Lewin's Challenge Image
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Guest
We can see that Professor Lewin is holding the camera up to his face, looking down, so that the sun is behind his head. The color is from a single drop of oil on a reflective surface in an area where a jackhammer is being used. At this point, most of the oil is on the edge of the drop. The sun's reflection down through and back up through the torus of slightly thicker oil at the edges of the drop cause the colors.
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thepunnery
I agree, it looks very much like a glory to me. As for what it's reflecting on...I thought it was ice, too, at first, but the caption pointed out that the picture was taken in June.
It's a construction site; maybe they're building an ice skating rink? Okay, maybe not. But that does look a lot like frost and a bit of powdered snow or scraped frost.
It's a construction site; maybe they're building an ice skating rink? Okay, maybe not. But that does look a lot like frost and a bit of powdered snow or scraped frost.
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Dr Norm
Solstice?
I don't really understand if there has been any sort of official confirmation of ahecht's answer, but I agree that it is at the very least doubtful that the APOD editors wouldn't know the answer yet would link to that 8/6 post in today's post.
I'm not the most knowledgable on physics/waves/etc, and I dont know if someone has mentioned this at some other point already, but I didn't see it mentioned in this thread, so maybe you guys could figure something out with this.
June 20th 2004 was the summer solstice. The sun would have been the farthest from earth that it will be over the course of the year, and also it would be at it's northern most point (the tropic of cancer), therefore the earth's tilt would be pointing Massacusettes more "directly at the sun" than any other day of the year.
Now maybe I'm just stupid and you guys were all assuming this already because I saw it's also the APOD for that day, but I just had to post it in case you weren't and it would have some impact on your thinking.
Norm
I'm not the most knowledgable on physics/waves/etc, and I dont know if someone has mentioned this at some other point already, but I didn't see it mentioned in this thread, so maybe you guys could figure something out with this.
June 20th 2004 was the summer solstice. The sun would have been the farthest from earth that it will be over the course of the year, and also it would be at it's northern most point (the tropic of cancer), therefore the earth's tilt would be pointing Massacusettes more "directly at the sun" than any other day of the year.
Now maybe I'm just stupid and you guys were all assuming this already because I saw it's also the APOD for that day, but I just had to post it in case you weren't and it would have some impact on your thinking.
Norm
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vamphunt
Look at ther face
I may be a bit crazed from being awake for 15 hours now. But look at the face. I think I see his eyes and a mouth. With the camra next to his head.
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kilo*man, Ann Arbor
Directly behind the photographer are two (or more) small apertures which are close together and through which a bright light is shining (perhaps the sun?). The apertures acts as lenses to focus the image of the bright light upon the surface that is being photographed. Thus the image of the light source is brighter than the surrounding dimly lit surface. The color rings are due to the diffraction patterns from the apertures interfering with one another and producing maxima for each wavelength.
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Tunç Tezel
I guess it is a rainbow. In rainbows, the inner area of the bow is much brighter than the outer parts, due to light scatterring random and some UV light.
One can call the center as glory (no really sure for this occasion though), which will be familiar to frequent flyers and airliner pilots. At least, it can be a similar mechanism.
My final guess is, this photo was taken by using a really wide angle or fisheye lens, using a bright street light, a floodlight or just the Sun. The rainbow was producad by refraction-reflection of this light through fine ice crystals of fresh frost formed on a previously frozen sheet of water on tarmac.
One can call the center as glory (no really sure for this occasion though), which will be familiar to frequent flyers and airliner pilots. At least, it can be a similar mechanism.
My final guess is, this photo was taken by using a really wide angle or fisheye lens, using a bright street light, a floodlight or just the Sun. The rainbow was producad by refraction-reflection of this light through fine ice crystals of fresh frost formed on a previously frozen sheet of water on tarmac.
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FG
Lewin's Challenge image
Another message in support of ahecht. Some years ago I produced a 'rainbow board' in a school by sticking small plastic beads to hardboard, which produced similar colours. Also I expect others will have pointed out this EPOD at http://epod.usra.edu/archive/epodviewer.php3?oid=148192
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jojojay@charter.net
the corona
sirs:
the "shadow" is a guy using a flash camera casting the "flash" onto some sort of surface.
i don't think it is a fellow shooting toward the ground, i.e., the reflective beads theory, for it order to do that his outline would have to be directly in the middle of the image and the he would have to be suspended directly above his focus and perpendicular to the ground.
then where would the fellow taking his picutre from behind (and above) be?
also, it is dark and cold, and outside, persumably, as the fellow appears heavily dressed.
i am thinking that it is someone projecting a flash onto the concave surface of a reflective mirror, it a telescope. hence the brightness in the image center, the concentricity of the colored rings on the outside of the reflected rings, and the slightly blurred quality of the rings (and the lack of real "clarity" in the color, as the mirror hardly would have been designed to reflect light in such a manner as to produce these kinds of images, i.e., the angles of reflection not being designed for this).
that's my guess, courtesy of high school physics almost 40 years ago.
jjj
the "shadow" is a guy using a flash camera casting the "flash" onto some sort of surface.
i don't think it is a fellow shooting toward the ground, i.e., the reflective beads theory, for it order to do that his outline would have to be directly in the middle of the image and the he would have to be suspended directly above his focus and perpendicular to the ground.
then where would the fellow taking his picutre from behind (and above) be?
also, it is dark and cold, and outside, persumably, as the fellow appears heavily dressed.
i am thinking that it is someone projecting a flash onto the concave surface of a reflective mirror, it a telescope. hence the brightness in the image center, the concentricity of the colored rings on the outside of the reflected rings, and the slightly blurred quality of the rings (and the lack of real "clarity" in the color, as the mirror hardly would have been designed to reflect light in such a manner as to produce these kinds of images, i.e., the angles of reflection not being designed for this).
that's my guess, courtesy of high school physics almost 40 years ago.
jjj
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ashuston
Identify this Phenomenon Walter Lewin (MIT)
ahecht has the correct answer, traffic paint beads spilled on the ground, producing the ‘Glory’ effect or Brocken spectra. I would also add it was taken around 10:20 am, as judged by the image distortion of the asphalt.
get some sleep people
get some sleep people
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jojojay@charter.net
the mystery image
dear sirs:
i have looked over the link, and other responses.
i don't think it is a photo of any ground surface with reflective materials, for two reasons:
1. unless the picture taker is shooting absolutely straight down at the surface, and perpendicular to the surface, any such image would be eliptical and not circular, and
2. that absolutely would not focus the color rings on the outer edge of the image. what theory of reflection/refraction could cause that.
the other thing that caught my eye was the theory of someone standing behind a sheet, or some such, but i still don't understand how it would make the color rings.
some mechanism has to split the light, and then focus the split light on the circumference of the image. i simply can't imagine how any sort of flat surface would do that, and i can't image any shape of prismatic material that would do it either.
the one thing that intrigues me about the image is the sort of "structural" texture of the illuminated surface, and i really don't know how to accomodate my theory to that, unless the light source were really bright and somehow slightly penetrated the glass surface of the ground mirror to illuminate it grain structure. don't know enough about glass to explain that.
john jay
i have looked over the link, and other responses.
i don't think it is a photo of any ground surface with reflective materials, for two reasons:
1. unless the picture taker is shooting absolutely straight down at the surface, and perpendicular to the surface, any such image would be eliptical and not circular, and
2. that absolutely would not focus the color rings on the outer edge of the image. what theory of reflection/refraction could cause that.
the other thing that caught my eye was the theory of someone standing behind a sheet, or some such, but i still don't understand how it would make the color rings.
some mechanism has to split the light, and then focus the split light on the circumference of the image. i simply can't imagine how any sort of flat surface would do that, and i can't image any shape of prismatic material that would do it either.
the one thing that intrigues me about the image is the sort of "structural" texture of the illuminated surface, and i really don't know how to accomodate my theory to that, unless the light source were really bright and somehow slightly penetrated the glass surface of the ground mirror to illuminate it grain structure. don't know enough about glass to explain that.
john jay
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makc
Re: Lewin's Challenge image
Just look at the link. Images are virtually the same! This is not a question any more.FG wrote:Another message in support of ahecht. Some years ago I produced a 'rainbow board' in a school by sticking small plastic beads to hardboard, which produced similar colours. Also I expect others will have pointed out this EPOD at http://epod.usra.edu/archive/epodviewer.php3?oid=148192
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h1ghf1ve
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jojojay@charter.net
mystery photo
sirs:
i think i've got it.
my previous theories bothered me, 'cuz i couldn't figure out how you'd get someone inside a telescope or in front of the mirror.
then it occurred to me.
what if you put a crystal or glass hemisphere on a pedastal in front of a concrete wall (hint: at the construction site in massachusetts, probably not many mirror telescopes in massachusetts), have a fellow stand in front of the hemisphere (about head level) and shoot the flash.
might not the outer edges of the hemisphere act as a prism to break up the light into its component parts and cast the image.
i don't like the idea of any natural phenomena as it appears to me that the camera flash is the only illumination, and if the image in the picture were backlit we would see him.
john jay
p.s. i am going to sleep.
i think i've got it.
my previous theories bothered me, 'cuz i couldn't figure out how you'd get someone inside a telescope or in front of the mirror.
then it occurred to me.
what if you put a crystal or glass hemisphere on a pedastal in front of a concrete wall (hint: at the construction site in massachusetts, probably not many mirror telescopes in massachusetts), have a fellow stand in front of the hemisphere (about head level) and shoot the flash.
might not the outer edges of the hemisphere act as a prism to break up the light into its component parts and cast the image.
i don't like the idea of any natural phenomena as it appears to me that the camera flash is the only illumination, and if the image in the picture were backlit we would see him.
john jay
p.s. i am going to sleep.
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btacie
heiligenschein
It's called a heiligenschein. It's similar to a glory.
Check it out.
http://www.sundog.clara.co.uk/droplets/heilig.htm
You can find examples all over the internet.
Instead of dew, it's the particles on the ground that he seems to have stirred up with his foot by looking at the dragmarks.
Mystery solved. Shows over folks.
I'll admit they do look cool though.[/img][/url]
Check it out.
http://www.sundog.clara.co.uk/droplets/heilig.htm
You can find examples all over the internet.
Instead of dew, it's the particles on the ground that he seems to have stirred up with his foot by looking at the dragmarks.
Mystery solved. Shows over folks.
I'll admit they do look cool though.[/img][/url]
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SteveRayle
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astroivar
halo
This seems to be some kind of heiligenschein or opposition effect, as looking at the shadow reveals that it is the antisolar point. The reason for the colors are probably a glory, as seen from an airplane at certain times. The reason for the sudden darkness outside the rainbow colors might be for the same reason that rainbows are brighter on the inside than the outside
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Dark Prince
Re: Lewin's challenge
Yes. Muhuhuhuahahahaha!peter maisonpierre wrote:It would appear that Lewin casts a saintly shadow. I'd guess the order & type of colors seen at the halo fringe must be indicative of rank. (did I win ?)
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Urania
Lewin's Challenge
The image was taken at a construction site at midsummer (June 20). I suspect the photographer was standing at the edge of a construction pit which was being sprayed with water to keep the dust down..perhaps early in the morning. With the Sun directly behind him, conditions would be right to produce the gegenschein/Glory. Check the links that accompany the APOD image for expanations of the phenomena.
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Steve
APOD Picture
I think its a glory for 3 reasons.
1. the effect is Circular
2. The spectrum of colours is red on outside, violet on inside
3. The Glory is Centred on the Camera (which is xcorrect, as the camera is taking the picture, of course.)
Not clear what is causing the spectrum od colours, but perhaps the photographer is photographing into a "mist" of Vapour which is difficult to see with the wall or whatever he is looking at. It certainly is a strange brownish colour. The sun must be shining directly behind him.
1. the effect is Circular
2. The spectrum of colours is red on outside, violet on inside
3. The Glory is Centred on the Camera (which is xcorrect, as the camera is taking the picture, of course.)
Not clear what is causing the spectrum od colours, but perhaps the photographer is photographing into a "mist" of Vapour which is difficult to see with the wall or whatever he is looking at. It certainly is a strange brownish colour. The sun must be shining directly behind him.