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PF Portland meet up!

  1. Aug 8, 2017 #1

    @BillTre @gregbernhardt @OmCheeto @Janus

    What a wonderful group of guys! 4 hours of really insightful interdisciplinary discussion and lots of funny stories!
  2. jcsd
  3. Aug 8, 2017 #2
    Nerds unite! The new PF boy band. I love it. Wish I were there. I was living in Tacoma from 2009-2016, why didn't you do this then? I could have driven down. Haha.

    Btw, you're not still wearing an 80's fanny pack, are you Om? Lol.
  4. Aug 8, 2017 #3


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    Where else am I going to keep all my sciencey stuff?
    I brought rocks, a notebook & pens, diffraction grating, solar filter material.
    I should have taken more than two notes, but I didn't want to look like a total nerd.

    One was simply "Tim Vermeer". Which I needed to google, as the explanation of what it was about, I found very confusing.

    Tim's Vermeer is a documentary film, directed by Teller, produced by his stage partner Penn Jillette and Farley Ziegler, about inventor Tim Jenison's efforts to duplicate the painting techniques of Johannes Vermeer, in order to test his theory that Vermeer painted with the help of optical devices. [ref: wiki]​

    The other was "Shadow Bands", as Greg tasked me with creating a thread on them, and why they are nearly impossible to photograph. I tried explaining what they looked like, and had to resort back to a report from an eclipse around 1900(?), where they said children were chasing shadow bands across the ground, as they looked like snakes.

    I don't remember, but one of the above two topics probably influenced the progression into the other topic. The theme being mainly that eyes are incredibly more sensitive to subtle hue changes than cameras are capable of capturing.

    I'm not sure I'll volunteer to come to another of these. As I've said in the past, people at PF are over-the-top smart, and these people are no exception. When BillTre tried explaining something about circularly polarized light, my head almost exploded. Ditto when even something as simple as "the local weather" peculiarity came up: 10 minutes of convective flows from Janus. :oldconfused:

    I think we need an "exploding brain" emoticon.

    It was nice to get Anna into the conversation. Her influence on me to study the physics behind rainbows; at least 100 hours. And that progressed into a conversation that involved both ZapperZ and Janus, as I once accidentally created a "crossed rainbow", and was curious if I could, through some weird Janus type ray-tracing mathematics, create a rainbow Mickey Mouse. Of course, I knew my brain would explode if I tried such a thing on my own. Perhaps I'll start a thread about that also. I think I mentioned to Anna; "Don't even try and think about rainbows beyond the basics, as things get really complicated, with all the variables involved."
    Here's a link to a simulator that shows what I was trying to explain about "raindrop size" affecting the theoretical number of rainbows you can see:

    I was also REALLY happy that everyone accepted my "Backhoe dude and the 100 guys with shovels" analogy, as usually when I tell that story, people just tell me I'm an egomaniac. Fortunately, I'm now an idiot, and don't have to deal with "that" kind of problem any more. Nice to know that Anna understands this.

    It was fun discussing how we misperceive fellow PFers.
    Me; "I always thought Binzing was in college, as he seemed over the top mature and smart, and it kind of freaked out when I met him at Da Vinci Days, and he was only 4 feet tall, and only 12 years old." :bugeye:
    Ehr mehr gerd. Just imagine 4 hours of this.......

    I'd better stop now.

    ps. Peeps, never ever miss an opportunity to meet fellow PF peeps. They are the best. :oldlove:
  5. Aug 9, 2017 #4


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    We had a lot of fun talking about many things.
    Thanks for organizing this Greg (and the forum too).
    I was really interested in meeting some people who I had only previously known through the internet. It worked out quite well.

    I never thought Om's head was going to explode! There wasn't even any steam coming out.
    And now that I have spent some time talking with him, a lot of stuff in his posts make a lot more sense to me (he has a certain way of thinking).

    After talking about the "shadow Bands" with people, I am interested (as Om is) in trying to see them during the eclipse and make a video.
    We'll see how it goes. Hopefully the Willamette Valley will not be as smoky as it currently is (due to forest fires).

    Also, Tim's Vermeer really is a nice film!
  6. Aug 9, 2017 #5


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    Oh, I forgot, I wanted to better explain this:

    Circularly polarized light (the polarization rotates).
    Needed for modern digital cameras since there are a lot of internal reflector/refractors to get some of the light to internal sensors for metering etc.
    Linearly polarized light will not always make it through all the internal reflectors/refractors making the metering undependable.
    The camera can have a linear polarizer (to produce the desired effects, such as reducing light from reflections off the water) with a quarter wave plate behind it (which turns the linearly polarized light into circularly polarized light.
    The circularly polarized light gets through the various optical paths within the camera OK.
  7. Aug 10, 2017 #6


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    I'm guessing now that it was the "circularly polarized" that put my brain in full stop mode.
    I can somewhat understand "regular" polarized light, but "circularly"? This implies that light is somehow "spinning".
    How the hell do you get light to spin?
    This implies that you can apply a torque to photons.
    And that's just "crazy talk".

    Hence, in my mind; "This 'Bill' guy is talking voodoo science, so I'll just stare at the bricks on the wall, until he finishes...."

    ps. And yes, I did go through the wiki article last night: Voodoo science, IMHO.
    pps. Ok, yes, I know it's a real phenomenon. But I'll be long dead before I understand how it works.
  8. Aug 10, 2017 #7


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    Let's see if I can clear up the fog.
    If you have two in phase sine waves (the red and green lines in the following diagram) and add them together you get the resulting yellow sine wave.
    SINE ADD1.png
    And if you shift them 90 out of phase with each other you get this resulting sine wave
    SINE ADD2.png
    This is the equivalent off adding the electric fields of two linearly polarized light waves which are polarized in the same plane. They add together to produce a summation wave in the same plane.

    Now let's consider two in-phase polarized waves that are polarized in planes at right angles to each other. The waves will still produce a summation wave, but since the fields are at right angles to each other you have to do a vector addition to get the result. This will look like this. (The black lines meet at the summation point for the resulting wave):
    You still end up with a plane wave, but one at an angle that falls between the first 2 waves.

    Lastly, consider what happens if the two polarized waves are 90 degree out of phase:
    You still need to do the vector addition to get the resulting wave (as shown where the black lines meet), but you don't get a linearly polarized wave as a result, you get this:
    The result is called circularly polarized light.

    Attached Files:

  9. Aug 10, 2017 #8


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    I think the quarter wave plate (a crystal which has different spacing of the atoms (or molecules) in different directions) which is used to change linearly polarized into circularly polarized light causes a phase shift between components of the polarized light wave that are in the different perpendicular planes.
  10. Aug 10, 2017 #9


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    That's my understanding also.
  11. Aug 11, 2017 #10


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    Greg, you do realize that almost everywhere you go to meet us long-time PF'ers, you and Anna kinda bring the average age down, don't you?

    {Oh my poor back and my creaky bones!}

    And btw, how in the world that *I* came up during a discussion in Portland? Is it due to that Mickey Mouse rainbow?

  12. Aug 11, 2017 #11


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    Speaking of Mickey Mouse rainbows, While I wasn't able to do one directly with Pov-Ray, I was able to assemble ray-traced components together with Paint shop.
  13. Aug 11, 2017 #12


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    Here's the post that I was talking about, with two perpendicular rainbows:


    where I inferred that; "If I can accidentally make two rainbows intersect at a right angle, then someone with an actual brain should be able to mathematically create any type of rainbow figure".

    I'm assuming I picked "Mickey Mouse" as he's mostly made of circles. (If you exclude the eyes, nose, and mouth).

    Here's what I was perceiving:

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