A Physics Review of Subatomic Particles
Overview: What Are Subatomic Particles?
Subatomic particles include those particles smaller than an atom. Some of those particles are charged, such as protons, which have a positive charge, and electrons, which have a negative charge. Some particles have brief lifetimes, and have only been observed since the development of particle accelerators. These form the basis of atomic theory.
Particles or Waves?
According to the theory of relativity, matter and energy are interchangeable. (Einstein showed their relationship in the famous equation E=mc2, or energy equals mass times the speed of light squared.) It was first shown that photons sometimes behave like particles and sometimes like waves, depending on the situation. These particles have fuzzy boundaries, and not all interactions between wave particles are as clear-cut as scientists first thought. In addition, other particles (not just photons) act like wave particles, waves sometimes, and particles sometimes.
What Are Quarks?
Quarks are a type of fundamental particle that are found in six different “flavors” called up, down, strange, charm, bottom, and top. Most of them have only been discovered in particle accelerators, as they are always found together and some types decay very rapidly. They are thought to be involved in electromagnetic energy, gravity, the strong interaction, and the weak interaction, and some types were thought to have been present in the earliest time frame of the universe, shortly after the Big Bang before matter cooled to form atomic particles.
What Are Composite Particles?
Some of the most common particles in the universe, such as protons and neutrons, are theorized to be made up of combinations of the fundamental particles, because of the way they decay in high-speed nuclear reactions. Protons have two up and one down quarks, and neutrons (which have neutral charge) contain two down and one up quarks. Atomic nuclei are made up of protons and neutrons, and the number of protons and neutrons in the nucleus determine the type of element.
An Exciting Discovery
Bosons are particles which are central to quantum physics, because they carry force. Scientists theorized that they occurred at various levels of nuclear reactions, but they decayed so rapidly that they had never been observed. It was theorized to have no spin or electrical charge. The products of its decay, however, transformed into particles that had mass. In 2013, the Higgs boson was discovered in supercollider experiments. It is much heavier than other particles, and decays into particles with mass rapidly, the way that scientists had predicted.
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