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Nuclear Forces (1666 – 1957)
Discoveries of the basic forces at work on the subatomic level lead to the realization that all interactions in the universe are the result of four fundamental forces of nature — the strong and weak nuclear forces, the electromagnetic force and gravitation. -
Microorganisms (1674)
Microscope lens grinder Anton Van Leeuwenhoek accidentally discovers microorganisms in a drop of water. Using his own microscopes, he observes sperm, bacteria and red blood cells. His observations lay the foundation for the sciences of bacteriology and microbiology. -
The Nature of Light (1704 – 1905)
Thought and experimentation by Isaac Newton, Thomas Young and Albert Einstein lead to an understanding of what light is, how it behaves, and how it is transmitted. Newton uses a prism to split white light into its constituent colors and another prism to mix the colors into white light, proving that colored light mixed together makes white light. Young establishes that light is a wave and that wavelength determines color. Finally, Einstein recognizes that light a -
Halley's Comet Has a Predictable Orbit (1705 – 1758)
Edmund Halley proves that comets orbit the sun like the planets and successfully predicts the return of Halley's Comet. He determines that comets seen in 1531 and 1607 are the same object following a 76-year orbit. Halley's prediction is proven in 1758 when the comet returns. Unfortunately, Halley had died in 1742, missing the momentous event. -
Electromagnetism (1807 – 1873)
Pioneering experiments uncover the relationship between electricity and magnetism and lead to a set of equations that express the basic laws governing them. One of those experiments unexpectedly yields results in a classroom. In 1820, Danish physicist Hans Christian Oersted is speaking to students about the possibility that electricity and magnetism are related. During the lecture, an experiment demonstrates the veracity of his theory in front of the whole class. -
Atomic Theory (1808)
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 (1820s – 1840s)
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. -
Rules of Heredity (1850s)
Austrian monk and botanist Gregor Mendel discovers how genetic information is passed down through generations. In experiments performed on pea plants, he notices that characteristics of a plant's offspring, such as height, exhibit recessive and dominant behavior. Mendel's findings are ridiculed during his lifetime and he dies never knowing that he would come to be known as the "father of genetics." -
Plastics (1869 and 1900s)
John Wesley Hyatt formulates celluloid plastic for use as a substitute for ivory in the manufacture of billiard balls. Celluloid is the first important synthetic plastic and is used as a substitute for expensive substances such as ivory, amber, horn and tortoiseshell. Later, Leo Baekeland invents hardened plastics, specifically Bakelite, a synthetic substitute for the shellac used in electronic insulation. -
Sex Cells (1884)
August Weismann identifies that sex cells must have divided differently to end up with only half of a chromosomal set. This very special division of sex cells is called meiosis. Weismann's experiments with reproduction in jellyfish lead him to the conclusion that variations in offspring result from the union of a substance from the parents. He refers to this substance as "germ plasm." -
E = mc^2 (1905)
Or energy is equal to mass times the speed of light squared. Albert Einstein's famous formula proves that mass and energy are different manifestations of the same thing, and that a very small amount of mass can be converted into a very large amount of energy. One profound implication of his discovery is that no object with mass can ever go faster than the speed of light. -
Ecosystem (1935)
Arthur George Tansley coins the term ecosystem and single-handedly bridges the biology in ecology with the physics, chemistry and other fields of science that describe the environment. An ecosystem is defined as a dynamic and complex whole that functions as an ecological unit. -
The Krebs Cycle (1937)
Hans Krebs identifies the many steps the cell takes to convert sugars, fats and proteins into energy. Also known as the citric acid cycle, it is a series of chemical reactions using oxygen as part of cellular respiration. The cycle contributes to the breakdown of carbohydrates, fats and proteins into carbon dioxide and water. -
DNA Is a Double Helix (1953)
James Watson and Francis Crick describe the DNA molecule. The scientists suggest that the DNA molecule is made of two chains of nucleotides, each in a helix, one going up and the other going down. Crick adds the idea that matching base pairs interlock in the middle of the double helix to keep the distance between the chains constant. They show that each strand of the DNA molecule is a template for the other, and that DNA can reproduce itself without changing its stru -
Australopithecus Afarensis or "Lucy" (1974)
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.
