two of the contributors were much younger than Einstein. It was a dying cry from the old guard of science that felt left behind by the new physics and incompetent because they didn’t know what to do with it. Before Einstein published his work, Newton’s theories were gospel among the scientific community. Einstein had the temerity to use space and time as a way to think of our Universe, not just an a priori condition in which we lived.
Before relativity, space was thought
to be best represented by Euclidean
geometry (above). Relativity requires
the extra dimension of time be
considered when representing
space (below).
   Many had a philosophic objection to relativity, based on Immanuel Kant’s assertion that space was intuitive and could not be perceived by observation or experience. Newton’s view that space was absolute and existed independently of what it contained, as defined by Euclidean geometry, had ruled for over two centuries unchallenged. 
   When asked about the book, Einstein retorted by saying “Why 100 authors? If I were wrong, then one would have been enough!”
   Einstein’s fame from the success of his ground-breaking theories had created a backlash. Even thought the book contains no outright anti-Semitism, six of the authors were either anti-Semitic and/or Nazi sympathizers. The rising Nazi movement denounced Einstein, calling relativity “Jewish physics”. Einstein left Germany in 1932 out of fear for his safety and never returned. The Nazis had put a price on his head, publishing his photo on the cover of one of their magazines with the caption “Not Yet Hanged”. Einstein moved to the United States, settling at the Institute for Advanced Study at Princeton in New Jersey.
   Of all the contributors to the book, the one that I found the most distressing was Emanuel Lasker. Lasker was a German mathematician, philosopher and the World Chess Champion for an incredible 27 years. Einstein and Lasker had met through a mutual friend in Berlin in 1927, and over the course of many walks together they exchanged opinions about a variety of topics. According to Einstein it was a somewhat lopsided exchange, in that Einstein received more than he gave. Nonetheless, they developed a close friendship. Given that Lasker was also Jewish and had been forced to leave Germany after the Nazis took power, it’s disheartening that he had gone against his friend, but apparently it didn’t bother Einstein.
   To Lasker, the notion that no matter how fast you travelled the observed speed of that light was constant was ridiculous. Einstein claimed to have “never considered in detail, either in writing or in our conversations, Emanuel Lasker’s critical essay on the theory of relativity” and thought of Lasker as a Renaissance man and uniquely independent. Many years later, when asked to write the forward to a posthumous biography on Lasker, Einstein was forced to address this reproach to relativity, saying that “…chess playing of a master ties him to the game, fetters his mind and shapes it to a certain extent so that his internal freedom and ease, no matter how strong he is, must inevitably be affected”. In other words, Lasker—while brilliant—lacked the capacity to think outside the box.