<story><title>People can sense single photons</title><url>http://www.nature.com/news/people-can-sense-single-photons-1.20282</url></story><parent_chain><item><author>white-flame</author><text>If you pay close attention in very low level light situations, you&amp;#x27;ll notice that what you do see (or at least what &lt;i&gt;I&lt;/i&gt; see) is actually reminiscent of the RGB graininess of low level light photographs.  That graininess is to my understanding caused by the variation of the number of photons hitting that portion of the receptors, which is unnoticeable when flooded with quadjillions of them in decent lighting.&lt;p&gt;So this is a nice semi-expected result in this experiment, though it does seem to be near the limit of default human perception.&lt;p&gt;I wonder how well somebody could train themselves to notice single-photon events, much like musicians can notice tiny audio events and variations.</text></item></parent_chain><comment><author>devindotcom</author><text>Actually, I would guess that the &amp;#x27;noise&amp;#x27; you see is from the highly noisy system of retinal ganglia and such... the eye is a wonderful thing but it has a few, shall we say, quirks. Check out this diagram:&lt;p&gt;&lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.corpshumain.ca&amp;#x2F;en&amp;#x2F;images&amp;#x2F;Retine_couches_couleur_(FF)_en.jpg&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.corpshumain.ca&amp;#x2F;en&amp;#x2F;images&amp;#x2F;Retine_couches_couleur_(...&lt;/a&gt;&lt;p&gt;Note that the light comes from the TOP and passes through all those layers before hitting the photosensitive one!&lt;p&gt;So - at the Earth&amp;#x27;s surface, even on a very dark night, I think you would be receiving far, far too many photons for them to each register as a sort of noise blob. More likely it is the natural noise of your nervous system as it does all the things that cells need to do and produces the slight visible side effect that&amp;#x27;s more pronounced in darkness and low contrast.&lt;p&gt;Edit: Also, since I remember this coming up in my neuro classes, this has been shown in less rigorous experimentation before:&lt;p&gt;&lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;math.ucr.edu&amp;#x2F;home&amp;#x2F;baez&amp;#x2F;physics&amp;#x2F;Quantum&amp;#x2F;see_a_photon.html&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;math.ucr.edu&amp;#x2F;home&amp;#x2F;baez&amp;#x2F;physics&amp;#x2F;Quantum&amp;#x2F;see_a_photon.h...&lt;/a&gt;</text></comment>
<story><title>People can sense single photons</title><url>http://www.nature.com/news/people-can-sense-single-photons-1.20282</url></story><parent_chain><item><author>white-flame</author><text>If you pay close attention in very low level light situations, you&amp;#x27;ll notice that what you do see (or at least what &lt;i&gt;I&lt;/i&gt; see) is actually reminiscent of the RGB graininess of low level light photographs.  That graininess is to my understanding caused by the variation of the number of photons hitting that portion of the receptors, which is unnoticeable when flooded with quadjillions of them in decent lighting.&lt;p&gt;So this is a nice semi-expected result in this experiment, though it does seem to be near the limit of default human perception.&lt;p&gt;I wonder how well somebody could train themselves to notice single-photon events, much like musicians can notice tiny audio events and variations.</text></item></parent_chain><comment><author>rcthompson</author><text>My understanding is that the &amp;quot;grain&amp;quot; is not necessarily caused by your eyes detecting isolated photons, but rather by the electrons in the light-absorbing molecules of your rods &amp;amp; cones becoming spontaneously excited by ambient heat energy rather than absorption of a photon. Either way, it shows that we can indeed consciously perceive single-molecule excitation events, whatever the cause.</text></comment>