London

===Royal Observatory, Greenwich and learned societies===
[[File:Tourists taking pictures at Prime Meridian monument, Greenwich Observatory, London.jpg|thumb|upright=1|right|Tourists queuing to take pictures on the line of the historic [[Prime meridian (Greenwich)|prime meridian]] at the [[Royal Observatory, Greenwich]].]]
Founded in 1675, the [[Royal Observatory, Greenwich|Royal Observatory]] in [[Greenwich]] was established to address the problem of calculating [[longitude]] for navigational purposes. This pioneering work in solving longitude featured in astronomer royal [[Nevil Maskelyne]]'s ''[[Nautical Almanac]]'' which made the Greenwich meridian the universal reference point, and helped lead to the international adoption of Greenwich as the [[prime meridian]] (0° longitude) in 1884.<ref>{{cite book |last1=Ridpath |first1=Ian |title=A Dictionary of Astronomy |date=2012 |publisher=Oxford University Press |page=198}}</ref>

Important scientific [[learned societies]] based in London include the [[Royal Society]]—the UK's national [[academy of sciences]] and the oldest national scientific institution in the world—founded in 1660,<ref>{{cite encyclopedia|title=Royal Society|encyclopedia=Encyclopædia Britannica|url=https://www.britannica.com/topic/Royal-Society|access-date=23 July 2022|last=Hunter|first=Michael}}</ref> and the [[Royal Institution]], founded in 1799. Since 1825, the [[Royal Institution Christmas Lectures]] have presented scientific subjects to a general audience, and speakers have included physicist and inventor [[Michael Faraday]], aerospace engineer [[Frank Whittle]], naturalist [[David Attenborough]] and evolutionary biologist [[Richard Dawkins]].<ref>{{cite web|title=History of the Christmas Lectures|url=http://www.rigb.org/christmas-lectures/history|publisher=The Royal Institution|access-date=22 April 2015}}</ref>