Episode 4

John Snow - https://en.wikipedia.org/wiki/John_Snow_(physician)Epidemiology -  https://en.wikipedia.org/wiki/EpidemiologyGeodesy - https://en.wikipedia.org/wiki/GeodesyMathematics of paperfolding - https://en.wikipedia.org/wiki/Mathematics_of_paper_foldingJames webb deep space telescope - https://en.wikipedia.org/wiki/James_Webb_Space_TelescopeHow we got to now - https://en.wikipedia.org/wiki/How_We_Got_to_NowLifting Chicago - https://en.wikipedia.org/wiki/Raising_of_ChicagoWinter is coming - http://arxiv.org/abs/1304.0445Orbital Mechanics - https://en.wikipedia.org/wiki/Orbital_mechanicsHalley - https://en.wikipedia.org/wiki/Halley%27s_Comethttps://en.wikipedia.org/wiki/Halley%27s_Comet#/media/File:Babylonian_tablet_recording_Halley%27s_comet.jpgPetr and Principia.  Thank you Royal Society, we love you. Dual Stars - http://www.sciencealert.com/scientists-find-two-distant-stars-touching-and-the-results-could-be-catastrophicHalf life of teaspoons - http://www.bmj.com/content/3