Yesterday I noted that a nuclear power plant involved a controlled nuclear chain reaction. If something goes wrong, the reaction could run out of control with a great release of energy and/or radioactive material into the surrounding area. This came to public awareness in 1979 with the Three Mile Island accident. This plant in Pennsylvania had a stuck valve that led to a loss of coolant. The reactor core heated up and in the process some radioactive material was released. No serious heath effects came from this accident, though there was a huge public panic and outcry, perhaps in part due to the movie the China Syndrome which came out around the same time.
Seven years later was a much more serious nuclear event, the Chernobyl disaster. A sudden power spike in one of the reactor cores led to an explosion, spewing radioactive material into the environment. Some of this material spread over much of Europe. 28 or 31 people were killed directly by acute radiation poisoning, with another 200 or so suffering from radiation sickness. Long term effect include a rise in the incidence of thyroid cancer, with thousands affected - perhaps up to 9000 deaths will result from this over time. There was also a huge financial impact due to the cost of the cleanup, the destruction of contaminated and potentially contaminated food, and the cordoning off of a large section of land in what is now the Ukraine, including the city of Pripyat, which is now a ghost town.
Continuing on with our series on energy, a nuclear power plant also involves heating up water to make steam to drive turbines to make electricity. The difference here is that the heat energy comes from a nuclear chain reaction. As one unstable nucleus undergoes fission, i.e. breaks apart, it spits out subatomic particles that crash into other nuclei. These break apart and spit out more particles, that hit even more nuclei, etc etc etc. Each step of this process produces energy. If this is controlled it is a power plant, if uncontrolled it is an atomic bomb. A BrickCon 2009 attendee built this nuclear power plant. The reactor core is in the bottom left, driving a turbine in the bottom right. He should have included a little Homer Simpson fig in the control room in the upper left. I'm guessing the upper right is a cooling tower.
Okay, I've let this slide, but I want to spend a few posts talking about energy. I noted a few days back that the bulk of electricity generation involves the heating of water to make steam, which then drives turbines. In most countries water is heated by the burning of fossil fuels (in the US this accounts for about 70% of electricity generation) such as coal. About 300 million years ago, dense forests got slowly buried underground. The process of time and pressure transformed this plant matter into what we know today as coal, so this is essentially stored and concentrated solar energy, from the ancient photosynthesis of those plants. Today we dig up this coal (here's an excellent Marion 182m Shovel used in coal mining by Redjack Ryan),
transport it, usually by train (coal car by Monteur),
and then burn the coal in a plant such as the Kingsnorth Power Station (here from Legoland Windsor).
BTW, the real Kingsnorth plant has been the site of several high profile protests by environmental activists. It seems that tiny little ABS activists have also been to Windsor:
The rumor is that scientists at CERN are about to announce the discovery of the Higgs boson. Here's a good description of the search for this particle by Jorge Chan of Piled Higher and Deeper (a comic I highly recommend):
Okay, for a LEGO angle, let me remind you of the great ATLAS detector built by Dr. Sascha Hehlhase of the Niels Bohr Institute that I previously blogged:
In the previous post I noted how most electricity is generated by the action of turbines transforming mechanical energy into electricity. By far the bulk of those turbines are driven by the motion of steam. Matter exists in three states - solid, liquid and gas. In the solid state the molecules are standing relatively still, in fixed position relative to each other. As such, a solid has both fixed shape and volume. As heat is added, the molecules will vibrate faster and faster, until they reach the point where the energy of the vibration overcomes the forces between the molecules that hold them together, and the molecules slip past each other. This is melting. In the liquid phase, the molecules are still all touching each other, so the volume stays the same, but the shape is variable (that is, when you pour water into a square container, it takes a square shape, but if you pour the same water into a round container it takes a round shape). Now here's the important part for our electricity story: as you add heat to a liquid, eventually the molecules move so quickly they break apart all together and go flying into the air. This is boiling. Since the molecules are not touching in the gas phase, the volume of a gas is variable. As you add heat to a gas, it expands. If you start with liquid water and heat it to boiling, the expanding gas can be directed past a turbine, and the movement of this turbine is what is then used to make electricity. More on the sources of heat tomorrow, but let's give a LEGO representation of the states of matter. After the first and second graders in the Marvelous Multiagers blogger's class had a lesson on the states of matter, some of them created a LEGO version during their playtime. As the teacher describes it, "The big white part is ice. There is a little blue because it's melting a little bit, haha. The big blue part is water. The little white part is a chimney with air coming out of it! We had just talked about how the heating or cooling can change the state of matter, so this really made my day!!". Quick aside - it's pretty much impossible to find a good LEGO image for steam. When you do searches you just come up with train engines and steampunk creations.
When you plug your computer, or anything else, into the wall socket, it is extremely probable that the electricity coming through was produced by some sort of electric generator. There are various types, and I'll ignore the differences between AC and DC generators, but all of these depend on a couple of important scientific principles - the conservation of energy and Faraday's law of induction. The conservation of energy states that energy is neither created nor destroyed, but simply changes form. For instance, if I lift the pencil on my desk into the air, my muscles are converting chemical energy from the food I ate into raising the potential energy of the pencil. If I let go of the pencil, that potential energy changes into kinetic energy as the pencil falls. When it hits the desk, you hear the sound, which comes from the kinetic energy of the pencil being converted to the vibrations in the desk and then the air. BTW, this demonstration is much more effective in class if you use a heavy textbook, which tends to wake up dozing freshmen. :) In an electrical generator, the kinetic energy of a spinning turbine (more on what makes that spin in future posts) is transformed into electric current. This is due to electromagnetic induction. In 1931, Faraday described how the motion of a wire relative to a magnetic field leads to a movement of electrons in that wire. If the wire is wrapped around a spinning core between the poles of a magnet (or this can also work if the magnet is doing the spinning).
Redearth76 built this generator using LEGO, neodymium magnets and 30 & 22 gauge wire. He measured 13 volts on the 30 gauge side and 1 volt on the 22 gauge side. He also notes that this is an AC generator, and the LED flashes different colors when positive and negative current is applied, so it blinks back and forth.
Here's another version by goldenbat007
Finally, for a purist version, electric motors work on the reverse of this principle. Instead of using the spinning of an axle to produce an electric current, they use an electric current to produce the motion of an axle. Simple motors can also serve as electric generators, as seen here with a LEGO motor by danky78.
LegoMachine1 built Beautiful minds:
"In honor of Sir Joseph Swan (1828-1914) and Thomas Alva Edison (1847-1931), the two men, which changed the way people live in homes around the world, inventing the incandescent light bulb. A bit of history: 'English Sir Joseph Wilson Swan in 1878 in Great Britain, patented the first light bulb ever made, but this, it proved impractical. The combustion system, was a thick filament carbon emitting gas, and very quickly, soot covered the interior of the bulb. Was then, the American Thomas Alva Edison, who in 1879 patented a high-strength thin filament, which did not emit gases. Swan also incorporated this improvement in his bulb, but was sued by Edison for patent infringement. In the end, common sense prevailed, Swan and Edison agreed, and in 1880, they created the Edison & Swan United Light Company. ..... and now light!"
I occasionally draw something like this on the board and ask my students what it is:
When they reply 'a cube' I correct them, saying that it is a two dimensional drawing that uses tricks of perspective that our mind interprets as a three dimensional cube. Two dimensional drawings of impossible objects take advantage of these tricks of perspective, but the tricks don't match up. So if you cover up one part of the drawing and then cover up the other part of the drawing, different sections appear to be going in different directions. For example, take the famous devil's fork:
If you cover up the right-hand portion, you see three prongs, but if you cover the left portion you see two prongs. However, the lines connect up so at some point the three become two, or the foreground becomes the background. But how to achieve this in three dimensions? The whole idea of an impossible object is that it is impossible. The answer, of course, is that you can only see these from one particular point of view. If you were to look at them from any other angle, you would see that the edges don't match up. For instance ...
Several of the Escher illustrations depicted over the past few days are impossible objects - two dimensional drawings that seem to be of three dimensional objects, but turn out to be optical illusions, unbuild-able in real life. One of the first impossible objects, and one of the inspirations for Escher's Waterfall and other works, is known as the Penrose triangle. This was actually first depicted by Oscar Reutersvärd in 1934, before Roger Penrose independently presented his version.
The Penrose Triangle was the basis for the Lugnet logo. Lugnet was one of the first major LEGO websites.
John Langrish made this mosaic of the Lugnet Logo.
The Penrose Triangle has been recreated in LEGO many times. Some of these depend on Photoshop trickery, but others are true three-dimensional creaions, such as this by Billy Baldwin.
Brixe63's Modulex version is more remniscent of Reutersvärd's original design.
Various other LEGO impossible objects have been built, such as Don Solo's archway.
Brixe63 has had great fun with the idea in her set of optical illusions.
Brixe63 also has this amazing Terrace, that is based on an impossible scene that was apparently first used by Sandro del Prete (who was influenced by Escher).
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