1905–1929 CE · special/general relativity and redshift–distance milestones · Europe · Science
Special relativity changed the relation of space and time; general relativity described gravitation through curved spacetime. Distance and redshift work by several astronomers then supported an expanding universe.
Atlas dossier · World WarsFree device narration · synchronized English captions · transcript available
Why it matters
Einstein’s 1905 special theory addressed motion, light, space and time; his 1915 field equations made gravitation part of spacetime geometry. The later theory did not simply cancel the earlier one. Their experimental tests and practical uses developed beyond the dates when the equations first appeared.
American Physical Society: A Century of Physics ↗Leavitt’s period–luminosity relation underpinned astronomical distance measurement, and Slipher measured many galactic redshifts. Lemaître connected relativity and observations to an expanding universe in 1927, before Hubble’s 1929 distance–redshift paper. Naming the Hubble–Lemaître law helps prevent one famous publication from absorbing the whole chain of evidence.
NASA: Hubble’s discovery of a new universe ↗A visual presentation accompanying this entry. Read each image’s attribution to distinguish archival records, later depictions and reconstructions.
Rights-cleared archival or official image · Public domain
Albert Einstein Head.jpg — Photograph by Orren Jack Turner, Princeton, N.J. Modified with Photoshop by PM_Poon and later by Dantadd.; Public domain; via Wikimedia Commons
Source and reuse terms ↗
Rights-cleared archival or official image · Public domain
Albert Einstein writing on a blackboard in Pasadena (1931).jpg — Associated Press; Public domain; via Wikimedia Commons
Source and reuse terms ↗
Rights-cleared archival or official image · CC BY-SA 4.0
Huntington Art Collections 13 - Edwin Hubble.jpg — Photograph by Mike Peel (www.mikepeel.net).; CC BY-SA 4.0; via Wikimedia Commons
Source and reuse terms ↗Interpretation note
This dossier distinguishes the event’s basic chronology from later arguments about meaning, responsibility and legacy. When comparing religious, national, Indigenous or scholarly interpretations, consult the primary and institutional sources above alongside peer-reviewed historical work.
Elsewhere in the world
17 December 1903 CE · first sustained, controlled powered airplane flights · AmericasPowered flightAt Kitty Hawk, the Wright brothers made four successful flights in a powered, heavier-than-air machine whose pilot could control pitch, roll and yaw.
1911–1949 CE · revolution, invasion and competing governments · AsiaChinese revolutions and divided sovereigntyThe 1911 Revolution ended Qing rule, but republican government remained contested through regional militarism, Nationalist–Communist conflict and Japanese invasion. In 1949 the PRC was proclaimed on the mainland while the ROC government relocated to Taiwan.
1913 CE · Ford moving-line milestone within longer mass-production history · AmericasAssembly lines and mass productionFord engineers and workers introduced moving lines in stages at Highland Park, combining earlier interchangeable-parts practice and division of labour to accelerate automobile assembly.