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You always hear people say that the universe is made of matter and energy

  1. Nov 13, 2012 #1
    but shouldnt "force" be the third. Like the EM force has physical influence on matter and energy, but it isnt considered to be matter or energy, right? So what is the EM force? Cause we say that gravity is just warped space, so what is electromagnetism? Warped space as well?
     
  2. jcsd
  3. Nov 13, 2012 #2
    What really should be said is that the universe is made of "fermions and bosons." Statements of matter-energy duality should be censured.

    The statement that "the universe is made of matter and energy" is meaningless. The statement is so badly posed, that it can't even be wrong. It can't be right and it can't be wrong. There is no fundamental difference between matter and energy. Here is my fantasy of how that phrase developed.

    I think that the statement probably originated before the French Revolution. It probably made sense to Lavoisier. There were two conservations laws known, one for matter and one for energy. Since the two quantities appeared independent in experiments done at the time, it was a good summation of the physics learned up to that time.

    Soon there was a third conservation law. Scientists found that linear momentum was also conserved. So there should have been a modified statement: "The universe is made of matter, energy, and linear momentum." Soon, there was a new paradign: The universe is made of matter, energy, linear momentum and angular momentum.

    Soon after that, the conservation of electric charge was discovered. The paradign was then, "The universe is made of matter, energy, linear momentum, angular momentum, and electric charge."

    The relativists (Einstein, Lorentz, et al.) discovered that energy and mass were equivalent. Since the word mass is often mistaken for matter, the statement became "The universe is made of energy, linear momentum, angular momentum and electric charge". Matter was thrown out of the epistemological curriculum.

    When Noether's theorem was published, everyone realized that there could be an infinite number of conserved quantities. Then some teachers board decided to go back to "The universe is made of matter and energy" !-)



    Modern physicists no longer say that the universe is made of matter and energy without adding a caveat. My current favorite is the fermion-boson duality.

    I attended some lectures by some high power physicists and they had an interesting addendum. Both of them said the following:

    "What most laymen call matter corresponds to particles that physicists call fermions. What most people call energy refers to force fields, which are generated by an exchange of bosons. Fermions usually interact through an exchange of bosons. So really, the universe is divided into fermions and bosons."

    BTW: Bosons corresponds more closely to what you call force then to the older ideas of energy. So if you want: "The universe is divided into fermions and the force fields by which fermions interact." Whatever. The duality of interest is fermions and bosons.

    Particles and entangled systems of particles can be classified as either fermions or bosons. Fermions have an odd number of half spin units and bosons have an even number of half spin units.

    Most laymen getting through high school chemistry learn about atoms and photons. Atoms are made of three types of fermions: electrons, protons and neutrons. Laymen often think of atoms as matter, not energy. Light is made out of photons, which are a type of boson. Laymen often think of light as a form of energy, not matter. Laymen also learn about gravitational energy. Gravity is hypothetically caused by an exchange of gravitons, which are bosons.

    So I think this is probably the best way to handle the matter-energy condondrum. Matter are things primarily made of fermions. Energy usually means force fields, which are usually made out of bosons. Dividing the universe into fermions and bosons is nearly equivalent to dividing the universe into matter and energy, but it has less ambiguity.

    This leads to difficult technical discussion. This may be long. However, I find that an interested laymen has the patience to listen to technical discussion. They do not have patience for cliches wrapped in ambiguity.
     
  4. Nov 13, 2012 #3

    K^2

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    Unfortunately, big chunk of what you'd normally call matter is also due to bosons. A better analogy is bricks and mortar. Think of fermions as bricks and bosons as mortar of what makes up the matter. Just like mortar adds substantially to weight of the wall, so do bosons make up a considerable fraction of the mass of matter.

    Also, protons and neutrons don't make the best introduction to fermions as building blocks of matter, because they are themselves not elementary. They have a whole mess of particles within them constantly being created an annihilated, with three irreducible quarks at any one time. Quarks are elementary fermions, and so are the electrons. They are really the building blocks of matter.
     
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