How Do Black Hole Animations Capture Optical Effects?

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Discussion Overview

The discussion revolves around the optical effects captured in black hole animations, exploring the methods used to create these visualizations and the implications of their representation of time and orbits. Participants express curiosity about the technical aspects of the animations, including the speed of the animations and the numerical methods employed in their creation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants express that describing black hole phenomena with words feels inadequate compared to visual representations.
  • There is a request for the availability of the equations used in the animations.
  • Several participants question whether the speed of the animation reflects real-time or is sped up, with some suggesting it is likely sped up due to the scale of the black holes.
  • One participant notes that the animation does not depict actual merging or spiraling of the black holes, emphasizing that its purpose is to illustrate optical effects.
  • Another participant estimates the distance between the black holes and discusses the implications for orbital periods, suggesting that approximating orbits as Newtonian is reasonable at this level of analysis.
  • Concerns are raised about the computational resources required to solve Einstein's Field Equations numerically for the animation, with differing opinions on whether the time reported for computation seems excessive.

Areas of Agreement / Disagreement

Participants generally agree that the animation serves to illustrate optical effects rather than actual dynamics of black holes. However, there is no consensus on the specifics of the animation's speed or the computational methods used, leading to multiple competing views on these aspects.

Contextual Notes

Participants express uncertainty regarding the exact nature of the animation's speed and the computational methods used, highlighting the complexity of simulating black hole interactions and the assumptions involved in their analyses.

Who May Find This Useful

This discussion may be of interest to those exploring astrophysics, computational modeling, and visual representation of complex physical phenomena, particularly in the context of black holes and general relativity.

anorlunda
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Very cool. Did they also make their equations available somewhere?
 
Also, I looked but could not find if the speed of the animation is real-time, or sped up. Did anybody see if they mentioned that?
 
berkeman said:
Also, I looked but could not find if the speed of the animation is real-time, or sped up. Did anybody see if they mentioned that?
My impression is that there is no attempt to show time or actual orbits. The objects in the animation never really merge or spiral inward. The purpose was to show optical effects.
 
It is almost certainly solved numerically and it is certainly sped up. These black holes are severla light minutes across.
 
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anorlunda said:
My impression is that there is no attempt to show time or actual orbits. The objects in the animation never really merge or spiral inward. The purpose was to show optical effects.
The holes aren't that close. The center to center distance is something like ten times the diameter of the inner bright ring around the larger hole. That ring is at the photon sphere, so the holes are something like thirty times the Schwarzschild radius of the larger hole distant from one another (I know they're Kerr holes, but back of the envelope). I don't think approximating the orbits as Newtonian is completely crazy at this level of hand waving, and that gives an orbital period of several hours. So definitely sped up.

I'm not sure how much time solving Einstein's Field Equations numerically would require in this case. The blurb reckons they used 2% of a 129,000 processor cluster for a day, or a little over 60,000 hours of computer time. That seems a little bit steep to me for just ray tracing (even nice high-res ray tracing in curved spacetime), so I lean towards it being a proper simulation (although that's, at best, only a partially educated guess).
 

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