Gravity is not a force

Status of the “gravity is not a force” claim

• Several commenters note that “gravity as spacetime curvature, not a force” has been standard GR pedagogy and popularized for decades, not a new idea.
• Others stress that many working physicists still casually talk of a “gravitational force” in appropriate limits (Newtonian approximation), so the distinction is often treated as semantic in practice.
• There is disagreement on whether insisting “gravity is not a force” clarifies or confuses; some see it as deep insight, others as unhelpful dogma.

Accelerometers, free fall, and proper acceleration

• Core GR argument: a real force causes proper acceleration, which an accelerometer measures; free‑falling objects show zero proper acceleration, so no gravitational force acts on them.
• Standing on the ground, an accelerometer reads ~1g upward due to the normal (electromagnetic) force from the surface preventing free fall.
• Multiple subthreads dissect how phone accelerometers actually work and why they read ~g at rest and ~0 in free fall; confusion over sign conventions and “force vs acceleration” is common.

Geodesics, curvature, and orbits

• In GR, free particles follow geodesics—“straight lines” in curved spacetime. What looks like spatial acceleration (falling, orbiting) is just straight motion in a curved 4D geometry.
• A force, in this view, is what pushes you off a geodesic (rocket thrust, contact forces, EM forces, radiation reaction on charged particles).
• Some question why a particle “must move” along a geodesic rather than remain spatially at rest; answers appeal to least‑action principles and the fact that you always move forward in time, with curvature mixing time and space directions.

Forces, frames, and pseudoforces

• Relativity treats all inertial frames as equivalent; accelerated frames introduce pseudoforces (centrifugal, etc.).
• One side argues calling gravity a pseudoforce “privileges” a flat background and misleads; another side says we can equivalently model gravity as a real force in flat spacetime or as curvature, and both pictures are useful.
• There is extended debate over inertia, centrifugal force, and whether distinguishing “real” vs “pseudo” forces is meaningful or pedagogically harmful.

Singularities and limits of GR

• Singularities are widely cited as evidence GR is incomplete: where the math diverges, the model “bluescreens.”
• Some emphasize GR as a bulk/continuum theory, analogous to fluid mechanics: excellent at large scales, expected to fail at very small/strong‑field scales (inside black holes).
• Coordinate vs physical singularities (event horizon vs central singularity) and the role of horizons as mathematical vs physical entities are discussed.

Geometry vs force formulations and unification

• Commenters note that other interactions can also be cast geometrically (e.g., Kaluza–Klein–type constructions), so “being geometry” may not be unique to gravity.
• Others argue flat spacetime is mathematically special (unique zero curvature, measurable deviations), so calling “flat” privileged is not obviously wrong.
• A recurring theme: there are (at least) two equivalent descriptions—curved spacetime with no gravity force, or flat spacetime with a gravitational force field—and which is “fundamental” is unclear; many see the choice as largely semantic and pedagogical.