On Thu, 13 Sep 2007 15:36:34 +0200, "Paul B. Andersen"
wrote:

Henri Wilson wrote:
On Sun, 09 Sep 2007 21:39:34 +0200, "Paul B. Andersen"
wrote:



It is simply a fact that interferometers like the VLTI do
image stars like l Carinae as a disk which you can measure
the diameter of.

You still haven't explained how the weak starlight that enters both detectors
is coherent. Since it comes from many parts of the star, I don't see that it
can be .....UNLESS of course you accept my unification theory.

This idiocy over and over and over!

'Coherent' isn't quite the correct expression, but since you use it
let 'coherent' in this context mean that the surface of equal phase
('wavefront') can be considered to be a plane.

Since you appear to be deaf, I will have to shout:

OF BLOODY COURSE THE LIGHT FROM DIFFERENT PARTS OF
A RESOLVED STAR ISN'T COHERENT OVER 600m!

It is the light from a _point_ (area resolution) on
the star that is coherent (plane wavefront).
The wavefronts from two different parts of the star
have an angle to each other, and is NOT coherent.

So you are claiming that a single light quanta can have a 'cross section' of
over 600 metres by the time it reaches Earth????

THATS WHY THEY ARE FOCUSED AT TWO DIFFERENT POINTS ON THE CCD!

Whether we are talking about a 600m telescope, or
an interferometer with two mirrors 600m apart,
WE GET AN IMAGE _BECAUSE_ THE LIGHT IS INCOHERENT!

This doesn't appear to have anything to do with iinterferometry.

The only kind of 'image' you can get from coherent light
is a single dot (airy disk).
we get an image _because_ the light from different
parts of the star is NOT coherent.

THE INTERFEROMETER WORKS BECAUSE THE LIGHT FROM DIFFERENT
PARTS OF THE STAR IS INCOHERENT.

So all you are talking about is a normal image.


Paul, it matters not one iota whether or not the star goes huff puff.
The main cause of the luminosity variation is cyclic c+.
...or do you still believe that most star curves can be matched with the BaTh
out of pure coincidence?
The issue is your claim that the diameter of stars like l Carinae
cannot be measured by interferometric measurements.

Do you now understand that it can?

I certainly do understand.... and the answer is clearly NO, IT CANNOT..

If telescopes work, so do interferometers.
The principle is the very same.

This reveals your ignorance of optics..

Have you now fathomed that, or will you still state stupidities like:
"Just tell me how photons emitted from opposite sides of a star can end up in
phase over a 600m wavefront".

Interferometry requires coherent light.
Please provide an explanation as to how light emitted from many parts of a
star's surface, maybe at slightly different times, can end up in phase 1800LYs
away and over a distance of 600m.

...and over and over and over.

Henri, you have to learn how a telescope works to
understand how an interferometer like the VLTI works.
You know neither.

Let me make a last attempt to make you understand.
Please consider the scenarios below.

If you don't bother to read it properly, don't respond.
-------------------------------------------------------

I am fed up with your autistic responses which only
reveal that you haven't read what you are responding to.

In all cases below, the observed object is l Carinae.
The angular diameter of l Carinae is ca. 3 mas.
Let us assume that lambda = 2u IR (like in the VLTI).

#1 A 8m aperture telescope:
---------------------------
The 'image' of the star is an airy disk.
http://support.svi.nl/wiki/AiryDisk
The diameter of the central disk is equivalent to 60mas.
The star is not resolved, and can be considered a point source.
That is to say - the wavefront can be considered to be a plane
over the aperture of the telescope.
(The phase difference between the wavefronts of light from
opposite sides of the star is too small to be significant.)

#2 A 600m aperture telescope:
-----------------------------
The image of the star is a disk equivalent to 3 mas.
(The diameter of the central airy disk of a point source
would be equivalent to 0.8mas. The resolution is 0.8mas)
The star is resolved.
The wavefronts from two points at the opposite sides of the star
will have an angle to each other (the light is not coherent),
and over the big aperture this angle will make a phase difference
big enough so that the two sides will be focused at different spots
on the CCD.

Hahahahaha! You must be kidding, surely....
How can incoherent light from two entirely different sources create
interference? It's probably not even the same wavelength..and who know when it
was emitted....

Hahahoohohahahah!


#3 A 600m aperture telescope consisting of 8m segments:
--------------------------------------------------------
The 'image' from each 8m segment will be an airy disk
with central disk equivalent to 60 mas.
But all the airy disks are focused on top of each other.
The interference pattern will be a disk equivalent
to 3 mas, which is identical to the image of the star in #2.

If we remove some of the segments, the image will get
'freckles', but it will still be basically the same image.

#4 A "telescope" consisting of two 8m segments 600m apart:
----------------------------------------------------------
This is an interferometer in principle like the VLTI.
It can be considered as #3 where all but two segments are removed.
The 'image' from each 8m segment will be an airy disk
with central disk equivalent to 60 mas.
These two airy disks are focused on top of each other.
The interference pattern will be a disk equivalent to 3mas.
The disk will have fringes in it, but it is still basically
the same image as in #2.

The wavefronts from two points at the opposite sides of the star
will have an angle to each other (the light is not coherent).
This means that since the segments are 600m apart, the phase
between the two wavefronts will be significantly different
in the two segments. That's why the two 60mas disks will
interfere in such a way that the streaked image of the star
appears.

Note this, Henri.
The interferometer works _because_ the light from
opposite sides of the star are sufficiently 'incoherent'
to be resolved.

No Paul, an interference pattern of some kind just happens to appear because
all the light from the star is unified in speed as it travels across space
(and maybe phase aligned as well).
The interference varies with c+v as the star orbits .

But you will of course ignore this, and keep asking
me to "provide an explanation as to how light emitted
from many parts of a star's surface, can end up in
phase over a distance of 600m."

I have explained why this question reveals your
ignorance for the last time now.

You really should study some genuine physics Paul....

Paul



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