Final Essay

Pick one of the following two options: Feynman lecture or Lincoln article for your final essay. The essay should be between 3-5 pages in length, double-spaced using 12-point font. The essay should not be 2 pages with a single word on the third page. This is not be a 3-page essay; it is a 2-page essay in need of a little bit of editing! Rather, your essay should be 800-1200 words long, or so. Below you will find some specific expectations and suggestions for the two options. But the best general advice is to write a fascinating, innovative essay that, after I have read your essay, makes me go, “Wow, that was fascinating and innovative!” The key is to engage your curiosity and demonstrate that to me. Remember: if you are headed off to college, these are the types of fundamental issues you should be thinking about: Feynman's lecture raises questions of free will vs. determinism while Lincoln asks what are the ultimate building blocks of the universe. These are really BIG and enduring questions to which all thoughtful people should seek answers.

The essay is due on Monday 5/20/13. You may turn it in during class or email it to me. If emailed, the essay should be sent as a PDF file.

BreakingNews.png* FYI: The current issue of Scientific American (June, 2013) has an article directly related to the lecture by Richard Feynman!! If you want to REALLY impress me with your essay, you should find a copy of that article and include a discussion of it in your essay. The article is a bit of a tough read in that it relies heavily on a good understanding of probability and how to interpret probabilities - but it is worth the effort. Below I have attached a copy of one of the references that is cited by the author of the Scientific American article. *


Option #1. Richard Feynman lecture on quantum mechanics

richard-feynman.jpgWatch the lecture by Richard Feynman on "Probability and Uncertainty in Quantum Mechanics" using the this link, or read the lecture that was published in the book "The Character of Physical Law" using this link. The full book is available online, as well.

Requirements for essay
First, summarize the key points from Feynman’s lecture, enough so you convince me you actually did watch (or read) it. Then, discuss the implications of this presentation by considering the following: The classical physics of Isaac Newton (as well as our basic intuition and our language) assumes particles follow “trajectories” which means the electrons or photons that are used in the double-slit experiment should pass through only one of two hole. Can such a viewpoint be consistent with the evidence presented by Feynman? Is the problem due to the limitations of our current technologies or is it due to the inherent properties of subatomic particles? How can “observing” the particle affect its behavior? Compare Feynman’s description of the double-slit problem with Thomas Young’s original experiment and/or the “Schrödinger’s cat” thought experiment. How does quantum uncertainty, as described by Feynman, compare with classical determinism, as embodied by “Laplace’s demon”? Note that you do not need to cover all of these issues; you can take a different direction entirely – so long as you write me an essay that is fascinating and innovative!

Background
For more on the classical version of this quantum experiment, you may want to watch this short video from MIT on the Young double slit experiment with light. This experiment will be done in class as a demo.


Morgan Freeman's "Through the wormhole" on the quantum version of the double-slit experiment.

Sean Carroll (CalTech) on the interpretations of quantum uncertainty.

Minute Physics on quantum mechanics, Schroedinger's cat thought experiment, and interpretations of quantum uncertainty.
- Schroedinger's cat
- many worlds interpretation
- parallel worlds (many worlds is one version of parallel universes)
- quantum uncertainty (can we predict everything?)

Schroedinger's cat thought experiment
This thought experiment raises the same issues as the double-slit experiment - namely something that appears to be doing two things simultaneously. In the double-slit experiment, the particles appear to pass through both slits at the same time. In Schroedinger's cat, the cat appears to be both dead and alive at the same time - or in a superposition of two states.

Laplace's demon: This idea is the classical version of quantum uncertainty or if we know the position and velocity of all objects in the universe, then we can predict the future and know the past completely. This idea is the basis for "classical determinism" (or the opposite of quantum uncertainty). Note even in classical, non-quantum systems, classical determinism can break down (or the so-called "butterfly effect").

Double-slit experiment - This short video shows the results of an actual experiment where a single electron is fired at a set of double slits. The same interference pattern is produced.

Experiment reproducing Feynman's proposed experiment.

Interview with Feynman:


* Hot off the press:
1. Hans Christian von Bayer. "Quantum Weirdness? It's all in your mind" Scientific American v308 n6 (June, 2013): 46-51. [unfortunately, the article is not available online and the interactive features have not been activated yet]
2. N. David Merman. "Quantum Mechanics: Fixing the shifty split" Physics Today v65 n7 (July, 2012): 8-10. [shorter article than above containing much of the same basic ideas]
3. Wikipedia article on Bayesian statistics - used in this interpretation of the probabilities and wave functions in quantum mechanics.
4. "Born Rule" (named for Max Born who came up with it and won the Nobel prize) relates the wave function (actually the square of the wave function) to probabilities of a quantum mechanical system being in a given state. Much of the problems in quantum mechanics comes from what exactly does this probability mean?

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Option #2. Article on modern physics

Read this article on modern physics: standard model of particles and a proposed extension of that model by Don Lincoln: [Recall that this article is password protected and the password is case sensitive; email me if you forgot the password handed out in class.]

Requirements for essay
What clues suggest that the fundamental particles in the standard model are themselves built from smaller components? What is a “preon”? How are they used to construct the particles in the standard model and their interactions? What holds the preons together? What are the problems with this theory? Is there any evidence to support it? What types of evidence might eventually be found in experiments? What alternatives have been suggested for the inner structure of particles in the standard model?

Relate the theory in the article to ideas of symmetry that we started the year considering. Consider Lincoln’s article on symmetry? Note that we, at one point, believed that compounds and mixtures like air, water, earth, and fire were the basic building blocks of nature; then atoms were thought to be “indivisible;” next we split these indivisible atoms into electrons, protons, and neutrons; now we believe some of these fundamental particles consist of yet smaller constituents called “quarks.” The article suggests yet another layer further down. How far can this process go, or could nature be build upon an infinite layer of diminishingly small pieces? Could this be considered a “scientific” theory or more of a “philosophical” idea? At some point might we no longer be able to perform experiments? Hint: what about Heisenberg’s uncertainty principle?

Again, think creatively but within the bounds imposed by nature herself. Your thinking should be largely scientific, not purely poetic – while at the same time, you should write an essay that is both fascinating and innovative!

Background
The author on the "standard model" which he is attempting to extend:



Don Lincoln has made several videos related to the standard model, including on the Higgs boson,anti-,matter, and the origins of the universe. The article also has some interactive features on-line (frankly, they are not very impressive!). He has also written on symmetry on NOVA's blog.

Wikipedia article on one preon model and on another preon model.

CERN's description of the standard model and, if you watch very carefully, you will see preons mentioned as one possible discovery that goes beyond the standard model. Recall that CERN is where the "large hadron collider" (LHC) is located and that is where the Higgs was discovered. The video pre-dates the discovery last July.

One complication to the "standard model" is that it may be incomplete. It has been proposed that an entire new set of "fundamental" particles may need to be postulated - or the number of basic building blocks may need to be doubled. This theory is called "supersymmetry." Such an idea raises questions of how the original set of 6 quarks and 6 leptons can be seen as really "fundamental." Each must be paired with a corresponding "anti-particle" and now with a "supersymmetric" partner. 12 building blocks becomes 24, then 48!

The "preon" theory is not fully accepted; it is new physics. See some alternative views from various physics blogs:
- preons may not not exist
- critique of article with comments by author

Lecture on symmetry by Prof. Chris Hill of FermiLab:


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