Schrodinger's Cat

Up to this point, I've covered mostly topics involving geology and light. To shake things up a bit, this post will cover something a bit different - quantum mechanics. Generally speaking, quantum things are too small to photograph without a powerful microscope. However, there is a good macroscopic analogy for one of the most important quantum processes. The Schrodinger's cat paradox was originally used by Erwin Schrodinger to show how silly quantum mechanics seemed when applied to the macroscopic world in which we live. In contrast, his cat paradox has turned into one of the most widely used analogies for explaining the quantum phenomenon of superposition.

If you're not familiar with the Schrodinger's cat paradox, here's how it goes:
(Note: Do NOT try this at home. This is a thought experiment only, not something actually carried out. Please do not needlessly harm animals.)

Start with a solid box. Inside the box is a vial of poison attached to a special device that contains an unstable atom. This unstable atom has a 50% chance of decaying within an hour. If the atom decays, the device will trigger a hammer to smash the vial of poison. Let's now place a cat inside the box and then close the box. If we wait an hour, there is a 50% chance that the device was trigger and the vial smashed. If that happened, we would expect to see a dead cat upon opening the box. However, there is also a 50% chance that nothing happened and the cat is still alive. So, without opening the box, is the cat dead or alive after an hour of waiting?

As long as we don't observe the cat by opening the bow and looking at it, we can say that it is in a state of being both dead and alive. Now, this doesn't make much sense. Obviously, an animal can only be dead or alive, not both. This is why it is a paradox and why Mr. Schrodinger used this as an example of how ridiculous the quantum theory of superposition seemed. Now, what exactly is superposition and why is it important?

From the cat paradox, you may have figured out what superposition is. In simple terms, superposition means that a quantum particle, such as an electron, can be in multiple states at the same time. There is one catch though - if you try to measure or observe the particle, it will assume only one of the states. Going back to the cat paradox, once you open the box and check to see what happened, the cat will be either alive or dead. You can no longer say that it exists in both states.

One consequence of this is that the act of measuring a system can affect how the system is behaving. This is something that rarely happens in the macroscopic world. If you use a ruler to measure the length of a pencil, the act of measuring will not change the length of the pencil. Its length will be exactly the same before and after you measure it. In the quantum world, however, things are different. Because particles are so small, even light can easily affect the properties of a particle. For example, when light collides with an electron, it can pass momentum to the electron and change its speed and/or path of motion. This consequence becomes significant when trying to do things on a quantum level, such as building a quantum computer. These computers use the fact that an atom can simultaneously be in multiple states to speed computations by doing more than one at the same time. However, to get the computation results you would need to interact with the atoms. This causes them to lose all but one of their current states and breaks the multiple-state basis of the computer.

There are experiments that modern day scientists can use to test the theory of superposition. Even though it was questioned back in the 1930s when the cat paradox was first introduced, it is now a well accepted theory. That said, from Mr. Schrodinger's days until now, one thing remains the same - the quantum world remains a very strange one that few people can even begin to fully understand.


Further Reading
Schrodinger's Cat Comes into View - By physicsworld.com
No. 347: Schrodinger's Cat - By John Lienhard at the University of Houston
Another step toward quantum computers: Using photons for memory - By Eric Gershon, phys.org
What Is Quantum Superposition? - By the Science Channel

The Life of a Star

(Apologies for the blurriness - long exposure photos require a tri-pod, which I didn't have on hand that night.)

Orion, the warrior. This is probably one of the most well known constellations, particularly Orion's belt. If you're not familiar with constellations, here's how to pick out Orion. The three stars that make a vertical line at center are Orion's belt. Just to the right of Orion's belt, there is a near horizontal chain of stars. This is Orion's sheathed sword hanging from his belt. The four brightest stars that form a box around the belt and sword are Orion's feet and shoulders. You may also notice a sub-horizontal arc of bright stars between the top of the frame and Orion's (highest) shoulder. This is the bow that he is using to hunt Taurus the bull, or so the legend goes.

If you look closely, you might notice that the lower of Orion's shoulders appears to have a reddish color as opposed to the more usual blueish white color of stars. This star is called Betelgeuse (generally pronounced "Beetle-juice") and is a type of star known as a red supergiant. Similarly to people, stars are born, change as they age, and eventually die. The very largest of the stars die young, sometimes after only a few tens of thousand years. The smaller stars, however, can look forward to a long life, often reaching the ripe old age of billions (our sun) or possibly even trillions of years. Astronomers use the Hertzsprung-Russell (or H-R) diagram to help find out what stage of life a star is in.

Stars spend most of their lifetimes as part of the main sequence. Our sun is roughly an average main sequence star - not a big, bright blue giant nor a small, dim red dwarf. The hotter the star is, the more blue it appears. Therefore, the red Betelgeuse is now cooler than it was as a youngster. As stars age, most move off of the main sequence and into the realms of the red giants and supergiants. (The smallest stars may never quite reach the "giant" phase.) When stars become red giants or supergiants, it is a sign that they are nearing the end of their lifetime. The smaller red giant stars, such as what our sun will become, release their outer atmospheres when they die. The "stardust" expands into space over time, forming a planetary nebula and leaving just the star's core, now called a white dwarf, at the center to slowly cool and fade away. The biggest giants and supergiants, however, meet a much more exciting end. They die in massive stellar explosions, supernovae, which send much of the star's matter flying through space. The remaining core cannot support its own weight anymore and collapses into a very dense neutron star or, in the case of the biggest of the big stars, a black hole.

For stars to continue living, they require energy just as we do. People and animals get their energy from breaking down the food that they eat. Stars, on the other, are more like plants, in the sense that they both make their own energy. However, stars do not require energy from an outside source like plants do when they take in sunlight to help produce their energy. Stars are actually made of their food - in a sense, they live by eating themselves. The most common element in the universe, by far, is hydrogen followed by helium, lithium, and so on down the periodic table. Stars get energy by fusing these small "light" elements into big "heavy" ones. Inside the core of a star, temperatures and pressures are so extreme that the electrons are ripped off the atoms to form a plasma of electrons and ions, the atomic nuclei that is made of protons and neutrons. This hot, dense plasma is the perfect environment for fusion to occur.

Within the hot, charged plasma soup at the star's center, collisions between nuclei are unavoidable. If the collision has enough energy involved, the two nuclei will fuse together into a single larger one. For example, two hydrogen nuclei can combine to create a helium nuclei. This is the process which builds about half of the elements on the periodic table. However, fusion will only release energy when small nuclei are involved. The larger the nuclei, the more energy it takes to fuse them and the less energy is released in the process. As the star turns more and more of its light nuclei into heavier ones, it becomes harder and harder for the star to continue fusing nuclei to get the energy it needs to survive. This is the stage of life that Betelgeuse and other red giant stars have reached. After reaching the red giant stage, the star will continue fusing nuclei until it reaches the point when fusion requires more energy than it produces. For smaller stars like the sun, this limit is reached when carbon is produced. The giant stars, however, can continue fusing nuclei until the entire core has been changed into iron.

Iron is the most stable of all elements. The elements that come before it on the periodic table can produce energy when they are fused together, and those after iron produce energy when they are split (fission). Fission is the process in nuclear bombs that use uranium or plutonium. Because a star cannot create nuclei heavier than iron with fusion, these nuclei can only form when there is enough energy for fusion without needing any energy to be produced - during the star's death. The extreme forces involved in supernovae are capable of creating the heavy nuclei. Since supernovae are basically giant explosions, both the heavy nuclei and the lighter nuclei that were never fused are thrown out into space and end up as part of the next generation of stars and planets. Eventually this stardust, created in extreme environments with fusion and scattered throughout the galaxy by explosions, is brought together in the perfect way to create beings capable of understanding this process - us. As it turns out, we all have an explosive past.


References
Orion - by the Peoria Astronomical Society
The Hertzsprung Russell Diagram - by Richard Powell
Supernovae - by C.R. Nave at Georgia State University
Periodic Table of the Elements - by Mark Winter at The University of Sheffield
Basics: What are Plasmas? - by Dr. Timothy Eastman at Plasmas International
Fission and Fusion - by Yoseph Murtanu on the ChemWiki by University of California, Davis

Geologic Faults

By far the most famous fault, in the US at least, is the San Andreas Fault in California. As a kid on the other side of the country, I always pictured it as one giant chasm that went on forever - similar to what you might see in a movie. Of course, I later learned what the San Andreas Fault really is and also that faults are not really giant gaps in the ground as the movies might have you believe. In fact, most faults, such as the one pictured above, are much smaller, sometimes even microscopic. Nor is California the only state with faults and earthquakes. Over half of the states in the US have at least a moderate earthquake risk, which can be seen on earthquake hazard maps published by the USGS.

Simply put, a fault is a crack in rock on which slip can occur. The rocks on top can either slip downward (normal fault), upward (reverse fault), or move side-to-side (transform fault). Can you figure out what type of fault is pictured? Hint: try to match the strata (or rock layers) on each side to see which way the rocks on top moved. This fault is far from California; it's located at the Seneca Stone quarry in the Finger Lakes region of New York. There is a big difference between this fault and the San Andreas.

Faults form for different reasons. The San Andreas Fault is a major fault because it lies at a plate boundary. The Earth's crust is made of multiple large pieces called tectonic plates. These plates "float" on the mantle and are slowly moving (a few inches per year). At plate boundaries, three main things can happen: one plate can move underneath the other, the plates can move apart, or they can move past each other sideways. Of course, they aren't moving continuously. Friction can cause the plates to get stuck on each other at the boundary. However, stress builds up if the plates are stuck. When the stress becomes large enough to overcome friction, the plates will slip and release the energy that had been stored. This energy is mostly released as waves in the Earth that we call earthquakes.

However, many faults don't occur on plate boundaries. Central New York, for one, is far from a plate boundary. Volcanic processes, such as magma intrusion and gas release, can create faults or enlarge cracks. Colliding plates create stress and strain throughout the plate, not just at the boundary. This can cause intra-plate faulting and create fold mountains. Old, brittle rocks tend to break more easily and will be more likely to have faults and cracks. For our New York fault, we can look at the geologic history of the region. The Finger Lakes were created by glaciers. When glaciers form, their weight causes the crust to sink - similar to what happens when you sit on a mattress. Eventually, the glaciers receded which allowed the crust to rise back up. The stress and strain associated with the crust's bending can create cracks in the rock. This would be a good guess to the origin of the fault in the picture.

Many faults are hidden beneath the surface. We only find them when they become active (i.e. move and create earthquakes) or when we dig into the ground for things like rock quarries, mining, and roads. At this moment, you could be sitting right above a fault and not even know it. Don't worry too much though. Few faults are large enough or have enough energy built up to create a major earthquake. The areas that do have to worry are well known and generally well prepared. Make sure to check out the earthquake hazard map to see how likely an earthquake is to occur near your house.



References and Further Information
San Andreas Fault - by David Lynch
Hazard Mapping Images and Data - by the US Geological Survey (USGS)
United States Geological Survey
Fault Motion - by the Incorporated Research Institutions for Seismology (IRIS)
Plate Boundaries - by Maggi Glasscoe at NASA's JPL
Fold Mountain - by National Geographic
Earthquake Facts & Earthquake Fantasy - by USGS