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The basic idea that matter is made up of tiny indivisible particles is an old idea that appeared in many ancient cultures. The word atom is derived from the ancient Greek word atomos, [a] which means "uncuttable". This ancient idea was based in philosophical reasoning rather than scientific reasoning.
Niels Henrik David Bohr (7 October 1885 – 18 November 1962) was a Danish theoretical physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922.
1897 J. J. Thomson discovered the electron; 1897 Emil Wiechert, Walter Kaufmann and J.J. Thomson discover the electron; 1898 Marie and Pierre Curie discovered the existence of the radioactive elements radium and polonium in their research of pitchblende; 1898 William Ramsay and Morris Travers discover neon, and negatively charged beta particles
In 1898, J. J. Thomson found that the positive charge of a hydrogen ion is equal to the negative charge of an electron, and these were then the smallest known charged particles. [22] Thomson later found that the positive charge in an atom is a positive multiple of an electron's negative charge. [23]
Magnenus was the first to arrive at a scientific estimate of the size of an "atom" (i.e. of what would today be called a molecule). Measuring how much incense had to be burned before it could be smelled everywhere in a large church, he calculated the number of molecules in a grain of incense to be of the order 10 18 , only about one order of ...
De Broglie's treatment of the Bohr atom was ultimately unsuccessful, but his hypothesis served as a starting point for Schrödinger's wave equation. Matter behaving as a wave was first demonstrated experimentally for electrons: a beam of electrons can exhibit diffraction, just like a beam of light or a water wave. Three years after de Broglie ...
Scientists have made many guesses for what dark matter could be, ranging from unknown particles to extra dimensions. But Hawking’s black holes theory has only lately come into play.
Many more types of subatomic particles have been found. Most such particles (but not electrons) were eventually found to be composed of even smaller particles such as quarks. Particle physics studies these smallest particles; nuclear physics studies atomic nuclei and their (immediate) constituents: protons and neutrons.