When the Lights Go Out

One of my readers posed the question: When I turn off the light in my bedroom at night, where does all the light go? Before we answer this, we need to make a few assumptions. Let’s assume that the bedroom is a perfect container: It has no windows for light to escape from and no cracks around the door so light can’t escape there either. Also, let’s say the walls are perfectly solid, and consist of a regular structure of atoms. Imagine a grid of hard spheres laying next to  each other. This is the surface of the walls. 
   First, we need to realize that light is a form of energy. While the light switch is on, it closes an electric circuit and electrons flow through the light bulb. The light bulb converts the energy from the electric current to light energy in the form of photons. Photons are tiny packet of electromagnetic energy and momentum. When you turn the light off, the circuit is broken, the energy stops flowing, and the light goes away. But where does it go?
   The photons travel across the room at the speed of light. When a photon hits the wall, its energy and momentum is either absorbed by the atoms in the wall, or are reflected to another wall where it again may get absorbed or reflected. One of the fundamental concepts of physics tells us that both energy and momentum are conserved, which means that an atom will get a small kick from absorbing a photon. It will move, and kick against its neighbor, etc. If enough photons get absorbed, this will result in the wall warming up slightly. So the light gets converted into thermal energy in the wall. This is what is meant by having a temperature. 
   If the wall were at absolute zero, these atoms do not move and are simply at rest, each one just touching the next. By saying that the wall has a temperature, we are really saying that it contains thermal energy. This thermal energy is the random vibration of the atoms around their equilibrium point. Such a vibration can travel through the grid of atoms in the form of a wave. One atom pushes the next, which pushes the next, etc. 
   When you turn off the light switch, the process just stops—the bulb stops generating photons, and the last set of photons hit walls until they’re all absorbed, all within a fraction of a second.

The Keystone Species of the Southern Ocean

A swarm of krill in the Southern Ocean

Worldwide there are about 85 species of krill, the largest of which is the Antarctic krill (Euphausia superba) which averages about five centimeters in length. Antarctic krill live in dense concentrations in the cold Southern Ocean. At any given time there are four or five billion individuals, and when they congregate for spawning they create a pink swarm so large that it can be seen from space.  
   Krill are crustaceans like crabs, shrimp and lobsters. But unlike their cousins that are bottom-feeders, krill are pelagic—they make their living in the open ocean. And unlike the plankton they feed on, krill are nektonic—they are able to swim independent of the ocean currents. 

The anatomy of the Arctic krill

   Antarctic krill feed on algae and phytoplankton that are suspended in the water column. They are preyed upon by nearly every Antarctic predator that exists. And if a predator doesn't eat krill, it feeds on the ones that do. A penguin's diet consists of nearly 100 percent krill. Blue whales rely on krill for almost all of their dietary requirement. During the summer months, an adult blue whale eats up to 40 million krill in a single day to fulfill its 1.5 million kilocalorie nutritional needs. Antarctic krill is the keystone species in the Southern Ocean, and without it, the ecosystem would collapse.
   Antarctic krill use intensive searching and rapid feeding techniques to take advantage of high plankton concentrations. Krill form dense schools that move horizontally in the water column when feeding. Krill spend their days avoiding predators in the cold depths of the Southern Ocean. At night, they drift up toward the surface to search for phytoplankton.

   Recent studies show Antarctic krill stocks have dropped by as much as 80 percent since the 1970s. Scientists attribute this decline in part to ice cover loss caused by global warming. This ice loss removes ice algae from the Southern Ocean which is a primary source of food for krill. NASA satellite data reveals that there has been continuous ice loss from Antarctica since 2002—more than 100 cubic kilometers of ice per year.

The Skies Near Mount Ranier

Located southeast of Seattle, Mount Rainier is the tallest volcano in the Cascade Range and the most topographically prominent mountain in the contiguous United States. Its summit is at an elevation of 4,392 meters and it has a topographic prominence of 4,027 meters. Because of this, many people from the Pacific Northwest are treated to the spectacular beauty of this snow-capped peak which dominates the landscape. But if you are really lucky, your view of Mount Ranier could be enhanced in some very unusual ways. 

A cloud shadow being cast from Mount Rainier. Photo by Nick Lippert.

   One way is by an amazing cloud shadow that only occurs with several factors happening concurrently. At the approach of winter, when the Sun rises farther to the south, it is possible for the first rays of light at sunrise to pass through a dip in the Cascade Range and catch the peak of Mount Ranier. If that sunrise is also accompanied by a cloud layer above the mountain, it will project a shadow onto the bottom of the cloud layer creating a spectacular cloud shadow. This could never happen in the Rockies because even though there are several peaks taller than Mount Ranier, none of them have the topographic prominence that is needed. And as the sun rises its light will scatter too much to cast a shadow behind it.

   Another strange yet beautiful cloud phenomenon that you can see near Mount Ranier is lenticular clouds. These are lens-shaped clouds that form at high altitude. Because of their smooth, saucer-like shape, lenticular clouds have been mistaken for UFOs. Lenticular clouds are formed when moist air travels vertically over the mountain and creates a standing wave pattern on the downwind side. Moisture condenses at the crest of the wave and evaporates at the wave trough, creating the characteristics lens shape. Even though the wind continues to move down the mountain, the lenticular cloud will remain stationary. Lenticular clouds can appear singly, or in clusters or stacks. Pilots will avoid lenticular clouds because of the dangerous wind shears that accompany them, but thrill-seeking hang gliders will use them to ride the wave for several kilometers.

A stacked lenticular cloud formation near Mount Ranier.

   At some point in the future Mount Ranier will give us the most-spectacular—yet terrifying—show of all: when it erupts. Even though Mount Ranier is quiet now and has been since the 1890s, geologists consider this stratovolcano to be episodically active, which means that it WILL erupt again at some point in the future. It’s for this reason, and the fact that Mount Ranier is located near a highly-populated area, that it was included as one of 16 “Decade Volcanoes” worthy of study in an attempt to reduce the severity of a future natural disasters. These Decade Volcanoes were studied as part of the United Nations International Decade for Natural Disaster Reduction during the 1990s.

Brocken Specter

Brocken specter as seen from 

the Golden Gate Bridge.

I love travelling through the mountains. The way the light plays off the mist in beautiful and sometimes eerie ways amazes me. If you're lucky enough to be at the right place at the right time, you might experience a rare and seemingly supernatural optical phenomenon called Brocken specter, named after the highest peak in the Harz mountains in Germany. 

   German Folklore dating back to the 17th century says that on the night of April 30 each year, exactly six months after Halloween, witches and sorcerers gather on the Brocken and revel with their gods as they await the arrival of spring. Among mountain climbers there is a superstition that a person who sees a Brocken specter will someday die on the mountain; local climbers have been so startled by the sudden appearance of a Brocken specter that they fall to their death, not realizing they are seeing their own harmless shadow.

Brocken specter from the 

Tanzawa Mountains in Japan.

   The Brocken specter appears when the setting sun casts a shadow from directly behind a climber at a higher altitude onto a cloud or mist at a lower altitude. When the shadow is cast upon a mist the sunlight surrounding it enters the suspended water droplets in the air and reflect back to the observer via diffraction, creating a rainbow-colored halo around the shadow's head. This halo is called solar glory. 

   The Brocken specter may appear to be huge because the fog hampers your depth perception. Only one's own shadow, seen in a mist, can converge with the antisolar point and combine with the solar glory to create the Brocken specter. Therefore, if you are travelling in a group you can only see your own Brocken specter.

Brocken specter from the Pamir Mountains of Tajikistan.

The Neanderthal Genome Project

The majority of the DNA used for the Neanderthal
Genome Project was obtained from the bone fragments
of three females who were excavated from the Vindija
Cave in Croatia. Image: Max Plank Institute for
Evolutionary Anthropology/Frank Vinken.

Found in Europe and parts of Asia, Neanderthal lived from about 400,000 years ago until 30,000 years ago. Neanderthals were comparable in size to Homo sapien, but more robust. They also had similar brain sizes, but their skulls were shaped differently. Researchers have long wondered why Neanderthal went extinct. Some think the lack of genetic diversity made it too hard to persevere through plagues while others think that their smaller, less sophisticated social groups played a part in their demise. We do know that their stronger build would have required more food which would have been a disadvantage during hard times.

   In 2010, scientists from the Max Plank Institute for Evolutionary Anthropology in Germany reported that they had completed a first draft of the Neanderthal genome. This research was based on analysis of four billion DNA base pairs. Through DNA analysis, we have learned insights that had been previously unknown through only fossil evidence. Their study suggests Neanderthals had an effective population smaller than that of modern humans, and lived in small, isolated groups. And although we share about 99.7% of the same DNA, only 1-4% of modern non-African humans have inherited DNA from Neanderthals, and Africans have no common lineage. Most likely, the interbreeding occurred early in the migration of humans out of Africa.

   DNA analysis has also proven fruitful in a recent discovery in a cave in Northern Spain. Researchers there found the butchered remains of an extended Neanderthal family that were killed and eaten by other Neanderthals. The bones were cracked open by stone tools for marrow, suggesting that they were cannibalized before the cave collapsed and buried their remains. Researchers found that the group was genetically very similar, confirming that Neanderthals had less genetic diversity than modern humans. They also discovered through DNA analysis that they lived in small groups of males that were closely related, and that the females came from other tribes, a social system called patrilocality. Clearly, our understanding of human evolution is benefitting greatly from DNA analysis.

NASA Takes Gold in the 567 Billion Meter Dash!

The first image taken by the NASA Curiosity rover after
the dust covers were removed from the cameras.

I watched in amazement last night as NASA pulled off a perfect landing to put Curiosity—the most complex rover ever built—on the Martian surface. Congratulations to all the hard-working men and women at NASA/JPL for not creating a 2.5 billion dollar crater instead! If they were terrified during those seven minutes from when Curiosity entered the Martian atmosphere travelling 20,000 kph until touchdown, I sure could not tell. Nothing but professionalism and ear to ear grins and high fives once it had landed. 
   Curiosity weighs in at 900 kg and is three meters long, larger than some small cars. It is equipped with 80 kg of instrumentation, including a variety of cameras and a laser that is powerful enough to vaporize rock. These are the most-advanced instruments ever used on the Martian surface. Curiosity will be able to determine mineral and soil composition, atmospheric processes, detect chemical biosignatures and characterize the surface radiation on Mars.
   The Mars Science Laboratory’s goals for this mission are to search Mars for signs of life, past or present, study the climate and geology of Mars, and plan for a future manned mission to Mars. The mission is scheduled to last for about two years, but if conditions are favorable, the rover could be in operation for much longer.
   In the weeks and months to come I will be writing more about this incredible mission and its discoveries. In the meantime, to celebrate NASA/JPL’s successfully landing, this week’s quiz is about Mars. See how much you know about the Red Planet.

Two Trees from Socotra

Socotra, part of the Republic of Yemen, is a small archipelago of four islands in the Arabian Sea off the Horn of Africa. Socotra’s isolation from the mainland combined with a tropical desert to semi-desert climate has lead to unique speciation, with more than a third of its plant life being found nowhere else on Earth. The islands contains a wide range of habitats: beaches, mountain ranges, plains and caves. Because of Socotra’s broad diversity it has been described as the strangest-looking place on Earth. 

The dragon blood tree (above) and the cucumber tree (below).

   One of the most impressive of Socotra’s plants is the dragon blood tree (Dracaena cinnabari), which looks very odd with an umbrella shape. Its red sap was thought to be the dragon’s blood of the ancients, sought after as a medicine and a dye since antiquity and highly prized by European Renaissance painters. It was also used as a varnish by 18th century Italian violin makers. 
   The unusual shape of the dragon blood tree is an adaptation for survival in the dry rocky soil where it is found. The large, packed crown furnishes shade and reduces evaporation which helps seedlings survive beneath the adult tree.
   Perhaps the strangest of all the trees on Socotra is the cucumber tree (Dendrosicyos socotranus), which looks like a giant cucumber with its bulbous trunk and tiny crown. It lives on the dry parts of the islands up to about 500 meters in elevation. It is the only tree in its plant family which includes melons, gourds, squashes, and yes, cucumbers.
   Cucumber tree seedlings are eaten by goats that graze on the islands. Mature trees are often cut down and made into pulp which is fed to livestock. The leaves of the cucumber tree are used by the local population to treat a variety of ailments.
   Socotra’s ecosystem is one of the most endangered in the world and it is listed as a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). Both the dragon blood tree and the cucumber tree are considered vulnerable species by the International Union for Conservation of Nature (IUCN).