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Aug. 12th, 2020 04:17 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
thedeemonУра, долгие часы прокрастинации на youtube оказались вознаграждены: персональное упоминание с занесением в почетный список бездельников на канале Fermilab. https://youtu.be/ZoJeWwtfdmQ?t=397
Предыдущее достижение моей карьеры в ютюб-физике - упоминание на The Science Asylum https://youtu.be/t0nGy2rsXYY?t=351 :)
Кстати, если кто интересуется популярными роликами вокруг физики и еще не знает эти каналы, рекомендую. А еще больше рекомендую PBS Space Time.
Предыдущее достижение моей карьеры в ютюб-физике - упоминание на The Science Asylum https://youtu.be/t0nGy2rsXYY?t=351 :)
Кстати, если кто интересуется популярными роликами вокруг физики и еще не знает эти каналы, рекомендую. А еще больше рекомендую PBS Space Time.
no subject
Date: 2020-08-12 04:47 pm (UTC)Dr.Don mistakes
Date: 2020-08-12 09:25 pm (UTC)I got disappointed by this video, because Dr.Don thinks that black hole photo is real.
Fermilab is also seem to be not fully aware about rapid gravitational collapse that fuels supernova:
~~~~~~~~~
https://youtu.be/ZoJeWwtfdmQ?t=66
Gravity at the core gets high enough to make a black hole and the outer layers get hot enough to get blown out into the universe as a supernova.
~~~~~~~~~
As a result, Dr.Don implies that supernova may blow out even if the core already turned into a black hole.
But black hole does not emit any meaningful amount of energy that would support supernova explosion.
Supernova explosion is only possible in case when a black hole around collapsing core did not form yet.
Re: Dr.Don mistakes
Date: 2020-08-13 06:29 am (UTC)He actually is saying "The density and ..."
Re: Dr.Don mistakes
Date: 2020-08-13 01:04 pm (UTC)Black hole -> Supernova explosion
Re: Dr.Don mistakes
Date: 2020-08-13 04:32 pm (UTC)"Black hole -> Supernova explosion" sequence
Date: 2020-08-13 04:51 pm (UTC)Yes, Don Lincoln's statement implies that "black hole formed" first and only then "outer layers get hot enough to get blown out".
Or, as a stretch, these 2 events happened simultaneously.
But not in reverse order.
Because if Don Lincoln meanth the reverse order -- why wouldn't he list these events in reverse order in his explanation?
> "A and B" doesn't necessarily mean "first A, then B".
Re: Dr.Don mistakes
Date: 2020-08-13 10:57 am (UTC)They popularize basics of modern physics to a wide audience and do it not too bad. Some episodes gave me insights regarding some things I missed or didn't pay attention to earlier.
Don Lincoln is an experimentalist in particle physics, so his episodes on particle physics are usually very good, while stuff about cosmology and GR may be sloppy or sometimes even incorrect (like when he used Newton's gravity formula near a black hole, which gives a quite incorrect result).
Your opinions on what they think and what they are aware of... are not adequate, in my opinion.
Re: Dr.Don mistakes
Date: 2020-08-13 02:14 pm (UTC)How do you know that Don Lincoln is not feeding your misconceptions?
He made several sloppy mistakes that you and I noticed. He likely made many other mistakes that you and I did not notice.
Or do you mean that occasional misconceptions do not matter much if most of the concepts he teaches correctly?
> Don Lincoln is an experimentalist in particle physics, so his episodes on particle physics are usually very good
Ok, may be. I did not watch these episodes.
But usually, sloppy analyst produces sloppy analysis somewhat consistently.
Ok, let's take a look:
~~~~
https://youtu.be/sTt27A8W4eY?t=218
Funding science is way better than that. Even if we take the lowball estimate of 20% return on investment, after a mere four eyar, you double your investment.
~~~~
This unscrupulous "lowball estimate of 20% return on investment" claim reminded me ponzi scheme promotions (like MLM by Lenya Golubkov).
Where did Don Lincoln took this "lowball estimate"?
My lowball estimate for ROI in fundamental Physics research -- is that it is in a negative territory (losses, not profits).
> Your opinions on what they think and what they are aware of... are not adequate
It is good to know.
All our opinions are recorded here.
After ~10 years it will be easier to evaluate our claims.
You will see that Messier 87 black hole "photo" will turn out to be a fake setup.
Similarly, misconception about possibility of self-fueling explosions in the outer levels of a cooling superstar -- will be gradually washed out from the popular physics lectures.
Re: Dr.Don mistakes
Date: 2020-08-13 04:24 pm (UTC)I compare his words against the things I learned in textbooks and lectures of other physicists. It usually checks out. Of course there could be mistakes went unnoticed, but that should be quite rare, so not significant.
Re: Dr.Don mistakes
Date: 2020-08-13 04:40 pm (UTC)"Usually checks out" is, usually, not sufficient to rely on.
The standard for scientific lectures should be "[almost] always checks out".
Re: Dr.Don mistakes
Date: 2020-08-13 11:13 am (UTC)(0) "So, fusion stops,
(1) gravity takes over, the outer layers of the star smash in heating up everything as they go,
(2) the density and gravity at the core get high enough to make a black hole
(3) and the outer layers get hot enough to get blown out into the universe as a supernova."
Here (0) causes (1).
(1) causes ((2) and (3)), two more or less independent effects of the same cause.
Re: Dr.Don mistakes
Date: 2020-08-13 01:23 pm (UTC)Yes.
> (1) gravity takes over,
Yes.
> the outer layers of the star smash in heating up everything as they go,
That is a mistake too.
Why would outer layers smash in heating up?
They should go toward the star's core, right?
> (2) the density and gravity at the core get high enough to make a black hole
Black hole may or may not form here, depending on the mass of collapsing matter.
I assume that Dr.Don knows that, but chooses to focus his explanation on the black hole forming scenario only.
> (3) and the outer layers get hot enough to get blown out into the universe as a supernova."
I understand this statement as: "The outer layers get hot enough by themselves, without the help from the core".
But "The outer layers get hot enough by themselves" is impossible, because gravitation pulls the outer layers material toward the core, not to each other. So the critical density [to generate energy for a supernova explosion] cannot be reached in the outer layers.
The critical density can only be reached at the core of the star.
Re: Dr.Don mistakes
Date: 2020-08-13 02:40 pm (UTC)That's what "smash in" means:
> Why would outer layers smash in heating up?
> But that is impossible, because ...
This is sloppy wording. It does not obviously follow that what follows makes that impossible.
1. Whatever part of the star does not bounce back - got to release the potential energy of that part.
2. Whatever part of the star gets blown out - does so by receiving that potential energy.
A common means of transfer is the heat: whatever does not bounce back, translates its potential energy into heat; whatever does bounce back, consumes heat, which translates into kinetic energy. The speed has no preferred direction, so some of that will drive parts of the star back to the core, some of that will drive parts of the star towards each other, some of that will drive parts of the star outwards to form a cloud of gas and dust - and a flash of light.
Re: Dr.Don mistakes
Date: 2020-08-13 03:20 pm (UTC)Are you talking about scenario when collapsing star's core is inside a black hole already?
Most of potential energy of the outer layers material is likely to go into that black hole.
> 2. Whatever part of the star gets blown out - does so by receiving that potential energy.
Why would that potential energy go in the direction opposite of the black hole?
Only a very small part of that potential energy of the outside layers will be releases outside of the event horizon of the black hole.
And even that small part of potential energy will be mostly swallowed by the black hole, because most of the the material is going to fall down.
> whatever does not bounce back, translates its potential energy into heat
Yes. Most of that "transformation into heat" is likely to happen inside of a black hole.
There will be no outward pressure from the black hole, but very strong gravitational pull toward the black hole.
Particles that are closer to the black hole - will accelerate toward the black hole faster than the particles that are a little bit further away.
That difference in acceleration -- means there is no reason for the density of outside layers to increase.
> The speed has no preferred direction
Why would there be "no preferred direction" if there is a huge mass (a black hole) nearby?
Re: Dr.Don mistakes
Date: 2020-08-14 06:25 am (UTC)Re: Dr.Don mistakes
Date: 2020-08-14 06:52 am (UTC)Misconceptions about something I teach?
> I don't know where to even begin.
Begin with the misconception that is the easiest to explain.
One misconception at a time.
> a series of lectures and a couple of thick books
Dr Don has more obvious misconceptions (that do not require such extensive research and explanation).