Earth rising over moon's horizon

NASA

Century of Science

Milestones

from ScienceNews

183 Milestones in
Our wild universe
and
All Connections

  1. 1900
    1. Cepheids as cosmic markers

      Henrietta Leavitt discovers that brighter Cepheid variable stars blink slower than dimmer ones, a relationship that gave astronomers a way to measure cosmic distances.

      Other worlds New vistas
  2. 1910
    1. Piltdown Man

      An amateur archaeologist reports finding fossils of a human ancestor near Piltdown, England. Piltdown Man is touted as evidence that a big brain evolved early in human evolution, but the fossils are later exposed as a hoax

    2. Continental drift

      Meteorologist Alfred Wegener suggests that Earth’s continents aren’t fixed in place, but drift around the globe.

      Shaking up Earth
    3. Earth’s story

      Geologist Arthur Holmes publishes The Age of the Earth, presenting the first complete geologic timescale and arguing for using radioactive materials as geologic clocks.

      Shaking up Earth
  3. 1920
    1. Kabwe skull pic

      The Natural History Museum/Alamy Stock Photo

      Kabwe skull

      Miners in what’s now Zambia unearth a roughly 300,000-year-old humanlike skull. Known as the Kabwe or Broken Hill skull, it’s the first ancient hominin fossil discovered in Africa.

      The human story
    2. black and white photo of Sigmund Freud

      Authenticated News/Getty Images

      Mental trio

      Psychoanalyst Sigmund Freud, shown, describes mental life as a series of conflicts between a person’s primitive instincts, or id, and moral conscience, or superego, mediated by the ego’s considerations of what’s socially acceptable.

      The science of us
    3. professional photos of Edgar Allen and Edward A. Doisy

      From left: NLM/NIH (CC BY 2.0); Washington Univ., NLM/NIH

      Estrogen found

      Two scientists at Washington University of St. Louis, Edgar Allen and Edward Doisy, first isolated estrogen in experimental mice and found that it was produced in the ovaries.

      The mystery of reproduction
    4. Dart and skull

      Science History Images/Alamy Stock Photo

      Taung Child

      The discovery in South Africa of a 2.8-million-year-old skull with a blend of apelike and humanlike traits hints that the earliest phases of human evolution happened in Africa. Raymond Dart, shown with the fossil, called the Taung Child, places it into a new genus: Australopithecus.

      The human story
    5. black and white photo of Cecilia Payne seated at a desk looking at the camera

      Smithsonian Institution/Flickr

      Stellar makeup

      Cecilia Payne (shown) discovers what stars are made of: mostly hydrogen and helium.

      Other worlds Unsung characters
    6. Peking Man

      Based on a tooth found at China’s Zhoukoudian site, Davidson Black identifies a new hominin species named Sinanthropus pekinensis (now called Homo erectus) that lived several hundred thousand years ago.

      The human story
    7. Ice Age Americans

      The discovery of a flint point alongside the remains of prehistoric buffalo in Folsom, N.M., helps convince anthropologists that humans have lived in the Americas since the Ice Age.

      The human story
    8. Culture first

      Anthropologist Margaret Mead’s book Coming of Age in Samoa controversially argues that casual sexuality and other cultural practices on a South Pacific island make adolescence smoother for girls there than girls in Western cultures.

      The science of us
  4. 1930
    1. Moral kids

      In his book The Moral Judgment of the Child, developmental psychologist Jean Piaget argues that children develop moral ideas in three broad stages largely via interactions with peers.

      The science of us
    2. Imperfect recall

      Pioneering memory researcher Frederic Bartlett publishes experiments showing that what people remember about past events consists of a mix of fact and culturally influenced fill-ins.

      The science of us
    3. Discovery of the neutron

      Physicist James Chadwick discovers an electrically neutral particle, the neutron, contained within atomic nuclei.

      Cracking the atom
    4. Dark matter

      Fritz Zwicky examines galaxies in the Coma cluster and determines that there is unseen mass, what scientists now call “dark matter.”

      Our wild universe Let’s talk
    5. historical image of Charles Richter

      New York Public Library/Science Source

      Shaking scale

      The Richter scale is proposed by seismologist Charles Richter (shown) to compare the magnitude of different earthquakes. The more accurate moment magnitude scale is now used for most earthquakes.

      Shaking up Earth
    6. Robust hominins

      In South Africa, Robert Broom identifies a robust form of hominin, named Paranthropus robustus, that had giant molar teeth and a skull built for heavy chewing. The species, now known to have lived 1.8 million to 1.2 million years ago, is evidence that more than one type of hominin once called the region home.

      The human story
    7. Science History Images/Alamy Stock Photo

      Shaping behaviors

      Psychologist B.F. Skinner, shown, presents evidence indicating that behaviors are strengthened or weakened by their consequences in his first book, The Behavior of Organisms.

      The science of us
    8. Science Source

      Nuclear fission

      In a discovery that portends the possibility of atomic bombs, Otto Hahn (right) and Fritz Strassmann report evidence that uranium atoms produce barium when bombarded with neutrons. As explained by their collaborator Lise Meitner (left) and her nephew Otto Frisch, this is fission, the splitting of atoms.

      Cracking the atom Unsung characters
  5. 1940
    1. Shell model of the nucleus

      Physicists Maria Goeppert Mayer and J. Hans D. Jensen develop a theory of the nucleus as composed of shells of protons and neutrons. It explains why nuclei with certain “magic numbers” of protons and neutrons are more stable.

      Cracking the atom
    2. Manhattan Project gets into gear

      With the formation of the Manhattan Engineer District, the United States kick-starts a massive project to build an atomic bomb, which employed more than 120,000 people at its peak.

      Cracking the atom
    3. National Nuclear Security Administration, Nevada Site Office/U.S. Dept of Energy

      Dropping the bomb

      In July, the United States tests the atomic bomb in the New Mexico desert. In August, the U.S. drops two bombs on Japan, killing more than 100,000 people and hastening the end of World War II.

      Cracking the atom
    4. Dynamo theory

      Physicist Walter M. Elsasser and geophysicist Edward Bullard separately propose between 1946 and 1949 that Earth’s magnetic field is a self-sustaining dynamo generated by the movement of fluid in the liquid outer core, which produces an electric current.

      Shaking up Earth
    5. x-ray of a skull

      J. L. Pool/J. Am. Geriatr. Soc 1954

      Electrodes for Parkinson’s

      J. Lawrence Pool is the first to implant electrodes into a woman with Parkinson’s disease.

      Our brains, our futures
    6. Neurons firing, wiring

      Canadian psychologist Donald Hebb publishes his account of how neurons reinforce each other’s activity, a description that’s now shorthanded, “fire together, wire together.”

      Our brains, our futures
  6. 1950
    1. Milky Way is a spiral

      William W. Morgan and colleagues present a model of the Milky Way’s shape made of cotton balls to the American Astronomical Society meeting, depicting the galaxy as a spiral. The team received a raucous ovation with stomping feet.

      Other worlds
    2. UC San Diego School of Medicine

      Hippocampus and memory

      A patient known as H.M. undergoes surgery to remove his hippocampus, later revealing the role that the brain structure plays in memory. Studies of his postmortem brain (shown) complicated the picture.

      Our brains, our futures
    3. photo of Canyon Diablo meteorite

      Geoffrey Notkin, Aerolite Meteorites of Tucson/Wikimedia Commons (CC BY-SA 2.5)

      Age of Earth

      Geochemist Clair Patterson sets the age of the Earth at 4.550 billion years, relying on ages of meteorites (including the Canyon Diablo meteorite, shown) that formed around the same time.

      Shaking up Earth
    4. Neutrino found

      Scientists detect the neutrino, an electrically neutral subatomic particle released in radioactive decay and other reactions. It had once been thought to be undetectable.

      Cracking the atom
    5. a person playing chess

      Jeremy Bishop/Unsplash

      Rational limits

      A decision-making model developed by economist Herbert Simon contends that people use experience-based rules of thumb to work around limited knowledge and time when dealing with complex challenges, such as playing chess.

      The science of us
    6. Parity violation

      Particles that are mirror images — those with opposite “handedness” or orientation of their spin — don’t necessarily behave identically. Chien-Shiung Wu and colleagues report the discovery of this phenomenon, called parity violation, in decays of cobalt-60 atoms.

      Cracking the atom
    7. Leakey luck begins

      At Olduvai Gorge in Tanzania, Mary Leakey finds the skull of a robust hominin. She and her husband, Louis Leakey, name it Zinjanthropus boisei (now called Paranthropus boisei). The discovery shifts the focus of hominin fieldwork to East Africa.

      The human story
    8. Vision insight

      David Hubel and Torsten Wiesel illuminate the visual system in the cat, opening up an area of inquiry for how brain systems handle information from the senses.

      Our brains, our futures
  7. 1960
    1. Birth control pill

      The U.S. Food and Drug Administration approves the first oral contraceptive, soon known simply as “the pill.”

      The mystery of reproduction
    2. a laboratory device with switches and dials

      Isabelle Adam/Flickr (CC BY-NC-ND 2.0)

      Shocking obedience

      Experimental studies of people’s willingness to follow orders to administer what they think are electric shocks to an unseen stranger gain fame and notoriety for social psychologist Stanley Milgram (Milgram’s “shock box” is shown).

      The science of us
    3. Hot spots

      Geophysicist J. Tuzo Wilson suggests that volcanic island chains form as plates move over upwellings of magma in the mantle.

      Shaking up Earth
    4. Handy man

      Louis Leakey and colleagues report that a collection of fossils found at Tanzania’s Olduvai Gorge are the earliest known remains from the genus Homo. The researchers fold the fossils into a new species, Homo habilis, thought to have lived about 2.4 million to 1.4 million years ago. The classification remains controversial.

      The human story
    5. black and white photo of Arno Penzias (left) and Robert Wilson (right)

      Keystone Press/Alamy Stock Photo

      Background radiation

      Arno Penzias (left) and Robert Wilson (right) discover the cosmic microwave background radiation, the relic radiation left over from the Big Bang.

    6. black and white photo of Beatrice Mintz

      Smithsonian Institution/Flickr

      Four-parent mouse

      Beatrice Mintz creates a mouse with two mothers and two fathers to demonstrate which parent’s genetic contribution ended up in which region of the body.

      The mystery of reproduction Unsung characters
    7. Strong connections

      Norwegian physiologist Terje Lømo observes that connections between nerve cells strengthen with use, a core principle of neuroscience called long-term potentiation.

      Our brains, our futures
    8. Harry Whittington looking at fossils

      Geological Survey of Canada

      Wonderful life

      Harry Whittington (shown) leads an expedition to Canada’s Burgess Shale, identifying a riot of new and unusual forms of animal life and boosting studies into the Cambrian explosion.

      Shaking up Earth
    9. Human-ape split dated

      By studying blood proteins, Vincent Sarich and Allan Wilson develop a “molecular clock” for primate evolution. The pair estimates that humans and African apes diverged about 5 million years ago. The latest estimates suggest that humans and chimpanzees, now known to be our closest living relative, diverged sometime between 9 million and 6 million years ago.

      The human story
  8. 1970
    1. Cell division

      Studying baker’s yeast, geneticist Leland H. Hartwell identifies genes that regulate how cells divide as well as proteins that halt division if a cell’s DNA is damaged.

      The mystery of reproduction
    2. Quarks and the November revolution

      Two teams of physicists find a new subatomic particle, the J/psi, which, it soon became clear, could be explained only by a new type of quark, the charm quark. This discovery and others during the period, known as the November revolution, quelled lingering doubts that quarks were real constituents of larger particles such as protons, neutrons and the J/psi.

      Cracking the atom
    3. Lunar origins

      Astronomers William Hartmann and Donald Davis propose in 1975 the Giant Impact Hypothesis, suggesting the moon formed out of material ejected from Earth after a large collision. Space scientist Alastair Cameron and astronomer William Ward developed the same idea independently, proposing it in 1976.

      Shaking up Earth
    4. Milankovitch cycles

      Scientists find that Earth’s ice ages over the last 500,000 years correlate to three different orbital variations — cycles lasting about 23,000 years, 42,000 years (now said to be 41,000) and 100,000 years, confirming a hypothesis proposed decades earlier by astronomer Milutin Milankovitch.

      Shaking up Earth
    5. Body planning

      Work reported by Edward Lewis in 1978 and Christiane Nüsslein-Volhard and Eric Wieschaus in 1980 reveals which genes control early embryonic development in fruit flies. The discoveries help explain congenital defects and lead to research on similar genes that determine the human body plan.

      The mystery of reproduction
    6. black and white photo of Vera Rubin

      AIP Emilio Segrè Visual Archives, Rubin Collection

      Dark matter levels up

      Vera Rubin (shown), Kent Ford and Norbert Thonnard measure the rotation rates of stars in outer parts of galaxies, strongly implying the existence of dark matter.

      Our wild universe Unsung characters
  9. 1980
    1. Cosmic collision

      Luis Alvarez and Walter Alvarez publish a report saying that a large space rock hitting Earth was responsible for the mass extinction event 66 million years ago that killed off all nonbird dinosaurs. The father-son team proposed the idea at American Geophysical Union’s annual meeting the year before.

      Shaking up Earth
    2. Alzheimer’s discovery

      George Glenner and Caine Wong discovered a “novel cerebrovascular amyloid protein.” That was amyloid-beta, the key component of plaques in the brains of people with Alzheimer’s disease.

      Our brains, our futures
    3. schematic diagram of the nervous system of C. elegans

      J.G. White et al/Proceedings of the Royal Society B 1986

      Worm connectome

      Scientists trace the wiring diagram of the nervous system of a C. elegans worm.

      Our brains, our futures
    4. Walls and voids

      Margaret Geller, John Huchra and Valérie de Lapparent map a section of the observable universe, revealing a structure that encompasses large walls and giant voids.

      Our wild universe
    5. African Eve

      A controversial study of modern-day people’s mitochondrial DNA, a type of DNA passed down from mother to child, suggests that all humans can trace their maternal ancestry back to a population that lived in Africa roughly 200,000 years ago.

      The human story
    6. Great ocean conveyor

      Geochemist Wallace Broecker describes a global system of ocean currents that transports heat and salt between surface and deep waters and around the globe, influencing regional climates. 

      Shaking up Earth
    7. Novel antidepressant

      The drug fluoxetine, or Prozac, received approval from the U.S. Food and Drug Administration as a treatment for major depression.

      Our brains, our futures
    8. Genetic screening

      Alan Handyside of London’s Hammersmith Hospital is able to check an embryo for genetic defects before implanting it into a mother’s uterus. This testing, known as preimplantation genetic diagnosis or PGD, enables parents carrying a genetic or chromosomal defect to avoid passing it to their children.

      The mystery of reproduction
  10. 1990
    1. illustration of the hubble space telescope

      NASA

      Hubble launch

      NASA launches the Hubble Space Telescope (shown), one of the sharpest eyes to ever peer into the cosmos.

    2. Mount Pinatubo erupting

      Hoa-Qui/Science Source

      Pinatubo’s shade

      A powerful eruption from the Philippines’ Mount Pinatubo (shown) ejects millions of tons of sulfur dioxide into the stratosphere, temporarily cooling the planet.  

      Shaking up Earth
    3. Screengrab of SN news of the week on COBE

      Science News

      Signs of inflation

      Cosmologists detect temperature fluctuations in the cosmic microwave background, variations that correspond to ripples in the density of matter shortly after the Big Bang, as expected from inflation.

      Our wild universe
    4. a sheep

      Getty Images

      First cloned mammal

      Dolly the Sheep (shown) is the first mammal cloned from the DNA of an adult mammal. Ian Wilmut and Keith Campbell of the Roslin Institute transferred the nucleus of an adult mammary gland cell into an egg cell, showing that adult DNA can be reprogrammed to grow a new organism.

      The mystery of reproduction
    5. Neutrinos have mass

      Physicists discover that neutrinos, long thought to be massless, have a tiny amount of mass. The find raises a slew of still-unanswered questions, whether neutrinos are their own antiparticles, for example, or whether the particles can help explain the scarcity of antimatter in the universe.

      Cracking the atom
    6. photo of Alan Trounson

      Tim Grainger/Monash Univ./Flickr (CC BY-NC-ND 2.0)

      Vitrification

      Australian researcher Alan Trounson reports successful vitrification, a method that freezes eggs so rapidly that no crystals can form. The technique boosts the success rate for using frozen eggs in assisted reproduction.

      The mystery of reproduction
  11. 2000
    1. Earliest hominin?

      A nearly complete skull found in Chad and dating to between 7 million and 6 million years ago may be from the earliest known hominin, Michel Brunet and colleagues announce. The team names the find Sahelanthropus tchadensis.

      The human story
    2. The hobbit

      A surprising find is reported from the Indonesian island of Flores: A small-brained, short-statured hominin lived there about 100,000 to 50,000 years ago. Named Homo floresiensis, but often called the hobbit, the species may be a case of island dwarfism.

      The human story
    3. an electrode with a dime behind it for scale

      braingate2.org

      Brain implant

      An implanted grid of electrodes called BrainGate allows a paralyzed man to check his e-mail and play games with his brain activity alone.

      Our brains, our futures
    4. Quark-gluon plasma

      Physicists at Brookhaven National Laboratory smash nuclei of gold atoms together to recreate the phase of matter thought to have existed in the early moments of the universe. The quark-gluon plasma is a hot, dense soup of quarks intermingling freely with gluons, which under normal conditions bind quarks into larger particles like protons and neutrons.

      Cracking the atom
    5. Bullet Cluster image

      MARKEVITCH, ET AL., CLOWE, ET AL., MAGELLAN, UNIV. OF ARIZONA, CXC, CFA, STSCI, ESO WFI, NAS

      Dark matter in space

      By studying an intergalactic collision (which formed the Bullet Cluster, shown), researchers report compelling evidence of dark matter’s presence in space.

      Our wild universe
    6. illustration of the Kepler space telescope in space with a starry background

      NASA

      Kepler up

      The Kepler space telescope (illustrated) found thousands of planets outside our solar system before it stopped operating in 2018.

      Other worlds
    7. Human-Neandertal interbreeding

      The Neandertal is the first ancient hominin to have its genetic blueprint, or genome, pieced together. Studies of the ancient DNA reveal humans mated with Neandertals

      The human story
  12. 2010
    1. Western blinders

      Cross-cultural researchers led by anthropologist Joseph Henrich review evidence that members of Western, educated, industrialized, rich and democratic (WEIRD) societies are among the least useful populations to study in order to generalize about how resources get shared and other features of human nature.

      The science of us
    2. Tohoku-oki quake

      A magnitude 9.0 earthquake in Japan and the tsunami it spawned kill more than 15,000 people and damaged reactors at the Fukushima power plant, triggering the worst nuclear disaster since Chernobyl in 1986.

      Shaking up Earth
    3. Fukushima accident

      After an earthquake and tsunami, reactors at the Fukushima Daiichi Nuclear Power Station lost power and cooling, resulting in partial meltdowns, explosions and releases of radioactive material. Over 100,000 people were evacuated as a result.

      Cracking the atom
    4. © CERN (CC BY-SA 4.0)

      Higgs is found

      Physicists at CERN near Geneva report discovery of the final particle predicted by the standard model, the Higgs boson. Its existence confirms scientists’ beliefs about how fundamental particles obtain mass.

      Cracking the atom
    5. Sonia Harmand holding fossil

      West Turkana Archaeological Project

      Earliest stone tools

      Archaeologist Sonia Harmand (shown) and colleagues report that flakes, cores and pounding platforms discovered in Kenya are the oldest known stone tools yet found. They are 3.3 million years old, predating the genus Homo by at least half a million years.

      The human story
    6. Homo naledi

      Lee Berger and colleagues report finding a small-brained species of Homo, named Homo naledi, in a South African cave. Although the team thinks H. naledi was an early member of the genus, later dating shows it lived only about 300,000 years ago, making it a contemporary of Homo sapiens.

      The human story
    7. CRISPR baby

      Chinese scientist Jiankui He uses CRISPR/Cas9 to create the first gene-edited babies — twin girls — to reduce their risk of contracting HIV. His actions lead to the formation of an international commission on the clinical use of gene editing.

      The mystery of reproduction
  13. 2020