Saturday, December 31, 2011

String Theory (continued)

Let’s continue with our discussion of string theory from last week, which says that all matter can be broken down to a fundamental particle, called a string. Atom are made up of protons, neutrons, and electrons. Electrons aren’t made of anything smaller. Protons and neutrons can be broken down further into quarks, which also can’t be broken down any further. For this reason, quarks and electrons are referred to as fundamental particles. Even though quarks and electrons behave very differently, string theory says that they are actually very similar, and that the differences between them are due to these strings vibrating at different frequencies, similar to how a violin makes different sounds.
   The most interesting thing about string theory is that it requires extra dimensions of space. These curled-up dimensions are too small to see or experience. There are a great many ways of curling up these extra dimensions. String theory require seven extra curled up dimensions, so when added to our three familiar dimensions of space plus time we get a total of 11 dimensions.
   You can think of multi-dimensional space as a garden hose. If the hose is viewed from far away, it appears to have only one dimension—length. Now think of a ball small enough to enter the hose. Such a ball would move more or less in one dimension. However, viewed close-up, one discovers that the hose contains a second dimension—its circumference. For an ant crawling inside, it would move in two dimensions. This extra dimension is only visible when up-close, or if the ball we use is small enough compared to the hose.
The CMB temperature fluctuations from WMAP data seen over the full 
sky. The average temperature is 2.725 degrees Kelvin, and the colors 
represent small temperature fluctuations. Red areas are warmer and 
blue areas are colder by about 0.0002 degrees.
   It might be possible to detect gravitons indirectly. Remember, gravitons are the hypothesized fundamental particles that carry the force of gravity. Experiments are in progress to detect gravitational waves and although these experiments cannot detect individual gravitons, they could provide information about gravitons. Gravitational waves were hypothesized by Einstein whenever two massive bodies are in tight orbit with one another, such as the binary white dwarf stars discusses previously in this column.
   At the Large Hadron Collider (LHC), scientists will soon be ready to run at energies high enough to allow for the testing of extra dimensions as predicted by string theory. The thinking is that if they can smash particles together at high enough energies, part of the collision debris might escape into an extra dimension. By calculating the total energy before and after such a collision, they can see if less energy is present after the collision. If so, it could mean that energy is flowing to an extra dimension.
   The Cosmic Microwave Background (CMB) radiation might also contain clues about strings. It is interesting to think that in the first moments after the big bang, all the matter of the Universe was contained in an extremely hot, dense stew of fundamental string particles. If so, we might be able to look for an imprint in the background radiation as the universe inflated.
   NASA’s Wilkinson Microwave Anisotrophy Probe (WMAP) has been gathering information about the nature of the Universe for nine years, finishing in September 2010, and has provided us with some fascinating information, mapping the CMB radiation to produce a map of the microwave sky, revealing what the Universe went through during the first trillionth of a second (inflation). The Planck space observatory, a project underway by the European Space Agency, will improve on this by a factor of three and is scheduled to deliver final results near the end of 2012.

Sunday, December 25, 2011

String Theory

One of the toughest problems in physics is unifying Einstein’s theory of general relativity, which describes gravity on a large scale, with quantum mechanics, which describes the other three fundamental forces acting on the atomic scale. Finding this “theory of everything” has stirred great debate in the scientific community. Devising experiments to test it has been unsuccessful so far, but that may soon change.
   After Einstein finished his work on general relativity, he spent the next three decades of his life trying to expand his theory of gravitation to include electromagnetism (the strong and weak nuclear forces had not yet been discovered). This search left Einstein isolated from the main body of physics which was consumed by the emerging field of quantum mechanics, and which Einstein never fully embraced. In the early 1940s, Einstein wrote “I have become a lonely old chap who is mainly known because he doesn’t wear socks and is exhibited as a curiosity on special occasions.” In 1950, he described his unified field theory and although his work was ahead of its time, his efforts were ultimately unsuccessful. Einstein’s dream of unifying the fundamental forces of nature would have to wait for physics and mathematics to catch up.
The worldsheet on the left shows a string splitting apart and 
the worldsheet on the right shows two strings joining together. 
The arrows indicate the direction of travel through spacetime.
   Since then, theoretical physicists have taken up the challenge. The most successful theory thus far is string theory. At its essence, string theory is an attempt at describing gravity at the quantum level. In string theory, all fundamental particles are not point like, but instead made out of tiny, one-dimensional, vibrating loops of string—like incredibly small rubber bands. These strings use gravitons to exchange the force of gravity back and forth. A graviton is a hypothetical particle that is itself another little loop of string. You start with a loop of string and that string splits in half, creating a second string. If you have many strings doing this at the same time, every once in a while the split strings will get mixed up with one another and exchange back and forth, and that is the origin of gravity in string theory. This splitting and joining can be viewed diagrammatically as a worldsheet. A worldsheet is the name coined by Leonard Susskind for a two-dimensional surface which describes the embedding of a string in spacetime.
   Leonard Susskind is widely regarded as the father of string theory. In 1969, he and other physicists began to explore the possibility that particles were made up of strings. What they discovered, to their amazement, was that these particles behaved as if they had gravitational forces between them. Split off little pieces, exchange them, and they create forces very similar to gravity.
   Initially, string theory was intended to describe protons and neutrons. But the strings that physicists describe now are a billion billion times smaller than a proton. Much smaller than we can see with any kind of microscope that exists and smaller than anything that can be detected by the Large Hadron Collider. Because of this, graviton detection is impossible. Even if we could build a detector the size of Jupiter, we would only be able to observe one graviton every 10 years at best and it would be impossible to distinguish it from a neutrino. And a neutrino shield would be so massive that it would collapse into a black hole!
   Next week we will finish up our discussion of string theory by talking about why it requires extra spacial dimensions and what experiments are underway to test string theory.

Monday, December 19, 2011

White Dwarfs

Three illustrations showing white dwarfs 
orbiting each other and then colliding.

Our Sun is said to be a main sequence star, meaning that it fuses hydrogen to form helium. What happens when it exhausts its supply of hydrogen fuel? Once hydrogen fusion stops, there is not enough pressure on the star's core to create a fusion reaction with helium. Because there is no longer any outward push from fusion, the star begins to collapse from the crush of gravity. This collapse create more and more pressure in the core until helium fusion begins, while some of the remaining hydrogen burns outside of the core. The products of helium fusion is carbon and oxygen. The star expands and becomes a red giant. Its life as a red giant is brief on an astronomical scale—only a few million years. It will then eject its outer layers as it reaches the end of its burn cycle, leaving behind a collapsed core known as a white dwarf surrounded by a planetary nebula. 
  A white dwarf is the final evolutionary state of about 97% of all the stars contained in the Milky Way. White dwarfs are very dense—they pack a mass comparable to that of our Sun into a volume similar to the size of our Earth. A white dwarf is composed mostly of the fusion products of helium: carbon and oxygen. It is also surrounded by a thin layer of helium, and sometimes hydrogen. Fusion quickly stops so the white dwarf has no source of energy and will cool over many billions of years, eventually to the point where it no longer shines at all.
  Astronomers have recently found two white dwarfs stars orbiting one another once every 39 minutes. Binary white dwarfs are exceedingly rare. Out of the 100 billion stars in our galaxy, only a few dozen have been found. Located about 7,800 light-years away in the constellation Cetus, these two stars orbit each other at a distance less than that from the Earth to the Moon.
  The fate of these stars is already determined. Because they orbit one another so closely, they produces gravitational waves, ripple-like distortions in spacetime that were predicted by Albert Einstein in his theory of general relativity. The gravitational waves carry away orbital energy, which has put the stars in an ever-tightening spiral. In about 40 million years, they will crash into one another and merge to form a new star. If their combined mass were more they would collide and turn supernova, but since they aren't massive enough, they will be reborn and begin to shine once again.

Monday, December 12, 2011

The Mystery of Antimatter

Despite the apparent variety of materials in the world around us, we know that everything is made of one thing: matter. But when the universe was born about 14 billion years ago in the Big Bang, two types of matter were created: ordinary matter, which we and everything around us are made, and antimatter, a kind of opposite version of matter. The existence of antimatter was first predicted by the British physicist Paul Dirac in 1928. We know antimatter exists because we can find traces of it in cosmic rays and because scientists have made small amounts of it in particle accelerators. The universe is vast, but it seems to be made almost entirely of matter. So where did all the antimatter go?

Experimental area at CERN’s Antiproton Decelerator The actual antiproton decelerator ring is behind the concrete shielding seen on the left.
   When matter and antimatter come into contact, they annihilate each other, creating vast amounts of energy in the process. A reaction between on gram of matter and one gram of antimatter would release the same energy as exploding 43,000 tons of dynamite. We think that equal amounts of matter and antimatter were created in the Big Bang, but something happened in the first few minutes after the Big Bang to shift the balance in favor if matter so that when matter and antimatter destroyed each other, some matter was left over. This was the matter that went on to form the universe that we know today. Physicists don’t understand why there was an imbalance between matter and antimatter. In fact, this is one of the biggest mysteries in science today. What we do know is that antimatter is a mirror-like reflection of matter, but not quite. Antimatter is said to violate CP-symmetry (CP stands for charge and parity), meaning that there is not total cancellation between particles and their antiparticles. Understanding this process will help us understand why we live in a universe made of matter and not antimatter. But to really understand antimatter we need an experiment that can recreate the conditions just after the Big Bang. 
   Scientist at the European Organization for Nuclear Research (CERN) are attempting to do just that with several ongoing antimatter experiments. Antimatter is difficult to create but even more difficult to keep without it reacting. CERN’s Antiproton Decelerator holds the antiparticles before injecting them into one of several ongoing experiments. They can hold antiparticles for up to 1,000 seconds—a lifetime in the realm of particle physics. These experiments all have one thing in common: they want to pinpoint the differences in antimatter when compared to matter. It is their hope that someday this mystery of the universe will be solved.

Sunday, November 27, 2011

The Jets of Enceladus

The jets in the southern hemisphere of Enceladus 
taken by the Cassini spacecraft in 2005.

I’ve always been intrigued by the moons in our solar system. Each has a unique personality. Take Enceladus for example. In 2005, while orbiting Saturn, the spacecraft Cassini observed this unique moon up close for the first time. It seems peaceful enough with an icy surface on its south pole. Without warning, geysers of water and ice are ejected, blasting hundreds of kilometers into space at over 2,000 kph, making it the largest snow-making machine in the solar system. The spray of icy particles coat the small moon, giving it a clean, white surface. It is the most-reflective body in our solar system.
   Enceladus has a frigid atmosphere, but it must have a liquid ocean beneath its icy surface. We know this because Cassini was able to capture and analyze the ice particles on several of its flybys, and it discovered that the ice was salty. So the ice must have come from salty ocean water since if it were surface ice there would be very little salt in it. Ocean water is ejected and freezes to form ice particles when it hits the frosty atmosphere. The subsurface water is heated enough to remain liquid through a combination of tidal heating and radioactive decay. Enceladus has a slightly elliptical obit of Saturn which causes gravitational flexing, generating heat. And where there is liquid water, you have environmental conditions favorable to the emergence of life.
   It is also thought that Saturn’s outermost ring, known as its E ring, is supplied by the material from the jets of Enceladus. Enceladus orbits in the densest part of the E ring. In 2009, Cassini found salty ice grains in Saturn’s E ring. About 200 kilograms of water vapor is ejected every second in these plumes. Smaller amounts of ice grains are also ejected. Without the Cassini mission which can sense these compounds in its close flybys, we would never know just how fascinating this moon is.

Thursday, November 17, 2011

A Turkey Tall Tale

Navigating the blood-brain barrier is tricky business.

With Thanksgiving just around the corner, it’s only fitting we examine the age-old belief that eating turkey makes you drowsy.
Turkey contains tryptophan, an amino acid that the human body doesn’t produce naturally. Tryptophan is essential to good health and must be acquired through diet. L-tryptophan is metabolized by the body to create serotonin and melatonin, neurotransmitters that act as calming agents in the brain and regulate sleep. So its easy to see why the turkey gets blamed when you’re snoozing on the couch after dinner, but it’s not so simple.
Metabolism of L-tryptophan into serotonin
and melatonin. Transformed functional
groups after each reaction shown in red.
  First off, turkey contains about the same amount of tryptophan as most other meats, 0.24 grams per 100 grams of food. Our bodies only need about 0.2 grams per day, and we get more than five times that amount in an average meal. So eating turkey is not going to make a huge difference in and of itself. If one were to consume pure tryptophan on an empty stomach, then yes, it would make you drowsy. But you would have to take it as a supplement. In turkey, however, it’s only one of several amino acids and must compete to cross the blood-brain barrier. And because it has a large molecular weight, it’s not easily absorbed.
  So what is making you drowsy after your Thanksgiving dinner? Carbohydrates, mostly. Carbohydrates cause the pancreas to produce insulin. When this occurs, some of the competing amino acids leave the bloodstream and enter muscle tissue. This causes a relative increase in the concentration of tryptophan in the bloodstream. The tryptophan is carried to the blood-brain barrier through glucose transporters (GLUTs). Some of it then crosses the barrier and is metabolized first to serotonin and then melatonin which makes you sleepy.
  There are other factors involved in the conspiracy to make you miss that last quarter of football. Eating two days worth of food in one meal will have an effect. Your body will have to direct more blood flow to aid in digestion at the expense of your other organs, including your nervous system. If you drink alcohol with your meal it will act as a depressant and increase your drowsiness. Fatty foods will also slow down digestion and sap your energy. Maybe the best course of action is to just sit back, relax, and let Mother Nature take its course.

Monday, November 14, 2011

The Science of Sue

Sue the T. rex. Notice the wishbone or furcula (circled),
the first such bone ever found on a T. rex.

Sue, the world’s biggest, most complete, and best preserved T. rex ever found, has been visited by millions at The Field Museum in Chicago. Many of Sue’s bones have rarely or never before been found in a T. rex. Plus, at 90% complete, Sue’s skeleton provides scientists with the unusual opportunity to reconstruct what T. rex may have looked like and how it moved when alive. Finding most of the bones from a single specimen gave scientists excellent detailed information about Sue’s anatomy and biology.
   T. rex is know for its tiny forelimbs, and Sue’s right arm is only the second nearly-complete arm ever found. It will help scientists better understand the strength and motion of this oddly small appendage. Sue’s arms are about the same size as human arms, making them too short to reach her mouth. Yet the bones are quite thick which indicates they would have been very powerful. Current thinking is that the arms were more useful to T. rex in its early life when it would have been proportionately larger.
   If you do visit Sue at the Field Museum, you won’t see all of her bones attached. For example, there are long thin bones that were formed just beneath Sue’s skin on her belly called gastralia. They are different from her ribs and scientists are trying to figure out their positioning and how they should be attached. They might have helped her breathe or perhaps they helped protect her internal organs. Usually, these delicate bones are incomplete or missing, but Sue has about 75% of her gastralia intact.
   Sue’s has a wishbone or furcula in her chest. This bone is the first ever found on a T. rex. Only carnivorous dinosaurs have a furcula and it’s one of the many links between dinosaurs and birds.
   The tail on Sue is the most complete tail ever found on a T. rex. A complete tail allows for an accurate measurement of the animal’s length.
   Perhaps the most significant part of Sue’s skeleton is her skull, and Sue’s is one of the most complete and best preserved T. rex skulls ever found. Its structure and arrangement provides some of the best clues about how Sue lived and related to her environment. Before being put on display, Sue’s skull spent 500 hours inside a powerful CT scanner. As a result, scientists can now learn about the structure of T. rex’s brain. These CT images show Sue’s brain cavity. The brain itself was about the size and shape of a big sweet potato. Sue had large olfactory bulbs and sinus cavities indicating she had a strong sense of smell which would have been important for hunting or scavenging for food.

Sunday, November 6, 2011

A Dinosaur Named Sue

Sue the T. rex, on display at the 
Field Museum in Chicago.

This is a story about a T. rex names Sue. In her 28 years of life she suffered many injuries and illnesses. A careful study of her bones tell us much about the hard life she lived. She suffered nine broken ribs, torn ligaments, infections and arthritis. Yet what probably killed her was a parasite. Holes in her lower jaw indicate she may have suffered from trichomonosis, a killer of modern-day birds of prey. If Sue had this disease, as indicated by the holes, it would have caused a serious infection in the back of the throat, making it very difficult to eat and breathe. So even if she did survive the infection, swallowing would have been so painful that she would have likely died of starvation. A difficult end to a difficult life.
   Fast forward 67 million years to the summer of 1990. Fossil hunter Sue Hendrickson was working near Faith, South Dakota, for the Black Hills Institute, a commercial fossil-collecting team. They were digging at the ranch of Maurice Williams and discovered that one of their trucks had a flat tire. While the team went into town to get it fixed, Sue stayed behind to investigate a weathered bluff she had noticed previously. Quickly she found some bone fragments that had fallen down the hillside. Looking to see where they fell from, she saw several vertebrae exposed in bluff face. Sue immediately knew they were bones from a large carnivorous dinosaur, possibly a T. rex. When her team returned, they verified her findings and named it Sue in her honor.
   After the Black Hills Institute finished excavating Sue, they knew they had an incredible specimen, possibly the best ever found. Sue was unique because she was so large and well preserved. Over 90% of her bones were intact. As word of their discovery spread, a fight erupted over the ownership of Sue. The Black Hills Institute had paid Mr. Williams $5,000 for permission to dig on his land and believed they owned the fossil. But Mr. Williams claimed that the money was only for permission to dig. And because the property fell within the boundaries of a Sioux reservation, the tribe also claimed ownership. Even the federal government became involved to determine if Sue had been found on federal land, launching an investigation against the Black Hills Institute. Meanwhile, Sue was locked away awaiting a decision as to who owned her. In the end, after a five-year legal battle, a judge determined that Sue belonged to Mr. Williams who promptly decided to sell Sue to the highest bidder.
   On October 4, 1997, Sue was put on the auction block at Sotheby’s in New York. In just eight short minutes Sue had a new owner. The Field Museum in Chicago bought Sue for a record $8.36 million. Sue made her public debut on May 17, 2000. The culmination of ten years of effort had finally brought the world’s biggest, most complete, and best preserved T. rex to a public stage and Sue’s fans were elated.
   Next week we’ll finish up our story about Sue and discover what has been learned since she has been in the care of the Field Museum.

Saturday, October 29, 2011

The Elwha River Gets a Makeover

The Elwha River, which runs through the heart of Olympic National Park in Washington State, is getting a makeover. Last month, the National Parks Service began removing the Upper Elwha Dam and the Glines Canyon Dam from the river. Both lack passageways for migrating salmon.

The five species of Pacific salmon which live in the Elwha River.
  The Elwha River provides habitat for five species of Pacific salmon: chinook, chum, coho, pink and sockeye. By removing the two dams it will open up more than 110 km of river and tributary habitat for these fish. Currently only about 3,000 salmon return each year to spawn in the eight kilometers of habitat below the dams. Ecologists predict that number could rise to 400,000 once the dams have been removed and the ecosystem fully restored.
Salmon are classified as diadromous, meaning they migrate between salt and fresh water. More specifically, they are anadromous, meaning that they spend most of their lives at sea and migrate to fresh water to spawn. Cutthroat trout, which also inhabits the Elwha, are anadromous too. The other type of diadromous fish are called catadromous. They spend most of their lives in fresh water and migrate to the sea to spawn. Most eels are catadromous.

The 182 million dollar project was funded by the Elwha River Ecosystem and Fisheries Restoration Act of 1992—the largest dam removal project in U.S. history. 
Since 1999, a total of 145 dams have been removed in the U.S., but none have been anywhere near the size of the Elwha dams which have trapped 14 million cubic meters of sediment since the first dam was completed in 1913. That’s enough sediment to fill 13 Empire State Buildings with some left over. The dams will have to be dismantled in stages to mitigate the effects of sediment removal on wildlife. It is expected that the restoration project will take another three years to complete. After the dams are removed, the area that lies under the lake will be revegitated to secure its banks from erosion.
Tearing down the dams is the culmination of eight years of preparation, including the design of a new fish hatchery for the Lower Elwha Klallam tribe that lives there. The hatchery will release fish into the Elwha to help repopulate it. The tribe has a special connection to the Elwha because historically the river provided them with everything they needed to live. For centuries, their culture revolved around salmon which was the most important part of their diet. They have great respect for the salmon which they celebrated through ceremonies and rituals.

The Elwha dam removal and restoration project provides a unique research opportunity. The watershed offers scientists ideal study conditions since most of the watershed lies within the protected boundaries of Olympic National Park. If successful, restoration efforts in the Elwha River watershed may become a template for other watersheds in less-than-ideal conditions.

Sunday, October 23, 2011

The Discovery of Electromagnetism

The first electromagnet, invented in by William Sturgeon.
It was made of 18 turns of copper wire on a U-shaped iron
core. When the wires were connected to a copper-zinc-acid
battery, the electromagnet could hold 4 kg. The cups
contained mercury as an early method of making an
electrical contact between wires. The one on the left acted
as a power switch.

Hans Christian Ørsted was a Danish scientist and philosopher that discovered the unique relationship between electric currents and magnetic fields. Ørsted had been investigating electric and magnetic properties for several years, and in 1820, while preparing for an experiment during a lecture at the University of Copenhagen, he noticed a compass needle, which happened to be lying next to a wire circuit, moved when he switched the electric current on and off. He had found evidence of a direct connection between electricity and magnetism. A few months later after more intensive investigations, he published his discovery that an electric current produces a magnetic field as it flows through a wire. Soon after, there was a tremendous outbreak of research in this new field of electromagnetism, and in 1824 the British scientist William Sturgeon invented the electromagnet. Today, electromagnets are used in a variety of ways, from electric motors, transformers and generator to electromagnetic suspension for MAGLEV trains. 
One of the early uses for this new technology was in stage magic. The French master magician Jean Eugène Robert-Houdin used a powerful electromagnet in one of his most famous tricks, The Light and Heavy Chest. Robert-Houdin brought a small wooden box on stage and declared that he had found a way to protect it from thieves. He would then ask a small child to lift it, which the child would do with ease. Then he would pick a full-grown man from the audience and ask him to lift the chest. And try as he might, the man could not lift the box. What was unknown to the audience is that the chest had an iron plate embedded in its based and under the stage was a powerful electromagnet which the magician could turn off and on by a hidden switch.
What made this trick even more incredible is that Robert-Houdin used it to help squelch a rebellion in French Algeria. In 1856, after his retirement, Robert-Houdin was asked by Napoleon III to help pacify the Marabouts there. The Marabouts were able to control their tribe with their “magical” abilities and had advised their leaders to rebel against the French. Napoleon wanted Robert-Houdin to show that French magic was more powerful. Robert-Houdin used The Light and Heavy Chest trick by inviting the strongest tribesman on stage and asking him to pick up the wooden chest, which he did with ease. Then Robert-Houdin announced that he was going to take his strength. Waving his wand he declared, “Now you are weak.…Try to lift the box.” The tribesman laughed at this and struggled with all his might trying to lift the chest, but it would not move! Then he tried to rip it apart, but the box had been rigged to give an electric shock when he tried to rip the handles off. Screaming in pain, the tribesman let go of the chest and ran out of the theater.
After his performances were done, he visited with the tribe leader and was given a scroll professing the tribes loyalty to France and praising his magical powers. Robert-Houdin went back to France with his mission accomplished, having suppressed any possible rebellion.

Monday, October 17, 2011

Meissner Effect

A demonstration of the Meisner effect: a superconductor in transition to its superconducting state in the presence of an applied magnetic field will cancel out nearly all magnetic fields within to achieve a locked levitation.

Saturday, October 15, 2011

Ever-expanding Universe

Congratulations to Perlmutter, Schmidt and Riess for being award the 2011 Nobel Prize in Physics for the discovery of the accelerating expansion of the Universe. For nearly a century, we have known that the Universe is expanding as a result of the Big Bang about 14 billion years ago. However, their discovery in 1998 that this expansion is accelerating is astounding and has turned cosmology on its head.
  By studying more than 50 distant supernovas over time they discovered that not only is the universe expanding, but at an ever-accelerating rate. Supernovas are exploding stars similar in mass to the Sun but much denser. Supernovas can briefly outshine a whole galaxy. What they discovered was that their light was weaker than expected—a sign that the expansion of the Universe is accelerating. 
  When we look at distant galaxies and supernovas we see that they are moving away from us, and more distant ones are moving away faster so really its not just an expansion away from us. Everything is moving away from everything else—space itself is getting bigger.
Estimated distribution of matter in the Universe.
  One would expect the expansion of the universe is something that would slow down, due to the gravitational attraction of every object to every other object in the universe. But we are not completely baffled. Einstein, in his general theory of relativity, predicted that even empty space has energy—what we call dark energy. The acceleration is thought to be driven by dark energy, but just exactly what that is remains perhaps the greatest mystery in physics today. What is known is that dark energy makes up about 74% of the Universe. This dark energy pushes space itself and causes distant galaxies to move away from us faster and faster, and this is where the acceleration comes from. So cosmologists are attempting to understand what is going on. Is it really dark energy or some modification of that, or is it a modification of Einstein’s theory of gravity? 
   Either way, it appears that the Universe will continue to expand, and galaxies will continue to move away from us. In 100 trillion years the last star will go dark and the Universe will become a very cold and lonely place. It reminds me of the science fiction short story "The Last Question" written by Isaac Asimov in 1956. In the story, the supercomputer known as AC was asked how the threat to human existence by an eventual heat death (lack of free energy) can be averted. Every time the question was posed, the computer responded "insufficient data", but in the last scene, the god-like descendants of humanity watch as the last stars flicker out as the Universe approaches its heat death. Humanity asks the computer one last time and even though it cannot answer, it continues to ponder the question even after all life ceases to exist. Eventually the computer comes up with an answer, but since there is nobody to report it to, it decides to show the answer by reversing entropy. The story ends with "And AC said: 'LET THERE BE LIGHT!' And there was light—"

Wednesday, October 5, 2011

Water Planet

Looking down at our planet from outer space, most of what you see is water. About 71% of Earth’s surface is covered by ocean, which is why Earth is sometimes called the Water Planet. But that name is a little deceiving when it comes to our ability to supply clean drinking water to the nearly seven billion people on the planet.

“Water of love, deep in the ground
But there ain’t no water here to be found
Someday baby when the river runs free
It’s gonna carry that water of love to me.”
—Mark Knopfler, Dire Straits

   Oceans account for 97.25% of our water. The other 2.75%—fresh water—is divided up between glaciers and polar ice (2.04%), ground water (0.68%), lakes and rivers (0.01%), and the rest in clouds, vapor and precipitation.

Visualizing Earth’s water supply as spheres.

   Think of it another way. If you could gather up all the water on the planet into a sphere it would have a diameter of 1,380 km, or about 40% that of the Moon. Pretty massive, right? But how much of that is drinkable? First lets remove all the salt water. That leaves us with a sphere that is 458 km in diameter. But most of this water—almost three-fourths of it—is locked up in glaciers and polar ice. If we remove that, our sphere of drinking water shrinks considerably, down to 265 km in diameter. Yet most of this water is still not available to drink, being trapped underground. The sum total of all the drinkable fresh water, available in lakes, rivers, and other reservoirs, would make a sphere just 66 km in diameter. So even though we live on the Water Planet, its easy to see why we have a Water Problem.
   Take Lake Mead for example. Fed by the mighty Colorado River, it’s the largest reservoir in the United States.  Since 2000, its water level has steadily declined from 370 m to a low of 330 m in November of 2010, only two meters above the critical level that would automatically trigger water rationing for much of the southwestern United States. And according to a 2008 study done by the Scripps Institution of Oceanography, there is a 50% chance that Lake Mead could run dry by 2021 if climate change and use projections hold true.

Tuesday, September 20, 2011

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.

Saturday, September 17, 2011

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.

Saturday, September 10, 2011

The Electromagnetic Spectrum

The relationship between frequency and wavelength 
iEM 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.

Monday, September 5, 2011

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.

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.

Monday, August 29, 2011

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!”

Saturday, August 13, 2011

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.

Monday, August 8, 2011

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.

Sunday, July 31, 2011

The Ice Diet

Today let’s examine the science behind the claim that you can lose weight by eating ice. The theory is this: eating ice will make the body burn up calories in order to maintain a constant body temperature. Seems reasonable, but let’s explore.
  The calorie is a unit of energy and is approximately equal to the amount of energy required to raise the temperature of one gram of water by one degree Celsius at standard atmospheric pressure. I say approximately because it varies slightly depending on the starting temperature of water and if contains any impurities or dissolved gasses. Even though the standard unit of energy in the SI system has been the joule since 1960, it has not caught on yet when talking about food energy (one calorie is about 4.2 J).
  So lets calculate how much ice you would have to eat in order to lose one kilogram. First we have to make a few assumptions: 1) The ice temperature is near 0° C.  2) The body will efficiently metabolize stored energy in order to melt the ice and raise its temperature to 37° C, the average body temperature for humans. 3) The actual mass of the ice consumed does not count towards our final weight.
  So for one gram of ice, the total energy needed to bring it to 37° C is 37 calories to raise its temperature plus another 80 calories to change it from solid ice to liquid water. This is known as its specific melting heat. Therefore, the total energy required is 117 calories. In order to lose one kilogram of body mass you have to reduce calorie intake by 7,700 Calories, so it looks like one would only have to eat 66 grams of ice, right? Well, there is one last detail. What we normally refer to as a calorie when talking about food is really a kilocalorie (1 kilocalorie = 1,000 calories, often written as 1 Calorie). So in actuality, instead of eating 66 grams of ice you would need to eat 66 kilograms of ice. Good luck!

Thursday, July 21, 2011

Mount Evans

Mount Evans Highway is the highest paved road in North America.

We will be heading back home tomorrow and one stop we are planning on making along the way is Mount Evans, Colorado. The drive up Mount Evans is called the road into the sky. From 2,300 m at Idaho Spring you climb to 4,300 m at the summit, driving through three altitudinal life zones: montane, subalpine and alpine.
  Montane means "of the mountain" and the montane zone is characterized by higher rainfall than the adjacent lowlands. It is usually well forested, being far below the tree line. 
  As you approach the tree line, you transition into the subalpine life zone. Here the trees usually become crooked and gnarled due to continual exposure to freezing winds which cause vegetation to become deformed. Here trees need to be sheltered by rocks or snow cover in order to survive. Typically these trees are of the fir, spruce or pine varieties and they are called Krummholz formation, from the German words krumm (crooked, bent, twisted) and holz (wood). Well established krummholz trees can live up to a thousand years. Grasses and shrubs are also found in the subalpine life zone.
  Above the tree line is the alpine life zone which is characterized by tundra. Here vegetation is close to the ground and consists of grasses, sedges and dwarf shrubs covered with lichens and mosses. Plants have to adapt to the harsh winds and cold temperatures of the alpine life zone in order to survive.
  Next week I will continue with more on Mount Evans and talk about the fauna which can be seen in each life zone.

Hoping to see some of the famous Mount Evans mountain goats!