APOD: Atmospheric Ring of Venus (2020 Jun 08)

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Expand view Topic review: APOD: Atmospheric Ring of Venus (2020 Jun 08)

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by neufer » Thu Jun 18, 2020 11:41 am

JohnD wrote: Thu Jun 18, 2020 8:36 am
Never thought of you in a strapless evening gown, neufer.

Don't want to, either!
  • I'm sure that it's bruned into your memory now :!:

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by JohnD » Thu Jun 18, 2020 8:36 am

Never thought of you in a strapless evening gown, neufer.

Don't want to, either!

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by neufer » Wed Jun 17, 2020 4:18 pm

Click to play embedded YouTube video.
JohnD wrote: Wed Jun 17, 2020 3:06 pm
Total thread diversion, but I blame neufer!

Neufer - The Reims Cathdral Labyrinth? Wow! Is that where the idea in Umberto Eco's mind arose, for the Library labyrinth in "The Name of the Rose"? YES! It did!

See:

https://www.architecturalpapers.ch/index.php?ID=75

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by JohnD » Wed Jun 17, 2020 3:06 pm

Total thread diversion, but I blame neufer!

Neufer - The Reims Cathdral Labyrinth? Wow! Is that where the idea in Umberto Eco's mind arose, for the Library labyrinth in "The Name of the Rose"? YES! It did! See: https://www.architecturalpapers.ch/index.php?ID=75

John

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by RJN » Wed Jun 17, 2020 1:55 pm

After perhaps more discussion between experts than ever before in APOD history, of which I was aware, the word "diffracting" has been changed to "scattering" on the main NASA APOD. I would not be surprised if this APOD image -- and perhaps similar images -- are referenced in future science papers analyzing apparent rings around planets near inferior conjunction!
- RJN

Ream's Labyrinth

by neufer » Tue Jun 09, 2020 3:07 pm

TheZuke! wrote: Tue Jun 09, 2020 2:24 pm
Well, neufer, that response is So Full of Sheet! :ssmile:
https://en.wikipedia.org/wiki/Labyrinth_of_the_Reims_Cathedral wrote:
Reims's Labyrinth

<<The Labyrinth of the Reims Cathedral was a church labyrinth installed on the floor of the nave of the Reims Cathedral. The labyrinth was the shape of a complex square with cut corners and sides of 34 feet. The paths were 11 inches wide, separated by lines of dark blue stone from Ardennes of a width of 4.50 inches. The labyrinth was made of soft stone that wore out beneath the feet of pilgrims. This stone was of the same kind as Pierre Libergier's tombstone that is now exhibit in the cathedral.

A distinctive aspect of the labyrinth was the inclusion within it of depictions of the master masons of the cathedral. In other churches and cathedrals, they are unknown and anonymous. Indeed, the identities of these master masons are precisely known, because a survey of the labyrinth was drawn in 1640 by Canon Cocquault and in 1779, just before its destruction, by Robin and Havé. These surveys also contained dates and descriptions of the masons' works.

The person at the center of the labyrinth is generally identified as Aubry de Humbert, Archbishop of Reims, who decided in 1211 to build a new cathedral in the place of the one destroyed by fire in 1210. The masons are represented hard at work, with their tools in hand. For example, Jean d'Orbais appears to draw a map on the floor.

Bernard de Soissons was in charge during the inauguration of the labyrinth. There is no trace of the fifth (and probably best-known) contractor, Robert de Coucy, who was in charge from 1290 to 1311 and who oversaw the carpentry and the roof.>>

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by TheZuke! » Tue Jun 09, 2020 2:24 pm

neufer wrote: Tue Jun 09, 2020 11:47 am
  • How many sheets could a sheet slitter slit
    if a sheet slitter could slit sheets :?:

The slitter question...

First of all we need to clear something up; and that little 'something' is the use of the word 'if' - the reason being that sheet slitters CAN slit sheets, so there's no 'if' about it. Sheet Slitter machines DO exist, so unless a sheet slitter is experiencing some sort of terrible mechanical malfunction then you can rest assured that a sheet slitter can indeed slit sheets. Sheet slitters are expensive machines and businesses wouldn’t buy them to slit their materials if they in fact couldn’t slit sheets.

So with that little slop of mud cleared away from our metaphorical wind-sheilds we can proceed with trying to come up with an answer to that annoying question ‘How many sheets could a sheet slitter slit if a sheet slitter could slit sheets?’. There is an answer to this question, of course there is an answer, we’re talking about a real machine that performs a real function in real businesses. But (and I’m sorry if you feel I’ve led you astray) I can’t give you the answer without knowing the following essential variables:
  • What material is being slit?
    How thick is the material being slit?
    What tension does the material need to be at when slit?
    Does the material being slit have an adhesive coating?
    How fast is the slitter being run at when slitting the sheets?
    What type of slitting is being used to slit the sheets? Is it razor, shear or crush-cut slitting?
So with the answers to the above questions it would be fairly easy to answer the question ‘How many sheets could a sheet slitter slit if a sheet slitter could slit sheets?’. Unless of course you’re asking how many sheets could be slit in the useful life span of a slitter machine (rather than how many sheets could be slit in any single job run) in which case the answer is roughly ‘very very many’, slitter machines are very robustly built and last for may years if maintained properly.

Well, neufer, that response is So Full of Sheet! :ssmile:

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by neufer » Tue Jun 09, 2020 2:18 pm

JohnD wrote: Tue Jun 09, 2020 12:16 pm
OLE!
Who woulda thunk I'm the manure one :?:
https://en.wikipedia.org/wiki/Aka_Manto wrote:
<<Aka Manto (赤マント, Red Cape), is a Japanese urban legend about a masked spirit who wears a red cloak, and who appears to people using toilets in public or school bathrooms. If a person is sitting on a toilet in a public or school bathroom, Aka Manto may appear, and will ask them if they want red paper/cape or blue paper/cape. If they choose the "red" option, they will be lacerated in such a manner that their dead body will be drenched in their own blood. If the individual chooses the "blue" option, the person's blood is drained from their body. If an individual attempts to outsmart Aka Manto by asking for a different color of paper or cape, it is often said that they will be dragged to an underworld or hell as a result. In some versions, choosing a "yellow" paper, cloak or cape will result in the occupant's head being forced into the toilet. Ignoring the spirit, or replying that one does not want or prefer either kind of paper, is said to make the spirit go away. In some accounts, rejecting both options and running away from Aka Manto will also result in the individual's survival, although sometimes Aka Manto will simply block the exit.>>

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by neufer » Tue Jun 09, 2020 11:47 am

JohnD wrote: Tue Jun 09, 2020 8:43 am
Posting two links to the same article as I posted doesn't contribute, neufer!

Where are your usual sideways looks at this?
T. S. Eliot: "Immature poets imitate; mature poets steal."

(Who woulda thunk I'm the mature one :?: )
JohnD wrote: Tue Jun 09, 2020 8:43 am
Speaking of sideways, diffraction is an effect that occurs at edges. The disc we see of a planet in transit has edges, but in reality the light passes surfaces with a wide radius, not a slit, but this effect is just as real:

https://www.physicsclassroom.com/class/ ... iffraction
https://sites.google.com/site/slitteranswer/ wrote:
  • How many sheets could a sheet slitter slit
    if a sheet slitter could slit sheets :?:

The slitter question...

First of all we need to clear something up; and that little 'something' is the use of the word 'if' - the reason being that sheet slitters CAN slit sheets, so there's no 'if' about it. Sheet Slitter machines DO exist, so unless a sheet slitter is experiencing some sort of terrible mechanical malfunction then you can rest assured that a sheet slitter can indeed slit sheets. Sheet slitters are expensive machines and businesses wouldn’t buy them to slit their materials if they in fact couldn’t slit sheets.

So with that little slop of mud cleared away from our metaphorical wind-sheilds we can proceed with trying to come up with an answer to that annoying question ‘How many sheets could a sheet slitter slit if a sheet slitter could slit sheets?’. There is an answer to this question, of course there is an answer, we’re talking about a real machine that performs a real function in real businesses. But (and I’m sorry if you feel I’ve led you astray) I can’t give you the answer without knowing the following essential variables:
  • What material is being slit?
    How thick is the material being slit?
    What tension does the material need to be at when slit?
    Does the material being slit have an adhesive coating?
    How fast is the slitter being run at when slitting the sheets?
    What type of slitting is being used to slit the sheets? Is it razor, shear or crush-cut slitting?
So with the answers to the above questions it would be fairly easy to answer the question ‘How many sheets could a sheet slitter slit if a sheet slitter could slit sheets?’. Unless of course you’re asking how many sheets could be slit in the useful life span of a slitter machine (rather than how many sheets could be slit in any single job run) in which case the answer is roughly ‘very very many’, slitter machines are very robustly built and last for may years if maintained properly.

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by JohnD » Tue Jun 09, 2020 8:43 am

Posting two links to the same article as I posted doesn't contribute, neufer!
Where are your usual sideways looks at this?

Speaking of sideways, diffraction is an effect that occurs at edges. The disc we see of a planet in transit has edges, but in reality the light passes surfaces with a wide radius, not a slit, but this effect is just as real: https://www.physicsclassroom.com/class/ ... iffraction

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by neufer » Mon Jun 08, 2020 10:49 pm

heehaw wrote: Mon Jun 08, 2020 9:40 pm
I seem to recall that early attempts to measure the size of the solar system via transit of Venus from Tahiti were messed up by Venus having its dense atmosphere, causing difficulty in being sure of the time of e.g. first contact.
Fuzzy resolution and solar limb darkening are mostly to blame for the black-drop effect.

Diffraction effects may contribute a lttile to this fuzzy resolution but...
the warm turbulent atmosphere in the solar direction is more likely the culprit.

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by heehaw » Mon Jun 08, 2020 9:40 pm

I seem to recall that early attempts to measure the size of the solar system via transit of Venus from Tahiti were messed up by Venus having its dense atmosphere, causing difficulty in being sure of the time of e.g. first contact.

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by neufer » Mon Jun 08, 2020 8:32 pm

RJN wrote: Mon Jun 08, 2020 6:35 pm
Today's APOD has been corrected -- on the main NASA APOD page -- to say that the bright ring around Venus is caused by diffraction rather than atmospheric refraction. I apologize for the oversight. I thank Michel Duval for pointing this out over email. Papers of his about this effect can be found here and here.
It would be nice if Michel Duval presented papers by OTHERS about this being a "diffraction effect".
  • Mark me as a skeptic :!:
The darkest umbra during a Lunar Eclipse is NOT totally black thanks to a "ring of fire" around the Earth due to atmospheric refraction plus Rayleigh scattering. This ~2º of light bending into the umbra is similar to what Venus's thicker atmosphere is accomplishing on its outer side in today's APOD.

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by MarkBour » Mon Jun 08, 2020 8:31 pm

JohnD wrote: Mon Jun 08, 2020 3:55 pm Gottit! Black drop effect!
https://atoptics.wordpress.com/2013/08/ ... henomenon/
Nice article, thanks!

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by RJN » Mon Jun 08, 2020 6:35 pm

Today's APOD has been corrected -- on the main NASA APOD page -- to say that the bright ring around Venus is caused by diffraction rather than atmospheric refraction. I apologize for the oversight. I thank Michel Duval for pointing this out over email. Papers of his about this effect can be found here: 
https://ui.adsabs.harvard.edu/abs/2005J ... D/abstract 
and here: 
http://articles.adsabs.harvard.edu/full ... .111..149D .
As stated in these papers, diffraction is also the cause of the "black drop effect", and so that effect and this brightening effect are related. 

As cited in the APOD text, it is common for any of a number of bright rings around an object passing angularly close to the Sun (or any bright background object) to be referred to as a "ring of fire". This need not be associated with the atmosphere that an occluding object might possess -- for example the Moon shows a "ring of fire" during an annular solar eclipse, but the Moon does not possess a thick atmosphere. 

- RJN 

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by johnnydeep » Mon Jun 08, 2020 5:17 pm

JohnD wrote: Mon Jun 08, 2020 3:55 pm Gottit! Black drop effect!
https://atoptics.wordpress.com/2013/08/ ... henomenon/
Cool. Aka "the shadow bridge effect". Despite reading that article I still don't quite understand what's happening optically. Is it just the overlapping fuzziness of the edges of approaching objects effectively magnifying the opacity?

Re: Huh?-Atmospheric Ring of Venus (2020 Jun 08)

by CHRIS2332 » Mon Jun 08, 2020 4:40 pm

CHRIS2332 wrote: Mon Jun 08, 2020 1:19 pm How can this occur?
From Earth Venus is too tiny to cover the face of the sun.
Right?
Where is the sun in relation to Venus here; off the screen?

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by JohnD » Mon Jun 08, 2020 3:55 pm

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by JohnD » Mon Jun 08, 2020 3:53 pm

I can't remember what it is called, but there was a problem in the 18/19th century with noting exactly when the edge of the disc of either Venus or Mercury touched the rim of the Sun. This had great importance for calculating their orbits. The effect was optical and to do with diffraction, of light at the planets and in the optics. Can anyone remind me of this?
John

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by johnnydeep » Mon Jun 08, 2020 3:41 pm

Ann wrote: Mon Jun 08, 2020 10:43 am
Donald Pelletier wrote: Mon Jun 08, 2020 7:07 am A ring around Mercury? Really? How is that possible? There is no thick atmosphere on this planet.
I'm baffled too. How can Mercury display a ring of fire during its transit of the Sun?

Ann
Yeah, doesn't make much sense to me either. But I did find this pic that sort of shows an orange ring around mercury during a solar transit. But perhaps that's just an optical artifact and not a real phenomenon?

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by shaileshs » Mon Jun 08, 2020 3:29 pm

shaileshs wrote: Mon Jun 08, 2020 4:20 am I wonder if there is/was any satellite/shuttle that was in a perfect position and angle near Venus where it's cameras would see Venus blocking full Sun behind it causing a ring around it the way we see it during solar eclipses ?
I'm surprised no one has any answer/comment on my query. Normally by now (after 12 hours) I see 2-3 responses at least. I guess people are busy resuming work on Monday..

Re: APOD: Atmospheric Ring of Venus (2020 Jun 08)

by Cousin Ricky » Mon Jun 08, 2020 3:16 pm

This image is beautiful!

Re: Huh?-Atmospheric Ring of Venus (2020 Jun 08)

by orin stepanek » Mon Jun 08, 2020 1:54 pm

CHRIS2332 wrote: Mon Jun 08, 2020 1:19 pm How can this occur?
From Earth Venus is too tiny to cover the face of the sun.
Right?
That's not what happened! As per APOD---
Venus did not pass directly in front of the Sun -- the complete atmospheric ring was caused by sunlight refracting through Venus' thick atmosphere.

Huh?-Atmospheric Ring of Venus (2020 Jun 08)

by CHRIS2332 » Mon Jun 08, 2020 1:19 pm

How can this occur?
From Earth Venus is too tiny to cover the face of the sun.
Right?

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