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Mar 1, 1543
The Earth Moves
Nicolaus Copernicus places the sun, not the Earth, at the center of the solar system. -
Aug 16, 1543
The Heliocentric Model
Astronomers had speculated about heliocentrism (the idea that the Earth revolves around the sun, not the other way around) since ancient times, but in 1543 Copernicus was the first person to actually demonstrate the math behind the idea to prove it was a viable concept. -
Jupiter Has Moons
Galileo Galilei discovers that Jupiter has moons like the Earth, proving that Copernicus, not Ptolemy, is right. Copernicus believes that Earth is not unique, but instead resembles the other planets, all of which orbit the sun. -
Oxygen
Joseph Priestley discovers oxygen; later. Priestley produces oxygen in experiments and describes its role in combustion and respiration. Then, by dissolving fixed air in water, he invents carbonated water. Priestley, oblivious to the importance of his discovery, calls the new gas "dephlogisticated air." Lavoisier gives oxygen its name and correctly describes its role in combustion. Lavoisier then works with others to devise a chemical nomenclature, which serves as the basis of the modern system -
Atomic Theory
John Dalton provides a way of linking invisible atoms to measurable quantities like the volume of a gas or mass of a mineral. His atomic theory states that elements consist of tiny particles called atoms. Thus, a pure element consists of identical atoms, all with the same mass, and compounds consist of atoms of different elements combined together. -
First Dinosaur Fossils Identified
In 1822, geologist William Buckland uncovers some really big teeth in England. At the time, there is no word to describe his finds. Twenty years later, in 1842, Sir Richard Owen comes up with the word "dinosaur" to describe several spectacular creatures whose fossils are discovered across England. Megalosaurus is the first dinosaur ever named. -
Periodic Table of the Elements
Dmitry Mendeleyev realizes that if all of the 63 known elements are arranged in order of increasing atomic weight, their properties are repeated according to certain periodic cycles. He formulates the periodic table of the elements and predicts the existence of elements that have not yet been discovered. Three of those elements are found during his lifetime: gallium, scandium and germanium. -
The Electron
J.J. Thomson discovers that the negatively charged particles emitted by cathode ray tubes are smaller than atoms and part of all atoms. He calls these particles, now known as electrons, "corpuscles." -
The Theory of Relativity
Albert Einstein proposed his theory of relativity in 1915. Summed up, the theory states that mass can warp both space and time, which allows large masses like stars to bend light. -
The universe is expanding
Edwin Hubble determines the distance to many nearby galaxies and discovers that the farther they are from us, the faster they are flying away from us. His calculations prove that the universe is expanding. -
Potential for Life Created
Graduate student Stanley Miller, combining the ideas of other scientists, reproduces the early atmosphere of Earth by creating a chamber containing only hydrogen, water, methane and ammonia. He boils the water and exposes the elements to an electric discharge like lightning, simulating Earth's early processes. After a week, Miller finds organic compounds have formed, including some amino acids, the "building blocks of life." -
Cosmic Microwave Background Radiation
Arno Penzias and Robert Wilson discover cosmic microwave background radiation, which they suspect is the afterglow of the big bang. Their measurements, combined with Edwin Hubble's earlier finding that the galaxies are rushing away, make a strong case for the big bang theory of the birth of the universe. -
Australopithecus Afarensis or "Lucy"
Donald Johanson discovers the partial skeleton of a 3.2 million-year-old female hominid in Ethiopia. Johnson dubs his find "Lucy" after the Beatles' song Lucy in the Sky With Diamonds, which was playing on the radio as the team celebrated the find. -
Toumai skull
Michel Brunet unearths the oldest hominid fossil to date in the desert of the central African nation of Chad. The fragments of this 6 to 7 million-year-old skull, with characteristics resembling humans, were found outside eastern and southern Africa, suggesting human evolution may have been taking place all across the continent. -
Humans Have 20,000 to 25,000 Genes
Upon sequencing the human genome, it's discovered that humans have approximately 20,000 to 25,000 genes, far fewer than most scientists had predicted. It is hoped that understanding the genome will boost the fields of medicine and biotechnology, eventually leading to cures for diseases such as cancer and Alzheimer's disease.