Tag Archive for: black holes

The Oppenheimer-Snyder Model of Gravitational Collapse: An Overview
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Part 1: OverviewPart 2: Mathematical DetailsPart 3: ImplicationsMost people who have spent any time at all studying GR are familiar with the…

Geodesic Congruences in FRW, Schwarzschild and Kerr Spacetimes
Introduction
The theory of geodesic congruences is extensively covered in many textbooks (see References); what follows in the introduction is a brief…

Gaia Astrometry: Detecting Gravitational Waves Effectively
Gravitational waves (GWs) are disturbances in spacetime produced by massive objects moving asymmetrically. Only the most massive and most relativistic…

VHE Gamma Rays from Sgr A*: Black Holes and CTA Observations
Black Hole Key PointsBlack holes (BHs) have a gravitational pull so strong that nothing, not even light, can escape.
BHs can be divided into two…

Black Hole Thermodynamics: Four Laws Explained — Guide
Overview
Black hole thermodynamics is summarized by four laws that closely parallel the laws of ordinary thermodynamics. Below I present each law, the…

Killing Vector Field & Surface Gravity in Kerr BH Explained
Killing Vector Field
The Killing vector field is a vector field on a differentiable manifold that preserves the spacetime metric. In other words, it generates…

Radial Infall into a Static Mass: Equations & Guide
From Exploring Black Holes by John Wheeler and Edwin Taylor. The relations below apply to any object falling radially toward a static, spherically symmetric…

The Schwarzschild Geometry: Physically Reasonable?
In the last article, we looked at various counterintuitive features of the Schwarzschild spacetime geometry, as illustrated in the Kruskal-Szekeres…

The Schwarzschild Geometry: Spacetime Diagrams
When we left off in part 2, we were looking at the metric for the Schwarzschild geometry in Kruskal-Szekeres coordinates:$$
ds^2 = \frac{32…

The Schwarzschild Geometry: Coordinates
At the end of part 1, we looked at the form the metric of the Schwarzschild geometry takes in Gullstrand-Painleve coordinates:$$
ds^2…

The Schwarzschild Geometry: Key Properties
Not long after Einstein published his Field Equation, the first exact solution was found by Karl Schwarzschild. This solution is one of the…

Do Black Holes Really Exist?
Introduction
The purpose of this article is to discuss the title question from several different viewpoints, to show that it isn't as simple as it looks.…

Why the Early Big Bang Universe Didn’t Form a Black Hole
Why the Big Bang Is Not a Black Hole
In the early universe, the matter was gathered together at very high density — so why wasn't it a black hole?
Big…

Time Dilation & Redshift of Schwarzschild Black Holes
Time dilation near a Schwarzschild black hole
The following is an overview of the time-dilation and gravitational-redshift effects of a static (Schwarzschild)…

Will All Matter Be Converted to Photons?
Will all matter be converted into black holes and then photons?
No. There is a misconception that a lot of laypeople seem to be picking up recently from…

An Equation for the Centrifugal Force Reversal Near A Black Hole
My goal in this article is to derive a simple equation for the proper acceleration of an observer traveling on a circular path around a Schwarzschild black…

Star Fate: From Nebulae to White Dwarfs and Black Holes
Star Fate: From Birth to Black Holes
Stars form in vast clouds of gas and dust called nebulae. Over time gravity pulls material together until the core…
