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Period: 400 BCE to 370 BCE
The Contributions of Democritus
Democritus was the first to propose the existence of atoms in 400 B.C. He reasoned that matter cannot be divided indefinitely and must consist of indivisible round particles called atoms. -
Period: to
The Contributions of Isaac Newton
Isaac Newton argued that the geometric nature of reflection and refraction of light could only be explained if light were made of particles, referred to as corpuscles, because waves do not tend to travel in straight lines. -
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The Contributions of John Dalton
Dalton hypothesized that the law of conservation of mass and the law of definite proportions could be explained using the idea of atoms. He proposed that all matter is made of tiny indivisible particles called atoms, which he imagined as "solid, massy, hard, impenetrable, movable particle(s)" -
Period: to
The Contributions of Einstein
Einstein believed light is a particle (photon) and the flow of photons is a wave. He maintained that photons have energy equal to "Planck's constant time's oscillation frequency," and this photon energy is the height of the oscillation frequency while the intensity of light is the number of photons.