Eli5 if gravity is an illusion caused by the curvature of spacetime why do we need to reconcile it with the standard mode.


I have heard it explained multiple time by different science educators that what we feel as gravity is a really just a consequence of curvature of spacetime and no real force is being applied. Why do we need to make gravity work with the standard model, and why are we looking for gravitons if there is no actual force and it is just caused by the geometry of the universe?

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If we want to call gravity “an illusion caused by the curvature of spacetime”, then we need a new name for the curvature of spacetime.

Otherwise, let’s just call the curvature “gravity”.

How do we reconcile this curvature, this gravity, with incredibly short distances and low energies, and quantization at those scales?

Quantum field theory is well integrated with special relativity and can handle the time and space warping associated with the relativistic speeds of subatomic particles. But it only works if you can assume flat and static spacetime. For most of the universe this isn’t a big deal- spacetime is sloped gently enough that at the tiny scales of quantum interactions you can just pretend it’s flat. But general relativity predicts the existence of singularities: regions of spacetime with infinite curvature. No matter how close you look there’s always going to be a steep well that breaks the mathematics of QFT.

Black holes are thought to contain singularities (or since they’re rotating, ringularities) and the primordial universe expanded from another singularity. If we hope to understand the inner workings of black holes and the primordial universe we need a model that either makes those singularities disappear or fits them into the context of quantum mechanics.

The search for “gravitons” is the search for an alternative theory of gravity born from the world of quantum mechanics. If we do find gravitons we may discover properties of gravity too subtle to have been modeled by GR.


Reconciling the curvature of spacetime with the standard model is what they’re trying to do.