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	<title>Comments on: Atoms, the Equivalence Principle, and Dueling Laureates</title>
	<atom:link href="http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/feed/" rel="self" type="application/rss+xml" />
	<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/</link>
	<description>Random samplings from a universe of ideas.</description>
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		<title>By: Matt B.</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-155185</link>
		<dc:creator>Matt B.</dc:creator>
		<pubDate>Fri, 04 Mar 2011 23:16:39 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-155185</guid>
		<description>Anonymous_Snowboarder, if it actually is &lt;i&gt;spare&lt;/i&gt; time, then it&#039;s okay.

As for the technobabble, a better phrasing is &quot;Time runs more slowly for an object when it is in in a deeper gravitational potential &lt;i&gt;than the observer&lt;/i&gt;.&quot; Because when &lt;i&gt;you&lt;/i&gt; are deep in a gravitational potential, everything runs more quickly than if you weren&#039;t as deep.</description>
		<content:encoded><![CDATA[<p>Anonymous_Snowboarder, if it actually is <i>spare</i> time, then it&#8217;s okay.</p>
<p>As for the technobabble, a better phrasing is &#8220;Time runs more slowly for an object when it is in in a deeper gravitational potential <i>than the observer</i>.&#8221; Because when <i>you</i> are deep in a gravitational potential, everything runs more quickly than if you weren&#8217;t as deep.</p>
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		<title>By: Dave</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154963</link>
		<dc:creator>Dave</dc:creator>
		<pubDate>Wed, 02 Mar 2011 17:23:38 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154963</guid>
		<description>Consider two hypotheticals:

If Chu watches a soccer game every week, should citizens complain?

If Chu spends every Saturday afternoon doing physics research, should citizens complain?

Science can be done as a hobby.</description>
		<content:encoded><![CDATA[<p>Consider two hypotheticals:</p>
<p>If Chu watches a soccer game every week, should citizens complain?</p>
<p>If Chu spends every Saturday afternoon doing physics research, should citizens complain?</p>
<p>Science can be done as a hobby.</p>
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		<title>By: Anonymous_Snowboarder</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154417</link>
		<dc:creator>Anonymous_Snowboarder</dc:creator>
		<pubDate>Fri, 25 Feb 2011 02:12:45 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154417</guid>
		<description>Regardless of the merits of the work (if any), this is highly objectionable if it was done while Energy Secretary.  &lt;i&gt;That&lt;/i&gt; is his full time job and frankly I don&#039;t think it allows for any free time for moon lighting.  Do you think the President should be writing for law journals in his spare time? Or the Sec. Defense perhaps indulging in writing a spy novel during his &lt;i&gt;spare&lt;/i&gt; time?   Any prior obligations are just that - prior - once you accept a position such as his.</description>
		<content:encoded><![CDATA[<p>Regardless of the merits of the work (if any), this is highly objectionable if it was done while Energy Secretary.  <i>That</i> is his full time job and frankly I don&#8217;t think it allows for any free time for moon lighting.  Do you think the President should be writing for law journals in his spare time? Or the Sec. Defense perhaps indulging in writing a spy novel during his <i>spare</i> time?   Any prior obligations are just that &#8211; prior &#8211; once you accept a position such as his.</p>
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		<title>By: wds</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154355</link>
		<dc:creator>wds</dc:creator>
		<pubDate>Thu, 24 Feb 2011 15:32:27 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154355</guid>
		<description>@Paul #8: One can only guess how much time the man still has for research, but likely this is something he was already working on before he switched jobs.</description>
		<content:encoded><![CDATA[<p>@Paul #8: One can only guess how much time the man still has for research, but likely this is something he was already working on before he switched jobs.</p>
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		<title>By: ian</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154354</link>
		<dc:creator>ian</dc:creator>
		<pubDate>Thu, 24 Feb 2011 15:23:41 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154354</guid>
		<description>The guy is a Nobel laureate. I&#039;m sure he can contribute to a paper or two without neglecting his job. Plus, it&#039;s in the national interest that he keep doing some science on the side.</description>
		<content:encoded><![CDATA[<p>The guy is a Nobel laureate. I&#8217;m sure he can contribute to a paper or two without neglecting his job. Plus, it&#8217;s in the national interest that he keep doing some science on the side.</p>
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		<title>By: Paul</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154352</link>
		<dc:creator>Paul</dc:creator>
		<pubDate>Thu, 24 Feb 2011 14:40:20 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154352</guid>
		<description>Why is the secretary listed as a coauthor anyways?  Was this work performed  before he took the post, or is he truly engaged in this work in his &#039;free time&#039;?</description>
		<content:encoded><![CDATA[<p>Why is the secretary listed as a coauthor anyways?  Was this work performed  before he took the post, or is he truly engaged in this work in his &#8216;free time&#8217;?</p>
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		<title>By: Jolyon</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154343</link>
		<dc:creator>Jolyon</dc:creator>
		<pubDate>Thu, 24 Feb 2011 05:56:02 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154343</guid>
		<description>There&#039;s a second paper which disputes whether or not the phase of an atom is a clock. http://arxiv.org/abs/1102.2587
I find this reference much easier to read than the Wolf et al paper, and I think that the argument presented here is more compelling.</description>
		<content:encoded><![CDATA[<p>There&#8217;s a second paper which disputes whether or not the phase of an atom is a clock. <a href="http://arxiv.org/abs/1102.2587" rel="nofollow">http://arxiv.org/abs/1102.2587</a><br />
I find this reference much easier to read than the Wolf et al paper, and I think that the argument presented here is more compelling.</p>
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		<title>By: Shantanu</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154342</link>
		<dc:creator>Shantanu</dc:creator>
		<pubDate>Thu, 24 Feb 2011 04:16:14 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154342</guid>
		<description>Sean, there is one more paper on this 
http://arxiv.org/abs/1102.2587
Also this is another example of why interpretation of results in experimental gravity is hard.
another example been the measurement of speed of gravity in jovian deflection experiment.
Sean, now that you finally blogged about this , maybe you could also do the same on that experiment(although its now 9 years old now)</description>
		<content:encoded><![CDATA[<p>Sean, there is one more paper on this<br />
<a href="http://arxiv.org/abs/1102.2587" rel="nofollow">http://arxiv.org/abs/1102.2587</a><br />
Also this is another example of why interpretation of results in experimental gravity is hard.<br />
another example been the measurement of speed of gravity in jovian deflection experiment.<br />
Sean, now that you finally blogged about this , maybe you could also do the same on that experiment(although its now 9 years old now)</p>
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		<title>By: Baby Bones</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154341</link>
		<dc:creator>Baby Bones</dc:creator>
		<pubDate>Thu, 24 Feb 2011 03:53:49 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154341</guid>
		<description>Actually, I read a criticism of atomic clocks not being good clocks for relativistic experiments back in high school in the 1970&#039;s. The book was Relativity Reexamined by Leon Brillouin, a treatise basically contentious of all things relativistic, but probably worth the notes on good clocks and bad clocks. 

Also, Julian Schwinger had an idea about the Mossbauer effect that went against his contemporaries, whereby there is no initial impulse on one atom from the decay that is transferred to other atoms of the lattice but rather the impulse is on the whole ionic lattice through their quantum superposition. That idea now sounds sounder, at least to me, since I heard that the protein folding problem was recently &#039;solved&#039; by two Chinese physicists. If large protein molecules can select a shape via a large superposition, such effects should also be present in metal lattices. So maybe the Mossbauer effect has a similar explanation, and that might affect the definition of a Mossbauer clock.</description>
		<content:encoded><![CDATA[<p>Actually, I read a criticism of atomic clocks not being good clocks for relativistic experiments back in high school in the 1970&#8242;s. The book was Relativity Reexamined by Leon Brillouin, a treatise basically contentious of all things relativistic, but probably worth the notes on good clocks and bad clocks. </p>
<p>Also, Julian Schwinger had an idea about the Mossbauer effect that went against his contemporaries, whereby there is no initial impulse on one atom from the decay that is transferred to other atoms of the lattice but rather the impulse is on the whole ionic lattice through their quantum superposition. That idea now sounds sounder, at least to me, since I heard that the protein folding problem was recently &#8216;solved&#8217; by two Chinese physicists. If large protein molecules can select a shape via a large superposition, such effects should also be present in metal lattices. So maybe the Mossbauer effect has a similar explanation, and that might affect the definition of a Mossbauer clock.</p>
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		<title>By: 23 February 2011 &#171; blueollie</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154336</link>
		<dc:creator>23 February 2011 &#171; blueollie</dc:creator>
		<pubDate>Thu, 24 Feb 2011 02:08:07 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154336</guid>
		<description>[...] does our Secretary of Energy do in his spare time? He thinks about things like this: Good to know that our Secretary of Energy, Steve Chu, is still able to unwind from a long day of [...]</description>
		<content:encoded><![CDATA[<p>[...] does our Secretary of Energy do in his spare time? He thinks about things like this: Good to know that our Secretary of Energy, Steve Chu, is still able to unwind from a long day of [...]</p>
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		<title>By: Carl Brannen</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154335</link>
		<dc:creator>Carl Brannen</dc:creator>
		<pubDate>Thu, 24 Feb 2011 02:00:45 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154335</guid>
		<description>I looked briefly at both papers and I think they&#039;re both right. Let me give a different way of looking at the Schwarzschild solution. Instead of Schwarzschild coordinates, use Gullstrand-Painleve (GP). See the wikipedia article for details, or better, see the generalization to Kerr metric (rotating black hole) coordinates in the &quot;river model of black holes&quot;: http://arxiv.org/abs/gr-qc/0411060

Anyway, in GP coordinates (which of course give the same physical results as any other GR coordinate choice), the gravitational potential does not change the time rate of clocks. Instead, objects closer to the gravitating body are modeled as moving. So the effect on clocks becomes a pure Doppler effect (the test body closer to the gravitating body is the traveling twin). This is basically a question of the universality of free fall.

I think that the real point of the Wolf et al paper is not that the experiment doesn&#039;t measure anything, but instead that we&#039;re lacking a theory that would predict a difference. If there&#039;s any problem, it&#039;s with the imagination of the gravitation theorists.</description>
		<content:encoded><![CDATA[<p>I looked briefly at both papers and I think they&#8217;re both right. Let me give a different way of looking at the Schwarzschild solution. Instead of Schwarzschild coordinates, use Gullstrand-Painleve (GP). See the wikipedia article for details, or better, see the generalization to Kerr metric (rotating black hole) coordinates in the &#8220;river model of black holes&#8221;: <a href="http://arxiv.org/abs/gr-qc/0411060" rel="nofollow">http://arxiv.org/abs/gr-qc/0411060</a></p>
<p>Anyway, in GP coordinates (which of course give the same physical results as any other GR coordinate choice), the gravitational potential does not change the time rate of clocks. Instead, objects closer to the gravitating body are modeled as moving. So the effect on clocks becomes a pure Doppler effect (the test body closer to the gravitating body is the traveling twin). This is basically a question of the universality of free fall.</p>
<p>I think that the real point of the Wolf et al paper is not that the experiment doesn&#8217;t measure anything, but instead that we&#8217;re lacking a theory that would predict a difference. If there&#8217;s any problem, it&#8217;s with the imagination of the gravitation theorists.</p>
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		<title>By: Sean</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154322</link>
		<dc:creator>Sean</dc:creator>
		<pubDate>Wed, 23 Feb 2011 17:19:24 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154322</guid>
		<description>Of course!  (Fooled my dissertation committee, anyway.)</description>
		<content:encoded><![CDATA[<p>Of course!  (Fooled my dissertation committee, anyway.)</p>
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		<title>By: Jasper</title>
		<link>http://blogs.discovermagazine.com/cosmicvariance/2011/02/23/atoms-the-equivalence-principle-and-dueling-laureates/comment-page-1/#comment-154321</link>
		<dc:creator>Jasper</dc:creator>
		<pubDate>Wed, 23 Feb 2011 17:10:54 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/cosmicvariance/?p=6246#comment-154321</guid>
		<description>... not that it actually IS technobabble, of course. :)</description>
		<content:encoded><![CDATA[<p>&#8230; not that it actually IS technobabble, of course. <img src='http://blogs.discovermagazine.com/cosmicvariance/wp-includes/images/smilies/icon_smile.gif' alt=':)' class='wp-smiley' /> </p>
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