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Venetian mathematician Giambattista Benedetti publishes two editions of Demonstratio proportionum motuum localium, developing his new doctrine of the speed of bodies in free fall.

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Galileo publishes La Billancetta, describing an accurate balance to weigh objects in air or water.

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Glass lenses are developed in the Netherlands and used for the first time in microscopes and telescopes.

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Galileo presents to Cesi, founder of the Lincean Academy, a "little eyeglass" (a microscope). The invention will enable the Linceans to study natural objects with unprecedented precision. They will start with bees, then move on to flies and dust mites.

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Isaac Newton discovers that white light is composed of different colors.

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The English physicist Sir Isaac Newton argues that light is composed of particles, which are refracted by acceleration toward a denser medium, and posits the existence of “aether” to transmit forces between the particles.

The first quantitative estimate of the speed of light was made in 1676 by Danish astronomer Ole Rømer. From the observation that the periods of Jupiter's innermost moon Io appeared to be shorter when the Earth was approaching Jupiter than when receding from it, he concluded that light travels at a finite speed, and estimated that it takes light 22 minutes to cross the diameter of Earth's orbit. Christiaan Huygens combined this estimate with an estimate for the diameter of the Earth's orbit to obtain an estimate of speed of light of 220000 km/s, 26% lower than the actual value.

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Benjamin Franklin describes electricity as a single fluid and distinguishes between positive and negative electricity in Experiments and Observations on Electricity. He shows that electricity can magnetize and demagnetize iron needles.

The lightning conductor is invented by Benjamin Franklin, whose experiments with lightning include a flying a kite in a thunderstorm. The kite experiment shows that lightning is a form of electricity, similar to the discharge from a Leyden jar.

Russian scientist Georg Wilhelm Richmann is killed performing a lightning experiment in St. Petersburg. Richmann is electrocuted in while trying to quantify the response of an insulated rod to a nearby storm. The incident, reported worldwide, underscored the dangers inherent in experimenting with insulated rods and in using protective rods with faulty ground connections.

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William Cullen observes the cooling effect of evaporating liquids and publishes the results in An Essay on the Cold Produced by Evaporating Fluids and Other Means of Producing Cold.

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Photometria by German physicist Johann Lambert is an investigation of light reflections from planets, introducing the term ALBEDO (whiteness) for the differing reflectivities of planetary bodies.

In experiments with primitive apparatus, Daniel Bernoulli decides that the electrical force obeys an inverse square law similar to that of gravity.

Joseph Black discovers latent heat by finding that ice, when melting, absorbs heat without changing in temperature. Later he measures the latent heat of steam — that is, the heat required to keep water boiling without raising its temperature.

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Leonhard Euler gives a general treatment of the motion of rigid bodies, including the precession and nutation of earth, in Theoria motus corporum solidorum seu rigidorum (Theory of the motion of solid and rigid bodies).

Horace-Bénédict de Saussure invents the electrometer, a device for measuring the electric potential by means of the attraction or repulsion of charged bodies.

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John Robison measures the repulsion between two charged bodies and shows that this force is inversely proportional to the distance between the two bodies.

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Swedish scientist Johan Carl Wilcke calculates the latent heat of ice (the amount of heat absorbed when ice turns into water).

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Alessandro Volta describes his electrofore perpetuo device for producing and storing a charge of static electricity. This device replaces the Leyden jar and eventually leads to modern electrical condensers.

Pierre-Simon Laplace states that if all of the forces on all objects in any one time are known, then the future can be completely predicted.

Charles-Augustin Coulomb invents the torsion balance.

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Coloumb's Théorie des machiones simple (Theory of simple machines) is a study of friction.

Johan Carl Wilcke introduces the concept of SPECIFIC HEAT.

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Horace-Bénédict de Saussure's Essais sur l'hygromé (Essay on measuring humidity) describes how to construct a hygrometer from human hair that can measure relative humidity.

George Atwood accurately determines the acceleration of a free-falling body.

Couloumb makes precise measurements of the forces of attraction and repulsion between charged bodies and between magnetic poles, using a torsion balance, demonstrating conclusively that electric charge and magnetism obey inverse-square laws like that of gravity. He also discovers that electrically charged bodies discharge spontaneously. In the 20th century, it is found that cosmic radiation is responsible for this discharge.

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Jacques-Alexandre Charles shows that different gases expand by the same amount for a given rise in temperature (Charles Law).

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The French chemist Antoine-Laurent de Lavoisier definitively states the Law of Conservation of Mass (although others had previously expressed similar ideas, including the ancient Greek Epicurus, the medieval Persian Nasir al-Din al-Tusi and the 18th Century scientists Mikhail Lomonosov, Joseph Black, Henry Cavendish and Jean Rey), and identifies (albeit slightly incorrectly) 23 elements which he claims can not be broken down into simpler substances.

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Luigi Galvani announces that electricity applied to severed frog's legs causes them to twitch and that frogs legs twitch in the presence of two different metals with no electric current present. The latter discovery eventually leads to Alessandro Volta's developing the electric battery.

Pierre Prévost develops his theory of exchanges of radiation of heat. He correctly shows that cold is merely the absence of heat and that all bodies continually radiate heat. If they seem not to radiate heat, it means that they are in heat equilibrium with their environment.

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Alessandro Volta demonstrates that the electric force observed by Galvani is not connected with living creatures, but can be obtained whenever two different metals are placed in a conducting fluid.

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Henry Cavendish determines the mass of Earth by measuring the gravity between two small masses and two large masses. This gives the gravitational constant G, which was the only unknown in Newton's equations. Solving for G enables Cavendish to establish that Earth is about 5.5 times as dense as water.

Enquiry concerning the source of heat which is excited by friction by Count Rumford (Benjamin Thompson) describes his experiments with boring cannons that show that the caloric theory of heat cannot be true, and that heat should be considered a kind of motion.

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Alessandro Volta announces his invention, made in 1799, of the electric battery, also known as the Voltaic pile. It consists of a stack of alternating zinc and silver discs separated by felt soaked in brine. It is the first source of a steady electric current.

William Herschel's "An investigation of the powers of prismatic colors to heat and illuminate objects" tells of his discovery of infrared radiation. While investigating the power of different parts of the spectrum to heat a thermometer, he finds that invisible light beyond the red produces the most heat.

The English scientist Thomas Young demonstrates, in his famous double-slit experiment, the interference of light and concludes that light is a wave, not a particle as Sir Isaac Newton had ruled.

Thomas Young's On the theory of light and colors is the first of three pivotal papers describing his wave theory of light.

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John Leslie's An experimental inquiry into the nature and propagation of heat establishes that the transmission of heat through radiation has the same properties as the propagation of light.

Pierre-Simon Laplace measures molecular forces in liquids and announces his theory of capillary forces.

The English chemist John Dalton develops his atomic theory, proposing that each chemical element is composed of atoms of a single unique type, and that, though they are both immutable and indestructible, they can combine to form more complex structures.

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Thomas Young introduces the concept of, and is the first to use the word, ENERGY.

Étienne-Louis Malus discovers that reflected light is polarized and introduces the term POLARIZATION.

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William Hyde Wollaston invents the camera lucida, a device for projecting an image onto a flat surface, such as drawing paper, on which the object can then be traced.

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Augustin Fresnel demonstrates with his mirror experiment the wave nature of light. He also gives an explanation of polarization.

Thomas Young and Augustin Fresnel demonstrated that light waves must be transverse vibrations.

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André-Marie Ampère formulates one of the basic laws of electromagnetism, the right-hand rule for the influence of an electric current on the magnet and demonstrates that two wires that are carrying an electric current will attract or repel each other, depending on whether the occurrence are in opposite where the same directions.

Dominique-François Arago discovers the magnetic effect of electricity passing through a copper wire, demonstrating that iron is not necessary for magnetism.

Augustin-Jean Fresnel invents the so-called Fresnel lens, a lens used in lighthouses.

The science of electrodynamics is born with the announcement of Hans Christian Ørsted's discovery of electromagnetism.

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Réflexions sur la puissance motrice du feu (On the motive power of fire) by Nicolas Léonard Sadi Carnot shows that work is done as heat passes from a high temperature to a low temperature; defines work; hints at the second law of thermodynamics; and suggests internal combustion engines.

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Theory of systems of rays by William Rowan Hamilton is a unification of the study of optics through the principle of "varying action". It contains his correct prediction of conical refraction. When his prediction is verified, he becomes a well-known and is knighted.

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Gustave-Gaspard Coriolis coins the term KINETIC ENERGY in On the calculation of mechanical action.

Joseph Henry shows that passing an electric current through a wire wrapped into coils produces a greater magnetic field than is produced when that same current is passed through a straight wire, and that an insulated wire wrapped around an iron core can produce a powerful electromagnet.

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Independently, Michael Faraday and Joseph Henry discover that electricity can be induced by changes in a magnetic field (electromagnetic induction), a discovery leading to the first electric generators.

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In correspondence, Michael Faraday and William Whewell introduce the terms ELECTRODE, ANODE, ION, CATHODE, ANION, CATION, ELECTROLYTE, and ELECTROLYSIS.

Mathematician Carl Friedrich Gauss (1777-1855) shows that the origin of the Earth's magnetic field must lie deep inside the Earth. He makes use of the measurements of the magnetic field made by the physicist Paul Erman in 1828.

Gustave-Gaspard Coriolis's Mémoire sur les equations du mouvement relatif des sytèms de corps (Memoir on the equations of relative movement of systems of bodies) describes the Coriolis effect: the deflection of a moving body caused by Earth's rotation. The Coriolis effect is important in the study of wind. However, the claim that the Coriolis effect determines the direction water rotates when going down a drain is a myth.

John Frederic Danielle invents the Daniell cell, the first reliable source of electric current, based on the interactions of copper and zinc.

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The English scientist Michael Faraday concludes from his work on electromagnetism that, contrary to scientific opinion of the time, the divisions between the various kinds of electricity are illusory. He also establishes that magnetism can affect rays of light, and that there is an underlying relationship between the two phenomena.

Alexandre-Edmond Becquerel shows that light can initiate chemical reactions that produce an electric current.

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German physician and physicist Julius Robert Mayer is the first to state the law of conservation of energy, noting specifically that heat and mechanical energy are two aspects of the same thing.

On the uniform motion of heat in homogeneous solid bodies, by William Thomson, aka Lord Kelvin (1824-1907), is published. Thomson's concern with the physics of cooling bodies will draw him into debates concerning the age of the Earth. In 1846 he calculates that the Earth can be no more than 100 million years old.

The change in the observed frequency of waves emitted from a source, moving relative to the observer, is described by Christian Johann Doppler (1803-1853). This phenomenon is now known as the Doppler Effect.

James Prescott Joule determines the mechanical equivalent of heat by measuring the rise in temperature produced in water by stirring it.

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Michael Faraday relates magnetism to light after finding the magnetic field effects the polarization of light in crystals. He proposes that light may be waves of electromagnetism. He also describes the phenomena of diamagnetism and paramagnetism, which he explains in terms of his concept of a magnetic field.

James Prescott Joule discovers that the length of an iron bar changes slightly when the bar is magnetized.

Über die Erhaltung der Kraft ("On the Conservation of Force"), by Hermann Ludwig von Helmholtz (1821-1894), is published. It articulates what later becomes known as the Conservation of Energy.

An absolute scale of temperatures is proposed by William Thomson (1824-1907). Thomson will become Baron Kelvin of Largs, in 1892, and the scale will come to bear his name.

Armand Hippolyte Louis Fizeau suggests that light from a source of moving away from the observer will be shifted toward the red end of the spectrum, a phenomenon known as redshift. This is closely related to, but not exactly the same as, the Doppler effect.

Armand Hippolyte Louis Fizeau measures the velocity of light in error by measuring the time it takes for a beam of light to pass between the teeth of a rotating gear. The light is reflected by a mirror and stopped by the next tooth of the gear. The result, 315,000 km/se4c (196,000 miles/sec), is within 5% of today's accepted value.

In describing Sadi Carnot's theory of heat, published in 1824, William Thomson (1824-1907) uses the term THERMODYNAMICS.

The speed of light is measured by physicist Armand Hippolyte Louis Fizeau (1819-1896) to be approximately 186,000 miles per second.

In Über die bewegende Kraft der Wärme, mathematical physicist Rudolf Julius Emanuel Clausius articulates what comes to be known as the Second Law of Thermodynamics. The law states that heat can only be transferred from a warmer body to a colder body. In 1865, he'll restate the Law, saying that in the closed system entropy always increases.

Léon Foucault demonstrates that the Earth rotates using a pendulum, suspended from the ceiling of a church.

Physicist William Thomson proposes a concept of "absolute zero", at which the energy of molecules is zero. He draws on Charles' Law to show that such a condition would hold at -273 degrees Celsius.

James Prescott Joule and William Thompson, later Lord Kelvin, establish that an expanding gas becomes cooler. This is now known as the Joule-Thompson effect.

Léon Foucault demonstrates that the velocity of light is lesson water than in air, tending to confirm the wave theory of light.

William John Macquorn Rankine introduces the concept of potential energy, or energy of position.

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Über die Art der Bewegung, welche wir Wäe nennen (On the type of motion turned heat) by Rudolf Clausius is establishes his kinetic theory of heat of the mathematical basis. It also explains how evaporation occurs.

Julius Plücker shows that cathode rays bend under the influence of a magnet, suggesting they are connected in some way with charge. This is an early step along the path that will lead in 1897 to the discovery that cathode rays are composed of electrons.

Gustav Kirchoff recognizes that sodium is found on the sun and discovers his black-body radiation law.

Physicist Gustav Robert Kirchhoff and chemist R. W. Bunsen explain that when light passes through a gas, or heated material, only certain wavelengths of the light are absorbed. Therefore, an analysis of the spectrum of the light can reveal the chemical makeup of the gas or material.

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James Clerk Maxwell's A dynamical theory of the electromagnetic field is the first of his publications to use Michael Faraday's concept of a field as the basis of the mathematical treatment of electricity and magnetism. It introduces Maxwell's equations to describe electromagnetism.

Rudolf Clausius invents the term ENTROPY to describe the degradation of energy in the closed system.

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George Johnstone Stoney notes that the wavelengths of three lines in the hydrogen spectrum are found to have simple ratios, and anticipation of Balmer's formula, an important step towards understanding the structure of the atom.

James Clerk Maxwell explains how his statistical theory of heat works by inventing MAXWELL'S DEMON, a mythical creature that can see and handle individual molecules. By opening a gate between two vessels containing a gas only one of fast molecules passing into one, the demon would make heat flow from cold to hot.

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James Clerk Maxwell's Electricity and Magnetism contains the basic laws of electromagnetism and predicts, in great detail, such phenomena as radio waves and pressure caused by light rays.

Irish physicist George J. Stoney estimates the charge of the then unknown electron to be about 10^-20 coulomb, close to the modern value of 1.6021892 x 10^-19. He also introduces the term ELECTRON.

The Cavendish laboratory at Cambridge is completed. Although widely believed to have been named after the 18th-century physicist Henry Cavendish, it is, in fact, named after the entire Cavendish family, because the 19th century steel-making descendent of Henry, William Cavendish, financed the laboratory. The structure of DNA was worked out at the Cavendish many years later by Watson and Crick.

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Eugen Goldstein shows that the radiation in a vacuum tube produced when an electric current is forced through the tube starts at the cathode. Goldstein introduces the term CATHODE RAY to describe the light emitted.

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Pierre Curie discovers the piezoelectric effect: certain substances produce an electric current when they are physically distorted, and conversely they are physically distorted when an electric current is applied to them. This effect has many applications, including, in the 21st century, the construction of high-end tweeters in stereo systems.

Hermann Ludwig von Helmholtz shows that the electrical charges in atoms are divided into definite integral portions, suggesting the idea that there is a smallest unit of electricity.

John William Strutt, Lord Rayleigh, discovers that the ratio of the atomic mass of oxygen to that of hydrogen is not 16 exactly, as had been assumed, but 15.882.

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Johann Jakob Balmer discovers the formula for the hydrogen spectrum that will later inspire Niels Bohr to develop his model of the atom.

William Crookes proposes that atomic weights measured by chemists are averages of the weights of different kinds of atoms of the same element (although it will not be until 1910 that Frederick Soddy identifies these different kinds of atoms as isotopes).

Albert Michelson and Edward Morley measure the velocity of light in two directions, attempting to detect the proper motion of Earth through the ether (a hypothesized fluid that was assumed to fill all space, providing a medium for the transport of electromagnetic waves). The Michelson Morley experiment reveals no evidence of motion.

Ernst Mach notes that airflow becomes disturbed at the speed of sound.

Heinrich Rudolf Hertz produces and detects radio waves for the first time. Radio waves will be called Hertzian waves until renamed by Marconi, who calls them radiotelegraphy waves.

George Francis Fitzgerald formulates the principle that objects shrink slightly in the direction they are traveling, now known as the Fitzgerald-Lorenz contraction, since Hendrik Antoon Lorentz reaches the same conclusion a few years later.

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Wilhelm Wien discovers that the maximum wavelength emitted by hot body varies inversely with its absolute temperature. Wien's law becomes useful in establishing the temperature of stars. The problems he has with deriving an equation to describe black-body radiation lead to Max Planck's introduction of the quantum in 1900.

Joseph John (J.J.) Thomson announces that he has found that the velocity of cathode rays is much lower than that of light.

Charles Thomson Rees Wilson develops the CLOUD CHAMBER, a box containing a gas that is saturated. When a charged particle passes through the gas, small droplets are formed that make the track of the particle visible. The cloud chamber becomes a powerful tool in particle physics.

Pierre Curie shows that as the temperature of the magnet is increased, there is a level at which the magnetism is disrupted and ceases to exist. This temperature is still called the Curie point.

Wilhelm Konrad Röntgen (Roentgen) discovers X-rays, which will soon be applied in the visualization of bodily structures and in the induction of genetic mutations (both intentionally and accidentally).

Antoine-Henri Becquerel discovers rays produced by uranium — the first observation of natural radioactivity.

Joseph John Thomson discovers the electron, the first known particle that is smaller than an atom, in part because he has better vacuum pumps that were previously available. He, and independently, Emil Wiechert, determine the ratio of mass to charge of the particles by deflecting them by electric and magnetic fields.

Marie Curie begins research of "uranium rays" that will lead to the discovery of radioactivity.

Marie and Pierre Curie discovered that thorium, gives off "uranium rays", which Marie renames RADIOACTIVITY.

British physicist Ernest Rutherford discovers the radioactivity from uranium has at least two different forms, which he calls alpha and beta rays.

Fritz Geisel, Antoine-Henri Becquerel, and Marie Curie proved the beta rays consist of high-speed electrons.

Paul Karl Ludwig Drude shows that moving electrons conduct electricity in metals.

Paul Ulrich Villard is the first to observe a radiation that is more penetrating than X-rays, now called gamma rays.

On December 14, Max Planck announces the first step toward quantum theory. He states that substances can emit light only at certain energies, which implies that some physical processes are not continuous, but occur only in specified amounts called quanta.

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Physicist Ernest Rutherford lectures the British Association that radioactivity could power the sun and maintain its heat, meaning the sun and Earth could be much older than Lord Kelvin's estimate.

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Albert Einstein proposes the special theory of relativity (E=mc²).

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