Can a Human See a Single Photon? (1996)
Would there be any interest in a series I&#x27;ve been thinking of putting together about all the fantastically counterintuitive ways your eye fools you without you even noticing? Example:<p><a href="https:&#x2F;&#x2F;media.giphy.com&#x2F;media&#x2F;3o7btPOMufN5FziFWg&#x2F;giphy.gif" rel="nofollow">https:&#x2F;&#x2F;media.giphy.com&#x2F;media&#x2F;3o7btPOMufN5FziFWg&#x2F;giphy.gif</a><p>The fact that colors influence colors around them means that there are far more than 256^3 viewable colors: the spatial axis is like a fourth channel.<p>Another fun one: If you take a paper plate and poke a hole in it, then take a toothpick and stick it in front of the hole, from the bottom, pointing upwards.... Then it&#x27;ll look like it&#x27;s coming <i>down</i> from the top! It&#x27;s very hard to explain in words, but basically it&#x27;s a pinhole camera, so everything appears upside-down. Your brain tries to compensate and flips it right side up, but it can&#x27;t quite do that with the toothpick-hole scenario. So when you push the toothpick up from the bottom, it looks like it&#x27;s coming down from the top.<p>Lastly: <a href="https:&#x2F;&#x2F;i.imgur.com&#x2F;epXYhJd.png" rel="nofollow">https:&#x2F;&#x2F;i.imgur.com&#x2F;epXYhJd.png</a> If you cover up the top half of the image, the bottom looks gray. But the strawberries look red.<p>A fun puzzle is, how do you see an individual pixel? Can you think of any common object that would help you do this?
 (No magnifying lenses, for example, and using a phone is sort of cheating.) Answer below.<p>...<p>Answer: pluck a hair out of your head and put it on your screen. The line along the edge of the hair will turn into a stairstep pattern, which is just another way of saying you can see individual pixels.