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DATE	EVENT
c. 3500 BC	Metal mirrors are used in Egypt
c. 2500 BC	Chinese place vertical poles in the ground to create a shadow in order to estimate time
c. 1430 BC	Egyptians measure the hours of day with shadow clocks fashioned out of a flat piece of wood with a raised arm.
c. 530 BC	Anaximenes of Turkey believes that air is the primary substance and can be changed into other substances (clouds, wind, rain) by thinning and thickening.
c. 520 BC	Anaximander of Greece thinks that the sun and moon are rings of fire surrounded by air.
c. 520 BC	Anaximander introduces the sundial to Greece.
c. 500 BC	Alcmaeon of the Pythagorean school believed that the eye has fire within it that seizes the object and forms an image in the eye.
c. 460 BC	Democritus of Greece, student of Leucippos, the first Greek atomist, believes that the world is composed of an infinite number of invisible atoms in a sea of nothingness.
c. 400's BC	Plato of Greece presents the theory that visual fire emanates from the eye, joins with light and comes into contact with emanations coming from the visible object in order to form the image.
c. 300's BC	Aristotle of Greece identifies the "watery" part of the eye as visually sensitive.
c. 300 BC	Euclid's bases his model of vision on geometry- rays proceed in straight lines from the eyes, the rays come together in the shape of a cone, and the visual object intercepts the rays.
c. 300 BC	Moist School of China understands how the image that passes through a pinhole is turned upside down.
c. 165 BC	Astronomers from China record sunspots
c. 150	Ptolemy of Greece notes the bending of light as it enters the Earth's atmosphere.
c. 850	Arabic philosopher Al-Kindi believes that vision is the result of something external entering the eye that causes a physiological effect.
c. 900	The Mayans use calendars based upon the astronomical observations. Today, these calendars are considered one of the most accurate ancient tools for measuring time. The calendars are off one day every 6000 years, more accurate than our modern calendars.
c. 1000	Arabic scientist Alhazen states that the light we see from luminous and illuminated objects enters the eye.
c. 1126-98	Islamic scientist Averoes identifies the retina as the photosensitive part of the eye.
1450	Leon Battista Alberti of Italy uses an instrument that resembles a weathervane with a small swinging metal plate for measuring wind speed. Its name is an anemometer.
c. 1600's	Galileo Galilei, Italy, made efforts to measure the speed of light. He concludes that the speed of light is too fast to measure with the instruments he has available.
1604	Johannes Kepler of Germany develops his theory of retinal vision and the retinal image, or picture.
1608	Dutch scientists Hans Lippershey and Zacharias Jansen construct the first telescopes used for magnifying distant objects on Earth.
1609, 1619	Johannes Kepler of Germany published his three laws of planetary motion. The first law describes the orbit of the Earth and other planets around the Sun as elliptical.
1621	Willebrord Snell, Holland, discovers that the refraction of light is determined by the sine of the angle made by the incident ray (Snell's Law)
c. 1630	Descartes of France believes that the vibrations of the particles that compose all bodies cause light.
1643	Evangelista Torricelli makes the first mercury barometer for measuring atmospheric pressure.
c. 1650	Pierre de Fermat, France, formulates the idea that light travels in the path that takes the least amount of time.
1668	Newton uses a concave mirror in designing the reflective telescope. Newton also invents the reflecting telescope and discovers using prisms that white light is a combination of all colors.
1665	Italian, Francesco Maria Grimaldi describes his experiments with diffraction of light and his theory that light is wave.
1678	Dutch physicist and astronomer Christiaan Huygens writes a treatise on light explaining the wave theory of light.
1704	Isaac Newton of England accepts the theory that light is particulate although those particles may vibrate.
1714	Gabriel Daniel Fahrenheit, Germany, builds a mercury thermometer and names the scale after himself.
1742	Anders Celsius, Sweden, invents the Celsius scale, using 0 for the boiling point of water and 100 for the freezing point.
1743	Jean Pierre Christin switches Celsius scale to be 0 for the freezing point and 100 for the boiling point of water.
1761	German physicist and astronomer Johann Heinrich Lambert, in his studies of the light reflections from planets, introduces the term "albedo" in order to describe the differing reflective properties of planets.
1771	German physicist and astronomer Johann Heinrich Lambert proposed global meteorological observations.
1779	Jan Ingenhousz of Holland discovers two distinct respiratory cycles in plants. At night, oxygen is absorbed and carbon dioxide is exhaled. In the day, carbon dioxide is absorbed and oxygen is exhaled.
1779	Jan Ingenhousz of Holland concludes that leaves need sunlight in order to produce oxygen.
1781	Joseph Priestly, England, begins making a connection between water and the components of air by showing that water forms when hydrogen is ignited in oxygen.
1800's	Thomas Young and Hermann von Helmholtz establish their theory of color vision.
1801	Thomas Young proves the wave theory of light by rediscovering that light passing through two narrow slits creates interference pattern.
1804	Nicolas de Saussure, Switzerland, shows that plants need carbon dioxide from air and nitrogen from the soil.
1807–1873	Jean Louis Agassiz of, Switzerland, research and formulates his theory that a great Ice Age had one gripped Europe.
1822	Joseph Niepce uses silver chloride to produce the earliest known photograph.
1847	James Joule of England discovers the law of conservation of energy by conducting experiments to confirm the transformation of mechanical energy into heat.
1848	Hippolyte Fizeau states that light from an object moving away from the observer shifts to the red part of the light spectrum, known as redshift.
1849	Hippolyte Fizeau measurs the speed of light in air within 5% of today's accepted speed.
1851	Hippolyte Fizeau concludes that the speed of light in water flowing in the same direction is faster than water flowing in the opposite direction of the light propagation.
1862	Using Henry Dirks creation, Henry Pepper debuts the world's first special effect. By using partially mirrored glass and light, he is able to create the illusion of an ghost. The effect is used in theatre and is known as Pepper's Ghost.
1865	Rudolf Clausius of Germany uses the word entropy to describe the degradation of energy.
1866	Ernst Heinrick, Germany, uses the word ecology for the first time.(Oecologie in German.)
1890	Thomas Edison's light bulb goes into production and is an immediate success.
1882	Theodore Engelmann, German botanist, measures oxygen produced by algae when exposed to different colored light.
1901	Eastman Kodak, United States, introduces the Brownie camera.
1902	Phillip von Lenard, Czechoslovakia, discovers that in the photoelectric effect of light, the energy released from the transmission of electrons is a factor of wavelength of light rather than light intensity.
1905	Albert Einstein publishes a theory of light. In his theory, light behaves like particles of energy. Later, particles will be termed photons.
1921	Albert Einstein receives the Nobel Prize for Physics for his discovery of the law of photoelectric effect.
1921	Albert Michelson measures the velocity of light with less than a .00001% error.
1928	Edwin Land of the U.S. developes a polarized light filter for cameras.
1940's	Yugoslavian scientist, Milutin Milankovic made calculations about the orbit of the Earth around the Sun revealing variations in the Earth's orbit and tilt. These variations help explain some of the changes in climate on Earth.
1945	Melvin Calvin, American, investigates photosynthesis by supplying a green plant with radioactive carbon dioxide and tracing the path of carbon.
1951	Columbia Broadcasting, United States, transmits the first commercial color television broadcast using a system developed by Peter Goldmark.
1955	Narinder Kapary, England, produces the first optical fibers.
1959	Xerox photocopier is introduced.
1968	US Air Force scientists show that radar can used to detect wind shifts.