The Siberian Tiger Project

The Siberian (or Amur) tiger is the largest of all the cats. Once numbering in the thousands, their population has dwindled to less than 400, mostly along a narrow range of mountains in southeastern Siberia, along the Sea of Japan.
   With a massive build, powerful limbs, and large canine teeth, these apex predators are built to hunt. Siberian tigers have long retractable claws for catching their prey which are pulled back into a protective sheath when walking to keep them razor sharp. They prey on the deer and wild pigs that live in their territory, which ranges from 250 to 450 square kilometers for an adult female.

A large male Siberian tiger can reach lengths of 

up to 3.3 m long and weigh as much as 300 kg, 

almost twice as large as an average adult lion.

   Tigers are nocturnal creatures for the most part, but the Siberian tiger is also active during the day. They have keen eyesight which can pick up even the slightest of movements and their hearing and sense of smell is also quite sensitive. 
   Female tigers have litters of two to four cubs every few years. The cubs are nursed for five or six months before they are old enough to leave their den and join mom on hunting trips. After a year they can hunt for themselves and by the time they reach three to five years old they will strike out on their own. 
   The Siberian tiger’s future is uncertain. In addition to the pressures from poaching and loss of habitat, researchers have concluded that the sub-species has fallen below the critical threshold where its genetic diversity can sustain a healthy population. The genetic base of the Siberian tiger is less than previously thought, with an effective population of only 14 individuals. Effective population is a measure of the genetic diversity of a species. So even though the actual population is stable or climbing, genetically-speaking this sub-species is nearly extinct. 
   Is it just a matter of time before the Siberian tiger joins the Javan, Caspian and Bali tiger sub-species in extinction? Not if members of the Siberian Tiger Project have a say.
   Since 1992 the Wildlife Conservation Society has supported the Siberian Tiger Project, a dedicated group of scientists that use radio-telemetry to monitor more than 60 tigers to help with research and conservation efforts. Wildlife biologists have studied their habits, reproduction, and how they interact with other species, especially humans. Current research is focused on cub mortality and their struggle to survive to adulthood. They have learned that young tigers may roam over 200 kilometers to find new territory when they leave their mother’s care. Researchers are also trying to combat poaching and understand its effect on tiger population. They have estimated that four out of five tiger deaths are caused by humans. They realize it is vitally important to protect female tigers so that they can live long enough to ensure the survival of their cubs to the next generation. If you would like to learn more about the Siberian Tiger Project and their efforts, watch this documentary.



If you enjoyed this article, you might also like my article on the Bengal Tigers of the Sundarbans.

When Light Meets Matter

Light refracted through a prism. The shorter the
wavelength, the more the light refracts, which is what
causes it to separate into its spectral colors.

Last week we learned that the electromagnetic spectrum encompasses much more than the visible light represented by the colors of the rainbow. In fact, visible light is less than one percent of the entire spectrum which includes radio wave, microwaves, infrared, ultraviolet, X-rays and gamma rays.
   As the name indicates, electromagnetic waves are composed of both electric and magnetic fields which oscillate perpendicular to one another and to the direction of travel. In the vacuum of space, these waves travel at the speed of light until they interact with matter. 
   When light interacts with matter it can do one of several things, depending on its wavelength and what kind of matter it encounters: it can be transmitted, reflected, refracted, diffracted, adsorbed or scattered.

   The simplest interaction with light is transmission, which occurs when light passes through the object without interacting. Light coming through window is a simple example of transmission.
   Reflection occurs when the incoming light hits a very smooth surface like a mirror and bounces off, like a mirror. 
   Refraction occurs when the incoming light travels through another medium, from air to glass for example. When this happens the light slows down and changes direction. This change in direction is dependent on the light’s wavelength so its spectrum of wavelengths are separated and spread out into a rainbow.
   Diffraction occurs when light hits an object that is similar in size to its wavelength. When light passes through a sufficiently-thin slit it will diffract and spread. If it’s visible light, this will also create a rainbow. 
   Absorption occurs when the incoming light hits an object and causes its atoms to vibrate, converting the energy into heat which is radiated. Anyone with a dark-colored car on a hot day will experience the effects of adsorption. 
   Scattering occurs when the incoming light bounces off an object in many different directions. A good example of this is known as Rayleigh scattering, where sunlight is scattered by the gasses in our atmosphere. This is what gives the sky its blue color.

The Electromagnetic Spectrum

The relationship between frequency and wavelength 
in EM waves (c is the speed of light).

Electromagnetic energy travels in waves that span a broad spectrum. These electromagnetic (EM) waves are ubiquitous, and without them life as we know it would not exits. EM waves form the foundation of the information age and the technologies we use every day: radio, television, consumer electronics, remote controls, cell phones, microwave ovens, X-rays and other medical technologies all use EM waves. EM waves transmit energy, but unlike water or sound waves, they do not need a medium to travel through. They move through the vacuum of space at the speed of light (about 300,000 km/s).
   EM waves have crests and troughs like all waves. The distance between consecutive crests is the wavelength. The number of crests that pass though a given point in one second is the wave's frequency which has a unit of measurement called the hertz (Hz), named after the great German physicist Heinrich Hertz. Hertz was the first to demonstrate the existence of EM waves and the first to send and receive radio waves.
   Radio waves, which have the longest wavelengths, are at the low-energy end of the spectrum and at the high-energy end of the spectrum, with the shortest wavelengths, are gamma rays. The other bands in between, ordered by decreasing wavelength, include microwaves, infrared, visible light, ultraviolet and X-rays. Its ironic that the band of radiation with the greatest significance to us—visible light—represents only a tiny fraction of the spectrum, from about 390 to 750 nanometers. Compare that to radio waves which range from a few millimeters to a kilometer in length or more. Our atmosphere filters out a large portions of the electromagnetic spectrum, but thankfully visible light passes through mostly unaffected.

The range of wavelengths in the electromagnetic spectrum compared to sizes found in everyday life.

  The frequency of any given EM wave is inversely proportionate to its wavelength: EM waves with long wavelengths have lower frequencies and EM waves with short wavelengths have higher frequencies. The equation that governs this relationship is ƒ = c / λ, where ƒ is the frequency, c is the speed of light, and λ (lambda) is the wavelength. So for a radio wave with a wavelength of one kilometer, its frequency would be 300,000 Hz or 300 kHz. In the United States, AM radio is broadcast at frequencies between 520 kHz and 1610 kHz. Using our formula, we can find that they correspond to wavelengths ranging from 186 to 577 meters. FM radio broadcasts at much higher frequencies: 87.8–108 megahertz (MHz). One megahertz is equal to 1,000 kilohertz, so that would correspond to wavelengths in the range of 2.7–3.4 meters—quite a difference!

  Over the next few weeks we will talk more about the various aspects of the electromagnetic spectrum, so if you have any questions related to this topic, let me know by posting them on my Facebook page.

The Mpemba Effect

A graph of freezing rates for two water samples demonstrating
the Mpemba effect. The gray line is water at 42.9°C and the black
line is water at 18.6°C. Note the hotter water spends considerably
less time in the 0–4°C range, likely due to convection.
Source: picotech.com.

As odd as it seems, sometimes warmer water freezes faster than cooler water. This observation is known as the Mpemba effect, names after Erasto Mpemba from Tanzania. Even though the effect had been known for years to layman such as plumbers and ice rink workers, the scientific community had not taken the claim seriously. But Mpemba, a high school student at the time, provoked a visiting physics professor to test his claim and to his surprise it held true. They published the results jointly in 1969. The Mpemba effect is only observed under certain conditions and there are many factors which can effect how quickly water cools. 
  Conduction is often the biggest factor. Take two similar containers, one containing cold water and the other containing an equal amount of hot water and place them both in the freezer. The hot container will melt any ice on the freezer shelf that it comes in contact with and refreeze as the container cools, creating a good thermal contact between the freezer shelf and the hot water container which will remove heat from the warmer water more quickly. On the other hand, the cooler water container will just sit on the layer of poorly-conducting freezer frost, so it will take longer to cool down. This is a pretty good explanation but even if you control for it by insulating the contact points to the freezer you can still observe the effect. 
  The explanation most-often cited is convection. As the warmer water rapidly cools at the surface, convection currents will develop and create an uneven distribution of temperature with hot water nearer the surface and therefore more evaporation from hot water than from cold. More evaporation means less mass to freeze so it would cool faster. And while this is probably the biggest contributing factor it’s not the only mechanism that drives the Mpemba effect, as not enough water would be lost to evaporation to account for the difference.
  Supercooling is another possible factor that contributes to the phenomenon. Initially cooler water is thought to dip farther below 0°C before freezing, but the mechanism for this is not well understood. Another factor could be the amount of dissolved gases which would be less in water that has been heated. But the most probable conclusion is that there just isn’t any single unique explanation as to why hot water sometimes cools more quickly than cold.

Common Sense in Science

"Common sense is the collection of prejudices 

acquired by age 18." —Albert Einstein

Did Albert Einstein have common sense? It depends on your definition of the term. Einstein once said that common sense is the collection of prejudices acquired by age 18, so by that definition, he did not. But in science, common sense is not all that useful because it is limited to the familiar world around us. It has been said that humans live in the middle world because our senses are limited and do not allow us to experience extremes. We cannot fully comprehend the very large (stars, galaxies), the very small (atoms, subatomic particles) or the very fast (the speed of light) to name a few examples. So when trying to tackle a difficult problem, common sense is more likely to get in the way than help solve the problem. As scientists, we need to rely on deduction, logic and evidence. 
  Einstein proved that time is relative when common sense would tell us that time is absolute and unchanging. That’s because on the scale of measurement that humans are used to, we can’t distinguish the tiny variations in time due to the effects of gravity or acceleration through space. Yet our world depends on it. Global positioning satellites have to constantly correct for relativistic effects because of their high velocity and the effects of Earth’s gravity. Otherwise they would be hopelessly inaccurate within a few hours. 
  Likewise, quantum mechanics challenges our common sense. Even Einstein had a hard time believing its core prediction that at small atomic scales, reality becomes a cloud of probabilities—even though his Noble prize winning work on light quanta in 1905 laid the groundwork for quantum mechanics. Over the last century quantum mechanics has perhaps been the most successfully tested theory in all of science.
  It is true that Einstein did not like to wear socks. After all, they would just get holes in them. And that he did not know his own phone number since it was easier for him to just look it up in the phone book. Once, as Einstein and a colleague walked together they notice an unusual plant growing along a garden walk. The colleague asked Einstein if he knew what the plant was. Einstein didn’t, and together they went to find the gardener to ask what it was. The gardener told them that it was a green bean plant. So now, if someone asks you if Einstein had common sense, you can tell them “Thankfully, no. And he doesn’t know beans either!”

The NSF Science Survey

Do you think you know more about science than the average American? Since you're reading this, my hypothesis is that you do. Let’s test it by taking the following survey that was originally given as part of the National Science Foundation’s 2006 study on the public’s knowledge of science.*
I will include your results (anonymously) in a future column where I analyze both the questions and answers, and compare them with the results from the original survey. Have your family and friends take the survey as well—the more that take it, the more accurate the results will be.




*NSF Poll # 2006-SCIENCE: Trend Dataset--Surveys of Public Understanding of Science and Technology. The Roper Center for Public Opinion Research Data Archive was the data distributor.

Mountain Goats and Telescopes

Mountain goats seem friendly to tourists, 

but really they just want to lick our sweat!

Today we will finish up our previous discussion of Mount Evans in Colorado. Travelling to the summit at 4,300 m we pass through montane and subalpine life zones before reaching the alpine zone. The largest mammal found in this high-altitude habitat is the Rocky Mountain goat, which are actually members of the antelope family. They are only found in North America, predominantly in the Rocky Mountains and the Cascade Range. They eat the abundant grasses, sedges and lichens found at this altitude with little worry about predators such as wolves or bears which are at lower elevations. The only predator they have to contend with at this elevation are golden eagles which can threaten their young.
   Mountain goats are primarily an alpine/subalpine species, remaining above or near the tree line for most of they year, but occasionally travelling to lower elevations. In winter they descend to lower elevations to find protection from the harsh winter elements and to obtain essential mineral nutrients by visiting natural salt and mineral licks that have become exposed by the winter weather. In the summer the goats are attracted to the summit tourist sites because they can lick the salts left behind by sweaty park visitors!
   They are excellent climbers and prefer to live on steep cliffs where few predators will follow. They have specialized split hooves that have a hard outer lining with soft, rubbery pads and dewclaws for extra grip. They have two layers of fur to protect them from the elements: a fine dense undercoat of wool and an outer layer of long hollow hairs.
   Mountain goats can be aggressive, but not usually towards humans. The billies will fight amongst themselves during breeding season and the nannies will fight with each other for herd dominance or to protect their kids.
   Also located near the summit of Mount Evans is the world’s third-highest telescope, the Meyer-Womble observatory. Operated by the University of Denver, its relative isolation and location east of the continental divide provides drier, less cloudy and less windy conditions compared to typical resort climates near Denver. Researchers use this telescope to study cosmic rays. Cosmic rays are high-energy charged particles that rain down on the Earth at nearly the speed of light before smashing into atoms in the upper atmosphere. Some by-products from these collisions reach the surface of the Earth resulting in a charged atmosphere or interacting to creating biologic mutations. We are normally shielded from these cosmic rays by our dense atmosphere at lower elevations, but the thin air at the summit does not offer the same amount of protection, making it an ideal location to study them.