I've long had this pet theory that soaring birds have a fine vision that allows them to see thermals (warm ascending currents) directly, through changes in the air's refraction index. I've searched a bit, but no research seems to ever have considered the question. Just a wild theory, though.
The NPR has a good explanation of how it works in their video:<p><a href="https://www.youtube.com/watch?v=px3oVGXr4mo" rel="nofollow">https://www.youtube.com/watch?v=px3oVGXr4mo</a>
Purely out of curiosity, has anyone used this in conjunction with a linguistics study to visualise sounds made during speech? I did a quick literature search but couldn't find anything. Not sure whether if features would be too subtle to see anything interesting...<p>Edit: Spoke too soon. Did find one paper[1] (though I can't read it) which uses it to compare the production of 's' and 'z' sounds. Would love to know if there are any more papers though.<p>[1] <a href="http://dx.doi.org/10.1121/1.4784877" rel="nofollow">http://dx.doi.org/10.1121/1.4784877</a>
Scientific American used to run a really cool "Amateur Scientist" column when I was a kid, edited by C.L. Stong. In the early 70s they ran a couple articles about people who'd built their own Schlieren optics. I was fascinated by them!<p>The articles appear to be pay-walled now (<a href="http://www.scientificamerican.com/article/the-amateur-scientist-1971-05/" rel="nofollow">http://www.scientificamerican.com/article/the-amateur-scient...</a> and <a href="http://www.scientificamerican.com/article/the-amateur-scientist-1974-08/" rel="nofollow">http://www.scientificamerican.com/article/the-amateur-scient...</a>).<p>It looks like the book that collected many of Stong's columns from the 50s and 60s predates those 2 articles (<a href="https://archive.org/details/TheAmateurScientist" rel="nofollow">https://archive.org/details/TheAmateurScientist</a>).<p>There's a CD-ROM available that supposedly contains the text & images for _all_ of the Scientific American "Amateur Scientist" from the '20s to the late '90s, which would presumably also have those articles: <a href="http://www.amazon.com/exec/obidos/ISBN%3D0970347626/sciencehobbyist/" rel="nofollow">http://www.amazon.com/exec/obidos/ISBN%3D0970347626/scienceh...</a>
And it's kindof accessible for hobbyists, here is the website of one individual who made his own setup: <a href="http://www.ian.org/Schlieren/" rel="nofollow">http://www.ian.org/Schlieren/</a><p>The most expensive component (except the camera) is the mirror. According to that website, it costs about $100 from an optics company.
And this is the sonic boom visualized by Schlieren photography: <a href="http://youtu.be/lbomsOPSSII" rel="nofollow">http://youtu.be/lbomsOPSSII</a>
related at all to?<p><a href="http://en.m.wikipedia.org/wiki/Adaptive_optics" rel="nofollow">http://en.m.wikipedia.org/wiki/Adaptive_optics</a>
The HN title is incorrect. This device doesn't show movement, it shows difference of the index of refraction. From the video description:<p>> <i>Demonstration of an optical technique that allows us to see small changes in the index of refraction in air. [...] Seen here are the heated gases from a candle flame and a hair dryer, helium gas, and sulfur hexafluoride gas.</i>