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- What is the relevance of the principle of equivalence in the general theory of relativity. Constant accelerating reference frames do not generate "tidal" forces in their frames.

I am studying the general theory of relativity(GTR). Covariance and the principle of equivalence are foundational pillars for the theory. I can understand the need for covariance but I don't see why the need for the principle of equivalence (POE). What I have seen so far is that the properties and curvature of spacetime due to mass/energy via the energy-momentum tensor(EMT) must be described by using the Riemann tensor, Ricci tensor, and the Ricci scalar, among other mathematical objects such as the Christoffel symbols. But these curvature measuring tensors and non-tensors are not applicable in an accelerating reference frame because real curvature does not occur in accelerating systems that are accelerating in flat spacetime. So why did EInstein cite the POE as a necessary foundation? Are Christoffel symbols even relevant in linearly accelerating reference frames? I understand that POE is defined for a homogenous gravitational field locally. But globally the POE does not admit tidal forces. So why even the need for the POE as a conceptual footing for GTR?

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