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  • a
  • absolute constant
    An absolute constant is a number that has the same value wherever it appears. Examples:

    π (pi) has the value 3.14159…(...) Read More

  • absolute space
    (Absolute space has recently been re-conceptualized and re-named as space that has "background-independence.")

    The(...) Read More

  • absolute square of a complex number
    The absolute square of a complex number is calculated by multiplying it by its conjugate. (The absolute square is not the(...) Read More
  • absolute time
    The concept of absolute time was a foundational concept of physics as articulated by Isaac Newton in the 1600’s. It was(...) Read More
  • acausal
    “Acausal” means not having a cause. In classical physics all events are believed to have a cause; none are acausal. In(...) Read More
  • acceleration
    Abbreviation: a

    In physics, acceleration is speeding up, slowing down, or changing direction. Acceleration contrasts(...) Read More

  • action-at-a-distance

    Action-at-a-distance is the creation of an effect without physically touching. An example is magnetism: a magnet pulls(...) Read More

  • algebraic constant
    An algebraic constant is a symbol that represents an unchanging number or is simply a number in an algebra equation. The(...) Read More
  • alpha
    In quantum physics, the ancient Greek letter α, alpha, represents an important constant of nature. Alpha is .00729735256…(...) Read More
  • amplitude of a wave
    The amplitude of a wave is its height, that is, half the distance from trough to crest. Amplitude can be measured for water(...) Read More
  • ancient physics
    Ancient physics was the physics of the ancient world, that is, of the Egyptians, Greeks, Indians (of India), and other(...) Read More
  • angular momentum
    (Symbol is L. Also called “rotational momentum” or “moment of momentum.”) Angular momentum is the momentum or oomph which an(...) Read More
  • anomaly
    An anomaly is an experimental result or an observation that doesn’t fit current scientific theories.

    Sometimes anomalies(...) Read More

  • antimatter
    Antimatter is not just the stuff of science fiction. It is as real as ordinary matter. Physicists call the matter that we(...) Read More
  • antiparticle
    An antiparticle is an antimatter version of a normal particle. For example, an antiquark is an antimatter quark. An(...) Read More
  • atom
    An atom is the tiniest component of an element which shares in the element’s properties. Break down matter any further and(...) Read More
  • atomic number
    The atomic number of an atom is the number of protons in its nucleus. For example, an atom of carbon has six protons and has(...) Read More
  • b
  • B
    B is the symbol that represents the strength and direction, in any particular location, of the magnetic field due to the(...) Read More
  • bare number
    For “bare number,” see “dimensionless number.” Read More
  • baryon
    Baryons are a category of subatomic particles in the nucleus of the atom. Protons and neutrons are examples of baryons.(...) Read More