350 BCE
Aristotle's Geocentric Universe
Aristotle proposes a static, spherical universe with Earth at the center, influencing cosmology for centuries. #cosmology #history
Chronological Storyline (44 Milestones)
1543 CE
Copernicus Proposes Heliocentric Model
Nicolaus Copernicus publishes 'De revolutionibus orbium coelestium,' challenging the geocentric view. #cosmology #history
By Unknown author - http://www.frombork.art.pl/Ang10.htm https://www.welt.de/img/kultur/mobile152954235/1212503297-ci102l-w1024/Kopernikus-Gemaelde-in-Krakau.jpg https://muzeum.torun.pl/wp-content/uploads/2023/03/Portert-Mikolaja-Kopernika-MOT.jpg, Public domain, https://commons.wikimedia.org/w/index.php?curid=147956893
1687 CE
Newton's Laws of Motion and Gravitation
Isaac Newton publishes 'Principia Mathematica,' laying foundations for classical mechanics and universal gravitation. #physics #history
1823 CE
Olbers' Paradox Formulated
Heinrich Olbers articulates the paradox that a static, infinite universe would have a bright night sky, questioning cosmology. #cosmology #astronomy
By Kmarinas86 - http://en.wikipedia.org/wiki/Image:Olber%27s_Paradox_-_All_Points.gif, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2949765
1871 CE
Lobachevsky's Non-Euclidean Geometry
Nikolai Lobachevsky develops hyperbolic geometry, expanding geometric possibilities for cosmology. #mathematics #history
By Lev Kryukov - http://cczy.blog.ru/?year=2009&month=11, Public domain, https://commons.wikimedia.org/w/index.php?curid=12821190
1915 CE
Einstein's General Relativity
Albert Einstein presents the field equations, describing gravity as spacetime curvature. #physics #relativity
By Simulating eXtreme Spacetimes Lensing (SXS) - https://www.ligo.caltech.edu/video/ligo20160211v3 (video link); see also http://www.black-holes.org/gw150914, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=46994894
1917 CE
Einstein Introduces the Cosmological Constant
To maintain a static universe, Einstein adds the cosmological constant (Λ) to his equations. #cosmology #history
By NASA/WMAP Science Team - Original version: NASA; modified by Cherkash, Public domain, https://commons.wikimedia.org/w/index.php?curid=11885244
1922 CE
Friedmann's Expanding Universe Solutions
Alexander Friedmann derives solutions to Einstein's equations allowing for an expanding universe. #cosmology #physics
By Unknown author - Cropped From, Public domain, https://commons.wikimedia.org/w/index.php?curid=2630080
1927 CE
Lemaître Proposes the Primeval Atom
Georges Lemaître independently derives expansion and suggests the universe began as a 'primeval atom.' #cosmology #bigbang
By Unknown author - https://societyforthehistoryofastronomy.com/wp-content/uploads/2023/01/AA14-June-20.pdf, Public domain, https://commons.wikimedia.org/w/index.php?curid=154504242
1929 CE
Hubble's Law of Cosmic Expansion
Edwin Hubble discovers the relationship between galaxy distance and redshift, confirming expansion. #astronomy #cosmology
By w:en:User:ScienceApologist - This image was copied from wikipedia:en. The original description was: The raisin bread model of the universe explains how each galaxy can perceive every other galaxy in the universe as receding from it. From the WMAP website., Public domain, https://commons.wikimedia.org/w/index.php?curid=2615116
1931 CE
Einstein Abandons the Cosmological Constant
After Hubble's discovery, Einstein calls the cosmological constant his 'biggest blunder.' #cosmology #history
1948 CE
Gamow's Big Bang Nucleosynthesis
George Gamow and colleagues predict light element formation in the early universe. #cosmology #physics
1948 CE
Steady State Theory Proposed
Bondi, Gold, and Hoyle propose the steady state universe with continuous matter creation, challenging Big Bang. #cosmology #history
By NASA / WMAP Science Team - http://map.gsfc.nasa.gov/media/121238/ilc_9yr_moll4096.png, Public domain, https://commons.wikimedia.org/w/index.php?curid=23285693
1964 CE
Discovery of Cosmic Microwave Background
Penzias and Wilson accidentally discover the CMB, strong evidence for the Big Bang. #astronomy #cosmology
By ESA and the Planck Collaboration - Cosmic Microwave Background, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=130789180
1965 CE
Zel'dovich Revives Cosmological Constant
Yakov Zel'dovich suggests the cosmological constant is related to vacuum energy. #cosmology #physics
By Stamp issuing authority - MARKA Publishing & Trading Centre. Printer - Association GOZNAK of the Ministry of Finance of the Russian Federation - http://www.wnsstamps.post/en/stamps/RU055.14, Public domain, https://commons.wikimedia.org/w/index.php?curid=39238861
1979 CE
Inflation Theory Proposed by Alan Guth
Alan Guth proposes cosmic inflation to solve horizon and flatness problems, later linked to vacuum energy. #cosmology #physics )
1981 CE
First Supernova Cosmology Project Begins
Early efforts to measure cosmic deceleration using Type Ia supernovae, eventually leading to dark energy discovery. #astronomy #cosmology
By ESO/L. Calçada - ESO, specifically 4K broadcast version locally encoded using these instructions, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=128439138
1987 CE
Supernova 1987A Observed
Closest supernova in modern times, providing critical data for cosmology and distance measurements. #astronomy #supernova
By NASA Goddard Space Flight Center from Greenbelt, MD, USA - New Hubble Observations of Supernova 1987A Trace Shock Wave, Public domain, https://commons.wikimedia.org/w/index.php?curid=69021019
1988 CE
First Observations of Dark Matter Effects
Vera Rubin's work on galaxy rotation curves provides evidence for dark matter, complementing dark energy studies. #astronomy #cosmology
By Photograph by Mark Godfrey, courtesy of AIP Emilio Segrè Visual Archives, Gift of Vera Rubin - https://repository.aip.org/node/111858, Attribution, https://commons.wikimedia.org/w/index.php?curid=177261379
1992 CE
COBE Satellite Measures CMB Anisotropy
NASA's COBE detects tiny temperature fluctuations in the CMB, supporting inflation and precision cosmology. #astronomy #cosmology
1993 CE
First Type Ia Supernova Cosmology Results
Preliminary results from the Supernova Cosmology Project suggest slower expansion than expected. #astronomy #cosmology
Jan 8, 1998 CE
Discovery of Accelerating Universe (Supernova Cosmology Project)
Simultaneously, the Supernova Cosmology Project announces similar findings of accelerated expansion. #cosmology #darkenergy
Jan 8, 1998 CE
Discovery of Accelerating Universe (High-Z Team)
The High-Z Supernova Search Team publishes evidence that the universe's expansion is accelerating, implying dark energy. #cosmology #darkenergy
By Unknown author - Peter Garnavich, University of Notre Dame, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=149271704
1999 CE
First Direct Evidence for Dark Energy
The term 'dark energy' enters common usage as the cause of cosmic acceleration. #cosmology #darkenergy
Jun 30, 2001 CE
WMAP Satellite Launched
NASA's Wilkinson Microwave Anisotropy Probe maps CMB with high precision, providing key cosmological parameters. #astronomy #cosmology
By NASA / WMAP Science Team - [1]; converted from the high-resolution TIFF version to a JPEG, Public domain, https://commons.wikimedia.org/w/index.php?curid=3944989
2003 CE
WMAP First-Year Data Released
WMAP results confirm the existence of dark energy and refine its density parameter. #cosmology #darkenergy
2004 CE
Quintessence Models Proposed
Theoretical models of dynamic dark energy, quintessence, are developed as alternatives to the cosmological constant. #cosmology #darkenergy )
2006 CE
Supernova Legacy Survey First Results
The SNLS provides high-redshift supernova data further constraining dark energy properties. #astronomy #darkenergy
May 14, 2009 CE
Planck Satellite Launched
ESA's Planck mission begins mapping the CMB with unprecedented resolution. #astronomy #cosmology )
By Photograph by Mike Peel (www.mikepeel.net). - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=14045307
Oct 4, 2011 CE
Nobel Prize for Dark Energy Discovery
Saul Perlmutter, Brian Schmidt, and Adam Riess awarded Nobel Prize for the discovery of the accelerating universe. #physics #nobel
By Photograph: JonathunderMedal: Erik Lindberg (1873-1966) - Derivative of File:NobelPrize.JPG, PD-US, https://en.wikipedia.org/w/index.php?curid=58432969
2012 CE
Baryon Acoustic Oscillation (BOSS) Results
BOSS survey measures BAO to probe dark energy, confirming its behavior consistent with Λ. #cosmology #darkenergy
Mar 21, 2013 CE
Planck 2013 Results Released
Planck data yields precision measurement of dark energy (68.3% of universe) and tightens constraints. #cosmology #darkenergy )
2015 CE
Dark Energy Survey (DES) First Year Results
DES uses multiple probes to study dark energy, providing new constraints on equation of state. #astronomy #darkenergy
By Felipe Menanteau and the Dark Energy Survey Collaboration - https://opensource.ncsa.illinois.edu/confluence/pages/viewpage.action?pageId=61604315, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=59740733
2016 CE
eBOSS Survey Begins
The extended Baryon Oscillation Spectroscopic Survey maps cosmic expansion over 11 billion years. #astronomy #cosmology
2017 CE
Kilonova GW170817 and Cosmological Constant
Gravitational wave detection provides independent measurement of Hubble constant, with implications for dark energy. #astronomy #gravitationalwaves
By LIGO Scientific Collaboration and Virgo Collaboration - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.161101 This W3C-unspecified plot was created with Matplotlib., CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=63455773
Jul 1, 2018 CE
Dark Energy Survey 3-Year Results
DES results show consistency with a cosmological constant, but allow for evolving dark energy. #cosmology #darkenergy
2019 CE
H0LiCOW Gravitational Lensing Results
Strong lensing time delays yield a precise Hubble constant, tension with CMB gives hints of new physics. #astronomy #cosmology
2020 CE
eBOSS Final Data Release
eBOSS maps 11 billion years of cosmic expansion, confirming the standard ΛCDM model. #cosmology #darkenergy
Oct 17, 2021 CE
James Webb Space Telescope Launch
JWST aims to observe early universe, potentially revealing clues about dark energy. #astronomy #telescope
By NASA - https://www.jwst.nasa.gov/content/webbLaunch/whereIsWebb.html, Public domain, https://commons.wikimedia.org/w/index.php?curid=114125719
2021 CE
DESI Instrument First Light
The Dark Energy Spectroscopic Instrument begins mapping galaxies to study dark energy. #astronomy #darkenergy
By Lawrence Berkeley National Lab/KPNO/NOIRLab/NSF/AURA - DESI crossfade 4, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=134717399
2022 CE
Dark Energy Survey Final Results
DES final combined analysis provides stringent constraints on dark energy equation of state. #cosmology #darkenergy
2023 CE
Euclid Mission Launched
ESA's Euclid mission launches to map dark energy and dark matter across cosmic time. #astronomy #darkenergy )
By European Space Agency - Euclid looking into the Universe, CC BY-SA 3.0 igo, https://commons.wikimedia.org/w/index.php?curid=128347141
2024 CE
DESI Early Data Release
DESI's first year of data provides new constraints on dark energy, hinting at possible deviation from Λ. #cosmology #darkenergy
2025 CE
Nancy Grace Roman Space Telescope Launch (Planned)
NASA's Roman mission aims to investigate dark energy with wide-field imaging. #astronomy #darkenergy
By NASA - https://roman.gsfc.nasa.gov/gallery-spacecraftillustrations.html, Public domain, https://commons.wikimedia.org/w/index.php?curid=136706293