Since electric charge is comprised of discrete units and and mass is formed by discrete units is it possible that space-time itself is discrete as well?

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    $\begingroup$ No. You run into problems with violating Lorentz invariance, because special relativity is built around continuous spacetime. I mentioned some of the experimental limits at physics.stackexchange.com/q/26906. $\endgroup$ – Matt Reece Mar 10 '14 at 5:35
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    $\begingroup$ As Matt says. Nevertheless there exist theories incorporating discretness and keeping their fingers crossed that locality demands will be accomodated by SR being an emergentent theory. See the answers of t'hooft physics.stackexchange.com/users/11205/g-t-hooft . Loop quantum gravity also inherently has locality problems en.wikipedia.org/wiki/Loop_quantum_gravity in addition to not accomodating the standard model of particle physics. $\endgroup$ – anna v Mar 10 '14 at 6:11
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    $\begingroup$ possible duplicate of Does the Planck scale imply that spacetime is discrete? $\endgroup$ – John Rennie Mar 10 '14 at 7:05
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    $\begingroup$ This should not be marked as a duplicate. This is the very question quantum theories of gravity are trying to answer. According to one of them (Quantum loop gravity), the universe is composed of a network of events, which are discrete. This has nothing to do with wether energy or mass are discrete. $\endgroup$ – PhilMacKay Mar 19 '14 at 16:11

Electric charge is discrete, however mass and energy aren't. They're entirely described through quantum mechanics. In fact, most phenomena at the quantum level can be described as a wave function which specifies its location as a continuous probability. So if you were to describe the universe in one word, it would be quantum not discrete.

  • $\begingroup$ Depends what you mean by discrete. After measurement, charge is always an integer, so it's discrete in that sense. (The same is not true of mass or energy. But then again, any finite system has a discrete set of possible energy levels, even if they're not integers.) $\endgroup$ – Nathaniel Mar 10 '14 at 5:22
  • $\begingroup$ @Nathaniel I'm probably wrong, but I thought charge wasn't always discrete. For example, in a conductor excess charge distributes itself uniformly over the surface, which is only possible if charge isn't discrete. $\endgroup$ – dfg Mar 10 '14 at 5:26
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    $\begingroup$ @dfg, classical electromagnetism is only an approximation. The charge carriers in conductors are electrons or ions, which have discrete charge. $\endgroup$ – user27578 Mar 10 '14 at 5:36
  • $\begingroup$ @dgh Fair enough $\endgroup$ – dfg Mar 10 '14 at 5:38
  • $\begingroup$ The discreteness of a energy levels in a bound system is a result of interference leaving only certain survivable standing waves in the long time limit, and is not enforced time-scales shorter than (size of the system)/(speed of light)---consider multi-photon excitation processes as an example. Accordingly, the post-inflation universe could be both finite and capable of supporting continuous energy levels. $\endgroup$ – dmckee --- ex-moderator kitten Mar 10 '14 at 15:14

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