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Everything posted by FizziksGuy

  1. Almost like you knew what you were doing... I hope you'll continue to give him a bit of a hard time about this! :wave)
  2. From New Scientist Magazine A BALL spinning in a vacuum should never slow down, since no outside forces are acting on it. At least that's what Newton would have said. But what if the vacuum itself creates a type of friction that puts the brakes on spinning objects? The effect, which might soon be detectable, could act on interstellar dust grains. In quantum mechanics, the uncertainty principle says we can never be sure that an apparent vacuum is truly empty. Instead, space is fizzing with photons that are constantly popping into and out of existence before they can be measured directly. Even though they appear only fleetingly, these "virtual" photons exert the same electromagnetic forces on the objects they encounter as normal photons do. Now, Alejandro Manjavacas and F. Javier García de Abajo of the Institute of Optics at the Spanish National Research Council in Madrid say these forces should slow down spinning objects. Just as a head-on collision packs a bigger punch than a tap between two cars one behind the other, a virtual photon hitting an object in the direction opposite to its spin collides with greater force than if it hits in the same direction. So over time, a spinning object will gradually slow down, even if equal numbers of virtual photons bombard it from all sides. The rotational energy it loses is then emitted as real, detectable photons (Physical Review A, DOI: 10.1103/PhysRevA.82.063827). The strength of the effect depends on the object's make-up and size. Objects whose electronic properties prevent them from easily absorbing electromagnetic waves, such as gold, may decelerate little or not at all. But small, low-density particles, which have less rotational momentum, slow down dramatically. The rate of deceleration also depends on temperature, since the hotter it is the more virtual photons pop in and out of existence, producing the friction. At room temperature, a 100-nanometre-wide grain of graphite, the kind that is abundant in interstellar dust, would take about 10 years to slow to about one-third of its initial speed. At 700 °C, an average temperature for hot areas of the universe, that same speed decrease would take only 90 days. In the cold of interstellar space, it would take 2.7 million years. Could this effect be tested in the lab? Manjavacas says the experiment would require an ultra-high vacuum and high-precision lasers to trap the nanoparticles, conditions that are "demanding but reachable in the foreseeable future". John Pendry of Imperial College in London calls the analysis a "fine piece of work" and says it could provide insights into whether quantum information is ever destroyed, for example, when it falls into a black hole. He says the real photons emitted during the deceleration process should contain information about the quantum state of the spinning particle, much as the photons thought to escape from black holes as Hawking radiation are thought to encode information about the holes. "This is one of the few elementary processes that converts what appears to be purely classical mechanical energy into a highly correlated quantum state," Pendry says. Read full article here...
  3. My goodness. That much energy would power an awful lot of Tickle-Me-Elmo's!
  4. FizziksGuy


    I'll see if I can't find a way to "Sticky" a link to this post... another you can do is treat it as a "group" blog, where more than one person can write/edit/post to it. I believe you can play with the settings from the top navigation bar where it says "blog settings." I'll do a bit more research, but I know that capability comes with our blogging/messaging software. Just as an aside, I can't begin to tell you guys how thrilled I am with the effort and thought you're putting in to your posts. Not only are you finding fun and unique physics applications, you're also building tools to help yourselves and the many students who will come after you. Well done!
  5. FizziksGuy


    Great physics demos notwithstanding, it was a very entertaining game... even for a Steelers fan painfully observing his team find new and exciting ways to snatch defeat from the jaws of victory.
  6. Anyone who can prove Santa is real with physics must know their stuff!
  7. http://abstrusegoose.com/338 [ATTACH=CONFIG]91[/ATTACH]
  8. FizziksGuy

    How much would this hurt?

    That'd wake you up in a hurry!
  9. FizziksGuy


    Great idea moe.ron!!! I think this will be a terrific asset for your class as well as classes to come. Perhaps when it's finished we can blow it up into a giant poster too. Question... did you mean to write Fr for the torque in this equation? Thanks for this valuable post!
  10. This could be a very challenging theoretical problem... or a very simple experiment with a force sensor. :-)
  11. FizziksGuy

    Physics of Running

    Terrific analysis of many of the energy conversions in the human body!
  12. FizziksGuy

    SHM in everyday life

    Isn't it amazing how you can find physics everywhere in life, even when you're not looking? If only that worked for apple pie...
  13. Not prompting... just asking.
  14. If such a technology did take off, do you think there could be any environmental repercussions due to the energy transfer from the wind into electrical power? How widespread would such wind generators have to propagate before there would be significant climatological effects? How would those effects be manifested?
  15. FizziksGuy

    Physics in space

    "May the force be equal to mass times acceleration" -- Charles Barkley
  16. You are supposed to use the formal lab report format to write it, and make sure your analysis includes answers to the questions asked in the lab report handout.
  17. FizziksGuy

    half way done!

    The good news and the bad news... E&M does involve probability and imaginary numbers. Probability at the nano-scale (which we may talk about with a guest speaker on Wednesday), and imaginary numbers first come into play in dealing with AC circuits. And we won't get into much depth with either of those in this semester.
  18. FizziksGuy

    Feynman vs Lewin.

    CalTech event in the spirit of Feynman's vision occuring today... http://tedxcaltech.com/
  19. http://science.discovery.com/brink/quiz/what-scientist-quiz.html You Are Edison... Brilliant, methodical, patient. Edisons believe in using teamwork to solve problems. They see the value in testing 800 compounds before finding the right one. It may not be as sexy as getting it right on the first try, but without thinkers like you, we'd all be in the dark. What does the quiz say about you?
  20. As many of you may have noticed, APlusPhysics has been rather slow as of late. In an attempt to remedy the situation, we have switched our hosting to a "grid hosting" arrangement, in which a number of servers provides simultaneous hosting and can allocate needed resources to accommodate spikes in activity on our website. You should see this in a speed improvement on the site, especially in the Forums, Blogs, and Course Notes sections. Looking forward to the much-needed improvement!!!
  21. Gain a competitive advantage with Wolfram Course Assistant Apps. Each app is custom designed specifically for today's popular courses. Wolfram Course Assistant Apps use an intuitive interface that guides you through the coursework to help you solve problems, not just give you the answers. As the makers of Mathematica and Wolfram|Alpha, we have been providing solutions in education for over 20 years. Now we're combining expert-level data, high-performance computation, and state-of-the-art interface design to give you the power to excel in all your classes—right in the palm of your hand.
  22. [ATTACH=CONFIG]79[/ATTACH] Light can control electrical properties of graphene ScienceDaily (2011-01-13) -- New research shows how light can be used to control the electrical properties of graphene, paving the way for graphene-based optoelectronic devices and highly sensitive sensors. ... > read full article
  23. FizziksGuy

    Feynman vs Lewin.

    Great point -- Richard Feynman did an amazing job of bringing complicated physics to the masses, and his lecture series is probably the most famous recording of an educational lecture in our history to date. Microsoft hosts 7 of the famous Feynman Lectures online at their Project Tuva site... check it out! To provide an idea of just how amazing he truly was, check out the first statement students heard in his introductory physics course at Caltech in the early 1960s. (PS, his lecture series was recorded and transcribed, along with pictures of his blackboard drawings, to create one of the most popular physics books of all time)

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