[{"id":299,"title":"Correspondence Between Sonic Booms and Photonic Booms","sha":"419a6cef1c78a962a1da8b46b65d8a8e","user_id":null,"state":"published","body":"A [sonic boom](https://en.wikipedia.org/wiki/Sonic_boom) is heard by an observer, for example, when a supersonic airplane passes by. A lesser known phenomenon dubbed a photonic boom is seen by an observer, for example, when an always-superluminal spot from a laser pointer sweeps by.\r\n\r\nBoth booms are perceived image pair-creation events. With sound, after the boom, the airplane is heard later from two diverging locations. [Lord Rayleigh](https://en.wikipedia.org/wiki/John_William_Strutt,_3rd_Baron_Rayleigh) [realized]( https://archive.org/stream/theorysound05raylgoog#page/n173/mode/2up) that one sound sequence from a supersonic source would be heard backwards. [Ahrens and Spors (2008)](https://www.researchgate.net/publication/230702229_Reproduction_of_Virtual_Sound_Sources_Moving_at_Supersonic_Speeds_in_Wave_Field_Synthesis) indicated confirmation of this in the lab, and [Randall Munroe](https://en.wikipedia.org/wiki/Randall_Munroe) summarized it on [what-if.xkcd](https://what-if.xkcd.com/37/). \r\n\r\nWith light, a photonic boom is seen first when the radial component toward the observer of the superluminal sweeping laser spot drops to subluminal [(Nemiroff 2015)](http://adsabs.harvard.edu/abs/2015PASA...32....1N). Subsequently, two laser spots are seen at diverging locations. Were the laser pointer showing a video, one video of this pair would be seen playing normally -- the other time-reversed. \r\n\r\nThe initial flash of the perceived light-spot pair-creation event of the photonic boom directly corresponds to the initial bang of the perceived sound pair-creation event of the sonic boom. \r\n","created_at":"2016-04-15T18:07:06.996Z","updated_at":"2016-04-17T06:00:42.071Z","zenodo_id":108006,"doi":"http://dx.doi.org/10.5281/zenodo.49871","subject":null,"tags":["physics","relativity","sonic boom","photonic boom"],"vote_count":0,"view_count":1,"score":0.1,"deleted":false,"muted":false,"tweeted":true,"attachment_file_name":null,"attachment_content_type":null,"attachment_file_size":null,"attachment_updated_at":null}]