It's my understanding the general mechanism of core collapse involves the adiabatic constant of the material, gamma. This is the exponent in the relation P V^(gamma) = constant.
For a normal, non-relativistic gas in which the particles have no internal degrees of freedom, gamma is 5/3. As a gas becomes more relativistic, and as photon pressure becomes more important, gamma declines toward 4/3.
For gamma = 4/3, a self-gravitating gas will be marginally stable: the energy needed to compress a sphere of the gas will be equal to the gravitational potential energy liberated by the compression. So, any effect that pushes gamma below 4/3 makes it unstable against collapse.
In a conventional core collapse SN this is photodissociation of nuclei, where energy gets soaked up in breaking apart nuclei into alpha particles and then free nucleons. In a pair-instability SN, this is increasing conversion of photons to electron-positron pairs.
The temperature involved for this is well above that needed for production of electron-positron pairs, so one may ask why that doesn't happen. I think it's because the cores of such stars are dense enough the electrons are degenerate, and there simply isn't "room" for new electrons to be added at an energy that would make pair production possible.
BTW, I don't think largeness is needed for photodisintegration to occur; this should happen even in garden variety type-II SN.
I just want to live long enough for space telescopes to evolve exponentially to observe kilonovas in the visual spectrum
I mean laser interferometers are an amazing advancement but just imagine seeing an earth-sized chunk of gold pop out of a kilonova (probably not my lifetime but eventually a human will see it happen)
Thank goodness this administration did not frack with Nancy Grace Roman Telescope, I thought the name alone would make them cancel it or rename it after him, wait maybe I shouldn't even mention that idea...
Check out the aragoscope [1]. It's not planned, but we would already have the technology as it doesn't rely on fragile and heavy lenses to be sent in orbit.
If you look at image 17 you can see that a simulated aragoscope that is in our technical reach could already resolve the Jupiter moons from almost 23 light years away. I hope as well that we will have something comparable while I am still around.
heh, funny you say that - I just yesterday almost bit at some obvious Nego-Trolling on here and remembered "Just don't engage".
Some people, for some reason at certain points in their life, just want to shit on other people's stuff, any way that they can, for... reasons.
I mean, clearly it's not to make themselves feel better, because how on Earth could that work?
There's no value in engaging, in any way whatsover. Sadly there's very little that can be done to prevent that form of human behaviour, without otherwise souring the experience for the generality.
It can make them feel better by giving them a chance to look down on someone else. (The "looking down" doesn't have to be the content of the post - the act of trolling is a form of looking down on someone.)
That’s what Singer’s civilization wants you to think before they send a Photoid or Dual-Vector foil (but later would require a supervisor’s approval which is a PITA)
Pair-instability can only happen in low-metalicity surroundings.
The big bang created hydrogen, helium, and small amounts of lithium. Any higher elements are created by stars, and a significant presence of those "metals" will take a star down a different path than pair-instability.
Low-metalicity environments are not likely to be friendly to life.
I like to think there's a solid argument against dark forest that even if you can destroy other intelligent systems, then hidden intelligent cautious systems may exist and see evidence of what you've done, so there's a potential consequence to destroying every intelligent system you identify.
And then also (maybe this is absurd) isn't there something intrinsic in intelligence to want to avoid conflict and desire peace?
Once a civilization reaches a certain tech level, it can do interstellar travel & by the time you find about it due to light speed delay, it might be far too late to strike - not to mention what size & tech level they might be by the point your first strike wave arrives given the time scales of sub light travel.
So it might be better to use the tried and tested terrestrial nuclear MAD doctrine & rather doe careful diplomacy with any newcomers, like a bunch of psychos each having a full arsenal of planet killing weapons (because that's what any sufficiently advanced civilization is).
In short - rather than Dark Forrest I imagine a harmonious if not utopic galaxy teaming with varied life that is on the first glance peaceful and cooperating.
With the occasional bunch of start systems evaporating once in a while, but we don't talk about those.
A more powerful hidden intelligent system will probably fear a medium power intelligent civlization that sets out to destroy "newcomers" as a civilization that might cause their destruction so the best course of action would be to destroy the medium power one before they become as powerful.
Once multiple destructions have occured, every sentient party capable of becoming aware will fear the others.
https://en.wikipedia.org/wiki/Pair-instability_supernova
For a normal, non-relativistic gas in which the particles have no internal degrees of freedom, gamma is 5/3. As a gas becomes more relativistic, and as photon pressure becomes more important, gamma declines toward 4/3.
For gamma = 4/3, a self-gravitating gas will be marginally stable: the energy needed to compress a sphere of the gas will be equal to the gravitational potential energy liberated by the compression. So, any effect that pushes gamma below 4/3 makes it unstable against collapse.
In a conventional core collapse SN this is photodissociation of nuclei, where energy gets soaked up in breaking apart nuclei into alpha particles and then free nucleons. In a pair-instability SN, this is increasing conversion of photons to electron-positron pairs.
https://en.wikipedia.org/wiki/Photodisintegration#Hypernovae
BTW, I don't think largeness is needed for photodisintegration to occur; this should happen even in garden variety type-II SN.
I mean laser interferometers are an amazing advancement but just imagine seeing an earth-sized chunk of gold pop out of a kilonova (probably not my lifetime but eventually a human will see it happen)
Thank goodness this administration did not frack with Nancy Grace Roman Telescope, I thought the name alone would make them cancel it or rename it after him, wait maybe I shouldn't even mention that idea...
* https://science.nasa.gov/mission/roman-space-telescope/
* https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telesc...
If you look at image 17 you can see that a simulated aragoscope that is in our technical reach could already resolve the Jupiter moons from almost 23 light years away. I hope as well that we will have something comparable while I am still around.
[1] https://www.nasa.gov/wp-content/uploads/2017/03/2014_phase_i...
it will block overwhelming starlight physically so objects around them can be imaged by existing telescopes
rather simple/clever, some things you just cannot do digitally
* https://www.nature.com/articles/s41550-026-02787-9
* https://www.youtube.com/watch?v=zdTsaf68wd8
For reference, there are 103 known main sequence stars within 20 light years.[1]
[1]: https://en.wikipedia.org/wiki/List_of_nearest_stars
I don't think it's possible to do worse, even for him.
I am wondering why there are so many of these accounts popping up. They seemingly only exist to antagonize. What do their operators get out of that?
Some people, for some reason at certain points in their life, just want to shit on other people's stuff, any way that they can, for... reasons.
I mean, clearly it's not to make themselves feel better, because how on Earth could that work?
There's no value in engaging, in any way whatsover. Sadly there's very little that can be done to prevent that form of human behaviour, without otherwise souring the experience for the generality.
*shrug, whatchagonnado?
When you're really, really angry you look for an outlet. Some people kick the dog, some abuse their gf/wife/kids, others troll on online forums.
What do they say about sugaring trauma?
That's the idea but it does not work. Self esteem is still negative afterwards
The big bang created hydrogen, helium, and small amounts of lithium. Any higher elements are created by stars, and a significant presence of those "metals" will take a star down a different path than pair-instability.
Low-metalicity environments are not likely to be friendly to life.
And then also (maybe this is absurd) isn't there something intrinsic in intelligence to want to avoid conflict and desire peace?
So it might be better to use the tried and tested terrestrial nuclear MAD doctrine & rather doe careful diplomacy with any newcomers, like a bunch of psychos each having a full arsenal of planet killing weapons (because that's what any sufficiently advanced civilization is).
In short - rather than Dark Forrest I imagine a harmonious if not utopic galaxy teaming with varied life that is on the first glance peaceful and cooperating.
With the occasional bunch of start systems evaporating once in a while, but we don't talk about those.
A more powerful hidden intelligent system will probably fear a medium power intelligent civlization that sets out to destroy "newcomers" as a civilization that might cause their destruction so the best course of action would be to destroy the medium power one before they become as powerful.
Once multiple destructions have occured, every sentient party capable of becoming aware will fear the others.
[1] https://en.wikipedia.org/wiki/Spontaneous_combustion