Quantum Optics https://scienceblogs.com/ en Physics Blogging Round-Up: ARPES, Optics, Band Gaps, Radiation Pressure, Home Science, and Catastrophe https://scienceblogs.com/principles/2016/04/19/physics-blogging-round-up-arpes-optics-band-gaps-radiation-pressure-home-science-and-catastrophe <span>Physics Blogging Round-Up: ARPES, Optics, Band Gaps, Radiation Pressure, Home Science, and Catastrophe</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>It's been a while since I last rounded up physics posts from Forbes, so there's a good bunch of stuff on this list:</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/03/22/how-do-physicists-know-what-electrons-are-doing-inside-matter/">How Do Physicists Know What Electrons Are Doing Inside Matter?</a>: An explanation of Angle-Resolved Photo-Electron Spectroscopy (ARPES), one of the major experimental techniques in condensed matter. I'm trying to figure out a way to list "got 1,800 people to read a blog post about ARPES" as one of my professional accomplishments on my CV.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/03/25/the-optics-of-supermans-x-ray-vision/">The Optics Of Superman's X-Ray Vision</a>: Spinning off a post of Rhett's, a look at why humanoid eyes just aren't set up to work with x-rays.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/03/30/why-do-solids-have-band-gaps/">Why Do Solids Have Band Gaps?</a>: A conceptual way to see why there are some energies that electrons simply can not have inside a periodic structure.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/03/31/how-tropical-birds-use-quantum-physics/">How Tropical Birds Use Quantum Physics</a>: Blue feathers on many birds aren't blue because of pigment, but thanks to the same physics that gives solids band gaps.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/04/08/why-do-we-teach-old-physics-because-it-works/">Why Do We Teach Old Physics? Because It Works</a>: We had another round of people lamenting the emphasis on "old" topics in introductory courses; here's my defense of the standard curricular order.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/04/12/how-hard-does-the-sun-push-on-the-earth/">How Hard Does The Sun Push On the Earth?</a> In which one of The Pip's silly superhero books gets me thinking about radiation pressure forces.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/04/13/how-to-use-a-laser-pointer-to-measure-tiny-things/">How To Use A Laser Pointer To Measure Tiny Things</a>: In which I use a green laser to settle the question of who in Chateau Steelypips has the thickest hair.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/04/15/dont-just-talk-about-science-with-your-kids-do-science-with-your-kids/">Don't Just Talk About Science With Your Kids, DO Science With Your Kids</a>: A simple home experiment, and a pitch for the importance of doing simple experiments at home.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/04/18/how-quantum-physics-starts-with-your-toaster/">How Quantum Physics Starts With Your Toaster</a>: A blog version of my half-hour fake class on the "ultraviolet catastrophe" and why Planck needed the quantum hypothesis to solve black-body radiation.</p> <p>Both blogs are likely to be on a sort of hiatus for the next little bit. I'm giving a talk at Mount Holyoke tonight, which will get me home really late, then Thursday and Friday I'm going to NYC for a <a href="http://spaceappsnyc.com/">space conference</a>. Then on Saturday, we're flying to Florida with the kids and my parents, and going on a Disney cruise in the Caribbean for all of next week. Which will provide a badly needed opportunity to kick back by the pool, because oh, God, so busy...</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Tue, 04/19/2016 - 02:15</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/blogs" hreflang="en">Blogs</a></div> <div class="field--item"><a href="/tag/condensed-matter" hreflang="en">Condensed Matter</a></div> <div class="field--item"><a href="/tag/education" hreflang="en">education</a></div> <div class="field--item"><a href="/tag/experiment" hreflang="en">Experiment</a></div> <div class="field--item"><a href="/tag/forbes-recap" hreflang="en">Forbes Recap</a></div> <div class="field--item"><a href="/tag/media-0" hreflang="en">In the Media</a></div> <div class="field--item"><a href="/tag/optics" hreflang="en">Optics</a></div> <div class="field--item"><a href="/tag/outreach" hreflang="en">Outreach</a></div> <div class="field--item"><a href="/tag/personal" hreflang="en">personal</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> </div> </div> <section> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2016/04/19/physics-blogging-round-up-arpes-optics-band-gaps-radiation-pressure-home-science-and-catastrophe%23comment-form">Log in</a> to post comments</li></ul> Tue, 19 Apr 2016 06:15:51 +0000 drorzel 49060 at https://scienceblogs.com Physics Blogging Round-Up: Gravity, Pigeonholes, Groundhogs, and Weirdness https://scienceblogs.com/principles/2016/02/05/physics-blogging-round-up-gravity-pigeonholes-groundhogs-and-weirdness <span>Physics Blogging Round-Up: Gravity, Pigeonholes, Groundhogs, and Weirdness</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>A long-ish stretch of time, but I was basically offline for a bunch of that because I needed to finish a chapter I was asked to contribute to an academic book. So there are only four physics posts from Forbes to promote this time:</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/01/19/the-expanse-and-gravity-beyond-the-equivalence-principle/">'The Expanse' Is A Rare Sci-Fi Show That Gets Simulated Gravity Right</a>: Another post on the SyFy adaptation of "James S. A. Corey"'s books, talking about a nifty bit of visual effects that nods at the Coriolis force you'd see on a rotating space station.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/01/22/what-is-the-quantum-pigeonhole-principle-and-why-is-it-weird/">What Is The Quantum Pigeonhole Principle And Why Is It Weird?</a>: A paper published in the Proceedings of the National Academy of Sciences got some press with claims that you can put three quantum particles in two boxes without having any two particles together. Digging into it more, it's both less and more weird than that description.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/02/02/groundhog-day-physics-four-stories-you-hear-over-and-over-again/">Groundhog Day Physics: Four Stories You Hear Over And Over Again</a>: In honor of our dippiest public holiday and a great Bill Murray movie, some physics stories that repeat regularly enough that you might be forgiven for thinking you were stuck in a time loop.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2016/02/03/how-do-you-deal-with-quantum-weirdness/">How Do You Deal With Quantum Weirdness?</a>: An attempt to explain the two major groupings of interpretations of quantum physics.</p> <p>I've got a bunch of travel coming up (about which more soonish), so blogging will remain a little sporadic, but hopefully not as comprehensively silent as I was for the last week or two of January.</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Fri, 02/05/2016 - 02:05</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/atoms-and-molecules" hreflang="en">Atoms and Molecules</a></div> <div class="field--item"><a href="/tag/blogs" hreflang="en">Blogs</a></div> <div class="field--item"><a href="/tag/books-0" hreflang="en">Books</a></div> <div class="field--item"><a href="/tag/forbes-recap" hreflang="en">Forbes Recap</a></div> <div class="field--item"><a href="/tag/media-0" hreflang="en">In the Media</a></div> <div class="field--item"><a href="/tag/news-0" hreflang="en">In the News</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/pop-culture" hreflang="en">Pop Culture</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/relativity" hreflang="en">Relativity</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> <div class="field--item"><a href="/tag/television-0" hreflang="en">Television</a></div> <div class="field--item"><a href="/tag/theory" hreflang="en">Theory</a></div> </div> </div> <section> <article data-comment-user-id="0" id="comment-1649113" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1454709311"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>Great article about simulated gravity and coriolis, but when it comes to pedantic explanations, no one does it better than these crazy Canadians: </p> <p><a href="https://www.youtube.com/watch?v=aRDOqiqBUQY">https://www.youtube.com/watch?v=aRDOqiqBUQY</a></p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1649113&amp;1=default&amp;2=en&amp;3=" token="ATxxYuQGLG93EfUX-DZz6q526ZYsfsdbBZyKQP6VYqc"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">CCPhysicist (not verified)</span> on 05 Feb 2016 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1649113">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2016/02/05/physics-blogging-round-up-gravity-pigeonholes-groundhogs-and-weirdness%23comment-form">Log in</a> to post comments</li></ul> Fri, 05 Feb 2016 07:05:25 +0000 drorzel 49016 at https://scienceblogs.com Me in the Media: Two New Interviews https://scienceblogs.com/principles/2015/10/30/me-in-the-media-two-new-interviews <span>Me in the Media: Two New Interviews</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>I've been slacking in my obligation to use this blog for self-promotion, but every now and then I remember, so here are two recent things where I was interviewed by other people:</p> <p>-- I spoke on the phone to a reporter from <em>Popular Mechanics</em> who was writing a story about "radionics" and "wishing boxes," a particular variety of pseudoscience sometimes justified with references to quantum mechanics. The <a href="http://www.popularmechanics.com/science/energy/a17984/spooky-action-at-a-distance/">resulting story</a> is now up, and quotes me:</p> <blockquote><p> It is hard to investigate the ethereal thinking around radionics, but physics is something that can be parsed. So I got in touch with Chad Orzel, a physics professor at Union College in New York and the author of several popular science books, including How To Teach Quantum Physics to Your Dog. This sounded about my speed, and I ran a few ideas about physics and radionics past him, particularly "quantum entanglement," which several people offered as evidence that radionics is possible.</p> <p>"Entanglement is a very strange phenomenon," says Orzel. "But it's a very real thing."</p> <p>[...]</p> <p>"People try to invoke this as a way of justifying ESP sorts of things: 'Well, maybe electrons in your brain are entangled with electrons somewhere else.' There's a couple of problems with it," Orzel says. </p></blockquote> <p>You'll have to click through to see what the couple of problems are, though...</p> <p>-- A little earlier, Irene Helenowski <a href="https://helenowskiirene.wordpress.com/2015/10/23/interview-with-chad-orzel/">interviewed me by email</a>. This went live last week, when I was in California, which is my excuse for not posting it until now.</p> <blockquote><p> <strong>Professor, how is Emmy doing these days?</strong></p> <p>She's doing well. She's getting on in years for a dog-- she's 13-- so she's slowed down a bit. But she's still pretty spry, and can about pull me off my feet when she really wants to get to something on one of our walks. </p> <p><strong>You discuss simulating a black hole at CERN. What is the current status on the scientists' progress with that project?</strong></p> <p>It's not so much simulating, as trying to _create_ a black hole. The idea is that if you can pack enough energy into two colliding protons, you can create a situation where they get close enough together, and have enough total energy that they form a tiny black hole.</p> <p>This is very much a long-shot possibility at the energy of the actually existing LHC-- if nothing exotic is going on, there's no way the LHC energy is enough to make a black hole. There are some exotic theories where gravity gets dramatically stronger at short distances, though, and if one of these turned out to be true, there's a chance you could get a black hole. This would evaporate through Hawking radiation almost immediately, spraying out a burst of particles that could identify it as a black hole rather than a more typical collision.</p> <p>There have been some searches for this in data from the first LHC run, and no sign of black holes has been seen. They just recently re-started at a higher energy (by a factor of two, not enough to make mini-black-holes likely), and I'm sure there will be more such searches. Nobody really expects this to pan out, but it would be tremendously exciting if it did. </p></blockquote> <p>Again, click through to read the rest.</p> <p>------------<br /> And while you're clicking on things, please consider taking a few minutes to respond to Paige Jarreau's <a href="http://bit.ly/mysciblogreaders">survey of blog readers</a>. It's for SCIENCE!, specifically her postdoctoral research on communicating science online.</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Fri, 10/30/2015 - 03:23</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/blogs" hreflang="en">Blogs</a></div> <div class="field--item"><a href="/tag/book-writing" hreflang="en">Book Writing</a></div> <div class="field--item"><a href="/tag/experiment" hreflang="en">Experiment</a></div> <div class="field--item"><a href="/tag/media-0" hreflang="en">In the Media</a></div> <div class="field--item"><a href="/tag/outreach" hreflang="en">Outreach</a></div> <div class="field--item"><a href="/tag/personal" hreflang="en">personal</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/physics-books" hreflang="en">Physics Books</a></div> <div class="field--item"><a href="/tag/publicity" hreflang="en">Publicity</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/relativity" hreflang="en">Relativity</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> <div class="field--item"><a href="/tag/theory" hreflang="en">Theory</a></div> </div> </div> <section> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/10/30/me-in-the-media-two-new-interviews%23comment-form">Log in</a> to post comments</li></ul> Fri, 30 Oct 2015 07:23:30 +0000 drorzel 48928 at https://scienceblogs.com Physics Blogging Round-Up: Two Weeks' Worth https://scienceblogs.com/principles/2015/08/14/physics-blogging-round-up-two-weeks-worth <span>Physics Blogging Round-Up: Two Weeks&#039; Worth</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>I forgot to do this last week, because I was busy preparing for SteelyPalooza on Saturday, but here are links to my recent physics posts over at Forbes:</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/08/03/the-rules-of-the-quantum-realm/">What 'Ant-Man' Gets Wrong About The Real Quantum Realm</a>: On the way home from the Schrödinger Sessions, I had some time to kill so I stopped to watch a summer blockbuster. The movie was enjoyable enough, thanks to charming performances from the key players, but the premise is dippy even for a comic-book movie. It does, however, provide a hook to talk about quantum physics, so...</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/08/05/great-books-for-non-physicists-who-want-to-understand-quantum-physics/">Great Books For Non-Physicists Who Want To Understand Quantum Physics</a>: I did a bit of name-and-title-dropping at the Schrödinger Sessions, and a few of the writers asked if I had a list of books I would recommend (other than, you know, <a href="http://dogphysics.com/book_info.html"><em>How to Teach [Quantum] Physics to your Dog</em></a>). I didn't have one already put together, so I made a new post listing a dozen good books to read.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/08/11/how-quantum-randomness-saves-relativity/">How Quantum Randomness Saves Relativity</a>: Inspired in part by the many discussions of entanglement at the Schrödinger Sessions, a discussion of why you can't actually use entangled particles to send messages faster than light. "Spooky action at a distance" is impossible because of "God playing dice," a cute bit of historical irony.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/08/13/what-has-quantum-mechanics-ever-done-for-us/">What Has Quantum Mechanics Ever Done For Us?</a> I know you get more and angrier comments on political posts, but for sheer "WTF?" weirdness in the comment section, nothing beats quantum physics. This is a short explanation of the quantum underpinnings of major modern technologies, in response to a crank who left a bunch of angry comments on a G+ link to the quantum randomness article.</p> <p>Not a huge number of posts for two weeks of blogging, but I'm very happy with them. And the quantum randomness one in particular is a nice counter to some myths about science communication-- over 20,000 people have clicked through to read an article that builds up to a citation of the no-cloning theorem. I'm pretty proud of that.</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Fri, 08/14/2015 - 04:08</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/blogs" hreflang="en">Blogs</a></div> <div class="field--item"><a href="/tag/books-0" hreflang="en">Books</a></div> <div class="field--item"><a href="/tag/forbes-recap" hreflang="en">Forbes Recap</a></div> <div class="field--item"><a href="/tag/media-0" hreflang="en">In the Media</a></div> <div class="field--item"><a href="/tag/links-dump" hreflang="en">Links Dump</a></div> <div class="field--item"><a href="/tag/movies-0" hreflang="en">Movies</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/physics-books" hreflang="en">Physics Books</a></div> <div class="field--item"><a href="/tag/pop-culture" hreflang="en">Pop Culture</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/relativity" hreflang="en">Relativity</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> <div class="field--item"><a href="/tag/science-books" hreflang="en">Science Books</a></div> </div> </div> <section> <article data-comment-user-id="0" id="comment-1648862" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1439633560"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>come correct my rant on reddit if you're so inclined. Cheers!</p> <p><a href="https://www.reddit.com/r/Physics/comments/3h2sh5/reddit_what_is_your_best_source_for_bs_free/cu3z1t7">https://www.reddit.com/r/Physics/comments/3h2sh5/reddit_what_is_your_be…</a></p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648862&amp;1=default&amp;2=en&amp;3=" token="n95Piql1rWuu12eqUitNHl2NKTcChAijOWgYMEb9lz4"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">singlemonad (not verified)</span> on 15 Aug 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648862">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> <article data-comment-user-id="0" id="comment-1648863" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1439844956"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>First thank you for your on-going contributions to understanding the new physics such as the "How Quantum Randomness Saves Relativity".<br /> Talking of which, in the video at around 1'12'' you talk of repeating the same experiment and getting the same result IF not interrupted by another experiment. I am writing a book which includes a section on time and that comment of yours is extremely profound. Do you know the name/authority for that observation?<br /> It seems, at the quantum levels at least, as if that repetition is taken as one unit of time until interrupted.<br /> .</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648863&amp;1=default&amp;2=en&amp;3=" token="nb_ADqs10BgTC3odP6m25sHLJnH7x3Rip4xtGHOTSmY"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">Remco van Santen (not verified)</span> on 17 Aug 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648863">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> <article data-comment-user-id="0" id="comment-1648864" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1439848570"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>Thanks Chad for taking the time to share your experience with this difficult arena of physics. One question please re what you said at about 1'12" of the video (How Quantum Randomness Saves Relativity). You say the experiment produces the same outcome until interrupted by another experiment.When reverting to the original experiment the outcome is again statistical in the first instance of the experiment.<br /> This seems very profound in the understanding of time for the book I am writing. Can you please indicate the name or reference to that please?<br /> It does seem by your example that time is a creation to keep events apart (when they are identical).</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648864&amp;1=default&amp;2=en&amp;3=" token="B-d97cP7372nIRnu-fDNryvS5UpSw7Oy0wJ7QsfVsEE"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">Remco van Santen (not verified)</span> on 17 Aug 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648864">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> <article data-comment-user-id="0" id="comment-1648865" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1440981701"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>I am a regular reader but have not commented before. This post reminded me of a recent apod (<a href="http://apod.nasa.gov/apod/ap150615.html">http://apod.nasa.gov/apod/ap150615.html</a>) about lunar corona. Where I got stuck was that they wrote "Lunar Coronae are one of the few quantum mechanical color effects that can be easily seen with the unaided eye." If this is standard diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud (as they explain) why are they singling it out as a "quantum effect"?</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648865&amp;1=default&amp;2=en&amp;3=" token="EoPk2Xp0V5E3IkncdXx60MsQlRt6VdxDA52bMh9Ods8"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="" content="Dr. Ritaban Chatetrjee">Dr. Ritaban Ch… (not verified)</span> on 30 Aug 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648865">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/08/14/physics-blogging-round-up-two-weeks-worth%23comment-form">Log in</a> to post comments</li></ul> Fri, 14 Aug 2015 08:08:36 +0000 drorzel 48853 at https://scienceblogs.com Back-of-the-Envelope Gravitational Which-Way https://scienceblogs.com/principles/2015/08/07/back-of-the-envelope-gravitational-which-way <span>Back-of-the-Envelope Gravitational Which-Way</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>There's a <a href="http://www.sciencemag.org/content/early/2015/08/05/science.aac6498">new <em>Science Express</em> paper on interfering clocks</a> today, which is <a href="http://physicsworld.com/cws/article/news/2015/aug/07/could-quantum-clocks-tread-two-different-paths-to-general-relativity">written up in <em>Physics World</em></a>, with comments from yours truly. The quote is from a much longer message I sent-- with no expectation that it would end up as anything other than a pull quote, I might add, but I thought the background would be helpful. Since I ended up doing a back-of-the-envelope estimate for that, though, I thought I would reproduce some of the reasoning here.</p> <p>The basic proposal idea here is to do an atom interferometer inside a Ramsey interferometer for making an atomic clock. That is, before sending the atoms into the beamsplitter, you prepare them in a superposition state, like the first step in making an atomic clock. This gets you a superposition state with a phase that oscillates at the frequency associated with the atomic transition, which is what you use to make the clock.</p> <p>In this case, though, the claim is that a different rate of "ticking" of the clocks along the different paths of the interferometer-- say because one is at a higher altitude than the other, and thus subject to a gravitational time dilation from general relativity-- could serve as a "which-way" measurement that would destroy the quantum interference effect. That is, the fact that the upper clock ticks more rapidly than the lower would let you distinguish which of the two paths the atom "really" followed on its way through, by making a clock measurement after you recombined the two paths. This would destroy the interference, which would reduce the contrast of the interference pattern. As a demonstration, they applied an artificial shift to the "clock" on one arm of their (horizontal) interferometer, and showed that when they make the resulting phase shift an odd multiple of π, the interference pattern gets wiped out.</p> <p>As I said to <em>Physics World</em>, you would need to talk to a real atom interferometrist to clarify the difference between what they're doing with the clock superposition state and a Ramsey-Bordé interferometer, and also to make sure there's a sharp distinction between the gravitational shift they're talking about and the phase shift people doing gravitational measurements with interferometers already measure. Assuming they're right, though, you can try to estimate whether this would really be measurable.</p> <p>The gravitational time dilation they're talking about as making the "which-way" distinction is, near the surface of the Earth, approximately:</p> <blockquote><p> $latex T \approx T_0 (1+\frac{gR}{c^2} )$ </p></blockquote> <p>where <i>T</i> is the time between ticks for the clock a distance <i>R</i> from the center of the Earth (something not too different from the radius of Earth), <i>T<sub>0</sub></i> the time for a clock far away from anything massive, and <i>g</i> the strength of gravity near the surface of the Earth. If you plug numbers in for two clocks at different elevations, this is a shift of about one part in 10<sup>16</sup> per meter of difference.</p> <p>(As a sanity check, that's about what they see in the <a href="http://scienceblogs.com/principles/2010/11/12/relativity-on-a-human-scale-op/">aluminum-ion clock experiment at NIST</a>: they raised one clock above the other by about 33cm, and see a shift of a bit under 5 parts in 10<sup>17</sup>. So I'm not completely off base, here...)</p> <p>The largest separation between paths I'm aware of in an atom interferometer is the <a href="http://scienceblogs.com/principles/2013/08/20/point-sources-and-towers-multiaxis-inertial-sensing-with-long-time-point-source-atom-interferometry/">10-meter tower interferometer</a> in the group of my old boss, Mark Kasevich. That's from 2013, with a separation of a centimeter and a half. I have heard, but not seen solid documentation of, that they've expanded this to half a meter or so. </p> <p>To get the interference-destroying effect, they applied a phase shift of <i>π</i> to one arm, which would correspond to half a "tick" of the clock-- that is, half the oscillation period. To see this gravitationally, you would need to have that part-in-10<sup>16</sup> shift amount of a difference of one oscillation period over the time in the interferometer (a couple of seconds for the 10-m tower). For a microwave clock transition like you have in the rubidium used in the Kasevich group, you're a factor of a million away-- the frequency is about 7,000,000,000Hz, so the shift would be on the short side of a microhertz. That's not going to do much.</p> <p>You might, however, get somewhere with one of the optical clock atoms, like strontium. the "clock" transition in Sr is in the visible region, at around 400,000,000,000,000Hz, so a part-in-10<sup>16</sup> shift is close to 1Hz. Over a couple of seconds, that's probably enough phase shift to significantly degrade the contrast, based on the graph in the new paper.</p> <p>How plausible is that? Well, it's not ridiculous. The 10-m tower experiments use a BEC of rubidium, and strontium has also been Bose condensed. So if you adapted the giant tower to use Sr rather than Rb (a challenge, but probably not impossible), you might be able to see something. Assuming you could distinguish this effect from the many, many other things that can degrade the contrast of an atom interferometer signal. (For that, I think you'd want to see a revival of the contrast, which means getting to a phase shift of 2π, and you could map the effect out by gradually increasing the separation through changing the momentum imparted by the laser beamsplitters in the interferometer.)</p> <p>Does this sort of thing have anything to say about the interaction of gravity and quantum mechanics? Probably not, in my semi-informed opinion. It's a much more clearly defined mechanism than you see in most theories invoking gravity as a reason for a loss of "quantum-ness" in macroscopic experiments (which tend to be of the form "We don't understand the quantum-to-classical transition, and we don't understand gravity, therefore they're related"), so it's at least something you <em>could</em> probe experimentally. It's a really small effect, though, even in the most impressive interference experiments done to date, and seems to require a rather special set of experimental conditions (both a vertically oriented interferometer and a superposition of internal states), so I think the implications for quantum foundations are probably minimal. </p> <p>It's a clever idea, though, and it would be interesting to see somebody give it a try.</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Fri, 08/07/2015 - 03:49</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/atoms-and-molecules" hreflang="en">Atoms and Molecules</a></div> <div class="field--item"><a href="/tag/estimation" hreflang="en">Estimation</a></div> <div class="field--item"><a href="/tag/experiment" hreflang="en">Experiment</a></div> <div class="field--item"><a href="/tag/news-0" hreflang="en">In the News</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/precision-measurement" hreflang="en">Precision Measurement</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/relativity" hreflang="en">Relativity</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> <div class="field--item"><a href="/tag/theory" hreflang="en">Theory</a></div> <div class="field--item"><a href="/tag/time" hreflang="en">Time</a></div> </div> </div> <section> <article data-comment-user-id="0" id="comment-1648844" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1439021241"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>Not too long ago I tweeted you a link to a thing I wrote, on the off-chance that it might catch your eye. To no-one's surprise it didn't, but the topic is relevant to this post.</p> <p>Here's the backstory. Earlier in the year I decided to see, just for fun, if I could guess a formula for gravitational time dilation near the surface of the earth. My tools were a crude notion of what general relativity entails, some high school Newtonian physics, and Ockham's Razor. I did not expect my result to be correct, not even approximately so, and was therefore astonished later to find that it checked out against results I found online.</p> <p>Until now, that is. Applying my formula to the same sanity check you used, I get a shift of 3.6 parts in 10^17. That's the right order of magnitude, but 3.6 isn't quite "a bit under 5", so perhaps my formula is not all that accurate after all.</p> <p>As I was saying, however, I decided to write up an explanation of how I acquired my result, and to present it as a faux popular science article aimed at an audience as scientifically literate as myself (i.e. not all that). I did this for three reasons:</p> <p>(1) You learn by doing, and I figured the exercise would benefit me.<br /> (2) An experienced science communicator might be persuaded to have a look and point out all the things I got wrong, and then I'd learn even more.<br /> (3) If I was actually onto something, then said science communicator might be inspired to write a blog post of their own, covering the same ground only better.</p> <p>My article (which is 1000 words long) is here: <a href="https://outerhoard.files.wordpress.com/2015/06/relativity.pdf">https://outerhoard.files.wordpress.com/2015/06/relativity.pdf</a></p> <p>Chad, if there's an idea in there that you can use for a blog post, you are welcome to it. My only request is to be notified if you do.</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648844&amp;1=default&amp;2=en&amp;3=" token="bzHsYb1Rq-3cEheZW59UxcYhl9-k1wLIiFuby7IjNSI"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">Adrian Morgan (not verified)</span> on 08 Aug 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648844">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> <article data-comment-user-id="50" id="comment-1648845" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1439022219"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>3.6 sounds about right, actually. My "a bit less than 5" is based on remembering that the version of the figure in my book has tick marks every 5e17, and the shift is not a full tick mark.</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648845&amp;1=default&amp;2=en&amp;3=" token="0B_wej9-wAcxpnKX0VPk0j77w84hcZCzkvdQIyXRpEQ"></drupal-render-placeholder> </div> <footer> <em>By <a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a> on 08 Aug 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648845">#permalink</a></em> <article typeof="schema:Person" about="/author/drorzel"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/author/drorzel" hreflang="en"><img src="/files/styles/thumbnail/public/pictures/after1-120x120.jpg?itok=XDhUCPqP" width="100" height="100" alt="Profile picture for user drorzel" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/08/07/back-of-the-envelope-gravitational-which-way%23comment-form">Log in</a> to post comments</li></ul> Fri, 07 Aug 2015 07:49:47 +0000 drorzel 48850 at https://scienceblogs.com Tiny Forces, Artificial Materials, and Wobbling Stars: Physics Post Round-Up https://scienceblogs.com/principles/2015/06/19/tiny-forces-artificial-materials-and-wobbling-stars-physics-post-round-up <span>Tiny Forces, Artificial Materials, and Wobbling Stars: Physics Post Round-Up</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>I've been really busy with year-end wrap-up stuff, but have also posted a bunch of stuff at Forbes. which I've fallen down on my obligation to promote here... So, somewhat belatedly, here's a collection of physics-y stuff that I've written recently:</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/06/10/using-atoms-to-measure-tiny-forces/">Using Atoms To Measure Tiny Forces</a>: A post reporting on some very cool atom interferometry experiments, one working to measure the very tiny (but known to exist) force of gravity, the other searching for a possible "fifth force" sort of thing.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/06/11/making-and-shaking-new-materials-with-ultracold-atoms/">Making And Shaking New Materials With Ultracold Atoms</a>: A post reporting on a couple more DAMOP talks, on Cheng Chin's group using physical shaking to simulate unusual band structures, and Cindy Regal's group using single atoms trapped in optical tweezers to study few-body physics.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/06/15/what-are-the-limits-of-physics/">What Are The Limits Of Physics?</a>: Having gone to a bunch of precision-measurement talks at DAMOP, I talk about three rough categories of effects that limit our ability to use experimental physics to understand the universe.</p> <p>-- <a href="http://www.forbes.com/sites/chadorzel/2015/06/18/using-ultrafast-lasers-to-look-for-earth-like-worlds/">Using Ultrafast Lasers To Look For Earth-Like Worlds</a>: A post about the ongoing "astro-comb" project using femtosecond lasers as reference sources to improve radial-velocity measurements for extrasolar planet hunting.</p> <p>The first two were banged out at breakfast while I was at DAMOP, so they're a little rough. I'm very happy with the other two, though. I also had a <a href="http://www.forbes.com/sites/chadorzel/2015/06/16/telling-stories-about-magic-in-a-world-of-science/">post about fictional magic</a> and <a href="http://www.forbes.com/sites/chadorzel/2015/06/17/what-are-academic-conferences-good-for/">one about the real purpose of conference talks</a>.</p> <p>As always, the traffic stats for these are sort of bizarre. Half-assed philosophy of science got about five times the hits of solid physics reports, but the academic conference thing drew so few views that I thought the analytics package might've crashed. Go figure.</p> <p>Anyway, that's what I've been up to. This weekend, I'm off to another meeting, the <a href="https://perimeterinstitute.ca/research/conferences/convergence">Convergence</a> workshop at Perimeter Institute. I'm function mostly as a journalist at this, which ought to be interesting.</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Fri, 06/19/2015 - 02:11</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/academia" hreflang="en">Academia</a></div> <div class="field--item"><a href="/tag/astronomy" hreflang="en">Astronomy</a></div> <div class="field--item"><a href="/tag/atoms-and-molecules" hreflang="en">Atoms and Molecules</a></div> <div class="field--item"><a href="/tag/cold-atoms" hreflang="en">Cold Atoms</a></div> <div class="field--item"><a href="/tag/condensed-matter" hreflang="en">Condensed Matter</a></div> <div class="field--item"><a href="/tag/experiment" hreflang="en">Experiment</a></div> <div class="field--item"><a href="/tag/media-0" hreflang="en">In the Media</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/precision-measurement" hreflang="en">Precision Measurement</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> </div> </div> <div class="field field--name-field-blog-categories field--type-entity-reference field--label-inline"> <div class="field--label">Categories</div> <div class="field--items"> <div class="field--item"><a href="/channel/physical-sciences" hreflang="en">Physical Sciences</a></div> </div> </div> <section> <article data-comment-user-id="0" id="comment-1648792" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1434884372"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>I especially liked the thought that different methods can accelerate pushing the boundaries in your post about the limits of physics. I hope something similar that happended for the dipole moment of the electron will happen for collider physics somehow.</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648792&amp;1=default&amp;2=en&amp;3=" token="L7_FSaVODu_p9Tt3Hg-4k26-AlWHR9DYWXRHxy3t9UU"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">Jakob (not verified)</span> on 21 Jun 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648792">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/06/19/tiny-forces-artificial-materials-and-wobbling-stars-physics-post-round-up%23comment-form">Log in</a> to post comments</li></ul> Fri, 19 Jun 2015 06:11:00 +0000 drorzel 48836 at https://scienceblogs.com Crude Monte Carlo Simulation of Light-Bulb Physics https://scienceblogs.com/principles/2015/05/26/crude-monte-carlo-simulation-of-light-bulb-physics <span>Crude Monte Carlo Simulation of Light-Bulb Physics</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>Last week, I did a post for Forbes on <a href="http://www.forbes.com/sites/chadorzel/2015/05/21/the-surprisingly-complicated-physics-of-a-light-bulb/">the surprisingly complicated physics of a light bulb</a>. Incandescent light bulbs produce a spectrum that's basically blackbody radiation, but if you think about it, that's kind of amazing given that the atoms making up the filament have quantized states, and can absorb and emit only discrete frequencies of light. The transition from the line spectra characteristic of particular atoms to the broad and smooth spectrum of black-body radiation is kind of amazing.</p> <p>The way you get from the one to the other is through repeated off-resonant scattering. The probability of any particular atom emitting a photon with a wavelength drastically different from its characteristic spectral lines is extremely low, but it can happen. And once it does, those new photons are unlikely to scatter again. So, in a sufficiently large sample of atoms, where an emitted photon is guaranteed to scatter many times on the way out, the light that finally escapes is pushed to longer wavelengths.</p> <p>That post is based on <a href="http://scienceblogs.com/principles/2013/09/25/things-ive-never-quite-understood-microscopic-picture-of-blackbody-radiation/">this old blog post thinking out loud about this stuff</a>, and more specifically on <a href="http://scitation.aip.org/content/aapt/journal/ajp/73/3/10.1119/1.1819931?ver=pdfcov">this AJP article that I was pointed to in the comments to that post</a>. The article includes a simple model showing how you can take a bunch of two-level "hydrogen" atoms that absorb and emit in the deep ultraviolet (Lyman-alpha light, in spectroscopic terms) and end up with a black-body spectrum once the sample gets sufficiently optically thick.</p> <p>It's a very nice paper, and I recommend reading it, but it does have one aspect that might feel like a cheat. The spectra they generate are based on solving the equations Einstein used in his famous 1917 paper on the statistical behavior of light quanta, assuming a particular temperature for the atoms. They do some work to get this in terms of the optical thickness of the sample, but they're always dealing with continuous functions, not discrete probabilistic absorption.</p> <p>On some level, what you'd really like to see is a Monte Carlo simulation of this sort of thing, where you look at absorption and emission events by individual atoms, and see how that builds up light at lower frequencies. So I wrote one.</p> <p>Well,sort of. My numerical simulation skills remain pretty rudimentary, but I cobbled together a crude thing in VPython. I put the code on Gist (GlowScript didn't like it), so you can point and laugh:</p> <script src="https://gist.github.com/orzelc/a36be32c84b79c9508b2.js"></script><p> So, what is this doing? Well, I imagined a collection of "atoms" with a single transition frequency that it likes to absorb or emit, but two lower-frequency modes of possible light. Why three? Because that lets me store the state of the light as a vector object in VPython, saving me from having to figure out how to do arrays with more components. I imagined a single photon of light at the main transition frequency coming into a large array of these atoms, which could absorb it and then re-emit something.</p> <p>A photon at the main transition frequency is represented by a vector (1,0,0), and is assumed to be absorbed (you could imagine lots of additional atoms that get skipped over). It can then emit a photon of one of three frequencies: the main transition (in which case the state vector goes back to (1,0,0)), a somewhat lower frequency (changing the vector to (0,1,0) with a 1% probability) or a really low frequency (changing the vector to (0,0,1) with a 0.01% probability).</p> <p>A medium-frequency photon has a 1% chance of being absorbed at the next step, and a low-frequency photon has a 0.01% chance of being absorbed. If either of these get absorbed, they preferentially emit back to the state-- so if the state is (0,0,1) and it gets absorbed, there's a 1% chance of going to (0,1,0) and a 0.01% chance of going to (1,0,0).</p> <p>Then this process gets repeated a whole bunch of times (ranging from 10 to 1,000,000), and we record the final state. That process then gets repeated 1000 times to give a probability of ending up in each of the three states. All this repetition leads to the following graph:</p> <div style="width: 610px;display:block;margin:0 auto;"><a href="/files/principles/files/2015/05/blackbody_sim.jpg"><img src="/files/principles/files/2015/05/blackbody_sim.jpg" alt="Results of the crude Monte Carlo simulation in the text." width="600" height="464" class="size-full wp-image-10054" /></a> Results of the crude Monte Carlo simulation in the text. </div> <p>The graph is a log-log plot (so each division increases by a factor of 10) showing the probability of ending up in each of the photon states-- the strongly absorbing resonant state, the medium-frequency state, and the weakly absorbing low-frequency state-- as a function of the number of absorption steps in the simulation.</p> <p>A small number of steps corresponds to an optically thin sample-- the initial photon gets absorbed and re-emitted at most 10 times on the way through. As you would expect, this mostly leaves you with light at the resonant frequency, with a low probability of finding either of the other two-- about a 10% chance of the medium-frequency photon, and 0.1% of the low-frequency state. Those are about what you would expect-- with a 1% probability of emitting into the medium state, you you would expect about a 10% chance that this would happen in a set of 10 scattering steps. </p> <p>As you increase the number of scattering steps, though, the chance of finding the lower frequency increases dramatically. By 200 absorptions, the probability of ending up in the medium state has shot up to about 90%, and after 1,000,000 absorptions there's a 60% chance of ending up in the weakly absorbing low-frequency state. This would presumably increase further for even more steps, but running through the loop a billion times took most of a lecture class period, and I don't have the patience to push it even further.</p> <p>What's going on here? Well, it's the process described in the AJP paper: there's a very low probability of scattering into an off-resonant state, and once that happens, those photons are unlikely to scatter again. Which means that, over a long cycle of scattering, these highly improbable events inevitably push the state of the light toward the low frequency.</p> <p>Now, there's a bunch of work to get from here to a black-body state (doing this right would need to start with a Maxwell-Boltzmann distribution of energies corresponding to some temperature, and include a lot more frequencies), but this illustrates the basic idea. Well enough for a blog post, anyway.</p> <p>------------</p> <p>(One technical note here: I dithered about what to use for the emission probability when an off-resonant photon scatters; this version of the simulation has it preferentially emit back to the same state that was originally absorbed (so (0,0,1) goes back to (0,0,1) most of the time, and only rarely to (1,0,0)). This is basically mapping a classical sort of frequency response onto the photon picture. The other thing you could do would be to treat it as a true absorption to the imaginary excited state, which would then emit with the same probability as the original state (so when a (0,0,1) state gets absorbed, it usually emits to (1,0,0) and only rarely back to (0,0,1). In that case, you see a similar sort of behavior, but the end result is rough parity between the three states.</p> <p>(For completeness, that graph looks like this:</p> <div style="width: 610px;display:block;margin:0 auto;"><a href="/files/principles/files/2015/05/blackbody_sim_2.jpg"><img src="/files/principles/files/2015/05/blackbody_sim_2.jpg" alt="Results of the Monte Carlo simulation described in the test, with a different emission probability.)" width="600" height="464" class="size-full wp-image-10055" /></a> Results of the Monte Carlo simulation described in the test, with a different emission probability. </div> <p>(As I said, I dithered about this for a while; I think the first graph is the right way to do it, and it's easier to see a path from that to the expected result of a black-body spectrum. I am not 100% confident in this, though; there might be some way to get from rough parity to a black-body spectrum through the Maxwell-Boltzmann distribution of energies. Which is why this is a blog post, and not a paper written up to submit to AJP.)</p> <p>(Though if anybody with genuine computational skills wanted to collaborate on doing a better job of this, I'd be happy to talk about that...)</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Tue, 05/26/2015 - 03:38</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/atoms-and-molecules" hreflang="en">Atoms and Molecules</a></div> <div class="field--item"><a href="/tag/computing" hreflang="en">Computing</a></div> <div class="field--item"><a href="/tag/education" hreflang="en">education</a></div> <div class="field--item"><a href="/tag/optics" hreflang="en">Optics</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> <div class="field--item"><a href="/tag/simulations" hreflang="en">Simulations</a></div> </div> </div> <section> <article data-comment-user-id="0" id="comment-1648774" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1432627229"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>Very cool! The whole way through I was thinking I'd really like to see the real blackbody spectrum emerge out of this... maybe we should talk about that collaboration? :-)</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648774&amp;1=default&amp;2=en&amp;3=" token="_9sKXjnJCW0zdkvsmKSzb8YRu8oG_BAxJeyrdBWXd2w"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">David Zaslavsky (not verified)</span> on 26 May 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648774">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> <article data-comment-user-id="0" id="comment-1648775" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1432632080"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>Coming from a condensed matter background, it's a bit unexpected to see talk of discrete quantized states in a metallic conductor. The analysis you describe would seem right for me in the context of a very large volume of diffuse tungsten atomic vapour, but in a metallic filament the proximity of nuclei plays havoc on the Bohr model. Instead, we typically describe the electrical and thermal properties of metals in terms of an electron gas. In the basic undergraduate model it's quite successfully modeled in terms of a large collection of non-interacting fermions in a rectangular quantum well.</p> <p>In that basic model, the Fermi sea fills up to a certain depth based on the electron density. At absolute zero you'd have a sharp boundary below which all energy states are filled, and above which all are empty. At non-zero temperature, we describe a diffuse interface with a width roughly the same as the Boltzmann energy width (1/40 eV at room temperature). Electrons that absorb thermal energy and are promoted into the nominally empty high-energy region are free to drop back into an effective continuum of unoccupied lower-energy states, emitting photons along the way. You don't expect to see sharp emission lines in this context.</p> <p>Now, I would be interested in finding out whether your model reproduces a black-body curve for the case that it describes, but I maintain that this would be showing us the behaviour of a low-density atomic vapour, and I believe that you'd still see sharp absorption and emission lines due to edge effects at the boundary of the vapour cloud, as not all photons get a chance to pass into the main body of the cloud.</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648775&amp;1=default&amp;2=en&amp;3=" token="H5tJo6pTUt0VqKljMyhJo0rHAvZFdSlpRHUHgL89snI"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">Christopher (not verified)</span> on 26 May 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648775">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> <article data-comment-user-id="0" id="comment-1648776" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1432649540"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>The little bit I remember from astro, concerning the formation of stellar spectral lines. At any given point in frequency and depth inside the atmosphere assume local thermodynamic equilibrium. Then the ratio of emission to absorption would be one, is the radiation field was the Plank distribution at the local temperature. So we can calculate the strength of the emission at a given frequency and beamangle by integrating over the optical depth, emission is delta opacity times the plank function, degraded by the absorption along the line of site (exp(-opacity). A back of the envelope approximation is to just use the Plank distribution at the temperature where the optical depth is unity. So if the bulb filament's temperature doesn't change too much with depth, you would expect a black body spectrum. Near line centers the emission is from very close to the surface. In more transparent frequencies the effective emission depth is greater. If you assume the radiation field at any given depth is near Plankian, then the scattered photons will also be (near) Plankian.</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648776&amp;1=default&amp;2=en&amp;3=" token="696MJRftgp1O7vaXpAmRIeoeOtRkd-VhVD8O0nYhYSs"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">Omega Centauri (not verified)</span> on 26 May 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648776">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/05/26/crude-monte-carlo-simulation-of-light-bulb-physics%23comment-form">Log in</a> to post comments</li></ul> Tue, 26 May 2015 07:38:24 +0000 drorzel 48826 at https://scienceblogs.com Amazing Blackbody Radiation and LHC Basics https://scienceblogs.com/principles/2015/05/22/amazing-blackbody-radiation-and-lhc-basics <span>Amazing Blackbody Radiation and LHC Basics</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>I was proctoring an exam yesterday in two different sections of the same class, so I had a <em>lot</em> of quite time. Which means I wrote not one but two new posts for Forbes...</p> <p>The first continues a loose series of posts about the exotic physics behind everyday objects (something I'm toying with as a possible theme for a new book...), looking at <a href="http://www.forbes.com/sites/chadorzel/2015/05/21/the-surprisingly-complicated-physics-of-a-light-bulb/">the surprisingly complicated physics of an incandescent light bulb</a>. A light bulb filament emits (to a reasonable approximation) black-body radiation, which is historically important as the starting point for quantum physics. But when you think about it, it's kind of amazing that you get a black-body spectrum from a large collection of atoms that absorb and emit at discrete frequencies...</p> <p>(As I type this, I have a crude Monte Carlo simulation running in VPython, so there will be more on this subject later...)</p> <p>The second post was prompted by the news that the LHC is <a href="http://home.web.cern.ch/about/updates/2015/05/first-images-collisions-13-tev">now colliding protons at 13TeV</a>, and offers <a href="http://www.forbes.com/sites/chadorzel/2015/05/21/things-to-know-as-the-large-hadron-collider-breaks-energy-records/">answers to some really basic questions about the LHC</a>.</p> <p>So, you know, if you'd like some physics-y stuff to read as you wait for the official start of the weekend, well, there you go...</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Fri, 05/22/2015 - 05:09</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/atoms-and-molecules" hreflang="en">Atoms and Molecules</a></div> <div class="field--item"><a href="/tag/experiment" hreflang="en">Experiment</a></div> <div class="field--item"><a href="/tag/media-0" hreflang="en">In the Media</a></div> <div class="field--item"><a href="/tag/optics" hreflang="en">Optics</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> <div class="field--item"><a href="/tag/theory" hreflang="en">Theory</a></div> </div> </div> <section> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/05/22/amazing-blackbody-radiation-and-lhc-basics%23comment-form">Log in</a> to post comments</li></ul> Fri, 22 May 2015 09:09:10 +0000 drorzel 48824 at https://scienceblogs.com Hyperactive Dogs and Fancy Motorcycles https://scienceblogs.com/principles/2015/05/05/hyperactive-dogs-and-fancy-motorcycles <span>Hyperactive Dogs and Fancy Motorcycles</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>I'm still in the late stages of an awful cold, but shook it off a bit to write a <a href="http://www.forbes.com/sites/chadorzel/2015/05/05/the-quantum-physics-of-fenced-in-dogs/">new conversation with Emmy, the Queen of Niskayuna</a> over at Forbes:</p> <blockquote><p> “HEY! YOU POODLES! STAY OFFA MY LAWN!”</p> <p>“Emmy! Stop barking!” I sit up. She’s at the gap between the fences, where she can see into the front yard.</p> <p>“But, those poodles..”</p> <p>“We’ve had this conversation. It’s a public street, other dogs are allowed to walk on it. No barking.” She comes over, sheepishly. “Why can’t you just lie down and enjoy the nice day, hmm?”</p> <p>“Well, I would. But, you know… Quantum.”</p> <p>“What?”</p> <p>“I would love to just lie in the sun, but I can’t. You should understand– it’s quantum physics.”</p> <p>I look at her. She looks back.</p> <p>I rub my temples. She wags her tail cheerfully.</p> <p>I’m going to regret this. “Oh, fine. How does quantum physics explain your inability to quietly bask in the sun without getting up every two minutes?”</p> <p>“I’m glad you asked. See, it’s all about confinement..." </p></blockquote> <p>There's also a human-centered explanation, after the conversation with Emmy, that brings in Richard Thompson:</p> <iframe width="560" height="315" src="https://www.youtube.com/embed/j0kJdrfzjAg" frameborder="0" allowfullscreen=""></iframe><p> So, if that combination sounds interesting, well, <a href="http://www.forbes.com/sites/chadorzel/2015/05/05/the-quantum-physics-of-fenced-in-dogs/">head over to Forbes and read the whole thing</a>...</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Tue, 05/05/2015 - 05:31</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/atoms-and-molecules" hreflang="en">Atoms and Molecules</a></div> <div class="field--item"><a href="/tag/books-0" hreflang="en">Books</a></div> <div class="field--item"><a href="/tag/how-teach" hreflang="en">How-to-Teach</a></div> <div class="field--item"><a href="/tag/music-0" hreflang="en">Music</a></div> <div class="field--item"><a href="/tag/outreach" hreflang="en">Outreach</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/physics-emmy" hreflang="en">Physics with Emmy</a></div> <div class="field--item"><a href="/tag/pop-culture" hreflang="en">Pop Culture</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> </div> </div> <section> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/05/05/hyperactive-dogs-and-fancy-motorcycles%23comment-form">Log in</a> to post comments</li></ul> Tue, 05 May 2015 09:31:51 +0000 drorzel 48816 at https://scienceblogs.com Einstein and Revolution https://scienceblogs.com/principles/2015/04/28/einstein-and-revolution <span>Einstein and Revolution</span> <div class="field field--name-body field--type-text-with-summary field--label-hidden field--item"><p>As mentioned over the weekend, I gave a talk last week for UCALL, part of a series on "The Radical Early 20th Century." I talked about how relativity is often perceived as revolutionary, but isn't really, while Einstein's really revolutionary 1905 paper is often overlooked. And, having put the time into thinking about the subject, I turned the basic theme into a <a href="http://www.forbes.com/sites/chadorzel/2015/04/28/einstein-a-radical-but-not-a-rebel/">new blog post over at Forbes</a>:</p> <blockquote><p> Albert Einstein is easily one of the most recognizable people in history, and everybody thinks they know why. He’s the guy who, in 1905, completely revolutionized physics, overthrowing the prior order with a stroke of a pen and ushering in the modern era.</p> <p>Only, he’s not. At least, not in the way you think. Einstein’s best known for the Theory of Relativity, the first part of which was published in 1905, but this was not, in fact, all that revolutionary. His actual revolutionary contribution to physics in that year was his paper on the photoelectric effect. This is somewhat overlooked, though it’s the one thing specifically mentioned in his Nobel Prize citation, and it played an essential role in launching quantum mechanics. </p></blockquote> <p>The actual lecture last week included a good deal more science, specifically a more detailed discussion of relativity with spacetime diagrams leading up to an explanation of why FTL travel is impossible, and a more detailed explanation of how Planck's quantum hypothesis fixes the blackbody radiation problem. But I'm keeping things non-technical at Forbes; maybe I'll upload the slides to SlideShare and post them here tomorrow. First, though, I need to grade a giant pile of exams...</p> </div> <span><a title="View user profile." href="/author/drorzel" lang="" about="/author/drorzel" typeof="schema:Person" property="schema:name" datatype="">drorzel</a></span> <span>Tue, 04/28/2015 - 07:04</span> <div class="field field--name-field-blog-tags field--type-entity-reference field--label-inline"> <div class="field--label">Tags</div> <div class="field--items"> <div class="field--item"><a href="/tag/history-science" hreflang="en">History of Science</a></div> <div class="field--item"><a href="/tag/physics" hreflang="en">Physics</a></div> <div class="field--item"><a href="/tag/quantum-optics" hreflang="en">Quantum Optics</a></div> <div class="field--item"><a href="/tag/relativity" hreflang="en">Relativity</a></div> <div class="field--item"><a href="/tag/science" hreflang="en">Science</a></div> </div> </div> <section> <article data-comment-user-id="0" id="comment-1648721" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1430229505"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>The Nobel prize was granted to Einstein in 1921 as a compromise. He had been nominated several times, for relativity theory, but the theory was viewed as being "jewish" and antisemitism was widespread. Granting the prize for the photoelectric effect seemed, at the time, to be less controversial. If anything, that goes against the idea that relativity was not Einstein's most revolutionary idea.</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648721&amp;1=default&amp;2=en&amp;3=" token="IAYwfWoUcJtK_dIpXtdZXOnZQnhszrUk7Y96VWfkSDY"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">David (not verified)</span> on 28 Apr 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648721">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> <article data-comment-user-id="0" id="comment-1648722" class="js-comment comment-wrapper clearfix"> <mark class="hidden" data-comment-timestamp="1430231261"></mark> <div class="well"> <strong></strong> <div class="field field--name-comment-body field--type-text-long field--label-hidden field--item"><p>All knowledge contributes to revolution, it changes us and our environment for ever. We are revolutionary creatures, come what may of it and we are packing a bigger and bigger punch.<br /> Fate has a habit of punching back and I dare say we have a serious contest on our hands. Originally the Catholic Church did its best to stem progress now other loud voices are trying to take control and at least guide our actions. Einstein had a great mind, great minds like great guns can be dangerous.</p> </div> <drupal-render-placeholder callback="comment.lazy_builders:renderLinks" arguments="0=1648722&amp;1=default&amp;2=en&amp;3=" token="VajKUYF7Y5bnHVo0tl4Pqp44vLSfb_KsdTB-ETBQsYQ"></drupal-render-placeholder> </div> <footer> <em>By <span lang="" typeof="schema:Person" property="schema:name" datatype="">magnocrat (not verified)</span> on 28 Apr 2015 <a href="https://scienceblogs.com/taxonomy/term/11484/feed#comment-1648722">#permalink</a></em> <article typeof="schema:Person" about="/user/0"> <div class="field field--name-user-picture field--type-image field--label-hidden field--item"> <a href="/user/0" hreflang="und"><img src="/files/styles/thumbnail/public/default_images/icon-user.png?itok=yQw_eG_q" width="100" height="100" alt="User Image" typeof="foaf:Image" class="img-responsive" /> </a> </div> </article> </footer> </article> </section> <ul class="links inline list-inline"><li class="comment-forbidden"><a href="/user/login?destination=/principles/2015/04/28/einstein-and-revolution%23comment-form">Log in</a> to post comments</li></ul> Tue, 28 Apr 2015 11:04:38 +0000 drorzel 48813 at https://scienceblogs.com