The river model of black holes

TL;DR

The paper introduces the river model as an intuitive, mathematically consistent way to visualize stationary black holes, depicting space as flowing like a river with velocity and twist, applicable to both non-rotating and rotating black holes.

Contribution

It develops a novel river model framework that describes stationary black holes using a six-component bivector field, including for rotating (Kerr-Newman) black holes, with explicit mathematical expressions.

Findings

River flows into black holes at escape velocity, reaching light speed at the horizon.

Inside the horizon, the river flows inward faster than light, carrying everything inward.

The model extends to rotating black holes, introducing a twist component to the river flow.

Abstract

This paper presents an under-appreciated way to conceptualize stationary black holes, which we call the river model. The river model is mathematically sound, yet simple enough that the basic picture can be understood by non-experts. %that can by understood by non-experts. In the river model, space itself flows like a river through a flat background, while objects move through the river according to the rules of special relativity. In a spherical black hole, the river of space falls into the black hole at the Newtonian escape velocity, hitting the speed of light at the horizon. Inside the horizon, the river flows inward faster than light, carrying everything with it. We show that the river model works also for rotating (Kerr-Newman) black holes, though with a surprising twist. As in the spherical case, the river of space can be regarded as moving through a flat background. However, the river does not spiral inward, as one might have anticipated, but rather falls inward with no azimuthal swirl at all. Instead, the river has at each point not only a velocity but also a rotation, or twist. That is, the river has a Lorentz structure, characterized by six numbers (velocity and rotation), not just three (velocity). As an object moves through the river, it changes its velocity and rotation in response to tidal changes in the velocity and twist of the river along its path. An explicit expression is given for the river field, a six-component bivector field that encodes the velocity and twist of the river at each point, and that encapsulates all the properties of a stationary rotating black hole.