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    Why does water evaporate when it's less than 212 F outside?

    I have a tray of ice cubes in my freezer that have been there for months and some of the cubes are as much as 75% reduced in size. The temperature is about minus 20 degrees C.
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    Why does water evaporate when it's less than 212 F outside?

    Perhaps this doesn't belong here but I have found myself amazed at this: I have a carbon steel small paring knife and when I have washed it I can smell the fairly strong odor of "rusted" iron coming from it. I can imagine iron oxide molecules evaporating off the metal surface. I find that...
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    Pressure and Lift around a Wing

    Yes that is one. Thanks for the photo.
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    Pressure and Lift around a Wing

    On the triangles, I think somehow you have misunderstood which "triangles" I meant. The ones I am talking about are very small long strips that are located on the leading edge of the inboard part of the wing. Their purpose is to disturb the airflow at high angles of attack and cause the inboard...
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    Pressure and Lift around a Wing

    I think this is the video I mentioned. Pulsed smoke flow in wind tunnel. Check at about 47 seconds.
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    Pressure and Lift around a Wing

    Fog37, In reply I think you might want to look at what happens at the leading edge of the wing. I am getting close to the limits of my understanding here. The air running into the leading edge curve is flung/forced upwards which compacts the air above the wing, at the same time making a lower...
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    Pressure and Lift around a Wing

    I don't understand fog37's initial statement that the air flowing over the top of the wing causes a downward pressure on the top of the wing. None the less:There was (is) an excellent video online of wind tunnel airflow over an airfoil with the flow shown by pulsed smoke. It really changed my...
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    UV light + electric current = boom?

    Negative results yesterday on the minimum gap UV experiment. I have had an interesting experience with very light soot in a computer tripping ground fault outlets so I am considering that combination and similar situations. A question for he OP: Did the controller fail, or is it still functional?
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    UV light + electric current = boom?

    Ah yes, but the circuit is in an enclosed "box", that will be a problem I think. Meanwhile, I found some LEDs in a parts drawer that are rated almost identically to the ratings of the spy pens. That is 405 nm and 5 mW, so I'm going to set up an experiment with AC line voltage and multiple...
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    UV light + electric current = boom?

    Good investigating OmCheeto, and calculating. I see the unit is an enclosed box, so much for just checking behind the panel. I'm just now thinking about how we could get the manufacturer to donate a unit or supply some detailed design information.
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    UV light + electric current = boom?

    As others have suggested, have a experienced electrical person carefully pull the wall plate and first and foremost check for exactly where the arc took place. That will be your best clue as to what happened. If there was sparking there should be some visible marks. The physical...
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    UV light + electric current = boom?

    Picked my curiosity so I compared images and this appears to be a spy pen? If so it is likely, from articles I have just read, to not be UV, but rather the upper end of the visible spectrum at 410 nm. Typically about 5mW LED. Moot point probably, high energy visible anyway. I'm interested in...
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    UV light + electric current = boom?

    Roger on the dimmer. Read it but didn't register/early morning with headache. I will suggest that there may be something a little more complex under those control arms with perhaps marginal contact or sensitive material/clearances that the UV could affect.
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    UV light + electric current = boom?

    I don't see any comment that the "switches" on the right side are variable controls and not off-on switches.
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    B Double slit and measurement

    Thanks, point well taken. Have to break out the books and/or look around online for how to calculate/understand that particular aspect of the subject. Oh, I did error in not saying that I am specifically interested in learning about the pattern when it is a single photon or particle at at a...
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    B Double slit and measurement

    Very well put itfitmewellputtoo. Somewhere in the forum I would like to post a question about the affect of the distance between the slits in the double slit experiment when using actual physical slits. I suspect there is some information to be found there. Likely already done, but I have not...
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    Do light and sound waves roll up and break like ocean waves?

    I can't think of anything for light yet, but perhaps for sound waves: Make a long bar consisting of layers of material that conduct sound at different velocities. If in fact that is a characteristic of different materials. Eg wood, plastic, metal. Then strike the bar on the end and then find...
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    Stargazing Protecting Optics (not eyes) During Solar Observing

    If that is your 6 incher there I would humbly suggest that the hole is too big. I have a factory cover for my 5 inch with a smaller hole and it is just enough to make a bright moon comfortable to look at. Just a suggestion; Why not make some smaller holes in pasteboard for example and tape...
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    Problem of electricity and electrons

    Of course one electron at a time doesn't make sense, but when one is thinking about what actually is going on in the wire, not just a formula, you think about all the possibilities. As in max and minimum. I do anyway. As to "feeding" one amp into a wire perhaps you could explain to me whether...
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    Problem of electricity and electrons

    I think you mean calculate, not measure? Would be interesting to calculate the minimum frequency movement that would equate to the orbital dimension of the valence electron for a given conductor. Does that make any sense?
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    Problem of electricity and electrons

    Say there OP, thanks so much for the link to electron drift. I have played around with calculations involving a 1 mm square wire and movement of "free electrons" through it for some time. Somehow never ran across that formula. Duh. When you think about electrons "bumping" from one valence...
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    Minute physics video: Why Are Airplane Engines So Big?

    Here is an example of how propellers work in the real world. I have a 1946 Taylorcraft. Something like a hot rod Cub if you know what that is. It has a 71 inch propeller and will climb at about 750 to 850 feet per minute depending on conditions. With a 74 inch prop it would be able to climb...
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    Stargazing Lightning ball - please help me to analyze this rare video

    I have seen ball lightning. It was many years ago and I was coming out of my grade-school graduation, at night, in a very small town in Southern Illinois. There was a large intense thunderstorm with a great deal of lightning, quite close, to the North of us. Suddenly, against the very dark...
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    Insights Planning to buy a first telescope? - Comments

    Jim, I thought just recently that I might try a simple check on the adjustment. Just turn one of the three main mirror screws 1/4 turn and then check if a ground image is clearer. Then return that adjustment back and do the same to the next adjusting screw. Any improvement would tell me I...
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    Insights Planning to buy a first telescope? - Comments

    I have a question about my Celestron 130EQ reflector. Previously I had a 70mm refractor and I remember being astounded at the sharpness and contrast of edge on views of the ridges on the moon that it gave. The 130 pulls in a lot more light; it is uncomfortably bright when looking at a full...
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    Stargazing Solar Con? Eclipse road trip to Makanda Illinois

    I have been considering going back to the Carbondale area from here in California, but it would be a real bummer to get there and have the weather be cloudy. I was raised in a small town in the area named Crainville until I was 15. My last name is Crain and yes there is a connection. Could...
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    B Determining the transition frequency

    https://www.google.com/search?q=6.7+ghz+methanol+maser+spectrum&biw=1280&bih=663&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi5qo6U4JrRAhUhwVQKHXRFDksQ_AUIBygC&dpr=1#imgrc=_ Some good spectrum visuals here. DC
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    B Determining the transition frequency

    https://arxiv.org/abs/astro-ph/0408094 This paper might help. Thanks for the question--I learned some interesting stuff while looking around on the subject. DC
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    B Identifying an RF signal...

    Well, that was supposed to be a youtube link. Just check out CODAR on line plenty of info. DC
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    B Identifying an RF signal...

    There is a signal that I pick up on my SDR (a lot like a Analyzer) on HF. Looks rather like what you describe. Called CODAR. Do you live "near" the ocean? Google CODAR. DC
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