- Our ancient ancestors believed there were atoms in matter long before anyone could discover atoms. It just made sense to them that there is a smallest bit of matter that can not be divided any further. The idea of the atom was that it was indivisible. Why not the same concept for space-time? Shouldn’t there be a distance so small it can not be sub-divided? Shouldn’t there be a small instant of time that can not be made any shorter?
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- Atoms were not physically characterized until 1905 when Einstein used them to explain Brownian Motion. Brownian Motion is observed with dust grains in a liquid. The dust is continually jittering in a random fashion. Einstein explained this as atoms bumping into the dust grains in a random statistical manner. He did the math to prove it.
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- It took 20 years later to get a deeper explanation of the working of atoms using Quantum Mechanics. And, another 30 years before the microscopic image of an atom was made by Erwin Muller.
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- Atoms became the building blocks in the explanation for matter and all the elements in the Periodic Table. Today physicists are trying to do the same thing with space-time. Does space-time itself have some fine-scale structure? Are there space-time atoms that are the smallest indivisible units of distance? The theories say there are and that distance is 10^-35 meters. The shortest distance we can measure using modern technology is 10^-18 meters . We are 17 orders of magnitude away from achieving such a feat.
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- Regardless of some empirical evidence theories are evolving to explain the existence of space-time atoms. One is called “ Loop Quantum Gravity” developed in the 1990’s. General Relativity is related to “loops” like electric and magnetic field lines are related to electromagnetic behavior. The math used on these field lines is treating them with “knot theory“. The math in turn is used to explain the behavior of gravity and relativity.
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- Another theory is “ string theory” applied to all particle interactions. When space-time is packed with energy as it was in the Big Bang, the fine structure of the space-time becomes dominant and the predictors of Loop Quantum Gravity diverge from those of General Relativity.
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- In this theory space-time is grainy, it is a breakup of the continuum into discrete intervals. A strange reversal occurs when gravity becomes so large it approaches a Big Bang or Blackhole Singularity. Loop Quantum Gravity suggests that the atomic structure of space-time changes the nature of gravity at very high energy densities, making it a repulsive force rather than an attractive force.
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- This is like a sponge that takes on some water, absorbing it until it is full, then, repulsing any more water. When energy densities become too large, repulsive forces come into play in the same way. The energy densities we are talking about are a trillion Solar Mass in the size of a proton.
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- When gravity becomes a repulsive force it causes space to expand. At some point densities thin out and gravity become the attractive force again. The inertia of this repulsive force is what kept the expansion of the Universe growing. When the acceleration of the expansion slowed down the excess energy was transferred into creating ordinary matter according to E = mc^2. That is how matter got created out of pure energy.
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- One scenario that comes out of Loop Quantum Gravity is that a previous Universe collapsed under the attractive force of gravity. The density grew so high that gravity switched to a repulsive force. And, the Universe started expanding again. In this way Universes are “ bouncing’ into existence from previous Universes.
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- Can the effects of Loop Quantum Gravity be measured to prove their existence?
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- Quantum fluctuations of space-time could affect the propagation of light over long distances. According to loop gravity, a light wave can not be continuous, it must fit on the lattice of the space that has a finite structure. The smaller the wavelength , the more the lattice structure distorts the light wave. As a consequence light at different wavelengths should travel at different speeds. Very tiny differences can add up over very long distances. Distant Gamma- Ray Bursts may be astronomers best hope of seeing these small effects.
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- When the ancient philosophers first proposed atoms to explain the composition of matter 25 centuries elapsed before atoms were experimentally established to exist. Space-time atoms may be discovered in a few decades. An announcement will be made shortly, stay tuned.
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