Dio,....after reading your comment on nuclear launch, I did a little more research. I heard in a movie that 20% of launch officers would not launch. Turns out, its a myth that I fell for. My apologies to anyone interested in launching. 
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Sorry,....I'm posting these 3 links for the benefit of members who read this thread and maybe didn't see these in today's Yahoo feed. 
https://finance.yahoo.com/news/quantum-threat-bitcoin-grows-google-202704544.html
I think this is a story for tomorrow mourning's "Washington Post" newspaper. https://www.msn.com/en-us/news/us/chatgpt-just-came-out-with-its-own-web-browser-use-it-with-caution/ar-AA1OXhs3?ocid=winp2fptaskbarhover&cvid=0e4000fbc79b44c6a6b12ccfe0ba8e15&ei=12
3 days ago
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#607
What was your guys' thoughts on the new Sora 2 Open AI released? I think it's ripe for funny videos and incriminating deepfakes.
RonaldJosephCote wrote:
Dio,....after reading your comment on nuclear launch, I did a little more research. I heard in a movie that 20% of launch officers would not launch. Turns out, its a myth that I fell for. My apologies to anyone interested in launching.
Not a problem...I have heard the same story multiple times over the years. I just wanted to be clear about how deterrence is fostered. The US actually makes sure that the basics of the process are not unknown to other countries, so that they will not muck around, knowing the launch process is not discretionary or lax.
That being said, while I did not dive into it (and will not), I'm sure many reading that process can see that there would be ways to attempt to falsely trigger a launch if some horrible organization/entity really wanted to start WW3. The process is narrow, and the officers don't have any means or discretion to doublecheck, I'll leave it at that. The best defense is that it takes true fanaticism to want to launch 100 warheads.
3 days ago
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#609
Elroch wrote:
@playerafar, very interesting fact about Hawking radiation which I have not seen before (just derived it from various known relationships).
The peak wavelength of the radiation emitted by a black hole is around 15.9 times the black hole radius.
True for all sizes of black hole.
That is very remarkable @Elroch .
Maybe related to that I was asking AI about the wavelengths and frequencies of 'gravity waves'.
And it indicated they have very long wavelengths and very low frequencies.
The AI seemed to confirm that such waves travel at c -
I didn't ask it yet - 'what if the source is in 'moving space'?'
But it indicated that some of the bigger wavelengths are bigger than 'across the observable universe.'
Then I asked it about an idea that the product of gravitational wavelength and frequency wouldn't necessarily have to be c.
It wasn't too keen on answering that one clearly.
But it seemed to assert that 'gravity waves' are not in the same 'family' as EM radiation.
3 days ago
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#610
There is no such thing as "moving space". The vacuum is Lorentz-invariant.
Of course, since gravitatational waves travel at the speed of light, their wavelengths are given as
c / nu
where nu is the frequency. The frequency is quite low because it comes from the orbital frequency of the merging black holes or neutron stars. It increases as the objects merge, orbiting faster and faster until a sudden "gloop" (technical word ) as they are replaced by a single black hole.
Given that the smallest orbital speed is closely related to the radii of the black holes, there is a loose geometric relationship to the wavelength of Hawking randiation (although this is of course associated with a single, not necessarily rotating, black hole).
I think it is correct to say that the peak frequency of the gravitational radiation from a merging pair of black holes is a few times the frequency of the Hawking radiation of the resulting black hole (thinking very crudely about the orbiting black holes, which might have orbits similar to 2 pi R).
Looks like I accidentally approximated 15.9 as 17 rather than 16 at one point. Annoying memory glitch!
3 days ago
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#611
Elroch wrote:
There is no such thing as "moving space". The vacuum is Lorentz-invariant.
Looks like I accidentally approximated 15.9 as 17 rather than 16 at one point. Annoying memory glitch!
I could have said 'expanding space' instead.
It seems that 'expanding space' might qualify as 'moving'.
I chose 'moving' because I'm not too keen on 'expanding space' ...
Presenting a sterling example of the problem of LLMs placating ignorance:
3 days ago
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#613
playerafar wrote:
Elroch wrote:
There is no such thing as "moving space". The vacuum is Lorentz-invariant.
Looks like I accidentally approximated 15.9 as 17 rather than 16 at one point. Annoying memory glitch!
I could have said 'expanding space' instead.
It seems that 'expanding space' might qualify as 'moving'.
I chose 'moving' because I'm not too keen on 'expanding space' ...
Likewise, the concept of space expanding is questionable.
It is rooted in a concept of points in space-time moving apart over time. This notion is flawed as the future path of points is not defined. There is a geodesic (inertial, acceleration-free) path for every single velocity at a point in space. If you pick two points and choose paths that are diverging, it seems space is expanding. If not, it appears it isn't. For the Universe, we tend to pick comoving frames, which have points moving apart. This is because, roughly speaking, this is what the matter is doing (with significant random variation). But there is no requirement to use paths that move roughly like the matter.
2 days ago
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#614
@Elroch
Regarding terminology - the term 'big bang' is preferable to 'universe' - I think -
because it doesn't require assumptions.
But many don't like 'big bang' because it causes them to think 'big bang theory'.
And regarding redshift - redshift is much more than 'theory'.
Its real. Its real evidence. Of a big bang.
But it gets 'soured' at least two ways.
1) most people don't want to check out the math of 'the doppler effect' that is redshift.
Which would mean they're 'taking it on faith'.
That math isn't heavy - provided one is just looking at the basics with no relativity in it.
but even that math - many don't want to consider it.
But its a mistake to call that 'willful ignorance'.
2) the nastier part of the 'souring'.
Which is factoring in 'space expanding or moving or being created'.
That requires more 'leaps of faith' and heavier math and begins to get into 'finite versus infinite universe' (because how can you have space expanding into itself?
Or 'a special kind of nothing' surrounding what is?
Either one of those last two is a 'hard sell'.
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Why do scientists push the numbered second one?
I think one of the reasons is that they cannot ignore Hubble's observations - and similiar work since. Real empiricial evidence.
Which indicates that redshift increases - the further away the redshift is coming from.
A big 'explosion' only - wouldn't be enough to account for that.
So - explanations beyond that are assigned and compared.
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Regarding 'paths and frames' - it would be worth it to see what AI says about that in the context you're mentioning.
2 days ago
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#615
Here's copilot's first reaction:
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"What “paths” and “frames” really mean in cosmology
Paths: In general relativity and cosmology, this usually refers to geodesics—the trajectories that particles or light follow through curved spacetime. In an expanding universe, these paths stretch as space itself expands, but they’re not “motion through space” in the usual sense. They’re motion with space.
Frames: This refers to reference frames, which define how observers measure time, distance, and velocity. In cosmology, the most common frame is the comoving frame, where galaxies are at rest and space expands between them. It’s a mathematical convenience, not a physical anchor."
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so I had it remove 'universe' because that's not a good premise - and not asked about.
And it put this for first paragraph instead.
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"Paths: In general relativity and cosmology, this usually refers to geodesics—the trajectories that particles or light follow through curved spacetime. In an expanding Big Bang, these paths stretch as space itself expands, but they’re not “motion through space” in the usual sense. They’re motion with space.
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Almost the same. But it does invoke 'space expands'.
Regarding a notion of black holes shrinking because of Hawking radiation - where 'quantum' gets around 'event horizon' ...
when pressed - the AI kind of folded to a suggestion of 'how come there couldn't be some quantum effects regarding the jets also?'
Did I 'bully' it? Some kind of 'sacrelige'?
I also mentioned the ideas (or facts) of cosmic background radiation and starlight being absorbed by black holes and a kind of overall 'temperature/energy balance' and it reacted with a suggestion that that's a mechanism of entropy.
I countered that that would be upset by more cosmic eggs out there to upset the entropy applecart.
If 'cosmic eggs' isn't liked - then 'precursors to big bangs' could be used.
2 days ago
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#616
I would point out that the statement about "paths stretch[ing]" is highly dubious, because it requires all the points in the path to be at the same time while, the definition of a path is a sequence of points in space-time. Even if they were all in a single frame they would be at different times, because of causality. So this concept requires picking another path for each point to map it to some point in the future. Then there is no simultaneity in relativity, so the is no unique time in the future to pick. The unsatisfactory way this is implicitly done is to use a comoving path to map points in the original path to points at the "same time" in the future. But there no such simultaneity, so again co-moving time (an approximate concept that is not fundamental) has to be used. All co-moving definitions are uncertain because galaxies are not perfectly arranged according to Hubble expansion - they have random local velocities.
Needless to say, to then define the length of the past, you need to pick a frame at every point in it. Again the imprecisely defined and non-fundamental co-moving frame would be used. Then what you have is a load of distances in different frames being added together, a calculation that can be done but which is not fundamental.
2 days ago
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#617
Elroch wrote:
I would point out that the statement about "paths stretch[ing]" is highly dubious, because it requires all the points in the path to be at the same time while, the definition of a path is a sequence of points in space-time. Even if they were all in a single frame they would be at different times, because of causality. So this concept requires picking another path for each point to map it to some point in the future. Then there is no simultaneity in relativity, so the is no unique time in the future to pick. The unsatisfactory way this is implicitly done is to use a comoving path to map points in the original path to points at the "same time" in the future. But there no such simultaneity, so again co-moving time (an approximate concept that is not fundamental) has to be used. All co-moving definitions are uncertain because galaxies are not perfectly arranged according to Hubble expansion - they have random local velocities.
Needless to say, to then define the length of the past, you need to pick a frame at every point in it. Again the imprecisely defined and non-fundamental co-moving frame would be used. Then what you have is a load of distances in different frames being added together, a calculation that can be done but which is not fundamental.
I am confident that your response there is a good one - that you likely put it about as well as could be put - given the exotic nature of relativity.
Confident even though you know hundreds of times what I know about relativity.
Because you wouldn't 'lie'. Hahahahahh.
Not your style. Except when being sarcastic.
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Normally - 'paths and frames' in regular english is quite straightforward.
But in relativity - those generic-looking words are at an entirely different level.
Would 'paths and frames' suffice as an alternative - or other way of putting it - regarding space moving or being created or 'expanding'?
Just now I had a conversation with the AI about a situation with two 'reference frames' and a complicated 'path' between them - and made it extra complicated - but got the AI to admit it didn't contain any relativity in it.
AI seems to take a position that if its got 'space stretching' in it - or semantic variants on that - or if its got 'time dilating' or both - then you've got relativity in such situations.
So I then asked it 'what about exotic situations like inside an atom or in a particle accelerator or in a black hole'. And it ended up answering - it depends on what you want to measure. But I had to get it to stop spouting nonsense first.
Like that space stretching would be a 'length contraction'.
Stretching isn't 'contraction'.
But I wouldn't be surprised if somebody says 'No - in relativity you get that !!'
2 days ago
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#618
"Path" is most generally a topological concept. It is the continous image of a line in a space.
In this context, the paths of interest are the physically feasible ones, which means they have continuous velocities which do not exceed the speed of light (this condition is frame independent). Such a path has a defined frame at every point (determined by the velocity) and has a proper time associated with traversing the path.
Two kinds of path are those at the speed of light everywhere (proper time is constant), and those with speeds always strictly less than the speed of light (so proper time is strictly increasing along them).
A special case of each are geodesic paths (or "inertial paths", or "ballistic paths", in various contexts), which have the additional condition of zero acceleration everywhere (another frame-independent condition). Examples include orbits.
A single velocity at the starting point defines a geodesic path. Intuitively, it is what happens to an unpowered object launched at a specific velocity and subject to no forces except gravity.
2 days ago
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#619
"A single velocity at the starting point defines a geodesic path. Intuitively, it is what happens to an unpowered object launched at a specific velocity and subject to no forces except gravity."
sounds like an artillery shell would qualify there.
'SIngle velocity'.
I don't know if this question will 'fly' but that makes me think:
What would be examples of 'plural velocity' at a starting point?
Its that time for me. So will have to check back later.
'accepted as true'. The same as 'abolutely correct'?
Pointless question.
I also askedAI - 'what if part of the jets we are seeing - is not coming from the accretion disks - but from the black holes themselves?'
It's coming from some where deep in the gravitational well. This is an inference from the observations.
Where are you hypothesising it comes from? If you are thinking of a classical model of a black hole and suggesting it comes from the other side of the event horizon, then the answer is simply no, it can't. It would require infinite energy to do so. Technically, a classical event horizon is always in the future anyhow if a black hole forms over time, and causality precludes it for that reason.
I was surprised to see no response to my calculation that the peak wavelength of Hawking radiation is always around 15.9 [EDITED TYPO] times the radius of a black hole, regardless of its size. This underlines how weak it is - this is very long wavelength radio waves for any known size of black hole. But it is also fascinating to me how large it is compared to the source!
For the black hole at the centre of the Milky Way, with radius 12 million kilometers, the Hawking Radiation is absurdly weak, and peaking at radio wavelength of around 200 million kilometers! Purely academic, as it has as much chance of being detected as a gnat farting during an atomic explosion.
The (again purely academic) significance of Hawking Radiation is primarily that in the very distant future, the Universe will be very cold and all the black holes will evaporate extremely slowly.
Another interesting fact: the total power emitted by a black hole as Hawking radiation is inversely proportional to the square of the mass. [Eg the Milky Way black hole emits 18.5 trillion times less Hawking radiation than a stellar mass black hole].
The reason for this relationship is that the temperature is inversely proportional to the mass, black body emission power per unit area is proportional to the fourth power of temperature, and the area of a black hole is proportional to the square of its mass [of course, total power = (power per area) * area]