Space discoveries from the year you were born
The 20th century saw a huge leap in astronomical discoveries and the advent of space exploration, both driven by advances in technology.
Astronomy and space provide some of the biggest science news in any given year. Humans love finding out new things about the universe we inhabit. The year you were born may have had a profound discovery, a landmark advance in human spaceflight, or simply the birth or death of someone who changed the way we see the cosmos.
Stacker set out to find the most notable space discoveries from over the last century. Some of the stories included here were selected to make sure certain important topics got covered, but many years required a difficult choice. Also, certain stories that didn't pan out—like the "alien microbes in a meteorite" headlines from 1996—aren't included, even if they received the most media attention that year. Finally, we only realized the full importance of some stories years after the fact, so Stacker has counted a few discoveries that didn’t make a big splash at the time but we now acknowledge as significant.
From the moon landings to learning how stars shine to realizing the universe is big—really big—the past 100 years have been a wild time. Here are just a few of the major discoveries in the years 1919 through 2018.
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1919: Albert Einstein's theory of gravity passes its first big test
British astrophysicist Arthur Eddington led an expedition to the African island of Principe to test Albert Einstein's theory of general relativity. According to that theory, gravity from the sun should bend the path of light from distant stars, but that prediction can only be tested during a total solar eclipse when sunlight is blocked by the moon. Eddington and his team found stars appearing in different positions than they would normally, exactly as predicted by relativity.
1920: Taking the measure of Betelgeuse
Betelgeuse is one of the brighter stars in the night sky, visible as part of the constellation Orion. Americans physicist Albert Michelson and astronomer Francis Pease used a special device known as an interferometer (of the same basic type as the LIGO gravitational wave detector) to measure the diameter of Betelgeuse. This is the first time such a measurement was made for a star other than the sun and showed Betelgeuse to be a supergiant star large enough to engulf the inner solar system.
1921: RIP Henrietta Leavitt, who taught how to measure the cosmos
Henrietta Swan Leavitt was an astronomer at Harvard College Observatory, hired as a "computer" assistant to the male researchers. However, her skill led her to discover a relationship between the brightness of certain stars called Cepheid variables and the length of their fluctuation cycle. Leavitt's discovery led directly to some of the most important observations in 20th-century astronomy.
1922: Formal definition of constellations
Many cultures identify constellations, relating them to mythology and using them for navigation. The International Astronomical Union (IAU) formally divided the sky up into 89 constellations with clear boundaries in 1922 as an aid to observers. Eight years later, the IAU removed Argo from the list to give us the modern 88 constellations.
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1923: Birth of Alan Shepard, first American in space
American astronaut Alan Shepard was born on Nov. 18, 1923. After serving in the United States Navy during World War II, he joined the original astronaut corps, becoming the first American man in space in 1961. Subsequently, he piloted the Apollo 14 lunar module, becoming the fifth person to walk on the moon.
1924: Hubble demonstrates other galaxies exist
American astronomer Edwin Hubble identified a Cepheid variable star in the Andromeda nebula, and used Henrietta Leavitt's discovery about these stars to determine the distance. He found the nebula was much farther away than the most distant known star in the Milky Way, firmly establishing that Andromeda was a separate galaxy. Hubble's discovery settled a centuries-old debate over whether the Milky Way constituted the entire universe, inaugurating the field of extragalactic astronomy. Hilariously, the Times misspelled Hubble's name.
1925: Cecilia Payne shows that stars are mostly hydrogen
British-born astronomer Cecilia Payne applied recent discoveries in the physics of gases to understand the spectrum of light emitted by stars. She learned that all stars are primarily made of hydrogen, despite their diverse appearances. Her 1925 doctorate thesis describing the 18 most abundant elements in stars set the stage for stellar astronomy for the rest of the century.
1926: Robert Goddard builds first liquid-fuel rockets
American physicist Robert Goddard devoted much of his spare time and energy to building rockets. The major triumph of this research was the first successful liquid-fuel rocket (nicknamed "Nell"), which used gasoline and liquified oxygen. Goddard's basic design was modified and improved by many subsequent rockets, and today he is recognized as one of the most important pioneers of rocketry.
1927: LeMaître calculates how the universe expands
Based on Einstein's general relativity, Belgian physicist/Catholic priest Georges LeMaître determined that galaxies should be moving farther apart, carried along by the expansion of spacetime. This led him to determine that farther galaxies would appear to be moving faster than closer ones, anticipating Hubble's observational discovery two years later.
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1928: Prediction of antimatter
British physicist Paul Dirac sought to combine the quantum theory of electrons and atoms with Einstein's theory of relativity. He discovered the merger naturally led to the prediction of positrons (confirmed experimentally in 1932): particles with the same mass as electrons, but opposite electrical charge. Other particles turned out to have antimatter partners as well, which led to exciting discoveries in cosmic ray astronomy and the study of the early universe.2018 All rights reserved.