Pre-history to 1000 CE: Stone circles, star catalogues, and early observatories
Stone circles and early writings are the first remnants we have of ancient humans and their relationship to the cosmos. Stone circles like Stonehenge, the Goseck Circle in Germany, and similar circles in Egypt, may have been constructed to mark events like solstices and to act as early calendars. Humans were also writing about celestial objects for as long as we’ve had writing, including star catalogues from ancient Babylon.
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1200 BCE
Ancient Babylonians write down the earliest known star catalogues, detailing constellations, stars, and planets.
150 CE
Ptolemy writes the Almagest, which canonizes the geocentric model of the universe. While ultimately incorrect, it standardizes predictive astronomy and the study of planetary motion.
6th century CE
Islamic-built observatories begin to appear. They use instruments to track star movements in greater detail than ever before.
9th century CE
Al-Battānī creates detailed astronomical charts and applies trigonometry to astronomical calculations. His works are widely read in Europe and will later influence Copernicus’ Sun-centered model of the universe.
964 CE
Abd al-Rahman al-Sufi makes the first recorded observations of objects beyond our galaxy: the Andromeda Galaxy and the Large Magellanic Cloud (a nearby dwarf galaxy) in his Book of Fixed Stars.
1608 to 1850: The telescope
In 1608, a Dutch spectacle maker named Hans Lipperhey files a patent for the first telescope. With a new way to look deeper into space, and building on earlier Islamic discoveries, European thinkers propose radical ideas about the Solar System, wandering stars called planets, and even our place in the universe.
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1610
Galileo Galilei uses a telescope to observe Jupiter’s moons and Saturn’s rings. He confirms that the Milky Way is composed of stars.
1750
Thomas Wright discusses the flattened shape of the Milky Way and believes nebulae are separate entities.
1755
Building on Wright’s work, Immanuel Kant argues that our galaxy is a rotating disk of stars held together by gravity.
1781
Charles Messier releases his final list of Messier Objects: objects in the sky that weren’t comets that he couldn’t explain as regular stars or planets. Of the 103 objects, 34 are now known to be galaxies.
1783
After years of debate, Uranus is accepted as a planet by the Royal Society, doubling the size of the known Solar System.
1846
Urbain Le Verrier uses the laws of Kepler and Newton to mathematically predict the existence of Neptune. Neptune had been observed accidentally years before, but was mistaken as a star. Le Verrier’s discovery marks a major leap forward in using celestial mechanics to explore the cosmos.
1850 to 1956: Technology takes us further
The 19th century witnesses an explosion of new observational technologies. Photography, spectroscopy, and radio telescopes, plus major insights into theoretical physics, help us see beyond what the human eye can detect. New tools also help us create permanent records of the sky.
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1860's
Gustav Kirchhoff and Robert Bunsen use spectroscopy to identify the composition, temperature, and motion of the Sun. Soon after, they analyze other celestial objects, and help differentiate nebulae from galaxies.
1888
Williamina Fleming discovers the Horsehead Nebula using a photographic plate. She also helps to create a common designation system for stars, and catalogues well over 10,000 celestial objects.
1912
Henrietta Swan Leavitt develops the Leavitt Law, which allows astronomers to accurately measure galactic distances.
1923
Edwin Hubble definitively proves there are other galaxies beyond the Milky Way. Many scientists previously believed that the mysterious “spiral nebulae” were smaller objects at the edge of our galaxy.
1930
Pluto is discovered by comparing photographic plates decades after the first photographs of the dwarf planet.
1933
Karl Jansky discovers radio waves emanating from the Milky Way, kicking off the age of radio astronomy.
1953
Gérard de Vaucouleurs discovers that the Virgo cluster of galaxies is part of a larger supercluster that includes the then-unexplained excess of nebulae around it.
1957 to 2000: Escape velocity
The Space Age officially kicks off on October 4, 1957, when Sputnik 1 is successfully launched into space. What follows is an explosion of new discoveries that challenge our assumptions about the universe.
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1962
NASA launches the first Orbiting Solar Observatory, becoming the first space-based telescope. Astronomers can now observe the sky without atmospheric distortion.
1987
A team of researchers observe that galaxies within about 200 million light years of the Milky Way are moving together toward some sort of "Great Attractor."
1989
Margaret Geller and John Huchra discover the "Great Wall," a sheet of galaxies more than 500 million light years long and 200 million wide, but only 15 million light years thick.
1992
Scientists carry out the first detailed observations of the cosmic microwave background, which helps us map the seeds of the early universe and its first galaxy clusters.
1992
The first definitive detection of exoplanets (planets orbiting stars other than the Sun). To date, 5,983 exoplanets have been discovered in 4,470 planetary systems.
1995
The Hubble Space Telescope releases its Deep Field survey. It reveals some 3,000 objects in one tiny spot measuring one 24-millionth of the whole sky, almost all of which are galaxies.
1998
Two independent projects, the Supernova Cosmology Project and the High-Z Supernova Search Team, discover that the universe is not only expanding, but its expansion is accelerating.
2000 – present: Accelerated expansion
Since 2000, major advancements in technology and physics have gone hand in hand, confirming theories and using them to probe further than ever. New tools like LIGO are detecting gravitational waves from black holes while global initiatives and large-scale surveys offer new images and insights.
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2013
The Hercules–Corona Borealis Great Wall, the largest known structure in the universe, is discovered through gamma-ray burst mapping. It is a galaxy filament, a collection of “great walls” of galaxies, and roughly 10 billion light years long, or 10.7 percent of the estimated length of the entire universe.
2015
LIGO makes the first direct observation of gravitational waves, providing the most concrete evidence of black holes until the Event Horizon Telescope images are released in 2019.
2019
The Event Horizon Telescope uses a global network of radio telescopes to create the first-ever image of a black hole, the supermassive black hole at the centre of the Messier 87 galaxy.
2020
The Sloan Digital Sky Survey publishes the largest, most detailed 3D map of the universe and confirms that different regions of the universe are expanding at different rates.
2022
The James Webb Space Telescope (JWST) observes the same deep field Hubble did in 1995, seeing galaxies up to 13 billion light years away.
2025
Rohan Naidu discovers MoM-z14, the farthest-known galaxy that formed about 280 million years after the big bang. It is about 33.8 billion light years from us.
About PI
Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.
