Inside NOVA

The Science of Free Will

2012-02-07T20:37:41Z

Do humans have free will? Philosophers have discussed and debated free will for thousands of years. The question used to be, "Do we get to decide our actions or does God dictate them?" Later it became, "Is our soul a separate entity from our body that tells our body what to do?" Today, science isn't in the business of testing for God or the soul, and we believe that the mind is a product and part of body. Thoughts are patterns of neurons firing in your brain.

Now, scientists are beginning to probe the connection between thought and action. In a series of blog posts over the coming week, I'll discover how far that research has come--and how far it has yet to go.

Part 1: Free Will in the Lab

As individuals, we believe that our thoughts bring about our actions. First we ask a question to ourselves: "What shall I do now?" Next we make the decision: "I will bake a cake now." Finally, we perform the action; we bake the cake. We believe we baked the cake because of that inner dialogue. But what if the brain "decided" to bake the cake long before the inner dialogue gave voice and awareness to the decision? The brain may have been sending signals to the body to go get the flour before we even thought, "I will bake a cake"! If this is true, you were going to bake that cake all along, and your thoughts arose in order to explain your actions to yourself--the thoughts are, to torture a metaphor, just the icing on a cake that your brain baked before you ever knew it.

With modern science we have the ability to watch brains as they function, something the ancient philosophers could barely have imagined. Does this mean we can now finally figure out how free will works? Can scientists witness our decisions in action? Or will it turn out that free will is just an illusion? The results of experiments in the field and what they mean for free will is hotly debated. In this series, I hope to untangle the science from the semantics and the data from the dogma--without getting stuck in the mire of metaphysics.

Free Will in the Lab

2012-02-07T20:34:45Z

This is the first part in a four part series on the science of free will.

First, some history. Though philosophers have debated free will for over 2000 years, scientists only began to take it on experimentally in the 1980s, when Benjamin Libet (1916-2007), a physiologist at the University of California San Francisco, performed a now-classic experiment. Libet instructed participants to flex their wrists whenever they felt the urge to do so, within a window of a few seconds. Subjects watched a rapidly moving clock and were instructed to note to themselves, and later report to the researchers, the time on the clock when they had come to a decision to move. At the same time, their brain activity was monitored by EEG. Libet was looking for a distinct change in brain activity that he called the "readiness potential," which he believed was an indicator of the brain preparing for movement.

Libet found that the readiness potential appeared, on average, 350 milliseconds before subjects reported that they had made a decision. This meant that the order of the events was: 1) A subject's brain prepared to move the wrist, 2) The subject said to himself, "I have decided to move my wrist," 3) The subject's wrist moved. To Libet, this suggested that the subject's decision was not truly the cause of the movement, since the brain was preparing the movement a fraction of a second before the subject made a conscious decision. Libet came to the conclusion that our conscious control over our actions is limited--or may not exist at all. Wow, sounds like free will just took a pretty hard blow. But did it really?

Jeff Miller of the University of Otago, New Zealand, was set on finding out whether the readiness potential signal was in fact a definite indicator of movement preparation. So, he recreated Libet's experiment, with a twist: This time, subjects did not move on every trial. His team found no evidence of stronger signal before a decision to move than before a decision not to move. They observed the readiness potential both before movements and when no movement happened, meaning it was not a consistent indicator of movement preparation. Since the readiness potential does not cause movement, something else could be the true cause of the movement, "maybe even the person's free will," said Miller.

What exactly does the readiness potential indicate, then? As Miller explained via email, he believes "it reflects some kind of general engagement with this task. I realize that's a very vague answer, but we need to pin down precisely what experimental conditions are necessary to produce this pattern of EEG activity before we can really say what it reflects."

Libet did leave some space in his conclusion for free will to exist, but in a more limited role. He thought there might be conditions in which the conscious mind takes over and "vetoes" spontaneous behavior. He noted that, "subjects have reported some recallable conscious urges were 'aborted.'" In these instances the subject's subconscious presented the urge, or option of how to act, and his conscious mind chose whether or not to act on it.

Critics like neuroscientist John Dylan Haynes, however, argue that the "veto" isn't necessarily a product of free will, either. "Every conscious process, even a veto, will have its brain correlate, its unconscious precursor," says Dylan Haynes. To Dylan Haynes, the very idea of a veto--or, as Mele refers to it, "free-won't"--is an artifact of the discredited philosophy known as "dualism," the notion that mind or consciousness and body or brain/subconscious activity are two separate entities.

Libet's critics also take issue with the design of his experiment, specifically with how subjective the self-reported timing method was. Marcel Brass of the University of Ghent, Belgium has worked on an experiment that proves that a subject's perception of the time of their intention can be manipulated by playing a tone at different intervals after they perform an action. Mark Hallett at the National Institute of Health worked on an experiment that aimed to provide a more objective measure of the time of intention using the subject's real-time decision of whether or not there was a thought to move when a tone occurred.

What did we get out of Libet's studies then? "The work was an excellent stimulus for useful discussions about the challenge of relating neuroscience to philosophical questions about consciousness and free will," says Miller. "Of course these are tough questions and they will not be settled any time soon."

To learn about the more recent work inspired by Libet's experiment, come back to read the next installments in this series.

Discovering Snowmastodon

2012-02-01T18:45:53Z

This excerpt from Digging Snowmastodon: Discovering an Ice Age World in the Colorado Rockies by Kirk Johnson and Ian Miller describes research featured in NOVA's Ice Age Death Trap, premiering Wednesday, February 1 at 9 p.m. ET on most PBS stations.

The digging team celebrates project completion. Courtesy Kirk Johnson

On September 20, the day after my birthday, a Gould Construction Inc. crew began to push dirt at the Ziegler Reservoir construction site near Snowmass Village in the Colorado Rockies. They had two months to dig the footing that would change a small lake into deep reservoir. They were using D6 Cats and big track hoes, loading huge dump trucks to haul away the dirt. Work progressed smoothly, with the trucks making dozens of trips each day and creating an ever-deepening hole.

Kent Olson, Gould's on-site foreman, found a brown bone while walking across the site and had that odd feeling that contractors get when they find bones. He talked about the bone with his boss, Mark Gould, and they showed it to Bob Mutaw, an archaeologist who worked for URS, the engineering firm that was overseeing the site. Mutaw looked over the bone and pronounced it bovine, probably an old milk cow. Kent wasn't so sure. The work continued, but the workers started making nervous jokes about old bones. Kent even played a practical joke by wrapping a big log in black plastic and sticking it on the tailgate of his project manager's truck. Then he casually mentioned that he had found a dinosaur bone. Not funny.

Gould's number-one dozer operator was Jesse Steele from Palisade, Colorado. Jesse is a polite, compact cowboy who wears a black hat and tips it when he greets a lady. He is also a third-generation dozer operator. As a toddler, he dozed in his grandfather's lap, in a dozer. He first drove a dozer at the age of five. When it comes to moving dirt, Jesse is a smooth operator.

At about four in the afternoon of October 14, Jesse was operating his D6, pushing through a thick brown layer of organic soil known as peat, when a pair of giant ribs flicked over the top of the blade. Jesse stopped the machine and hopped out to take a look. The ground in front of his blade was littered with big brown bones. Instead of getting excited, Jesse got scared.

Kent came over and together they began to gather the bones. They found a partial jawbone with an 8-inch-long tooth. They found a tusk. They found big vertebrae. It was clear that this was a big skeleton. Joe Enzer came over to the find, took one look, turned to Kent and said, "This is not a cow, and there is no way we can ever call it a cow." Kent took the bones home that night and got on the Internet. It didn't take him long to realize that Jesse had run over the skeleton of a mammoth.

This book is the story of what happened over the next nine months as Jesse's mammoth turned into the most significant high-elevation ice age fossil site in the world and the biggest fossil dig in Colorado history.

****

Thursday, November 4 - Wednesday, November 10, 2010

On November 6, several more geologists and paleontologists arrived on site. With their additional brain power we debated how and when this glacial lake had formed and how long it had lasted. We were still waiting for the results from the radiocarbon samples that we had sent to Florida, and we were all still operating under the assumption that the quality of preservation suggested that the site couldn't be much older than 13,000 years.

We now had a pretty big crew of scientists and volunteers on site and were focusing our efforts on excavating the mammoth under the tent. We had smaller crews digging down in the hole where the mastodon and sloth bones had been found. We were in general agreement that the silt layer between the moraine and the peat was barren of fossils. Mark Gould, who had supervised the excavation of nearly 80,000 yards of sediment over the last month, was convinced that his guys had seen no bones in the silt.

Early in the afternoon, this conviction was changed by a dramatic event. Jesse was slowly pushing his dozer through the silt layer at the bottom of the hole with Dane and Ian running blade. Just below the tent, the dozer unearthed a 3-foot-long bone that initially looked like another tusk. Upon close inspection, we realized that the bone was the core of an absolutely immense bison horn. It had been broken into three pieces and there were fresh breaks, indicating that the horn had been sheared from a skull. The pieces exposed the center of the horn, which was formed of a coarse, butterscotch-colored honeycomb latticework. It looked good enough to eat.

We stopped the dozer and spread out with shovels, trying to find the skull. Eight of us looked for the better part of two hours with absolutely no luck. Finally we gave up, grudgingly deciding that the horn must have been a solitary fragment. With that decision, we asked Jesse to fire up the dozer and take another next pass. Amazingly, this time the dozer pushed up a second immense horn. And this time we were able find the spot in the silt where the horn had come from. After an hour of shoveling, we uncovered an incredibly large skull. Both horns fit back to the skull, and we came face-to-face with a huge bison. Productivity dropped way down as the entire crew gathered around to watch the beast emerge from the silt.

We carefully wrapped the two horns and applied burlap and plaster to the giant skull. It was hard to tell that day, but when measured, the skull was an amazing 6 foot 4 inches from broken horn tip to broken horn tip.

The bison discovery prompted volunteers Bill and Judy Peterson to hand me a $100 bill, the first financial contribution to the project. It had also profoundly affected Cathy Dea, who had helped to encase the skull in plaster, and in the process had coated herself in plaster and mud. She looked like a muddy urchin, but the look on her face was one of rapturous delight. A good fossil can do that to you.

For Russ Graham, an expert in ice age bison, this big beast rang some bells. Based on his knowledge, the big-horned bison went extinct more than 40,000 years ago. Russ suggested that our idea that the site was only 13,000 years old was probably wrong. While waiting for the radiocarbon dates to come back in a few days, people started to make wagers about the age of the site.

This was only the first of several mysteries that would appear as the huge excavation stretched over 70 days. NOVA's Ice Age Death Trap chronicles what happened next.

Ice Age Death Trap premieres Wednesday, February 1 at 9 p.m. ET on most PBS stations. Please check your local listings to confirm when it will air near you.

Building an Antarctic Seismic Station

2012-01-20T19:24:23Z

In the beginning of December, I arrived at Byrd camp in the middle of the West Antarctic ice sheet to begin working on the POLENET project, which uses a network of seismic and GPS equipment to reveal the structure of the continent and the behavior of the ice sheet. Byrd Camp is our base as we fly to sites around the continent where previous teams have installed stations. The remote camp is home to about 35 people. This includes the scientists working on POLENET, pilots from Kenn Borek Air who fly the Twin Otter and Basler airplanes to our sites, and a hard-working camp staff made up of weather observers, kitchen staff (who happen to be excellent cooks!), and people who do daily tasks around camp.

Camp itself is made up of several semi-permanent tents that house the galley, washroom (aka Byrd Bath), science equipment, and pilot sleep quarters, plus a meeting tent where we can watch movies and hold science lectures. Most of us sleep in "tent city," a big plot of mountain tents that is further away from the loud, heavy equipment used at camp.

Byrd camp, my home sweet home in the Antarctic.

Each evening, the POLENET team gathers to figure out where we want to fly the following morning. The process is a little tricky because in order to fly, the weather must be good every step of the way: at Byrd camp, at the site we are flying to (which could be as far as 600 miles from Byrd), and at a fuel cache along the route in case the plane needs to re-fuel during the trip. If the weather forecast does not look good at any of these places, we'll be grounded.

To make things more complicated, the weather in Antarctica fluctuates rapidly, and the plan that we develop each night must often change in the morning when the pilots get an updated forecast. This makes for some hectic mornings of getting the right people and equipment organized to fly because the planes can only hold a certain amount of weight and the equipment needed varies from site to site.

While at Byrd, I visited six seismic sites. Some were only temporary stations that were installed a few years ago and needed to be removed completely from the ice. At other sites that are more permanent, we collect stored data and perform maintenance that will keep the stations running for another year. Although the setup of a seismic site may not look like much on the surface of the snow, inside all the buried boxes is an intricate suite of equipment that will record earthquakes from around the world. The following picture is of a temporary site that we had to completely dig out and remove.

Digging out a temporary site...or preparing a five-star snow fort?

On the right side of the photo you can see a circular red dome. Under this dome is the actual seismometer, which is insulated in a foam box and buried to shield it from the wind. The sensor is extremely delicate and is composed of three masses in a spring-like system, each one positioned in order to record ground motion in either the east-west, north-south, or up-down direction. A cable runs from the sensor through the snow and into the orange box on the left side of the photo, where it connects to a piece of equipment called a datalogger. The datalogger records these movements as data that can be viewed on a computer. Several times a day, the datalogger will transfer the digitized data to a small box called a baler that contains memory sticks. When we visit a seismic site, we can remove the baler to get all of the seismic data recorded over the last year or two.

Inside the Little Orange Box.

But how do we keep this station powered up and running all year long in the harsh Antarctic weather? In the back of the station photo you can spot a set of three solar panels. A cable runs from these solar panels through the snow and into the orange box, where it is connected to a power module. The datalogger is also connected to this power module, along with 10 car batteries. During the six months of sunlight in Antarctica, referred to as austral summer, the solar panels keep the car batteries charged, providing power for the station. During austral winter when there is no sunlight, the batteries provide enough power to keep the station running. Just for comparison, when we install sites in other parts of the world we only need one car battery because the solar panels receive sunlight every day.

You also might notice an antenna on top of the solar panels. This is a GPS antenna that provides the time at the station. Without extremely accurate timing down to about a hundredth of a second, our data will be useless because we won't know how long it takes seismic waves from an earthquake to reach the station.

When everything functions correctly, we get excellent data. Below you'll see a signal from the earthquake that struck Japan on March 11, 2011, recorded at one of our seismic sites called Siple Dome. You can see how the earthquake looks on the up-down, north-south, and east-west components of the seismometer. We will use this data, along with data from many other earthquakes around the world, to make a map of the structure of the earth beneath Antarctica. Here's hoping that the rest of the data collected this season looks as good!

The March 11, 2011 earthquake, as seen by a POLENET station.

How to Make an Element

2012-01-13T18:33:48Z

The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star stuff. --Carl Sagan

Almost all of the elements in the universe originated in the high-pressure hearts of stars or during a star's violent death. But some elements are not "star stuff." Hydrogen and helium trace their lineage back to the big bang. Other elements, like francium and plutonium, are only produced in trace amounts by the decay of uranium--and by trace amounts, I mean that if you gathered all the naturally occurring plutonium in the world, you'd have roughly 0.05 grams of it.

In fact, the periodic table might well have ended after plutonium if scientists had not picked up where nature left off. In the last 75 years, scientists have added an additional 24 elements to the periodic table and created several others that are so rare we can only speculate about their existence in nature. We have redefined matter and are perhaps the only planet that has ever seen elements heavier than plutonium. But how much further can we go?

To answer this question, it is important to understand the anatomy of an element. Everyone has heard of the periodic table of elements, or at least seen it hanging on the wall of a high school science classroom. This infamous table classifies all the atoms in the universe into 118 different types, known as elements. An atom is composed of two parts: a nucleus and an electron cloud. The nucleus is in the heart of an atom and composed of positive particles called protons and neutral particles called neutrons. Negatively charged electrons buzz around the nucleus in the electron cloud.

A stylized view of the lithium atom. Made by Halfdan. Via the Wikimedia Commons.

An atom looks a little like the picture to the right--except atoms are a thousand-million times smaller than you see them here. (If this were the real size of an atom, you would be roughly the size of the sun!) Even though all the components of an atom are important, the periodic table ignores the number of neutrons and electrons and defines an atom based solely on the number of protons it has in its nucleus. All atoms with six protons are carbon, regardless of how many neutrons or electrons they have; nitrogen is element seven because it has seven protons, and so on until we reach ununoctium with 118 protons.

So creating a brand new element requires loading an atom's nucleus with more protons. Stars create new elements in their cores by squeezing elements together in a process called nuclear fusion. First, stars fuse hydrogen atoms into helium. Helium atoms then fuse to create beryllium, and so on, until fusion in the star's core has created every element up to iron. Iron is the last element stars create in their cores, and a kiss of death for any star with the moxie (that is, the mass) to make it to this point. As astronomer Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics describes it, "Once a star has built an iron core, there is no way it can generate energy by fusion. The star, radiating energy at a prodigious rate, becomes like a teenager with a credit card. Using resources much faster than can be replenished, it is perched on the edge of disaster."

But the edge of disaster for these massive stars is the threshold of life for the rest of the periodic table. In a star's last second of life, its core compacts so tightly that it becomes as dense as an atomic nucleus. When no more matter can squeeze into the core, the star explodes with the energy of an octillion (10^27) atomic bombs. In this violent explosion, more than half the elements on the periodic table are born. Intense heat from the explosion catalyzes nuclear reactions that were not possible in the core. Escaping elements are bombarded with neutrons, which split inside the nucleus into protons and electrons, generating new unique elements. Iron turns into gold, gold turns into lead, and so on until uranium, the heaviest naturally star-born element, is forged from the ashes.

This spectacular shower of life and death creates everything. Well, almost everything. There are another 27 elements on the periodic table after uranium that were not created by stars. Some elements are produced in trace amounts by the decay of other elements. But even the long radioactive decay chain is not enough to produce the ultra-heavy elements at the end of the periodic table. The periodic table would have ended altogether if scientists had not pushed the boundaries of natural physics and ventured deeper into the world of super heavy elements.

To make new elements, scientists borrowed some advice from the heavens. The transuranium elements (elements 95 through 100) were forged by bombarding uranium with neutrons and waiting for the impregnated nucleus to become radioactive and convert its extra neutron into a proton, electron, and a charge-less, nearly massless, antineutrino. But after fermium (element 100), the irradiate-and-wait technique stops working. Particle physicists "stepped up their game" and upgraded their atomic fodder from neutrons to other elements. The trick was to get the nuclei of the two atoms to fuse into one giant nucleus, generating an entirely unique atom. Scientists started small--firing helium (2) at einsteinium (99) to beget mendelevium (101); launching neon (10) at uranium (92) to engender nobelium (102). Eventually, scientists busted out the big guns and bombarded lead (82) with zinc (30) to beget copernicium (112) and californium (98) with calcium (20) to produce element 118, provisionally called ununoctium.

But why do scientists succeed where the stars fail? The truth is, the stars don't fail. In the storm of their deaths, some stars probably do forge super heavy elements--even elements heavier than we've created--but these elements don't survive long in the turbulent chaos of a supernova. Super-heavy elements are so fragile they live only a matter of microseconds before they decay into a jumble of atomic scrap metal.

There is a limit to the number of protons and neutrons that can squeeze inside an atomic nucleus, but we haven't found it yet. Protons are positively charged, and because like-charges repel, the protons are in a continuous "this nucleus ain't big enough for the both of us" duel. The neutrons have no charge and quell some of the tension by weaseling between the protons. The entire nucleus is held together by the strong force--a mysterious force that acts like a bungee cord and pulls everything together. But eventually, the proton's repulsion overwhelms the strong force, and not even the neutral neutrons can prevent the emigration of alpha particles (two neutrons and two protons) from the nucleus. So the real question is: How big can we go?

As we close the gap between what does exist and what can exist, the laws of physics will eventually stop us from venturing deeper into the world of synthetic matter. Scientists will continue to push the limit of "physically possible," but for now it appears the periodic table is nearing its completion.

Kepler-22 b, A Potentially Habitable Planet

2011-12-07T15:06:37Z

The Kepler mission has confirmed its first potentially habitable world, a planet 600 light-years from Earth in a 289-day orbit around a smaller, cooler version of our sun. The planet is a "super-Earth," with a radius that measures 2.4 times that of Earth, putting it about halfway in size between Earth and Uranus. The discovery is a major milestone for the Kepler team: the first confirmation of a Kepler super-Earth in that temperate sweet spot called the habitable zone, the range of orbital distances at which a planet might be the right temperature to harbor liquid water and, potentially, life on its surface.

The planet, dubbed Kepler-22 b (in the great poetic tradition that compels astronomers to name their quarries as if they were so many lines of tax code), is not the first potentially habitable world uncovered around another star. As Dennis Overbye recounts in this New York Times story, the search for the "Goldilocks planet" has turned up a string of contenders. But membership in this elite group changes as new data streams in. A planet once thought to be "just right" turned out to be too hot; another once-prime candidate may not, it turns out, exist at all. And though astronomers have a good gauge of Kepler-22 b's girth, they don't yet know its mass, which is necessary to calculate its density and to begin to make an educated guess about its composition: rocky, like Earth, or gaseous, like Uranus or Neptune. As far as we know, only rocky planets can harbor life.

So if Kepler-22 b isn't exactly the "first" that some headlines make it out to be, why all the attention? Remember the old adage that for every cockroach you see, there could be 100 more hiding in the walls? For the Kepler space telescope, Kepler-22 b is that first cockroach. Kepler has already identified 2,326 planet candidates--"candidates" because they have not all been confirmed and some will turn out to be false positives. Of those candidates, as many as 900 are less than two times the size of the Earth, 48 orbit within their star's habitable zone, and up to ten could have the magic combination of the two: both the right size and the right distance to be truly Earthlike.

Kepler-22 b shows that Kepler is doing just what is was designed to do: sniff out potentially Earth-like planets. There's every reason to think that Kepler-22 b is just the first of a deluge of discoveries in the years to come.

For Inside NOVA's coverage of the last "Goldilocks planet," see Someplace Like Home

For more on how extrasolar planets are discovered, watch NOVA scienceNOW's Hunt for Alien Earths

For a deeper look at habitability, check out NOVA's Finding Life Beyond Earth

Traveling to Antarctica

2011-12-05T16:08:11Z

After boarding three commercial flights, one Air Force C17, and traveling for nearly 33 hours, I finally arrived in one of the most remote places on Earth: Antarctica. For the next five weeks, I will be based out of a small field camp in the western part of the continent called Byrd (named after the great Antarctic explorer Richard Byrd) to begin working on part of a project called POLENET, or the Polar Earth Observing Network. This particular project involves collecting GPS and seismic data that will help answer questions about the structure of the continent, the behavior of the Antarctic ice sheet, and how these may be related. My role will be to work primarily with the seismic instrumentation in West Antarctica, helping to collect data and perform any necessary maintenance on already installed instruments.

Your correspondent, officially a Happy Camper.

You may be thinking this all sounds interesting and exciting, but how exactly do earthquakes help us learn about the structure of Antarctica? Seismology is not strictly the study of earthquakes. Seismologists also use seismic waves from earthquakes to study the Earth. Just like an X-ray will expose details of the body invisible to the human eye, the behavior of seismic waves expose details of the Earth from the shallowest crustal layers all the way down to the core of our planet.

When an earthquake occurs, seismic waves travel through the Earth and are recorded at seismic monitoring stations. These waves move at different speeds depending upon the type of material they are traveling through. For example, a seismic wave will slow down when traveling through warmer layers. Seismologists can figure out how fast a wave is moving through different parts of the Earth by looking at the wave arrival time at a network of seismic stations. The more stations there are, and the more densely they are sited, the more detail can be observed about the underlying structure. By installing seismometers in Antarctica, we are able to figure out how the crust differs all points all across the continent.

Why do we care? It is important to understand the interaction between the ice sheet and the underlying bedrock. Think about placing a heavy weight on top of a thick sponge. The weight will create a depression in the sponge. But what happens when you remove this weight? The sponge will bounce back to its original shape. The Earth's crust behaves in a similar way, but areas of warm, weak crust depress much more than areas of strong, rigid crust when put under the same weight. As the ice melts and relieves some of the weight on the continent, the crust begins to move vertically like the sponge; that motion is detected by the GPS instruments. By combining seismic data about the type of crust beneath the ice with the GPS data showing the amount of vertical motion each year, geologists can improve their calculations of the scale and rate of ice melt. This has a direct impact on sea-level change. In a time when global warming is a hot topic in science, it is important to figure out how the polar regions of the world are being affected and what that may mean for the future.

Before I can travel to Byrd field camp, there are a few things I need to do to prepare for the extreme environment I'll be living in. I have spent this past week at the U.S. base McMurdo going through different training courses, including a snow school that is referred to around here as "Happy Camper." This hands-on two day training takes place on the outskirts of McMurdo, conveniently far enough away to discourage those who may have thoughts of walking back to the cozy base. Throughout the course we learned skills like how to use camping stoves, set up tents, erect snow walls to shelter our tents from the wind, build survival trenches for emergency situations, and operate a high-frequency radio. Although some of the more adventurous "campers" chose to sleep in their survival trenches, I opted to stay in a tent and learned some good tricks for keeping warm in the process. By putting two bottles filled with hot water inside my sleeping bag, I was very comfortable throughout the night and could also keep my hat, gloves, and neck guard warm for the next morning.

To wrap up the training we ran through some scenarios, including how to find a lost team member in the event of a white-out. This involved wearing white buckets on our heads so we were not able to see anything, which I'm sure is always entertaining for the instructors. The camping experience was surprisingly very enjoyable, especially because I had the opportunity to meet a lot of other scientists and learn more about other projects taking place in Antarctica. In the end I'd say I was a very happy camper and am ready to head to Byrd!

Stay tuned for Rachel's follow-up from Byrd camp. For more on POLENET and living the scientific life in the Antarctic, visit POLENET on the web.

Who Let the Cat out of the Bag?

2011-11-16T14:48:03Z

"Erwin Schrödinger is going through airport security when an official asks to check his bag. After opening the bag, the official is appalled and shouts, "Sir, did you know there is a dead cat in your bag!" And Schrödinger calmly replies, "Well now there is."

If you're asking, "Who is Schrödinger? And why does he have a dead cat in his bag?" you probably missed the punch line of the joke. Don't worry--we'll get there, but before we investigate Schrödinger's "cat in a box" quantum-blurring-mind-boggling thought experiment, I want you to take a deep breath and plug your nose--because we're about to dive into some deep quantum mechanics.

Photograph of Toby the cat copyright Kevin Steele.

Quantum mechanics is a branch of physics that scientists use to describe the behaviors of small particles (like electrons). But unlike classical physics--which describes the behaviors of big objects like baseballs and rockets--quantum mechanics doesn't deal in nice exact answers. Instead, it deals in probabilities. For example, if I asked the question, "Where is Suzy?" classical mechanics would predict, "Suzy is on the couch," while quantum mechanics would tell us that "Suzy is probably on the couch, but she might also be in the bathroom, or walking in the garden, and there is a small but nonzero chance that Suzy is currently enjoying tea on the far side of the moon."

So if scientists can use classical mechanics to predict the exact trajectory of a NASA spacecraft headed for Mars, why can't they use quantum mechanics to predict something as simple as the location of an electron?

Warning: This is where things start to get weird...and a little disturbing. There is an inherent indeterminacy embedded in quantum mechanics that prevents scientists from predicting variables like position and momentum exactly. But what causes this indeterminacy? Ask Einstein and he would say indeterminacy is a reflection of our own ignorance. But ask Niels Bohr and he would argue that particles don't have finite positions or momentums until they are measured by an observer, at which point the act of measurement itself forces the particle to "take a stand" and choose a state. Pascual Jordan, one of the fathers of quantum mechanics, put it this way: "Observations not only disturb what is to be measured, they produce it...we compel (the particle) to assume a definite position."

This is the underlying concept of the "cat in the bag" joke. Erwin Schrödinger, one of the masterminds of quantum theory, devised a thought experiment purely to highlight the absurdity of Bohr's interpretation. In his thought experiment, Schrödinger sets up a scene where a cat is placed in a box with one of Bohr's "indecisive particles," but the life or death of that cat depends upon which state the particle chooses. If the particle chooses one state (let's call it state A), the cat lives, but if the particle chooses the other state (state B), poisonous gas is released into the box and the cat dies. Applying Bohr's view of indeterminacy to this situation, the particle doesn't have a definite state and exists as a sort of hybrid--both A and B at once--that physicists call a "superposition." But think about what this means for the cat. If the particle exists in a superposition of states A and B, the cat also must exist in a superposition of two states, dead and alive. But as soon as an observer opens the box (or bag), the sheer act of observation "compels" the particle to exist in either A or B, and thus the cat must be either dead or alive. This situation is rather awkward if the first observer is oblivious to the experiment--like airport security.

Why would Bohr advocate something that sounds so ridiculous? And why would Schrödinger's derisive analogy become the poster child of quantum theory? Even today there is no consensus on a "right" interpretation of quantum theory. (For more on this debate, visit NOVA's physics blog, The Nature of Reality.) However, experimental results confirm that measurements (like peeking inside Schrödinger's bag) can affect and even determine the state of quantum systems. Quantum particles behave like they "know" when they're being watched, and adjust their behavior accordingly, like a group of mischievous youngsters keenly aware of an adult presence in the room.

Perhaps the "measurement problem," as it is called, is not all that strange--it merely seems so because we lack the words to explain it. If a quantum particle tried to convey to us what it feels like to be a quantum particle, it would be like a cube explaining to a square what it feels like to be 3-D. The only language that bridges the two different worlds--quantum and classical, 2-D and 3-D--is mathematics. And mathematically, we can describe this strange quantum world incredibly accurately using probability.

Happily for cats, today Schrödinger's thought experiment is used only as a mascot for quantum theory and not as a standard of thought. Theorists are still working to explain the measurement problem with fresh interpretations of quantum mechanics that could resolve the apparent paradox. So cats everywhere are safe...at least for now.

Remembering Norman Ramsey

2011-11-09T14:08:44Z

In his theory of special relativity, Einstein showed that the very idea of simultaneity--of two events occurring at the same time in different places--is flawed. Simultaneity is all relative, Einstein argued; it depends on your perspective or, technically, your reference frame. Yet we at NOVA note the passing of Norman Ramsey, the physicist whose work led to the most accurate timekeeping devices in history, with special poignancy due to a personal sense of simultaneity; we are just about to begin our exploration of time in tonight's episode of The Fabric of the Cosmos.

Norman Ramsey shared the 1989 Nobel Prize in physics for his contributions to the invention of the hydrogen maser and the cesium atomic clock. Ramsey began working on atomic spectroscopy, a way of discovering the structure of atoms by analyzing the wavelengths of light that they release and absorb, at Columbia University in the late 1940's. He then moved to Harvard and in 1949 invented a new way to measure the frequency of photons released by atoms and molecules with even greater accuracy. In 1960, Ramsey contributed to the invention of the hydrogen maser, which was also put to use as a timekeeping device. Ramsey literally helped redefine time, not as something to be measured by the motion of Earth and Sun, but to be "ticked off" by the vibrations of an atom.

Today's best atomic clocks are so accurate that they won't gain or lose a second for the next 138 million years. Atomic clocks are critical to GPS and modern communications; they help radio astronomers see the universe with pinpoint precision; and ironically, they have even been used to confirm Einstein's ideas about the plasticity of time. Ramsey did not at first realize that his work would have these far-reaching applications. In fact, as recounted by The New York Times, he once said, "I didn't even know there was a problem about clocks initially. My wristwatch was pretty good."

For more about Ramsey's work, we recommend coverage from:

The New York Times

Nobelprize.org

PhysicsWorld

National Geographic

Catching A Space Wave

2011-11-02T15:21:23Z

Is our universe rippling with gravitational waves? Scientists studying the nature of space, time, and gravity believe that it is, and they are on the hunt to detect one of these waves directly. So what exactly is a gravitational wave? Imagine sliding yourself slowly into a still pond. As you glide down and immerse yourself in water, the glassy surface remains largely undisturbed. Now, picture flinging yourself from a rope swing and cannonballing down, crashing through the water's surface at full force. Large waves slosh up around you, getting smaller as they make their way onto the banks of the pond and outward across the water.

That's the idea behind gravitational waves. Einstein predicted that they happen all the time as bodies of mass splash through the fabric of space and time. And when big events happen--when two super dense, massive stars collide, for instance--cannonball waves course through spacetime. Now, extremely sensitive detectors around the world, and maybe even out of this world, are waiting for those gravitational waves to wash over them. And when that happens, scientists will not only have more evidence for Einstein's already hugely successful theory of general relativity; they will also have a new tool for mapping our cosmos.

General relativity tells us that space is like a vast pond. Space distorts around mass just the way water warps around a swimmer. Celestial bodies slowly doggy-paddling through the spacetime pond don't make too many ripples. Butterfly-stroking black holes, on the other hand, cause quite the disturbance. But by the time their ripples reach the Earth, they're so small they are practically impossible to observe.

So how do you detect the near-undetectable? Gravitational waves distort the space they push through; as space lengthens in one direction, it contracts in another. So in the 1970s, scientists at Cal Tech and MIT used their combined brainpower to secure funding for what they called LIGO, the Laser Interferometry Gravitational-Wave Observatory. (They hyphenated "Gravitational-Wave" to make sure they wound up with a cool acronym.)

Laser interferometry is a technology used in many branches of science, but the idea is always the same. Split one beam of light into two. Shoot those two beams off in two different directions. Each beam travels the exact same distance before it bounces off of a mirror and makes it way back to the detector. Because the speed of light in a vacuum is always 186,000 miles per second, the beams should return to the detector at exactly the same time. But if something disturbs the paths of those light beams, the beams interfere with each other. That disturbance will be reflected in a distinct pattern in the return-trip data--thus the name "interferometer."

LIGO uses this principle on a huge scale. Both of LIGO's locations, in Hanford, Washington and Livingston, Louisiana, are home to detectors with two 2.5 mile-long arms stretching out in different directions. (The two distant locations help the researchers confirm that any motion they detect is in fact due to gravitational waves, and not local geologic movement.) The mirrors and the detector are surrounded by stabilizing devices designed to isolate them from typical Earth-bound jostling. If a wave comes sailing through, one arm will contract while the other stretches. The light bouncing off the mirror at the end of the shortened arm will return to the detector sooner than the beam shooting down the lengthened arm. When the LIGO scientists see this time discrepancy, they will have seen a gravitational wave.

So far, they haven't seen anything at all. LIGO has been up and running since 2001 and there has been nary a trace of a gravitational wave. But scientists aren't taking this to mean that these waves don't exist; their instrument just isn't quite sensitive enough to catch them. LIGO is now in line for upgrades that will make it ten times more sensitive. When the modifications are complete (tentatively expected in 2014), LIGO will become the so-called Advanced LIGO, and scientists predict they will be swimming in positive results.

But an interferometer need not patiently wait for waves here on terra firma. Space agencies around the world are looking into devices designed to detect gravitational waves from space. An orbiting interferometer would consist of a triangle-shaped system that would circle the earth, scanning the skies for the tidal-wave signals of huge gravitational events. Thanks to tight budgets, though, these projects are stuck on the drawing board.

Why dedicate all this time and technology to gravitational waves? Einstein's theory of general relativity has been thoroughly tested since it was proposed in 1915. Why do we need another test of its validity? "Seeing" gravitational waves will give us more than yet another verification of relativity. The information from the signals coming in to the detectors can paint a picture of what is happening in distant reaches of the universe. Scientists could piece together the collision of massive black holes. They could see the explosive birth of an incredibly dense neutron star. They could even detect the remnants of the gravitational wave that shot off at the Big Bang, giving them a clearer picture of the events that gave rise to our universe. Gravitational wave detectors could clarify the skies by illuminating the many massive wonders wading through space.

Finding Life Beyond...Carbon?

2011-10-24T18:37:05Z

If you watched Finding Life Beyond Earth last week, you might be wondering, what's the big deal about carbon-based life? Spock discovered silicon-based life in episode twenty-five of the original Star Trek series. And Star Wars' bounty hunter Zuckuss is ammonium based. How can scientists say these two hegemons of geek culture are wrong? Why does life have to be based on organic molecules?

The answer to this question is actually right in front of you. I'll give you a hint--it's big, colorful, and located directly below this paragraph. It's the periodic table! The information in the periodic table of elements is sufficient to convince scientists that life has to be carbon based--you just have to know how to interpret it.

The answer is in here! Image via Wikipedia
.

Let's start with carbon's box on the periodic table. Carbon is element number six, which tells us that it has six negatively charged electrons buzzing around six positively charged protons in the nucleus. That's the information we're given--now let's apply a basic knowledge of chemistry and interpret it.

Atoms house their electrons in concentric energy shells. The first energy shell holds two electrons, the second and third hold eight. (There are more, but let's stop here for now.) Atoms fill their shells sequentially, and they always like to end with a full shell--even if that means giving away electrons. Sodium, for instance, has one electron dangling in its third energy shell and instead of trying to gain seven more electrons, sodium simply gives this electron away. Other atoms steal electrons to fill their outermost shell. Chlorine is one electron short of filling its outer shell, so it plucks an electron from an element, like sodium, and turns into a stable, negatively-charged version of itself.

]]> But poor carbon has four electrons in its outermost shell. Losing all four electrons is unthinkable, but gaining four is nearly impossible. The only way carbon can fill this shell is to share its electrons with other atoms. Every time carbon picks up a new electron, it doesn't just get the electron, but the entire atom! This process secures carbon to other atoms in what is known as a covalent bond. Carbon can share up to three electrons with a single atom, making it capable of forming single, double, and triple bonds.

Carbon is so desperate for those four electrons that it has low standards for bonding. Some atoms, like oxygen, are pickier and will only bond if the right element comes along. But carbon can (and will) bond to almost anything with unpaired electrons. The upside of this atomic promiscuity is that carbon can form varied and complex structures. Carbon atoms can link together into long chains, rings, and complex three-dimensional structures, or bond with other atoms like nitrogen and oxygen to create varied molecules with a diversity of functions.

But if you're looking at the periodic table, you might be wondering, "Silicon has four electrons in its outermost shell. How come life isn't silicon based?" Good point! Many people (including the writers of Star Trek) have speculated that life could be based on silicon. But we don't see rock creatures scooting around earth because silicon is a less aggressive bonder than carbon. Silicon has an atomic number of fourteen--fourteen electrons and fourteen protons. Instead of wanting to fill its second shell (like carbon,) silicon needs to fill its third shell. The third electron shell is much further away from the nucleus and therefore its electrons feel a weaker pull towards the nucleus.

To visualize this, imagine a group of students (electrons) surrounding a pizza (nucleus), with one slice of pizza for each student. When the pizza is small, the group of students is small and they can huddle together. But if the pizza is big, the group of students is big, and some students inevitably get pushed to the outside ring. In this outside ring they can't see or smell the pizza, and thus they tend to wander. If silicon's own electrons are wandering, why would electrons from other atoms want to join them? It comes down to this--silicon is just not as "attractive" as carbon (yes, pun intended). Silicon still bonds, but the bonds are weaker and more monotonous. Sure, silicon makes great rocks, but not great building blocks!

At this point, you're probably thinking, "But there are ninety more elements on the periodic table. Surely one of them must have chemistry capable of life?" This brings us to the fun part of the article--the elemental elimination game!

Let's start with everything left of the column containing carbon: the alkali, transition, and semi-metals. To begin with, most of these elements have weak holds on their outer most electrons and can exist in positively-charged forms. If life were made out of these types of atoms, we could potentially dissolve in water, which clearly wouldn't work. (Just ask the Wicked Witch of the West.) Besides, most of these atoms prefer to exist in crystalline structures.

This alone eliminates 80% of the naturally occurring elements. Now let's move to the far right side of the periodic table. Take a look at fluorine: all of the elements in and to the right of this column are either already full with electrons or so greedy that they steal electrons with no intention of sharing. Fluorine and chlorine will occasionally slip into "electron sharing" relationships, but they are much more fickle than steadfast carbon, and life cannot be built on a capricious element.

Also, in the atomic world, size does matter, so we can eliminate all the elements that are too big to do the job right. Elements like arsenic and selenium are like silicon--bulky, clumsy, and just not as attractive as carbon. When these elements slip into organic molecules, they often cause more trouble than good. (Arsenic is highly toxic because it can, in fact, replace phosphorus in organic reactions, but its large size hinders organic processes.) So now we're left with five elements: carbon, nitrogen, oxygen, phosphorus, and sulfur, and guess what? Each one of these elements is highly abundant in organic material. But out of these five, carbon is the only one capable of holding four stable bonds and linking into long chains with other carbon atoms. These last four elements are perfectly suited as organic sidekicks, but they lack the versatility, fortitude, and ubiquitous nature that make carbon the backbone of life.

Seeking Signs of Life

2011-10-19T19:32:27Z

Imagine for a moment that astronomers have finally discovered an Earth-like planet orbiting another star. After the papers are published, the headlines run, the tweets tweeted, one question will still be burning: Is anyone home?

Discovering a habitable planet is just the first tiny step toward discovering an inhabited planet. So how would astronomers begin to determine whether a newly-discovered Earth-like planet actually harbors life?

First, explains Soren Meibom, we must find out whether the planet has been around long enough for life to take hold. "On Earth it took roughly a billion years for the most primitive microbial forms of life to evolve and another three to three and a half billion years for animals and humans," says Meibom. "Therefore, as we look for life beyond Earth, and in particular beyond our own solar system, the question of time becomes highly relevant."

Because stars and their planets form together, to get at the age of a planet, all you need to know is the age of its star. Sounds easy enough. But in practice, determining a star's age is not so simple. After they are born, stars enter a middle age that continues until shortly before their death; over the course of that sustained middle age, which may last for billions of years, the star's appearance is essentially unchanged. Meibom compares a star to a person who emerges from infanthood as a fully-grown adult, then keeps her smooth skin and brunette hair for eight decades until, finally, she goes grey, gains a dowager's hump, and slips on some orthotics in the time it takes her to finish the early-bird special. (See Meibom's visual interpretation below.)

If people aged as stars age. Image courtesty Soren Meibom.

To pin down stars' ages, Meibom and his colleagues are turning to one property of that does change over time: the rate at which a star spins. "A star's rotation slows down steadily with time, like a top spinning on a table, and can be used as a clock to determine its age," says Meibom. "We can measure a star's rotation period by looking for changes in its brightness caused by dark spots on its surface--the stellar equivalent of sunspots. Any time a spot crosses the star's face, it dims slightly. Once the spot rotates out of view, the star's light brightens again. By watching how long it takes for a spot to rotate into view, across the star and out of view again, we learn how fast the star is spinning." Meibom is now using the Kepler space telescope to do just that.

So if a star and its planets are "of age," then what? It might be possible to look for "biosignatures" in a planet's atmosphere. An alien astronomer looking toward Earth, for instance, would see oxygen produced by plants and bacteria, ozone from the interaction of ultraviolet radiation and oxygen molecules, and nitrous oxide from microbial reactions. If we could pick out similar signatures in the atmosphere of an alien world, we would have strong reason to suspect that life might be present there. As astronomer Lisa Kaltenegger told NOVA back in 2009, "If you have a look at our own Earth, you actually have CO2, you have water, methane, and you have ozone or oxygen...That's the golden fingerprint you're looking for" in the spectrum of a habitable exoplanet.

The most conspicuous biosignatures in Earth's atmosphere are products of tiny microbes, not the plants and animals that loom so large in our notion of "life," points out Harvard astronomer Dimitar Sasselov. Our own planet was transformed by microbial life over the course of more than two billion years; so an exoplanet with lots of oxygen in its atmosphere may not be carpeted in forests, but it may have oceans full of green algae. That algae could be paving the way for more complex, energy-hungry forms of life, says Sasselov.

Technology is only now catching up to this ambitious project, though. Measuring an exoplanet atmosphere directly is only practical if the planet is very large and sits far from its parent star--not a great recipe for a habitable world. If an exoplanet happens to pass in front of its star from the vantage point of our telescopes, astronomers can probe its atmosphere indirectly, by comparing starlight that has passed through the planet's atmosphere to starlight that meets our telescopes directly, when the planet is "behind" the star.

Habitable planets will also make juicy targets for SETI--that is, the search for signals from extraterrestrial intelligence. SETI usually means "listening" for radio waves produced, either incidentally or as a beacon, by an alien civilization. (Think Contact.) Some astronomers have also proposed looking for optical signals produced by high-powered lasers.

The discovery of a bona fide habitable world will bring us closer to finding life beyond Earth, but there is still plenty of work to be done before we know whether we have company in the cosmos--or whether we are truly alone among the stars.

For more information on Soren Meibom's work, check out his recent public lecture at the Harvard-Smithsonian Center for Astrophysics, or watch him explain his results at a press conference from last year's meeting of the American Astronomical Society.

NOVA's Finding Life Beyond Earth will premiere Wednesday, October 19 on most PBS stations. Beginning on Thursday, can also watch it online. Check your local listings to confirm when it will be airing near you.

Steve Jobs: The Man That Changed the World

2011-10-07T18:28:10Z

Steve Jobs' death at the age of 56 is profoundly sad. His story was the American dream writ large--a California boy with nothing but an idea and a lot of chutzpah, who, with Steve Wozniak, built a computer in his parents' garage and gave birth to the fastest-growing company in American history. Jobs' passing has sparked millions of well-deserved tributes. He's being remembered as a genius. Which he was. A visionary. He was that, too. And he's being called the Thomas Edison of the baby-boom generation. But that, believe it or not, may be selling Steve Jobs a little short.

To watch and read the transcript of the 1990 Steve Jobs interview featured in The Machine That Changed the World, visit the WGBH Open Vault archive.

Finding a comparison to the influence of Steve Jobs might require going back to the 15th century. That's when Johannes Gutenberg, a German blacksmith, introduced the moveable type printing press, which is widely regarded as the most important invention of the modern period. The printing press made books affordable, spread learning to the masses, and laid the material basis for the modern knowledge-based economy.

Unlike Gutenberg, Steve Jobs didn't invent the computer. He didn't even invent the personal computer. But with the introduction of the Macintosh in 1984, with its intuitive graphical interface, a user-friendly device called a mouse, an affordable price, and a brilliant marketing effort, Steve Jobs put the power of the computer into the hands of the masses, ultimately changing forever almost every aspect of the way we live, work, create, communicate, innovate, get and share information, and spend our leisure time.

The printing press was the first machine that changed the world. The computer is arguably the second. That idea was the intellectual underpinning (and the title) of a groundbreaking NOVA mini-series that I was fortunate enough to work on two decades ago. It was the brainchild of Executive Producer Jon Palfreman and overseen by Paula Apsell, NOVA's Senior Executive Producer.

Production on The Machine That Changed the World began in 1989. Everybody in the computer community was excited about the prospect of a television series produced by NOVA that would bring the story of the computer to life; and many luminaries would participate in the series either on camera, as content advisors, or both. There were the founding fathers who most people outside of computer science have never heard of: Presper Eckert, Thomas Watson, Jr., Herman Goldstine, John Backus, Robert Noyce, Gordon Moore, and others. There were the rebels of the 1960s and 1970s: Alan Kay, Doug Englebart, Larry Tessler, Bill Gates, Steve Wozniak, and so on. But there was only one rock star, and that was Steve Jobs.

As we started the series, we were warned time and time again. "You'll never get Steve Jobs on camera," those who knew him told us. But we didn't believe it. How could Steve Jobs, we wondered with no small amount of arrogance, allow a history of the computer to be told without participating in it? But his aversion to the media and the seemingly impenetrable privacy shield with which he surrounded himself were brought home to us when he finally responded to our multiple requests for an interview with an emphatic "No, thank you."

But we had an ace up our sleeve by the name of Robert Noyce. A legend in the computer world as the co-inventor of the microchip and co-founder of Intel, Bob Noyce was a strong supporter of The Machine That Changed the World and served on our advisory board. Like most in Silicon Valley, Steve Jobs revered Bob Noyce, and a one-paragraph letter from Noyce changed Jobs' "no" into a "yes," giving our series one of a limited number of interviews Steve Jobs gave in his short lifetime. (Sadly, it's also likely that our series contains the last interview ever recorded with Bob Noyce, who died in the spring of 1990, about a month after our camera crew recorded his story.)

Steve Jobs, who was 35 when we interviewed him for The Machine That Changed the World, was a vital, vibrant, visionary. His untimely death can only make us wonder what else he would have accomplished if given more time.

Heisenberg Humor

2011-10-06T15:28:40Z

Professor Werner Heisenberg is speeding down the highway, when a cop pulls him over. The cop walks up to his car and asks, "Excuse me sir, do you know how fast you were going?" And Heisenberg responds, "No...but I know exactly where I am!"

Watch the full episode. See more NOVA.

If you understood this joke, read no further. However, if you're still a little confused, get ready to dive into some uncensored quantum mechanics. (Just kidding, I've removed the nastiest bits for you!)

This joke is based on the Heisenberg uncertainty principle--one of the fundamental tenets of quantum mechanics. The uncertainty principle can be summed up as: "The more precisely the position of a particle is determined, the less precisely the momentum is known in this instant, and vice versa." But to understand this statement, and hence the joke, it is first necessary to take on some quantum mechanics.

Quantum mechanics describes the behaviors of small particles, like electrons whizzing around an atomic nucleus. Compared to classical mechanics, which explains the behaviors of big objects like baseballs, airplanes, skiers--basically anything you encounter in your daily life--quantum mechanics seems very strange. To understand quantum mechanics, you need to let go of everything you've ever observed on the macro-scale and accept that there is a tiny world governed by its own unique laws.

The first principle of quantum mechanics you need to know in order to understand the joke is this: Subatomic particles are inherently fuzzy. An electron is not a fireball zooming around a chunky nucleus, but a negatively charged blanket that sometimes acts like a sheet crumbled into a ball and sometimes like a quilt spread across a bed. And because of this inherent fuzziness, the properties that describe the behaviors of these particles--such as position and momentum--are inherently fuzzy as well.

But the uncertainty principle is more specific than "particles are fuzzy." It holds that it is possible to determine either the position or the momentum of a particle, but it is impossible to determine both simultaneously. In other words, the more precisely we measure the momentum of a particle, the less precisely we can measure its position, and visa versa.

Are you laughing yet? Or are you beginning to wonder why the act of measurement seems to have such elevated importance? The way Heisenberg saw it, measuring any observable property of a particle actually affects that property. In this view, an electron doesn't even have a finite position and momentum until a scientist attempts to measure it, at which point the electron is forced to choose a state--like an atomic game of musical chairs where each player exists in every chair until the music stops. Not every physicist likes this interpretation of quantum mechanics--it always galled Einstein--but it's the one I'm sticking to for simplicity. After all, we're just trying to understand a joke here!

Still no guffaws? Okay, then it's time for an equation. As perplexing as the uncertainty principle is, it is represented by a very simple one: The product of the uncertainty in position and the uncertainty in momentum will always be greater than or equal to a constant. In other words, these two uncertainties are inversely related--if one increases, the other falls by a proportional amount.

However, the uncertainty principle can only be directly observed on the atomic scale. So sorry, Dr. Heisenberg, but it looks like you're getting a ticket after all.

Where were you when you found out about dark energy?

2011-10-04T15:34:26Z

Here is my list of Top Olde-Timey Things I Will One Day Tell My Incredulous, Hypothetical Grandchildren to prove how very old I am and how much life has changed:

We used to write letters on paper and put them in metal boxes, from which actual human beings (in uniforms!) gathered them up and helped deliver them to their destinations.
Telephones used to be bolted to the wall, with dials attached, and they couldn't give you directions or even tell you which sushi place made the best avocado rolls.
We used to think that that the expansion of the universe was slowing down; that empty space was, basically, empty space; and that we had the majority of the stuff in the universe pretty much figured out.

The discovery that the expansion of the universe is not slowing down--that it is, in fact speeding up, driven by a mysterious "dark energy"--happened when I was in my first year of college. My astronomy professor was so excited about the discovery that we got to have class outside, under a tree, so that we could be closer to this nature thing that was turning out to be so full of baffling surprises.

Now that Saul Perlmutter, Brian Schmidt and Adam Riess have won the Nobel Prize for this discovery, it seems inconceivable that that moment under the tree--the time when we discovered that more than 70% of the universe was a complete mystery--is barely more than a decade old. How amazing that such a profound revelation happened in such recent history.

So as we at NOVA congratulate the winners of this year's Nobel Prize in physics, let's also celebrate living at a wonderful time in the history of science: A time when scientists are still busily mapping out the boundaries of what we don't know, and when the universe is ripe with questions, just waiting to be answered.