Editing 1904 in science (section)

==Mathematics==
* [[Henri Poincaré]] discovers the [[Poincaré homology sphere]], leading him to formulate the [[Poincaré conjecture]].
* [[Helge von Koch]] describes the "[[Koch snowflake]]", one of the earliest [[fractal]] [[curve]]s described.<ref>"Sur une courbe continue sans tangente, obtenue par une construction géométrique élémentaire".</ref><ref>{{cite book|last=Addison|first=Paul S.|title=Fractals and Chaos: An Illustrated Course|publisher=Institute of Physics|location=Bristol|year=1997|isbn=0-7503-0400-6|page=19}}</ref>
* [[Charles Spearman]] develops his [[Spearman's rank correlation coefficient|rank correlation coefficient]].<ref>{{cite book|first=Tony|last=Crilly|title=50 Mathematical Ideas you really need to know|location=London|publisher=Quercus|year=2007|isbn=978-1-84724-008-8|page=145}}</ref>
* [[Ernst Zermelo]] formulates the [[axiom of choice]] to formalize his proof of the [[well-ordering theorem]].<ref>{{cite journal|first=Ernst|last=Zermelo|year=1904|url=http://gdz.sub.uni-goettingen.de/no_cache/en/dms/load/img/?IDDOC=28526|format=reprint|title=Beweis, dass jede Menge wohlgeordnet werden kann|journal=[[Mathematische Annalen]]|volume=59|issue=4|pages=514–16|doi=10.1007/BF01445300|s2cid=124189935}}</ref>