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Oppenheim's idea of "waving space-time" is based upon asking why gravity should have a quantum nature like that which has been discovered for the universe's other fundamental forces — electromagnetism, and the strong and weak nuclear forces. Gravity, he argues, isn't like these other forces. After all, it is the only one of the four that can define the very geometry of space-time, and the fields of quantum physics evolve upon this geometry.

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"We feel gravity because matter causes space-time to bend. Time flows at unequal rates at different locations," Oppenheim writes in a paper discussing his theory published in the journal Physical Review X. "The rate at which time flows and the causal structure [the fact that cause always precedes effect] it provides may be required to have a classical description in order for quantum theory to be well-formulated."

https://www.space.com/wavy-space-time-theory-quantum-mechanics-general-relativity