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I Why Sea Level sometimes gives an illusion being at height

  1. Nov 28, 2016 #1
    Why Sea Level sometimes gives you an illusion being at height like a small mountain? Specially when you are driving down of the mountain? Please find the attached image to see what I am referring to.
     

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  3. Nov 28, 2016 #2
    It only appears to be at a height because your view is aimed downward as you go down the mountain. So in your field of view, the horizon is higher up than it would be if you were level. Imagine you are sitting in a classroom and looking directly at the blackboard. If you now look down toward the floor, the blackboard appears higher in your field of view.
     
  4. Nov 28, 2016 #3

    rbelli1

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    Also remember you are on a sphere or at least a close approximation of one.

    BoB
     
  5. Nov 29, 2016 #4

    A.T.

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    If you are driving down a mountain, then it's not an illusion that you are on a mountain.
     
  6. Nov 29, 2016 #5
    I have even stopped the car, stand still and took a look; still sea looks at height of mountain. Now if you consider the close approximation of being in spear or mountain and looking down (it seems way exaggerated compared to being at pole and being at equator; I am only at small hill !!!). That is why it is harder for me to understand that I am looking down that is the reason. I understand the classroom example, but I tried to level my head and eye towards the horizon. :(
     
  7. Nov 29, 2016 #6

    sophiecentaur

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    Is it not just because our sense of what is actually 'horizontal' is not very well developed? There is really no reason why Evolution would have given us the ability to resolve such small angles. Certainly, nothing that we experience in a smoothly rolling motorcar will be familiar with our basic senses. Let's face it, it was only when Newton came on the scene that people had much idea of such things at all. We get all our clues from what we can see and that's dominated by nearby things.
     
  8. Nov 30, 2016 #7

    CWatters

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    There aren't many visual clues to distinguish the difference between the two cases...
    Sea level.jpg
     
  9. Nov 30, 2016 #8

    CWatters

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  10. Dec 1, 2016 #9
    As per my view this become happened because of human senses are adapted for use on the ground, when you are driving down of the mountain you faced sensory illusions.
     
  11. Dec 1, 2016 #10

    sophiecentaur

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    There are many examples of streams and canals that appear to be running uphill. There is a water channel (disused Victorian Industry) on Dartmoor (South West of England) which seems to be sloping uphill, whichever direction you view it from.
     
  12. Dec 1, 2016 #11
    Clear dry day - possible temperature inversion. That could create a superior mirage and make the horizon look higher than it otherwise would.

    Perhaps you can go to the location in Google Earth, make sure vertical exaggeration is 1:1.
    Go down to street level in the same location and see if the horizon looks the same.

    (I tried to see if I could discover the location from the clues in the image but all I concluded is that you are probably right handed, driving at just over 40 mph and listening to FM 89.5 and located on the West coast of the US driving in a roughly WNW direction in the late afternoon)
     
  13. Dec 1, 2016 #12

    sophiecentaur

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    But everywhere looks distorted and more or less horizontal. The camera was not designed to give topographical information - just to be wide angle and tolerant of the road slope.
     
  14. Dec 1, 2016 #13

    You are about right for the location. It is San Diego, Delmar County, I took the exit High bluff drive towards the ocean. Anyways this is what I found on your super mirage theory.
    http://www.dailymail.co.uk/sciencet...rgana-mirage-hidden-iceberg-Titanic-late.html

    I would like to know if there is anyway if I can confirm any of the theories. I will try the suggestions here. I will drive down on weekend again and see. Thanks.
     
  15. Dec 1, 2016 #14
    The picture was taken on Del Mar Heights looking WSW towards the Nob Avenue intersection from about here:
    32°56'54.48" N 117°15'34.97" W
    The Street View image is on a more humid day and the horizon looks just as high if not higher. It is hard to compensate for the (presumed) greater height that the Street View camera took the shot from, and to be sure that the atmospheric conditions are different... but overall I don't think this view supports my suggestion that it was as a result of a mirage.
     
  16. Dec 3, 2016 #15

    A.T.

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  17. Dec 5, 2016 #16

    sophiecentaur

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    Well well.
    But what do you call 'up hill' under those conditions? Could be a moot point.
    I have to take issue with "what would happen of the Earth stopped spinning?" part of that article. It takes things in totally the wrong direction, imho. It's just another of those exercises in nonsense scenarios which would involve unbelievable amounts of Energy and Organisation to achieve. They should be throttled at birth, as far as I am concerned.
    [Edit: Ye gods - I just re-read this. It sounds far more grumpy than I intended!!]
     
    Last edited: Dec 5, 2016
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