| Topic: |
Science > Physics |
| User: |
"Rushtown" |
| Date: |
21 Nov 2004 05:34:53 PM |
| Object: |
Retina as the screen in double slit experiment? |
Assume a living creature with a very large eyeball, very densely covered with
photo receptors. Assume further that when one photon of light hits one of
those receptors that a record is made (for awhile).
The double slit experiment could be set up using this creatures retina as the
screen where the interference pattern is recorded. After thousands of
individual photons were sent through the experiment we would have the familier
interference pattern recorded on the retina.
This supposedly means we could not discover which slit each photon went
through. That's not true in this experiment---my mythical creature has been
keeping score--faithfully recording, for each photon, the individual slit he
saw that photon come through. (or maybe he'll say he saw each photon come
through both slits)
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| User: "OG" |
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| Title: Re: Retina as the screen in double slit experiment? |
21 Nov 2004 06:55:02 PM |
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"Rushtown" <rushtown@aol.com> wrote in message
news:20041121183453.21945.00001118@mb-m06.aol.com...
Assume a living creature with a very large eyeball, very densely
covered with
photo receptors. Assume further that when one photon of light hits
one of
those receptors that a record is made (for awhile).
The double slit experiment could be set up using this creatures retina
as the
screen where the interference pattern is recorded. After thousands
of
individual photons were sent through the experiment we would have the
familier
interference pattern recorded on the retina.
This supposedly means we could not discover which slit each photon
went
through. That's not true in this experiment---my mythical creature
has been
keeping score--faithfully recording, for each photon, the individual
slit he
saw that photon come through. (or maybe he'll say he saw each photon
come
through both slits)
That's a bit like saying you can tell whether some light detected in
YOUR eye went through the top, bottom, right or left side of your
cornea. It can't be done.
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| User: "Edward Green" |
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| Title: Re: Retina as the screen in double slit experiment? |
22 Nov 2004 07:10:22 PM |
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"OG" <owen@gwynnefamily.org.uk> wrote in message news:<30crmuF2uer3eU1@uni-berlin.de>...
"Rushtown" <rushtown@aol.com> wrote in message
news:20041121183453.21945.00001118@mb-m06.aol.com...
my mythical creature has been
keeping score--faithfully recording, for each photon, the individual
slit he saw that photon come through. <...>
That's a bit like saying you can tell whether some light detected in
YOUR eye went through the top, bottom, right or left side of your
cornea. It can't be done.
You mean you can't form images of what you see, and tell the direction
of a source? Then you are legally blind.
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| User: "OG" |
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| Title: Re: Retina as the screen in double slit experiment? |
23 Nov 2004 04:04:48 PM |
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"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411221710.d93405a@posting.google.com...
"OG" <owen@gwynnefamily.org.uk> wrote in message
news:<30crmuF2uer3eU1@uni-berlin.de>...
"Rushtown" <rushtown@aol.com> wrote in message
news:20041121183453.21945.00001118@mb-m06.aol.com...
my mythical creature has been
keeping score--faithfully recording, for each photon, the
individual
slit he saw that photon come through. <...>
That's a bit like saying you can tell whether some light detected in
YOUR eye went through the top, bottom, right or left side of your
cornea. It can't be done.
You mean you can't form images of what you see, and tell the direction
of a source? Then you are legally blind.
I assume you've never done a ray diagram of the eye.
Imagine looking at a pin - Light from the tip of the pin emerges in all
directions, some of which is incident on the eye's pupil. Refraction at
the curved cornea and the lens brings this light to focus on the
retina - however it is emphatically *not* possible to determine which
part of the pupil admits a particular photon.
You can see an image, but the path is uncertain.
hope this helps.
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| User: "Edward Green" |
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| Title: Re: Retina as the screen in double slit experiment? |
25 Nov 2004 10:24:40 PM |
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"OG" <owen@gwynnefamily.org.uk> wrote in message news:<30hqg1F30hcavU1@uni-berlin.de>...
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411221710.d93405a@posting.google.com...
"OG" <owen@gwynnefamily.org.uk> wrote in message
news:<30crmuF2uer3eU1@uni-berlin.de>...
"Rushtown" <rushtown@aol.com> wrote in message
news:20041121183453.21945.00001118@mb-m06.aol.com...
my mythical creature has been
keeping score--faithfully recording, for each photon, the
individual
slit he saw that photon come through. <...>
That's a bit like saying you can tell whether some light detected in
YOUR eye went through the top, bottom, right or left side of your
cornea. It can't be done.
You mean you can't form images of what you see, and tell the direction
of a source? Then you are legally blind.
I assume you've never done a ray diagram of the eye.
Imagine looking at a pin - Light from the tip of the pin emerges in all
directions, some of which is incident on the eye's pupil. Refraction at
the curved cornea and the lens brings this light to focus on the
retina - however it is emphatically *not* possible to determine which
part of the pupil admits a particular photon.
You can see an image, but the path is uncertain.
It's pointless to argue that the experiment won't work, because it has
been done, and the observer -- in this case a mechanical analogue of
the eye -- can indeed record "the individual slit he saw the photon
come through"! So while not technically wrong you are being
orthogonal, and it remains to understand why, and to interpret the
quoted phrase.
Let the pin in your construction correspond to the slit: then it is
indeed impossible to determine the path taken from the pin (slit)
through the cornea (lens) to the retina (detector), beyond having
pentrated the pupil (aperture) somewhere. But you should predict
(following your construction) that it is possible to determine the
location of its source: the light started at the pin! And given two
pins (slits) with a sufficient angular separation, you should predict
that we can determine whether the source of light arriving at the
retina was pin 1 or pin 2: rays starting at one point source arrive at
a distinct point on the retina.
However, ray optics is an approximation to wave optics, and using this
latter model we have less justification in accepting "the slit he saw
the photon come through" at face value as a description of the
observation. You objected that with the ray construction we can't
determine which path was taken through the _lens_, but with wave
optics we can't even determine which path was taken through the
_slits_! The wave propagated through both -- just as your ray
construction propagates through all parts of the lens.
So you were on the right track, but didn't go far enough -- your
alleged objection in fact predicts the observed results, and supports
the original interpretation, but it points to a reason to question
this interpretation.
.
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| User: "OG" |
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| Title: Re: Retina as the screen in double slit experiment? |
26 Nov 2004 01:23:33 PM |
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"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411252024.ca8adc2@posting.google.com...
"OG" <owen@gwynnefamily.org.uk> wrote in message
news:<30hqg1F30hcavU1@uni-berlin.de>...
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411221710.d93405a@posting.google.com...
"OG" <owen@gwynnefamily.org.uk> wrote in message
news:<30crmuF2uer3eU1@uni-berlin.de>...
"Rushtown" <rushtown@aol.com> wrote in message
news:20041121183453.21945.00001118@mb-m06.aol.com...
You mean you can't form images of what you see, and tell the
direction
of a source? Then you are legally blind.
I assume you've never done a ray diagram of the eye.
Imagine looking at a pin - Light from the tip of the pin emerges in
all
directions, some of which is incident on the eye's pupil. Refraction
at
the curved cornea and the lens brings this light to focus on the
retina - however it is emphatically *not* possible to determine
which
part of the pupil admits a particular photon.
You can see an image, but the path is uncertain.
It's pointless to argue that the experiment won't work, because it has
been done, and the observer -- in this case a mechanical analogue of
the eye -- can indeed record "the individual slit he saw the photon
come through"! So while not technically wrong you are being
orthogonal, and it remains to understand why, and to interpret the
quoted phrase.
You seem to be confusing the focussed 'image' of the slits produced on
the retina and the 'Interference pattern' which is an unfocussed image
behind the slits.
Let the pin in your construction correspond to the slit: then it is
indeed impossible to determine the path taken from the pin (slit)
through the cornea (lens) to the retina (detector), beyond having
pentrated the pupil (aperture) somewhere. But you should predict
(following your construction) that it is possible to determine the
location of its source: the light started at the pin! And given two
pins (slits) with a sufficient angular separation, you should predict
that we can determine whether the source of light arriving at the
retina was pin 1 or pin 2: rays starting at one point source arrive at
a distinct point on the retina.
Are you talking about the Afshar experiment here? I've downloaded a copy
of his paper; you will, of course, have noted that he didn't use a
single photon source, so I don't think its fair to say that 'the
experiment has been done' - at least if you are referring to
Rushworth's 'experiment' in the original post. However, that is
irrelevant to the image/interference pattern distinction.
However, ray optics is an approximation to wave optics, and using this
latter model we have less justification in accepting "the slit he saw
the photon come through" at face value as a description of the
observation. You objected that with the ray construction we can't
determine which path was taken through the _lens_, but with wave
optics we can't even determine which path was taken through the
_slits_! The wave propagated through both -- just as your ray
construction propagates through all parts of the lens.
So you were on the right track, but didn't go far enough -- your
alleged objection in fact predicts the observed results, and supports
the original interpretation, but it points to a reason to question
this interpretation.
Again, I think the distinction between the focussed 'image' and the
unfocussed 'interference pattern' needs to be stressed.
.
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| User: "Edward Green" |
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| Title: Re: Retina as the screen in double slit experiment? |
27 Nov 2004 07:48:25 AM |
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"OG" <owen@gwynnefamily.org.uk> wrote in message news:<30pe5lF2uggo8U1@uni-berlin.de>...
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411252024.ca8adc2@posting.google.com...
It's pointless to argue that the experiment won't work, because it has
been done, and the observer -- in this case a mechanical analogue of
the eye -- can indeed record "the individual slit he saw the photon
come through"! So while not technically wrong you are being
orthogonal, and it remains to understand why, and to interpret the
quoted phrase.
You seem to be confusing the focussed 'image' of the slits produced on
the retina and the 'Interference pattern' which is an unfocussed image
behind the slits.
No, I'm not. The OP made this confusion in the first post, and I
pointed it out to him. Go back and look. Also please look up the
recent Afshar experiment, which this discussion is really about.
Let the pin in your construction correspond to the slit: then it is
indeed impossible to determine the path taken from the pin (slit)
through the cornea (lens) to the retina (detector), beyond having
pentrated the pupil (aperture) somewhere. But you should predict
(following your construction) that it is possible to determine the
location of its source: the light started at the pin! And given two
pins (slits) with a sufficient angular separation, you should predict
that we can determine whether the source of light arriving at the
retina was pin 1 or pin 2: rays starting at one point source arrive at
a distinct point on the retina.
Are you talking about the Afshar experiment here?
Ah. So you did make the connection!
I've downloaded a copy
of his paper; you will, of course, have noted that he didn't use a
single photon source, so I don't think its fair to say that 'the
experiment has been done' - at least if you are referring to
Rushworth's 'experiment' in the original post.
I reread Rush_town_'s post, and I don't seen anything about a single
photon source.
However, that is
irrelevant to the image/interference pattern distinction.
Please point out to me exactly where I confused the two?
However, ray optics is an approximation to wave optics, and using this
latter model we have less justification in accepting "the slit he saw
the photon come through" at face value as a description of the
observation. You objected that with the ray construction we can't
determine which path was taken through the _lens_, but with wave
optics we can't even determine which path was taken through the
_slits_! The wave propagated through both -- just as your ray
construction propagates through all parts of the lens.
So you were on the right track, but didn't go far enough -- your
alleged objection in fact predicts the observed results, and supports
the original interpretation, but it points to a reason to question
this interpretation.
Again, I think the distinction between the focussed 'image' and the
unfocussed 'interference pattern' needs to be stressed.
You, sir, appear, to the untutored eye and all that, to be waffling.
.
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| User: "OG" |
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| Title: Re: Retina as the screen in double slit experiment? |
27 Nov 2004 04:58:42 PM |
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"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411270548.53fd42ec@posting.google.com...
"OG" <owen@gwynnefamily.org.uk> wrote in message
news:<30pe5lF2uggo8U1@uni-berlin.de>...
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411252024.ca8adc2@posting.google.com...
It's pointless to argue that the experiment won't work, because it
has
been done, and the observer -- in this case a mechanical analogue
of
the eye -- can indeed record "the individual slit he saw the
photon
come through"! So while not technically wrong you are being
orthogonal, and it remains to understand why, and to interpret the
quoted phrase.
You seem to be confusing the focussed 'image' of the slits produced
on
the retina and the 'Interference pattern' which is an unfocussed
image
behind the slits.
No, I'm not. The OP made this confusion in the first post, and I
pointed it out to him. Go back and look. Also please look up the
recent Afshar experiment, which this discussion is really about.
I'm not so sure that the original post really was about the Afshar
experiment.
In which case you are saying that the OP is in error because he's not
talking about the experiment that you are thinking about.
.
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| User: "OG" |
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| Title: Re: Retina as the screen in double slit experiment? |
27 Nov 2004 05:12:31 PM |
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"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:eca320d0.0411270548.53fd42ec@posting.google.com...
"OG" <owen@gwynnefamily.org.uk> wrote in message
news:<30pe5lF2uggo8U1@uni-berlin.de>...
Are you talking about the Afshar experiment here?
Ah. So you did make the connection!
I've downloaded a copy
of his paper; you will, of course, have noted that he didn't use a
single photon source, so I don't think its fair to say that 'the
experiment has been done' - at least if you are referring to
Rushworth's 'experiment' in the original post.
I reread Rush_town_'s post, and I don't seen anything about a single
photon source.
He/she certainly refers to single photons being detected (second
sentence).
On the other hand the OP definitely talks about detecting an IP on the
retina. I took this at face value and explained that under these
circumstances the detection of the photon will not give an indication of
which slit it came through.
Nothing there about Afshar.
.
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| User: "Paul Cardinale" |
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| Title: Re: Retina as the screen in double slit experiment? |
23 Nov 2004 09:25:00 AM |
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(Edward Green) wrote in message news:<eca320d0.0411221710.d93405a@posting.google.com>...
"OG" <owen@gwynnefamily.org.uk> wrote in message news:<30crmuF2uer3eU1@uni-berlin.de>...
"Rushtown" <rushtown@aol.com> wrote in message
news:20041121183453.21945.00001118@mb-m06.aol.com...
my mythical creature has been
keeping score--faithfully recording, for each photon, the individual
slit he saw that photon come through. <...>
That's a bit like saying you can tell whether some light detected in
YOUR eye went through the top, bottom, right or left side of your
cornea. It can't be done.
You mean you can't form images of what you see, and tell the direction
of a source? Then you are legally blind.
Wow. I award you two setos and a wilson.
.
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| User: "Edward Green" |
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| Title: Re: Retina as the screen in double slit experiment? |
22 Nov 2004 01:13:53 AM |
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(Rushtown) wrote in message news:<20041121183453.21945.00001118@mb-m06.aol.com>...
Assume a living creature with a very large eyeball, very densely covered with
photo receptors. Assume further that when one photon of light hits one of
those receptors that a record is made (for awhile).
The double slit experiment could be set up using this creatures retina as the
screen where the interference pattern is recorded. After thousands of
individual photons were sent through the experiment we would have the familier
interference pattern recorded on the retina.
This supposedly means we could not discover which slit each photon went
through. That's not true in this experiment---my mythical creature has been
keeping score--faithfully recording, for each photon, the individual slit he
saw that photon come through. (or maybe he'll say he saw each photon come
through both slits)
Nice thought, but you've missed the bandwagon which just drove by:
this is essentially the Afshar experiment just discussed here, with
the exception that he used photodectors and a lens as his "eye" -- the
human one, so I'm told, is not quite sensitive enough to detect single
photons.
There is also one problem with your analysis: there is no two slit
interference pattern on the retina. There is, in fact, an image of
the two slits, as we would expect. And it turns out that if the human
eye were sufficiently sensitive, we would see flashes of light
coninciding with either slit. As for verifying that persistence of
the interference pattern, this is done passively, by placing a grid in
an intermediate plane at the calculated nulls, and demonstrating that
the intensity falls off insigificantly (I assume Afshar calibrated
this by checking the same placement and one illuminated slit).
As to whether seeing -- literally -- which slit the flash coincided
with is evidence for the spacetime trajectory of a particle passing
through that slit can be debated.
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| User: "CSharpner" |
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| Title: Re: Retina as the screen in double slit experiment? |
30 Nov 2004 12:08:38 PM |
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(Rushtown) wrote in message news:<20041121183453.21945.00001118@mb-m06.aol.com>...
Assume a living creature with a very large eyeball, very densely covered with
photo receptors. Assume further that when one photon of light hits one of
those receptors that a record is made (for awhile).
The double slit experiment could be set up using this creatures retina as the
screen where the interference pattern is recorded. After thousands of
individual photons were sent through the experiment we would have the familier
interference pattern recorded on the retina.
This supposedly means we could not discover which slit each photon went
through. That's not true in this experiment---my mythical creature has been
keeping score--faithfully recording, for each photon, the individual slit he
saw that photon come through. (or maybe he'll say he saw each photon come
through both slits)
The brain interprets *where* the light came from based on *where* on
the retina the photon(s) hit. If you've got photons from different
sources striking the same spot on the retina, the brain has no way to
determine where the photon(s) really came from. The brain will
interpret the source of the light as coming from whatever part of the
image the brain "sees" as having a flash over it. If you were to
produce an interference pattern on the retina, note that you'd have
MULTIPLE hit spots on the retina. The brain would "see" this
interference pattern as an image overlayed on top of what it was
already seeing... each part of the pattern seemingly coming from a
different place.
Just think of the retina as a biological CCD with bio-pixels. The
interference pattern paints an image on the surface of the retina and
each part of that image is perceived to be coming from a different,
physical location. The owner of that eye would not see all parts of
the pattern coming from only 2 slit sources.
There is some 3D holographic technology work being done (or at least,
was being done 5 or 6 years or so ago) to paint a computer screen's
image directly onto the eyeball with a low powered laser. Last I
heard, they were having some success with this. Note that the viewer
sees a 2D image, NOT a single point light source, even though the
entire 2D scene is projected from a single point laser light source.
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| User: "Sam Wormley" |
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| Title: Re: Retina as the screen in double slit experiment? |
21 Nov 2004 10:07:42 PM |
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Rushtown wrote:
Assume a living creature with a very large eyeball, very densely covered with
photo receptors. Assume further that when one photon of light hits one of
those receptors that a record is made (for awhile).
Young's Double Slit Experiment
http://scienceworld.wolfram.com/physics/YoungsDoubleSlitExperiment.html
http://scienceworld.wolfram.com/physics/DoubleSlitInterference.html
Fraunhofer Diffraction--Double Slit
http://scienceworld.wolfram.com/physics/FraunhoferDiffractionDoubleSlit.html
PHYSICS NEWS UPDATE
http://www.aip.org/enews/physnews/2002/split/613-1.htm
The American Institute of Physics Bulletin of Physics News
Number 613 November 13, 2002 by Phillip F. Schewe, Ben Stein, and James
Riordon
A BI-PHOTON DE BROGLIE WAVELENGTH has been directly measured in an
interference experiment for the first time. In the early days of quantum
mechanics, Louis de Broglie argued that if waves could act like particles
(photoelectric effect) then why couldn't particles act like waves? They
could, as was borne out in numerous experiments (the double-slit experiment
for electrons was voted the "most beautiful" experiment in a recent poll-see
Physics World, Sept 2002). In fact intact atoms in motion and even
molecules can be thought of as "de Broglie waves." Molecules as large as
buckyballs (carbon-60) have been sent through an interferometer, creating a
characteristic interference pattern (see Update 579,
http://www.aip.org/enews/physnews/2002/split/579-1.html). The measured
wavelength for a composite object like C-60 will in part depend on the
internal bonds of the molecule. What then if the corporate object is a
pair of entangled photons?
One of the more fascinating predictions made regarding quantum entanglement
(Jacobson et al., Physical Review Letters, 12 Jun 1995) was the suggestion
that the de Broglie wavelength for an ensemble consisting of N entangled
photons (each with a wavelength of L) would be L/N. This proposition has
been verified now by physicists at Osaka University (Keiichi Edamatsu,
81-6-6850-6507, eda@mp.es.osaka-u.ac.jp) for the case of two entangled
photons. The daughter photons were created by the process of parametric
down-conversion, in which an incident photon entering a special crystal will
split into two correlated photons. These photons are then sent through an
interferometer (see figure at http://www.aip.org/mgr/png/2002/169.htm). The
resultant interference pattern shows that the photons behave as if they
acted as a single entity with a wavelength half that for either photon
alone, a feature which might improve the sharpness of future quantum
lithography (the narrowness of lines on a circuit board being no better than
the wavelength of light used in the fabrication process). But since the
parent photon already had this shorter wavelength, what will have been
gained by splitting the photon in half? The advantage will come when, at
some point in the future it will be possible to generate entangled photons
from non-entangled photons of the same wavelength, a process called
hyper-parametric scattering. (Edamatsu et al., Physical Review Letters, 18
November 2002)
Also: http://www.google.com/search?q=%22double-slit%22+site%3Awww.aip.org+update
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