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Paul B. Andersen wanted to know...

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  Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-07-31 14:33 +0000
    Re: Paul B. Andersen wanted to know... The Starmaker <starmaker@ix.netcom.com> - 2022-07-31 10:57 -0700
    Re: Paul B. Andersen wanted to know... "Paul B. Andersen" <paul.b.andersen@paulba.no> - 2022-07-31 19:59 +0200
      Re: Paul B. Andersen wanted to know... Maciej Wozniak <maluwozniak@gmail.com> - 2022-07-31 12:00 -0700
      Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-07-31 22:18 +0000
        Re: Paul B. Andersen wanted to know... "Paul B. Andersen" <paul.b.andersen@paulba.no> - 2022-08-01 19:21 +0200
          Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-08-01 18:46 +0000
            Re: Paul B. Andersen wanted to know... "Paul B. Andersen" <paul.b.andersen@paulba.no> - 2022-08-02 14:40 +0200
              Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-08-02 14:58 +0000
                Re: Paul B. Andersen wanted to know... "Paul B. Andersen" <paul.b.andersen@paulba.no> - 2022-08-02 22:35 +0200
                  Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-08-02 21:11 +0000
                    Re: Paul B. Andersen wanted to know... "Paul B. Andersen" <paul.b.andersen@paulba.no> - 2022-08-03 11:24 +0200
                      Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-08-03 12:46 +0000
                        Re: Paul B. Andersen wanted to know... "Paul B. Andersen" <paul.b.andersen@paulba.no> - 2022-08-04 11:46 +0200
                          Re: Paul B. Andersen wanted to know... Maciej Wozniak <maluwozniak@gmail.com> - 2022-08-04 02:49 -0700
                            Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-08-04 11:27 +0000
                              Re: Paul B. Andersen wanted to know... Maciej Wozniak <maluwozniak@gmail.com> - 2022-08-04 05:02 -0700
                              Re: Paul B. Andersen wanted to know... Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-04 06:58 -0700
                                Re: Paul B. Andersen wanted to know... Maciej Wozniak <maluwozniak@gmail.com> - 2022-08-04 07:40 -0700
                                Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-08-04 14:51 +0000
                                  Re: Paul B. Andersen wanted to know... Maciej Wozniak <maluwozniak@gmail.com> - 2022-08-04 07:55 -0700
                                  Re: Paul B. Andersen wanted to know... Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-04 10:06 -0700
                                    Re: Paul B. Andersen wanted to know... Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-04 22:17 -0700
                                Re: Paul B. Andersen wanted to know... JanPB <filmart@gmail.com> - 2022-08-09 01:00 -0700
                                  Re: Paul B. Andersen wanted to know... JanPB <filmart@gmail.com> - 2022-08-09 01:02 -0700
                                  Re: Paul B. Andersen wanted to know... Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-09 02:03 -0700
                                    Re: Paul B. Andersen wanted to know... nospam@de-ster.demon.nl (J. J. Lodder) - 2022-08-09 11:49 +0200
                                      Re: Paul B. Andersen wanted to know... Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-09 04:25 -0700
                                        Re: Paul B. Andersen wanted to know... nospam@de-ster.demon.nl (J. J. Lodder) - 2022-08-09 14:23 +0200
                                      Re: Paul B. Andersen wanted to know... JanPB <filmart@gmail.com> - 2022-08-09 06:10 -0700
                                    Re: Paul B. Andersen wanted to know... JanPB <filmart@gmail.com> - 2022-08-09 06:03 -0700
                                  Re: Paul B. Andersen wanted to know... Juan Di pasqua <toed@iavdattg.ev> - 2022-08-09 10:57 +0000
                                    Re: Paul B. Andersen wanted to know... JanPB <filmart@gmail.com> - 2022-08-09 06:04 -0700
                          Re: Paul B. Andersen wanted to know... Richard Hachel <r.hachel@tiscali.fr> - 2022-08-04 11:11 +0000
                            Re: Paul B. Andersen wanted to know... "Paul B. Andersen" <paul.b.andersen@paulba.no> - 2022-08-05 08:48 +0200
                              Re: Paul B. Andersen wanted to know... The Starmaker <starmaker@ix.netcom.com> - 2022-08-05 10:23 -0700
                                Re: Paul B. Andersen wanted to know... The Starmaker <starmaker@ix.netcom.com> - 2022-08-08 21:53 -0700
      Re: Paul B. Andersen wanted to know... Neal Giordano <bqwc@gcfikwuf.ja> - 2022-08-01 14:33 +0000
      Re: Paul B. Andersen wanted to know... RichD <r_delaney2001@yahoo.com> - 2022-08-08 18:35 -0700
        Re: Paul B. Andersen wanted to know... Buck Baggio <toed@iavdattg.ev> - 2022-08-10 12:52 +0000

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#589254

On Thursday, 4 August 2022 at 16:51:25 UTC+2, Richard Hachel wrote:

> Everything else is your fantasies and your arrogance of the type: "Doctor 
> Hachel is shit, we are smarter and more educated than him". 
> 
> Just that behavior. 

There are no others between The Shit's believers.
What do you think they're atracted to this idiocy with?

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#589265

On Thursday, August 4, 2022 at 9:51:25 AM UTC-5, Richard Hachel wrote:
> Le 04/08/2022 à 15:58, Prokaryotic Capase Homolog a écrit : 
> > On Thursday, August 4, 2022 at 6:27:09 AM UTC-5, Richard Hachel wrote: 
> > 
> >> I try to explain that when a person sees an object coming towards them at 
> >> 0.8c, they actually see this object coming at 4c, because of the 
> >> longitudinal Doppler effect. 
> > 
> > You need to carefully distinguish between what you *see* versus 
> > what you *measure/observe*.
> Your answer is very violent. 
> 
> You take your opponent for a fool, and you reverse the roles. 

What you are blowing up about is a TRIVIAL point concerning time delays
that has nothing to do with *measurements*, but is an optical effect that 
must be *routinely* corrected for.

Let's say that at time 0 years, a spaceship is 100 light years distant. Light 
from the spaceship arrives at t = 100 years.

After 1 year, the spaceship is 99.2 light years distant. Light from the 
spaceship arrives at t = 1 + 99.2 years = 100.2 years.

So you are taking 0.8 light years divided by (100.2 - 100) = 4 c.

That number has nothing very much to do with anything, certainly not
relativity. 

The effect of optical time delays must always be corrected for and is 
something that everybody already knows how to correct for.

You remind me of Henry Wilson insisting that everybody falsely assumes
that the transverse light beams in MMX are tilted, and he kept that stance
despite years of being shown that he was wrong.

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#589289

On Thursday, August 4, 2022 at 12:06:08 PM UTC-5, Prokaryotic Capase Homolog wrote:
> On Thursday, August 4, 2022 at 9:51:25 AM UTC-5, Richard Hachel wrote: 
> > Le 04/08/2022 à 15:58, Prokaryotic Capase Homolog a écrit : 
> > > On Thursday, August 4, 2022 at 6:27:09 AM UTC-5, Richard Hachel wrote: 
> > > 
> > >> I try to explain that when a person sees an object coming towards them at 
> > >> 0.8c, they actually see this object coming at 4c, because of the 
> > >> longitudinal Doppler effect. 
> > > 
> > > You need to carefully distinguish between what you *see* versus 
> > > what you *measure/observe*. 
> > Your answer is very violent. 
> > 
> > You take your opponent for a fool, and you reverse the roles.
> What you are blowing up about is a TRIVIAL point concerning time delays 
> that has nothing to do with *measurements*, but is an optical effect that 
> must be *routinely* corrected for. 
> 
> Let's say that at time 0 years, a spaceship is 100 light years distant. Light 
> from the spaceship arrives at t = 100 years. 
> 
> After 1 year, the spaceship is 99.2 light years distant. Light from the 
> spaceship arrives at t = 1 + 99.2 years = 100.2 years. 
> 
> So you are taking 0.8 light years divided by (100.2 - 100) = 4 c. 
> 
> That number has nothing very much to do with anything, certainly not 
> relativity. 
> 
> The effect of optical time delays must always be corrected for and is 
> something that everybody already knows how to correct for. 
> 
> You remind me of Henry Wilson insisting that everybody falsely assumes 
> that the transverse light beams in MMX are tilted, and he kept that stance 
> despite years of being shown that he was wrong.

Most reports of superluminal motion deal with apparent FTL *transverse*
motions rather than longitudinal motions that you discuss due to the 
relative ease of measuring angular displacement rather than measuring 
changes in longitudinal distance. The principle, however, is exactly the 
same. A high speed feature (of, say, a relativistic jet or the ejecta of a 
nova) is observed at time t_1, and is observed later at time t_2 with a 
measurable lateral displacement at a point considerably closer to us. 
The apparent transverse velocity is in many cases faster than the speed
of light.   

Apparent superluminal motions have been observed since 1901.
The point is, you have NOT made any sort of revolutionary discovery,
and there is no violation of special relativity, which you apparently do
not understand with any degree of competency.

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#589607

On Thursday, August 4, 2022 at 6:58:26 AM UTC-7, prokaryotic.c...@gmail.com wrote:
> On Thursday, August 4, 2022 at 6:27:09 AM UTC-5, Richard Hachel wrote: 
> 
> > I try to explain that when a person sees an object coming towards them at 
> > 0.8c, they actually see this object coming at 4c, because of the 
> > longitudinal Doppler effect.
> You need to carefully distinguish between what you *see* versus 
> what you *measure/observe*. 
> 
> This is one of my favorite animations for a cube in transverse motion: 
> https://en.wikipedia.org/wiki/Special_relativity#Measurement_versus_visual_appearance 

Someone will correct me but I think a small part of this Wikipedia entry is
misleading. It says in the 3rd paragraph:

"A sphere in motion retains the appearance of a sphere, although images
on the surface of the sphere will appear distorted."

It should say: "A sphere in motion retains the circular outline, although
the surface of the sphere and the images on it will appear distorted."

...or some such, the distortion of the sphere surface may not be easy to
see without binocular (stereoscopic) observation.

The reason for that is that visual observation is a mapping between two
conic (light cone) sections by 3D spacelike planes (i.e., two 2D manifolds,
since 3 + 3 - 4 = 2) representing the visual field of the object and the
sensor/film/retina/etc. The key fact is that this mapping between those
manifolds is conformal (Penrose calls it "sky mapping"). Therefore, it
always maps circles to circles, thus an outline of a sphere will always
appear circular *visually*. But the sphere surface itself gets distorted,
not just the image painted on it.

Corrections welcome, it's been a while since I did any calculations about
this (the Berlin Wall was still standing anyway).

--
Jan

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#589608

On Tuesday, August 9, 2022 at 1:00:02 AM UTC-7, I wrote:
>
> The reason for that is that visual observation is a mapping between two 
> conic (light cone) sections by 3D spacelike planes 

Correction: "...two conic (light cone) sections by 3D spacelike manifolds".

--
Jan

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#589609

On Tuesday, August 9, 2022 at 3:00:02 AM UTC-5, JanPB wrote:
> On Thursday, August 4, 2022 at 6:58:26 AM UTC-7, prokaryotic.c...@gmail.com wrote: 
> > On Thursday, August 4, 2022 at 6:27:09 AM UTC-5, Richard Hachel wrote: 
> > 
> > > I try to explain that when a person sees an object coming towards them at 
> > > 0.8c, they actually see this object coming at 4c, because of the 
> > > longitudinal Doppler effect. 
> > You need to carefully distinguish between what you *see* versus 
> > what you *measure/observe*. 
> > 
> > This is one of my favorite animations for a cube in transverse motion: 
> > https://en.wikipedia.org/wiki/Special_relativity#Measurement_versus_visual_appearance
> Someone will correct me but I think a small part of this Wikipedia entry is 
> misleading. It says in the 3rd paragraph: 
> 
> "A sphere in motion retains the appearance of a sphere, although images 
> on the surface of the sphere will appear distorted." 
> 
> It should say: "A sphere in motion retains the circular outline, although 
> the surface of the sphere and the images on it will appear distorted." 
> 
> ...or some such, the distortion of the sphere surface may not be easy to 
> see without binocular (stereoscopic) observation. 
> 
> The reason for that is that visual observation is a mapping between two 
> conic (light cone) sections by 3D spacelike planes (i.e., two 2D manifolds, 
> since 3 + 3 - 4 = 2) representing the visual field of the object and the 
> sensor/film/retina/etc. The key fact is that this mapping between those 
> manifolds is conformal (Penrose calls it "sky mapping"). Therefore, it 
> always maps circles to circles, thus an outline of a sphere will always 
> appear circular *visually*. But the sphere surface itself gets distorted, 
> not just the image painted on it. 
> 
> Corrections welcome, it's been a while since I did any calculations about 
> this (the Berlin Wall was still standing anyway). 

Thanks. That's pretty much what I *meant* to say, but you've 
very clearly pointed out that my *expression* of what I intended 
to say left a bit to be desired. 

I'll make the fix. I hope you don't mind that I intend to just 
plagiarize your wording???

I had worked on an animation of this, but I gave up on the 
animation because I couldn't quite render properly what the
math was telling me. Exactly as you state, "the distortion of 
the sphere surface may not be easy to see without binocular 
(stereoscopic) observation," and the problem with 3D graphics
has been that I was a cross-eyed viewer, whereas the great
majority of 3D graphics are designed for parallel-eyed viewing.

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#589610

Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com>
wrote:

> On Tuesday, August 9, 2022 at 3:00:02 AM UTC-5, JanPB wrote:
> > On Thursday, August 4, 2022 at 6:58:26 AM UTC-7, prokaryotic.c...@gmai:
> > > On Thursday, August 4, 2022 at 6:27:09 AM UTC-5, Richard Hachel wrote:
> > > 
> > > > I try to explain that when a person sees an object coming towards
> > > > them at 0.8c, they actually see this object coming at 4c, because of
> > > > the longitudinal Doppler effect.
> > > You need to carefully distinguish between what you *see* versus 
> > > what you *measure/observe*. 
> > > 
> > > This is one of my favorite animations for a cube in transverse motion:
> > > https://en.wikipedia.org/wiki/Special_relativity#Measurement_versus_visual
_appearance
> > Someone will correct me but I think a small part of this Wikipedia entry is
> > misleading. It says in the 3rd paragraph: 
> > 
> > "A sphere in motion retains the appearance of a sphere, although images
> > on the surface of the sphere will appear distorted." 
> > 
> > It should say: "A sphere in motion retains the circular outline, although
> > the surface of the sphere and the images on it will appear distorted."
> > 
> > ...or some such, the distortion of the sphere surface may not be easy to
> > see without binocular (stereoscopic) observation. 
> > 
> > The reason for that is that visual observation is a mapping between two
> > conic (light cone) sections by 3D spacelike planes (i.e., two 2D manifolds,
> > since 3 + 3 - 4 = 2) representing the visual field of the object and the
> > sensor/film/retina/etc. The key fact is that this mapping between those
> > manifolds is conformal (Penrose calls it "sky mapping"). Therefore, it
> > always maps circles to circles, thus an outline of a sphere will always
> > appear circular *visually*. But the sphere surface itself gets distorted,
> > not just the image painted on it. 
> > 
> > Corrections welcome, it's been a while since I did any calculations about
> > this (the Berlin Wall was still standing anyway). 
> 
> Thanks. That's pretty much what I *meant* to say, but you've 
> very clearly pointed out that my *expression* of what I intended 
> to say left a bit to be desired. 
> 
> I'll make the fix. I hope you don't mind that I intend to just 
> plagiarize your wording???
> 
> I had worked on an animation of this, but I gave up on the 
> animation because I couldn't quite render properly what the
> math was telling me. Exactly as you state, "the distortion of 
> the sphere surface may not be easy to see without binocular 
> (stereoscopic) observation," and the problem with 3D graphics
> has been that I was a cross-eyed viewer, whereas the great
> majority of 3D graphics are designed for parallel-eyed viewing.

There are many pictures of it available on the web, for example
<https://www.researchgate.net/figure/The-visual-appearances-of-objects-moving-at-relativistic-speeds-All-the-objects-in-the_fig1_220183634>
A general derivation for the appearance of wire-frame objects
can be found at
<https://iopscience.iop.org/article/10.1088/0143-0807/35/6/065025>
<Thomas Müller and Sebastian Boblest 2014 Eur. J. Phys. 35 065025>
Paywalled, unfortunately,

Jan

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#589616

On Tuesday, August 9, 2022 at 4:49:30 AM UTC-5, J. J. Lodder wrote:
> Prokaryotic Capase Homolog <prokaryotic.c...@gmail.com> 

> > I had worked on an animation of this, but I gave up on the 
> > animation because I couldn't quite render properly what the 
> > math was telling me. Exactly as you state, "the distortion of 
> > the sphere surface may not be easy to see without binocular 
> > (stereoscopic) observation," and the problem with 3D graphics 
> > has been that I was a cross-eyed viewer, whereas the great 
> > majority of 3D graphics are designed for parallel-eyed viewing.
> There are many pictures of it available on the web, for example 
> <https://www.researchgate.net/figure/The-visual-appearances-of-objects-moving-at-relativistic-speeds-All-the-objects-in-the_fig1_220183634> 
> A general derivation for the appearance of wire-frame objects 
> can be found at 
> <https://iopscience.iop.org/article/10.1088/0143-0807/35/6/065025> 
> <Thomas Müller and Sebastian Boblest 2014 Eur. J. Phys. 35 065025> 
> Paywalled, unfortunately, 

I already own a copy of Müller and Boblest, thanks!. The state 
university is just 20 minutes down the road, and visitors get
one hour access to the "community" computers, so paywalls
have been no problem.

When I was creating my animation, however, I found something
very gratifying with starting with the LTs and knowing *exactly*
my reasons for placing each pixel. So while I could have used
the shortcut of canned routines, I preferred creating them from
scratch. :-)  

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#589619

Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com>
wrote:

> On Tuesday, August 9, 2022 at 4:49:30 AM UTC-5, J. J. Lodder wrote:
> > Prokaryotic Capase Homolog <prokaryotic.c...@gmail.com> 
> 
> > > I had worked on an animation of this, but I gave up on the 
> > > animation because I couldn't quite render properly what the 
> > > math was telling me. Exactly as you state, "the distortion of 
> > > the sphere surface may not be easy to see without binocular 
> > > (stereoscopic) observation," and the problem with 3D graphics 
> > > has been that I was a cross-eyed viewer, whereas the great 
> > > majority of 3D graphics are designed for parallel-eyed viewing.
> > There are many pictures of it available on the web, for example 
> > <https://www.researchgate.net/figure/The-visual-appearances-of-objects-movin
g-at-relativistic-speeds-All-the-objects-in-the_fig1_220183634> 
> > A general derivation for the appearance of wire-frame objects 
> > can be found at 
> > <https://iopscience.iop.org/article/10.1088/0143-0807/35/6/065025> 
> > <Thomas Müller and Sebastian Boblest 2014 Eur. J. Phys. 35 065025> 
> > Paywalled, unfortunately, 
> 
> I already own a copy of Müller and Boblest, thanks!. The state 
> university is just 20 minutes down the road, and visitors get
> one hour access to the "community" computers, so paywalls
> have been no problem.
> 
> When I was creating my animation, however, I found something
> very gratifying with starting with the LTs and knowing *exactly*
> my reasons for placing each pixel. So while I could have used
> the shortcut of canned routines, I preferred creating them from
> scratch. :-)  

There is a pioneering article on it, perhaps in Am. J. Phys.
(from long ago)
The author was the first to notice that the illustrations
in Gamow's Mr. Tompkins were wrong, physically speaking.
(unless for someone equipped with faster than local light vision)

I would have to search for it,

Jan

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#589627

On Tuesday, August 9, 2022 at 2:49:30 AM UTC-7, J. J. Lodder wrote:
> Prokaryotic Capase Homolog <prokaryotic.c...@gmail.com> 
> wrote:
> > On Tuesday, August 9, 2022 at 3:00:02 AM UTC-5, JanPB wrote:
> > > On Thursday, August 4, 2022 at 6:58:26 AM UTC-7, prokaryotic.c...@gmai:
> > > > On Thursday, August 4, 2022 at 6:27:09 AM UTC-5, Richard Hachel wrote: 
> > > > 
> > > > > I try to explain that when a person sees an object coming towards 
> > > > > them at 0.8c, they actually see this object coming at 4c, because of 
> > > > > the longitudinal Doppler effect. 
> > > > You need to carefully distinguish between what you *see* versus 
> > > > what you *measure/observe*. 
> > > > 
> > > > This is one of my favorite animations for a cube in transverse motion: 
> > > > https://en.wikipedia.org/wiki/Special_relativity#Measurement_versus_visual 
> _appearance 
> > > Someone will correct me but I think a small part of this Wikipedia entry is 
> > > misleading. It says in the 3rd paragraph: 
> > > 
> > > "A sphere in motion retains the appearance of a sphere, although images 
> > > on the surface of the sphere will appear distorted." 
> > > 
> > > It should say: "A sphere in motion retains the circular outline, although 
> > > the surface of the sphere and the images on it will appear distorted." 
> > > 
> > > ...or some such, the distortion of the sphere surface may not be easy to 
> > > see without binocular (stereoscopic) observation. 
> > > 
> > > The reason for that is that visual observation is a mapping between two 
> > > conic (light cone) sections by 3D spacelike planes (i.e., two 2D manifolds, 
> > > since 3 + 3 - 4 = 2) representing the visual field of the object and the 
> > > sensor/film/retina/etc. The key fact is that this mapping between those 
> > > manifolds is conformal (Penrose calls it "sky mapping"). Therefore, it 
> > > always maps circles to circles, thus an outline of a sphere will always 
> > > appear circular *visually*. But the sphere surface itself gets distorted, 
> > > not just the image painted on it. 
> > > 
> > > Corrections welcome, it's been a while since I did any calculations about 
> > > this (the Berlin Wall was still standing anyway). 
> > 
> > Thanks. That's pretty much what I *meant* to say, but you've 
> > very clearly pointed out that my *expression* of what I intended 
> > to say left a bit to be desired. 
> > 
> > I'll make the fix. I hope you don't mind that I intend to just 
> > plagiarize your wording??? 
> > 
> > I had worked on an animation of this, but I gave up on the 
> > animation because I couldn't quite render properly what the 
> > math was telling me. Exactly as you state, "the distortion of 
> > the sphere surface may not be easy to see without binocular 
> > (stereoscopic) observation," and the problem with 3D graphics 
> > has been that I was a cross-eyed viewer, whereas the great 
> > majority of 3D graphics are designed for parallel-eyed viewing.
> There are many pictures of it available on the web, for example 
> <https://www.researchgate.net/figure/The-visual-appearances-of-objects-moving-at-relativistic-speeds-All-the-objects-in-the_fig1_220183634> 
> A general derivation for the appearance of wire-frame objects 
> can be found at 
> <https://iopscience.iop.org/article/10.1088/0143-0807/35/6/065025> 
> <Thomas Müller and Sebastian Boblest 2014 Eur. J. Phys. 35 065025> 
> Paywalled, unfortunately, 

It's at <cough>sci-hub</cough>.

--
Jan

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#589623

On Tuesday, August 9, 2022 at 2:03:15 AM UTC-7, prokaryotic.c...@gmail.com wrote:
> On Tuesday, August 9, 2022 at 3:00:02 AM UTC-5, JanPB wrote: 
> > On Thursday, August 4, 2022 at 6:58:26 AM UTC-7, prokaryotic.c...@gmail.com wrote: 
> > > On Thursday, August 4, 2022 at 6:27:09 AM UTC-5, Richard Hachel wrote: 
> > > 
> > > > I try to explain that when a person sees an object coming towards them at 
> > > > 0.8c, they actually see this object coming at 4c, because of the 
> > > > longitudinal Doppler effect. 
> > > You need to carefully distinguish between what you *see* versus 
> > > what you *measure/observe*. 
> > > 
> > > This is one of my favorite animations for a cube in transverse motion: 
> > > https://en.wikipedia.org/wiki/Special_relativity#Measurement_versus_visual_appearance 
> > Someone will correct me but I think a small part of this Wikipedia entry is 
> > misleading. It says in the 3rd paragraph: 
> > 
> > "A sphere in motion retains the appearance of a sphere, although images 
> > on the surface of the sphere will appear distorted." 
> > 
> > It should say: "A sphere in motion retains the circular outline, although 
> > the surface of the sphere and the images on it will appear distorted." 
> > 
> > ...or some such, the distortion of the sphere surface may not be easy to 
> > see without binocular (stereoscopic) observation. 
> > 
> > The reason for that is that visual observation is a mapping between two 
> > conic (light cone) sections by 3D spacelike planes (i.e., two 2D manifolds, 
> > since 3 + 3 - 4 = 2) representing the visual field of the object and the 
> > sensor/film/retina/etc. The key fact is that this mapping between those 
> > manifolds is conformal (Penrose calls it "sky mapping"). Therefore, it 
> > always maps circles to circles, thus an outline of a sphere will always 
> > appear circular *visually*. But the sphere surface itself gets distorted, 
> > not just the image painted on it. 
> > 
> > Corrections welcome, it's been a while since I did any calculations about 
> > this (the Berlin Wall was still standing anyway).
> Thanks. That's pretty much what I *meant* to say, but you've 
> very clearly pointed out that my *expression* of what I intended 
> to say left a bit to be desired. 
> 
> I'll make the fix. I hope you don't mind that I intend to just 
> plagiarize your wording??? 

Of course I don't mind. I think Penrose & Rindler do this elegantly in their
"Spinors and space-time", forget which volume.

> I had worked on an animation of this, but I gave up on the 
> animation because I couldn't quite render properly what the 
> math was telling me. Exactly as you state, "the distortion of
> the sphere surface may not be easy to see without binocular
> (stereoscopic) observation," and the problem with 3D graphics 
> has been that I was a cross-eyed viewer, whereas the great 
> majority of 3D graphics are designed for parallel-eyed viewing.

Ah yes, it's my pet peeve as well. Most stereoscopic images and
clips are using that terrible, accursed, impossible-to-use parallel
(distal) viewing. OTOH the cross-eyed (proximal) viewing is very
easy and does not require any special devices. It's used in
stereochemistry textbooks 99% of the time (because they know
what they are doing).

It would be very easy for that web page to add a stereoscopic MP4.

--
Jan

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#589615

JanPB wrote:

> It should say: "A sphere in motion retains the circular outline,
> although the surface of the sphere and the images on it will appear
> distorted."

you contradict yourself, then. You can't "retain" anything when it become 
distorted. In fact that sphere approaches the shape of a disk along that 
direction.

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#589624

On Tuesday, August 9, 2022 at 3:57:09 AM UTC-7, Juan Di pasqua wrote:
> JanPB wrote: 
> 
> > It should say: "A sphere in motion retains the circular outline, 
> > although the surface of the sphere and the images on it will appear 
> > distorted."
> you contradict yourself, then. You can't "retain" anything when it become 
> distorted. In fact that sphere approaches the shape of a disk along that 
> direction.

Reread what I wrote.

--
Jan

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#589242

Le 04/08/2022 à 11:46, "Paul B. Andersen" a écrit :

>>> Q3:
>>> Is distance = speed X time?
>> 
>> Yes.
> 
> OK.
> So you agree that immediately after the turnaround
> the distance to the Earth in the traveller's rest frame is
> D = v⋅T = 7.2 light years.
> 
> Thanks for finally admitting that you were wrong when
> you claimed that this distance was 36 light years.

 

I see you still haven't had the click.

You don't understand what I say, and the truth of what I say.

I beg you to make a very small effort (you or a possible reader interested 
in the subject) to understand why it is obviously necessary to put 
x=Tr.Vapp and not x=Tr.Vo

You don't have this fantastic stroke of genius and logic yet (but don't 
despair).

As Jesus Christ said: "The theory of relativity goes through Richard 
Hachel, and he looks like a sinner who has found only very small fish, 
suddenly he pulls a huge and good fish to him. So he rejects all the 
little fish overboard, and he brings the big fish home".

I beg you once again to have a few coffees, to go lie down on the bed, to 
close your eyes, and to meditate for a long time: "But why Vapp and not Vo 
at Hachel's?"

The immense light will perhaps occur and you will be the first man in the 
world to say: "My God!!! Hooray!!! I understood Richard Hachel!!"

R.H. 

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#589294

Den 04.08.2022 13:11, skrev Richard Hachel:
> 
> As Jesus Christ said: "The theory of relativity goes through Richard 
> Hachel, and he looks like a sinner who has found only very small fish, 
> suddenly he pulls a huge and good fish to him. So he rejects all the 
> little fish overboard, and he brings the big fish home".
> 

Why am I not laughing?

We leave it at that.

-- 
Paul

https://paulba.no/

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#589314

Paul B. Andersen 




The secret to Paul B. Anderson is...

the letter B.


Do you know the secret to the letter B.????


Not what it spells out..
but, what is the secret meaning behind the letter ...B?

In otherwords, Why is there a B. in there in the first place?


How come it doesn't read Paul Andersen?


Why put the letter B. inbetween Paul B. Andersen????


Can you answer that secret? 



-- 
The Starmaker -- To question the unquestionable, ask the unaskable,
 to think the unthinkable, mention the unmentionable, say the unsayable,
and challenge
 the unchallengeable.

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#589603

The Starmaker wrote:
> 
> Paul B. Andersen
> 
> The secret to Paul B. Anderson is...
> 
> the letter B.
> 
> Do you know the secret to the letter B.????
> 
> Not what it spells out..
> but, what is the secret meaning behind the letter ...B?
> 
> In otherwords, Why is there a B. in there in the first place?
> 
> How come it doesn't read Paul Andersen?
> 
> Why put the letter B. inbetween Paul B. Andersen????
> 
> Can you answer that secret?

All yous have to remember is that...
Paul B. Anderson
is just a collection of atoms
that calls itself
Paul B. Anderson
and the B.
is just the
'illusions of grandeur'...

dat thinks it has a 
hotline to God.

Paul B. Anderson
is just a collection of atoms
that calls itself
Paul B. Anderson



irrelevant 


-- 
The Starmaker -- To question the unquestionable, ask the unaskable,
 to think the unthinkable, mention the unmentionable, say the unsayable, and challenge
 the unchallengeable.

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#589026

Paul B. Andersen wrote:

> On the way back he will see the Earth clock run fast by
> sqrt((1+0.8)/(1-0.8)) = 3.
> So when he is back after another 9 years on his clock,
> he will see the Earth clock showing (3+3*9) years = 30 years.
> 
> Keep asking what you want to know, Richard.
> I will always answer a nice guy like you.

nonsense. The spatial resolution of GPS is very low. You failed again.

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#589598

On July 31, Paul B. Andersen wrote:
> Richard Hachel wanted to know how can a traveler who observes 
> for nine years the earth returning towards him at an apparent 
> speed of 4c, can he see it evolve on 7.2al? 
> The traveller can't observe the earth returning towards 
> him at an apparent speed of 4c. 
> What he _can_ visually observe is this: 
> On the way out he will see the Earth clock run slow 
> by sqrt((1-0.8)/(1+0.8)) = 1/3. 
> So when he turns around when his clock shows 9 years, 
> he will see the Earth clock shows 3 years. 
> 
> On the way back he will see the Earth clock run fast 
> by sqrt((1+0.8)/(1-0.8)) = 3. 
> So when he is back after another 9 years on his clock, 
> he will see the Earth clock showing (3+3*9) years = 30 years. 

Something wrong here.

Tim Traveller sends photos of his clock to Earthbound Ed.  By 
symmetry, on the outbound leg, Ed sees Tim's clock run slow.  
Then, on the return leg, he sees Tim's clock run fast.  Using 
your numbers above,  Ed will see Tim's clock showing 30 years.


--
Rich

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#589697

RichD wrote:

> Something wrong here.
> 
> Tim Traveller sends photos of his clock to Earthbound Ed.  By symmetry,
> on the outbound leg, Ed sees Tim's clock run slow. Then, on the return
> leg, he sees Tim's clock run fast.  Using your numbers above,  Ed will
> see Tim's clock showing 30 years.

assuming he knows the speed of the Tim, to decode the signal of the 
photos. The return like wise, but will not show it faster.

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