All Questions
Tagged with black-holes photons
100
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3
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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 $2M$ ...
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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, $\Delta T=6\pi M$...
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The Calculation of the Volume of a Photon Sphere around a Black Hole
So, I chose this question for my chemistry assignment which is "How many moles of photons will it take to fill up the volume of the photon sphere around Sagittarius A". I realized there is ...
- 11
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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 ...
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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 ...
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4
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Do black holes emit no light or does light fall back in black holes?
Black holes have such a strong gravity that escape velocity from it is more than speed of light which basically means nothing could escape it.
Everything in the universe have escape velocity. For ...
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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 ...
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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
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Photon Sphere Planck Recalibration
Say a black hole's Schwarzchild radius is equal to the Planck length then a horizontal formula can be established as
$A = 4\pi \ell^2$
[1]. I've tried to find an analogue of this set up online but can'...
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votes
1
answer
106
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What is the formula for the radius of the photon sphere of a charge black hole? [closed]
What is the formula for the radius of the photon sphere of a charge black hole?
I've found the formula for a Schwarzschild black hole and a Kerr black hole but despite some googling but I can't find ...
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2
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350
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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
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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 ...
- 2,245
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121
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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
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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{\...
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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 ...
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