All Questions
45
questions
3
votes
3
answers
182
views
Photonic black holes
"Can a photon turn into a black hole?" - usually the answer to this question is - it can't, because it has zero rest mass. However, when we derive the Schwarzchild Metric initially the $2M$ ...
- 1,161
1
vote
0
answers
81
views
Photon speed for an observer at the photon sphere [closed]
I am asked to compute the orbital period of a photon, in the Scwarzschild spacetime, at the photon sphere for an observer at the same radius, $r^\star=3M$. I have computed the result, $\Delta T=6\pi M$...
3
votes
3
answers
364
views
Falling angle of a photon near the event horizon
I have been doing simulations using Mathematica of light and matter paths (plotted in the $r, \phi$ Schwarzschild coordinates) around a black hole, in the Schwarzschild metric. This was in order to ...
- 31
-1
votes
1
answer
138
views
Is it possible for the trajectory of a photon in curved time space to be circular?
I am currently working on some work with neutron stars so this led me to calculations of photon trajectories in curved spacetime.
These are the steps I followed to write code that would produce ...
- 1
1
vote
3
answers
221
views
Is there a frequency limit for the pendulum near a black hole, and is this related to photons and the UV-cutoff?
I imagine a swinging pendulum being held outside a black hole, supported by the normal force of a rocket. The rocket is hovering the swinging pendulum right above the event horizon in the strong ...
- 95
1
vote
1
answer
188
views
Can photons form a black hole?
Can photons form black holes the same way as other matter? If there happens to be enough of them concentrated in an area of space so that enough energy exists within a radius to form an event horizon, ...
- 113
1
vote
2
answers
356
views
Why is the photon sphere spherical, but the accretion disk not?
As far as I understand, photons are massless, but are still subject to gravity, must follow the distortions of spacetime (including framedragging etc.), period.
Now the only answer on this site ...
- 29k
0
votes
1
answer
72
views
If the black hole attracts photons do they do the same with respect the black hole?
If two bodies interact they interchange force carriers and as 3rd Newton law states as the one body influences the other in the same way the other body would be doing the same to the first body. So am ...
- 2,255
1
vote
1
answer
121
views
Calculating divergence and flux of geodesic word lines
Given a family of neighbouring geodesic word lines, is there a way of calculating properties such as their divergence or flux? maybe by converting the tangent vectors of the world lines to a vector ...
- 633
2
votes
0
answers
88
views
Numerical calculation of spherical photon orbits near Kerr black hole
I'm using RK4 method for solving differential equation
$$\frac{d\theta}{d\phi}=\pm(2-2r)\frac{\sqrt{Q-\left(\frac{\Phi^2}{\sin^2\theta}-1\right)\cos^2}\theta}{2r+\left(r^2+\cos^2\theta-2r\right)\frac{\...
- 333
-2
votes
1
answer
118
views
How can a black hole have electromagnetic field? [duplicate]
I know that everything that is shaped from gravity force is rotating, and gravity is a central force, but I want to know how we can understand that a black hole has an angular momentum? By which sign ...
- 39
19
votes
3
answers
2k
views
How close does a photon have to get to a black hole to do a full loop?
How close does a photon have to get to a black hole to do ONE full loop? By full loop I mean it curves once around the black hole, and then it ends up on the same trajectory as it was one before it ...
- 2,908
3
votes
1
answer
639
views
Radial motion of a photon in Schwarzschild spacetime
For photon worldlines in the equatorial plane of the Schwarzschild coordinate system ($\theta=\frac{\pi}{2}$) in Schwarzschild space-time, the metric equation is given by,
$$-\Big(1-\frac{2GM}{r}\Big)...
- 498
2
votes
1
answer
79
views
Orbital Photon Speed at the equatorial plane of a rotating black hole
I've been trying to calculate $d\phi/dt$ of photons orbiting a Kerr black hole (Kerr metric in Boyer-Lindquist coordinates) on the equatorial plane, both counter and along with its rotation. So I used ...
0
votes
1
answer
126
views
Can black holes move at the speed of light? If so, what would its curvature look like? [closed]
This question has more to do with the curvature of moving bodies but I will first start with this.
If a photon has enough energy, then it could presumably become a black hole (kugelblitz). I see no ...
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