Starship Asterisk*

JohnD wrote: ↑Mon Apr 15, 2019 3:15 pm
When I was first brought to "civilisation", I was wild. In fact I was furious. But I learnt to live with The Man, to conform, to shave (all over) and even to wear a suit (Three-piece, natch) But getting someone to make me a shirt that fits? A 68 inch chest appear to be beyond your technology. That just leaves me fuming.

https://en.wikipedia.org/wiki/Mirror_test#Primates_2 wrote:

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<<The mirror test – sometimes called the mark test, mirror self-recognition test (MSR), red spot technique, or rouge test – is the traditional method for attempting to measure self-awareness. However, there has been agreement that animals can be self-aware in ways not measured by the mirror test, such as distinguishing between their own and others' songs and scents. On the other hand, animals that can pass the MSR do not necessarily have self-awareness.

In the classic MSR test, an animal is anaesthetised and then marked (e.g., painted, or a sticker attached) on an area of the body the animal cannot normally see. When the animal recovers from the anesthetic, it is given access to a mirror. If the animal then touches or investigates the mark, it is taken as an indication that the animal perceives the reflected image as itself, rather than of another animal. Very few species have passed the MSR test. As of 2015, only great apes (including humans), a single Asiatic elephant, dolphins, orcas and the Eurasian magpie have passed the MSR test. A wide range of species have been reported to fail the test, including several species of monkey, giant pandas, sea lions, and dogs.

Findings for gorillas are mixed. At least four studies have reported that gorillas failed the MSR test. It has been suggested that the gorilla may be the only great ape "which lacks the conceptual ability necessary for self-recognition". Other studies have found more positive results, but have tested gorillas with extensive human contact, and required modification of the test by habituating the gorillas to the mirror and not using anaesthetic. Koko reportedly passed the MSR test, this was without anaesthetic. In gorillas, protracted eye contact is an aggressive gesture and they may therefore fail the mirror test because they deliberately avoid making eye contact with their reflections. This could also explain why only gorillas with extensive human interaction and a certain degree of separation from other gorillas and usual gorilla behaviour are more predisposed to passing the test.>>

DnhoJ wrote: ↑Mon Apr 15, 2019 10:41 am
And you will realise that as you move, even a fraction of a inch, your eyes receive a different 'beam' of photons. Because, within the bounds of internal refraction/reflection the photons go in all directions. The bounds of distorted space around a BH are not so limited.

And, to use a 'beam' of light is to reinforce the self- and terran-cetric attitude. There is no cohesive, aimed pathway for the photons, just a random distribution that you happen to be in the way of.

JohnD wrote: ↑Mon Apr 15, 2019 10:41 am And you will realise that as you move, even a fraction of a inch, your eyes receive a different 'beam' of photons. Because, within the bounds of internal refraction/reflection the photons go in all directions. The bounds of distorted space around a BH are not so limited.

And, to use a 'beam' of light is to reinforce the self- and terran-cetric attitude. There is no cohesive, aimed pathway for the photons, just a random distribution that you happen to be in the way of.

JohnD wrote: ↑Mon Apr 15, 2019 8:01 am
Chris, and neufer,

What I'm objecting to is the terracentric bias in the diagram, as bad as any Pre-Copernican. There is no beam of photons directed at the Earth, unless a BH has a focussing property - which it may have, see jets! Photons come at it from ALL directions, and are deviated (will that do instead of "affected"?) in ALL directions.

JohnD wrote: ↑Sun Apr 14, 2019 6:17 pm Sure, but the affected photons are reradiated in ALL directions.
John

JohnD wrote: ↑Sun Apr 14, 2019 6:05 pm Respect to neufer, but that illustration is surely misleading? Light from all directions will be distorted by skimming the Event Horizon, to be redirected in all directions. To show a collimated, parallel beam in Earth's direction is a misdirection!

neufer wrote: ↑Fri Apr 12, 2019 3:58 pm

Ann wrote: ↑Fri Apr 12, 2019 3:36 pm
So, Chris, do you think that the black hole's shadow could come from gravity-induced reddening?

The black hole's shadow has EVERYTHING to do with gravitational lensing of the hot accretion disk behind the black hole.

• It is closely related to the larger Einstein rings of
  more distant [and TOTALLY un-gravity-induced reddened] radiation sources.

https://www.syfy.com/syfywire/the-first-image-of-the-event-horizon-of-a-black-hole wrote:.

Credit: Nicolle R. Fuller/NSF

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The path of light around a black hole gets severely distorted by gravity. In this diagram, the Earth is off to the right, and light form material behind the black hole gets bent toward us, leaving a [somewhat larger] “hole/shadow” where the black hole itself is.

Fred the Cat wrote: ↑Sat Apr 13, 2019 5:18 pm

neufer wrote: ↑Fri Apr 12, 2019 5:18 pm John Wheeler (who coined the terms of black hole and wormhole)..

The " whole" story is actually a book filled with discussion about their singular “wholiness”.

It would have been shadowy if they turned out to be blue but Ann would have been in bliss.

neufer wrote: ↑Fri Apr 12, 2019 5:18 pm John Wheeler (who coined the terms of black hole and wormhole)..

Ann wrote: ↑Sat Apr 13, 2019 7:26 am I just saw this youtube video. Because I am as dense as I am, and because it always takes a long time for me to digest new things, I can't say that I understood it to the point that I could repeat it and explain it myself.

But I think that one of the points made in the video was that Doppler blueshift and redshift make one half of the ring around the black hole shadow brighter and one half of the ring fainter. The brighter part of the ring represents blueshifted photons moving towards us, and the fainter half of the ring represents redshifted photons moving away from us.

Ann wrote: ↑Sat Apr 13, 2019 7:26 am I just saw this youtube video. Because I am as dense as I am, and because it always takes a long time for me to digest new things, I can't say that I understood it to the point that I could repeat it and explain it myself.

But I think that one of the points made in the video was that Doppler blueshift and redshift make one half of the ring around the black hole shadow brighter and one half of the ring fainter. The brighter part of the ring represents blueshifted photons moving towards us, and the fainter half of the ring represents redshifted photons moving away from us.

Ann

RocketRon wrote: ↑Sat Apr 13, 2019 4:07 am

Chris Peterson wrote: ↑Fri Apr 12, 2019 1:16 pm There are a dozen links in the caption and subsequent pages of discussion here to sites that explain, at all different levels of detail, how this image was made, what wavelength was used, how interferometry works, what the different parts of the image are showing us and why they look the way they do as a consequence of general relativity. There are also superb and easily used resources like Wikipedia where you can quickly look up concepts like "reddening" and see what they mean.

Sure there are.
But perhaps I didn't make it clear enough, its the methodolgy behind this ALGORITHM that is of interest here.

Sure, others have used similar techniques.
Have they published specific details of their algorithms, or do we just take it on blind faith.
Peer review is supposed to be how it works, and the scientific method is to question everything,
especially if its not obvious how they pulled a rabbit out of the hat.

Chris Peterson wrote: ↑Fri Apr 12, 2019 1:16 pm There are a dozen links in the caption and subsequent pages of discussion here to sites that explain, at all different levels of detail, how this image was made, what wavelength was used, how interferometry works, what the different parts of the image are showing us and why they look the way they do as a consequence of general relativity. There are also superb and easily used resources like Wikipedia where you can quickly look up concepts like "reddening" and see what they mean.

Chris Peterson wrote: ↑Fri Apr 12, 2019 1:16 pm BTW, this is hardly the first image produced this way, or the first one to be featured on APOD. A number of images have been shown which were created by radio telescope arrays, and they all use similar processing, because the method is straightforward and based on well understood math and optics. The exceptional thing about this image was the technology that increased the spatial resolution, and the consequences of this particular observation in terms of strengthening support for GR.

https://blogs.futura-sciences.com/e-luminet/2015/01/20/black-hole-illuminations-13-back-basics/ wrote:

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Black Hole Imaging (1/3): Back to the basics
January 20, 2015 Jean-Pierre LUMINET

<<The case of a black hole of mass M, here assumed to be non-rotating, thus described by the Schwarzschild geometry. The essential difference from the preceding examples is that a black hole has not a tangible hard surface against which light rays can strike and be reflected. It is the black hole’s gravitational field which deviates the light rays. The black hole’s sphere of influence is not therefore a single sphere – the event horizon – but extends to infinity. The trajectories of light rays are not altered by the impact with a surface, but are curved by the gravitational field. In the experiment where it is illuminated, the black hole’s gravitational field deviates several light rays towards the observer. The image of the black hole consists of a series of illuminated spots. On the left, at 2.96 times the Schwarzschild radius of the black hole (equal to 2M), the ‘primary’ image is produced by light rays which have been deviated by 90°. On the right, at 2.61 times the Schwarzschild radius the ‘secondary’ image is produced by light rays which have been deviated through another half circle (a total of 270°). The complete calculation of the geodesics of the Schwarzschild space-time corresponding to the light ray trajectories shows that there is an infinity of images; the third one corresponds to light which has been deviated by 450°, and so on adding a half turn each time. However, in practice, the images of order higher than two have such a low intensity and are so close to the primary and secondary images that they cannot be resolved.

We can therefore conclude that among the various celestial bodies which are not intrinsically bright, black holes are far from being the darkest. They are easier to detect than a black painted sphere or a highly reflective sphere!

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The black hole in glory

A variant on the preceding experiment consists of illuminating a black hole
and observing the light reflected back in the same direction.
[And/or illuminating the black hole from behind.]
............................................................................................

In the case of black holes with a glory effect, only the outer ring would be visible, as it is not possible to resolve the rings of higher orders. This is not only a matter of brightness, but also a matter of resolution.

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The image of the actual black hole is magnified to 3√3/2 ≈ 2.6 times its real diameter. This is because a large part of the incident beam is captured by the black hole: not just the radiation which directly strikes the event horizon but also that which passes within 5.2M of the centre (the true radius of the black hole being equal to 2M). The black disk appears to be surrounded by a series of concentric light rings. The external ring, at radius 5.34 M, is produced by light rays deviated by 180°, the inner rings by light rays deviated by additional turns. The final result is like the glory effect, well-known in traditional optics: when sunlight is scattered by innumerable water droplets in mist, it is sometimes possible to see in reflection the shadow of one’s own head surrounded by brilliant rings of light centred on the line of sight.

In 2002, David Holz and John Wheeler have suggested that the primary ring could be detectable in the case of a stellar mass black hole located at the border of our solar system and reflecting the light of our star, the Sun. John Wheeler (who coined the terms of black hole and wormhole) entitled the article “Retro-MACHO : pi in the sky”, meaning both that isolated stellar mass black holes belonged to the category of Massive Astrophysical Compact Halo Objects, a candidate for baryonic dark matter, and their detectability thanks to the deflection of light by the “magic angle” 180°.>>

Ann wrote: ↑Fri Apr 12, 2019 3:36 pm
So, Chris, do you think that the black hole's shadow could come from gravity-induced reddening?

• It is closely related to the larger Einstein rings of
  more distant [and TOTALLY un-gravity-induced reddened] radiation sources.

https://www.syfy.com/syfywire/the-first-image-of-the-event-horizon-of-a-black-hole wrote:.

Credit: Nicolle R. Fuller/NSF

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.
.
.
The path of light around a black hole gets severely distorted by gravity. In this diagram, the Earth is off to the right, and light form material behind the black hole gets bent toward us, leaving a [somewhat larger] “hole/shadow” where the black hole itself is.