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B Reflected sunlight

  1. Feb 19, 2017 #1
    I read in a book about a man who saw the sun reflected off a distant object on a mountain some 73 miles away in clear visibility. He saw this on many occasions and always wondered what it could be. He states that he asked two of his friends who were going that way if they would check it out for him.

    Some days later after his friends returned, then said they had no problem finding it. It turned out to be a bottle. I find this hard to believe. Surely the reflection could only be seen at a certain angle and as soon as one strays a short distance out of that angle, the reflected light from the bottle could not be seen? Not only that but by the time those looking for it had travelled a few hours, the angle of the sun would also have changed. So how on earth could they locate a bottle on a huge mountain? When one gets to that mountain, they would have had a huge area to search. Surely they would have no way of knowing that was the source of reflected light?

    The other question is, could the reflected light from a mere bottle travel 73 miles?
     
  2. jcsd
  3. Feb 19, 2017 #2

    blue_leaf77

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    What book is it?
     
  4. Feb 19, 2017 #3
    Maybe because the bottle is curved, so can accommodate many different angles of incidence and reflection.

    From atop high mountains you can see over 100 miles away. If there is a high-contrast bright spot at that distance, I think it could be noticeable.
     
  5. Feb 19, 2017 #4

    anorlunda

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    The effectiveness of the signal mirror is what you are having a hard time imagining. For millennia, sailors have used them to get rescued at sea.

    Read about iridium flares for reality even harder to believe.


    https://en.m.wikipedia.org/wiki/Satellite_flare

    Better still, view iridium flares yourself. I use the android app Predisat-pro to tell me where and when to look. The app uses data from the heavens above Web site.
     
  6. Feb 19, 2017 #5

    anorlunda

    Staff: Mentor

    Also see

    In special lighting circumstances, they can be even better. Especially when you are looking east at sunset, or west at sunrise. If you are in twilight and the mirror is on a mountain peak in sunlight, effectiveness is at its peak.

    I am not an expert on vision, but I believe that our vision processing makes brief changes more noticeable than static images. Thus, the ability to resolve tiny static images is not the same as the ability to see flashes.
     
    Last edited by a moderator: May 8, 2017
  7. Feb 19, 2017 #6
    Hi Blue Leaf 77, I am almost afraid to say.....it is a book called Millennial Hospitality by Charles James Hall who claims to have met aliens while he served as a meteorologist with the US military in the 1960's. He says he is now a Nuclear Physicist. My sceptical nature likes to challenge everything and there are a number of issues in his book that don't add up. This particular question is just one. Tom.
     
  8. Feb 19, 2017 #7
    Good point about the curved bottle. Thanks
     
  9. Feb 19, 2017 #8
    Thanks, interesting
     
  10. Feb 19, 2017 #9
    thanks for that info
     
  11. Feb 19, 2017 #10
    Excellent info, thanks
     
  12. Feb 19, 2017 #11

    CWatters

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    Perhaps his friends just told him it was a bottle so they didn't have to spend ages looking for it.
     
  13. Feb 19, 2017 #12

    blue_leaf77

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    Human eyes' angular resolution is 0.0003 rad. At 73 miles distance, our eyes cannot distinguish objects within 35 meters. If he was satisfied with his friend's answer that it was just a bottle, he must have forgotten that fact.
     
  14. Feb 20, 2017 #13
    After the 'bottle' was found and removed, there are no further reports of the reflection, so that must have resolved the 'curiosity.' If we are to believe the story, then it was the bottle that was causing the reflection.

    I live many thousands of miles away, in Ireland, and there are mountains about 25 miles from me. If I saw a reflection coming from the mountain side and got in my car to find its source, by the time I got to the foot of the mountain, I doubt if I would have a clue where to start looking, so it still seems quite improbable that the reflecting bottle could be found easily and tends to make me skeptical of this part of the bottle story.
     
  15. Feb 20, 2017 #14

    sophiecentaur

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    Yes. I would imagine it was not the first time they had to deal with his fanciful notions.
    For the reflection to be bright enough in his direction, the beam width would need to have been very small. The probability of one flash from the 'bottle' is, perhaps, finite but the next day or even a minute later, the beam would no longer be aimed at the observer. The distance involved is comparable with the distance of satellites in LEO and we only see them after sunset (with a dark background and little scattered light). There are many bottle-sized facets on satellites so we could expect a constant view of sparkles from passing satellites all day. (There are thousands of the little devils up there.)
    Perhaps the explanation is reflection a passing aeroplane at low altitude (coming in to land, perhaps) at a nearby airfield. (Forget the bottle)
     
  16. Feb 20, 2017 #15
    Calculations of resolution usually deal with two close sources of equal brightness. You also have to take into account contrast. If an object is very bright, it can be noticeable despite having a very small angular extent, such as a star.
     
  17. Feb 20, 2017 #16

    blue_leaf77

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    My point is that there can be another shiny object in the vicinity of the bottle that also contributes to the rays that impinge on the observer's eyes, apart from the bottle, without he/she being able to tell them apart. Not to mention that this other object might be much more reflective than a bottle, for example a sheet of metal.
     
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