4 ms·

I would assume that given the extreme redshift this can be explained by the combination of acoustic oscillation overdensities and gravothermal catastrophe but t

I would assume that given the extreme redshift this can be explained by the combination of acoustic oscillation overdensities and gravothermal catastrophe but there is probably some unmentioned reason why it can't.

ajross 2y ago
This sounds like a line stolen from an old Star Trek script, FWIW. For those who need more context, the ideas here are real: https://physics.stackexchange.com/questions/249679/gravothermal-catastrophe-looking-for-simple-explanation https://physics.stackexchange.com/questions/249679/gravother... https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations
- orbisvicis 2y ago
  Wait - If I throw a bowling ball really fast in a vacuum, does its temperature increase?
  - ajross 2y ago
    Yes. But if you take an existing slow ("cold") bowling ball in orbit around a mass concentration and hit it with a fast ("hot") one, it will be moving faster immediately. But now it's trajectory will take it out into a longer orbit where it slows down and spends more time moving near apogee, where it looks "cold". So you end up with this paradoxical situation where a "hot" mass starts to interact with a "cold" one and ends up making it even colder, so it collapses.
    - orbisvicis 2y ago
      I'm having trouble wrapping my head around how a measure with an absolute value (temperature) can relate to a measure with no absolute reference (velocity). In a purely inelastic collision, all the energy should be transfered to velocity, and thus the temperature not increase. A pure elastic collision would be the opposite. Similarly, if the ball and launcher are moving away relative to a given point, and the ball is launched towards that given point so that it is moving slower relatively, did the temperature increase or decrease? And with rotational velocity, if you double the radius the velocity halves because the total energy (and therefore temperature?) remains constant. Imagine if I used an inertialess drive to move faster - would my temperature have increased?
      - Filligree 2y ago
        Temperature is a property of assemblies of particles, and in this case the “particles” are the bowling balls (dust, rocks), not necessarily atoms. Nothing in the formulation requires it to be atoms. Of course then you get rocks sitting at a different internal temperature than the temperature of the overall cloud of rocks, and yes, over time that would reach an equilibrium. However, heat transfer in space, for large objects, is slow enough that this can be a very long time indeed.
        orbisvicis 2y ago
        Thank you. I appreciate the explanation.
whatshisface 2y ago
Gravothermal catastrophes make clusters bigger, in order to make stars the potential energy of gas clouds has to go down.
- OgsyedIE 2y ago
  That's what I'm suggesting - the catastrophe proceeded to the point that all members of the cluster were either ejected (far away enough to be indiscernable relative to the quasar) or absorbed by the quasar core. Thinking some more about it, there are probably some ways to constrain the amount of time it takes for a past runaway to have occurred that rules this explanation out.

ajross 2y ago

This sounds like a line stolen from an old Star Trek script, FWIW. For those who need more context, the ideas here are real: https://physics.stackexchange.com/questions/249679/gravothermal-catastrophe-looking-for-simple-explanation https://physics.stackexchange.com/questions/249679/gravother... https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations

orbisvicis 2y ago
Wait - If I throw a bowling ball really fast in a vacuum, does its temperature increase?
- ajross 2y ago
  Yes. But if you take an existing slow ("cold") bowling ball in orbit around a mass concentration and hit it with a fast ("hot") one, it will be moving faster immediately. But now it's trajectory will take it out into a longer orbit where it slows down and spends more time moving near apogee, where it looks "cold". So you end up with this paradoxical situation where a "hot" mass starts to interact with a "cold" one and ends up making it even colder, so it collapses.
  - orbisvicis 2y ago
    I'm having trouble wrapping my head around how a measure with an absolute value (temperature) can relate to a measure with no absolute reference (velocity). In a purely inelastic collision, all the energy should be transfered to velocity, and thus the temperature not increase. A pure elastic collision would be the opposite. Similarly, if the ball and launcher are moving away relative to a given point, and the ball is launched towards that given point so that it is moving slower relatively, did the temperature increase or decrease? And with rotational velocity, if you double the radius the velocity halves because the total energy (and therefore temperature?) remains constant. Imagine if I used an inertialess drive to move faster - would my temperature have increased?
    - Filligree 2y ago
      Temperature is a property of assemblies of particles, and in this case the “particles” are the bowling balls (dust, rocks), not necessarily atoms. Nothing in the formulation requires it to be atoms. Of course then you get rocks sitting at a different internal temperature than the temperature of the overall cloud of rocks, and yes, over time that would reach an equilibrium. However, heat transfer in space, for large objects, is slow enough that this can be a very long time indeed.
      - orbisvicis 2y ago
        Thank you. I appreciate the explanation.

whatshisface 2y ago

Gravothermal catastrophes make clusters bigger, in order to make stars the potential energy of gas clouds has to go down.

OgsyedIE 2y ago
That's what I'm suggesting - the catastrophe proceeded to the point that all members of the cluster were either ejected (far away enough to be indiscernable relative to the quasar) or absorbed by the quasar core. Thinking some more about it, there are probably some ways to constrain the amount of time it takes for a past runaway to have occurred that rules this explanation out.