Rethinking Black Holes Without Spacetime Curvature
The standard model of gravity, based on general relativity, describes gravitation not as a force but as the curvature of spacetime produced by mass and energy. This geometric interpretation has had significant predictive and explanatory success, especially in describing the behavior of massive bodies and light near what are termed “black holes.” However, if we discard the notion of curved spacetime and instead treat gravity as a force mediated by gravitons—massless spin-2 bosons in a flat spacetime quantum field theory—the implications for black holes become radically different.
In a quantum field-based model of gravity, gravitational attraction would arise from the exchange of gravitons between particles with mass-energy, analogous to how electromagnetic forces are mediated by photons. This poses a direct challenge to the classical black hole model. If black holes have an event horizon from which nothing can escape, then gravitons—like photons—should be trapped as well. But if they are trapped, they cannot mediate gravity outside the horizon. This contradiction implies that under a strict quantum particle-exchange view, traditional event horizons cannot exist. For gravitational effects to be felt outside, gravitons must escape, which means either the horizon must be leaky or must not exist at all.
This logic also extends to photons. If gravitons can escape, photons should as well. Consequently, black holes, in the conventional sense of being perfectly black and causally sealed by an event horizon, would not exist in such a framework. Instead, the objects we currently interpret as black holes—based on gravitational lensing, accretion disk dynamics, and high-energy emissions—could be extremely dense, compact bodies without singularities or horizons.
These alternatives are not purely speculative. Theoretical models like gravastars, boson stars, fuzzballs, and Planck stars have been proposed to describe ultra-compact objects that behave like black holes observationally, but have no horizons or singularities. These models replace the GR black hole with exotic matter or fundamental quantum structures that are governed by as-yet-undetermined physics at extreme densities.
Even in a flat spacetime scenario, such objects could still bend light dramatically. The exchange of gravitons between mass-energy and passing photons could cause deflection of light, replicating the lensing effects we attribute to curved spacetime. The paths of photons would be altered by gravitational interactions, not because spacetime itself is curved, but because of the momentum exchange occurring in the strong gravitational field region. As a result, light bending, redshifting, and shadow formation could all emerge from quantum interactions alone.
Therefore, a supermassive compact object under a quantum gravity model—without invoking spacetime curvature—could still look like what we currently identify as a black hole. It could produce similar observational signatures: a black hole shadow, gravitational lensing, high-energy jets, and the emission of gravitational waves during mergers. But internally, it would be something entirely different: no singularity, no true event horizon, and no breakdown of physical law at a point of infinite density.
This model would not only challenge the current interpretation of black holes but also provide a path toward reconciling gravity with quantum field theory. The empirical indistinguishability between curved spacetime and flat-spacetime force-exchange models—at least with current instruments—makes this an open question. What we call black holes might ultimately be placeholders for physics we haven't yet modeled accurately, rather than literal manifestations of general relativity's singularities.
