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Does my Thumb warp spacetime?

  1. Sep 6, 2010 #1
    Simple Experiment. Find a bookshelf full of books in a well lit area (such as a library or bookstore.) Find a seat about 10 feet away facing the bookshelf. Hold out your right hand in a fist with your thumb pointing out little less than a foot from your face just outside your peripheral vision. Now focus on the bookshelf and slowly move your thumb into view. Try to focus through the edge of your thumb onto the books without focusing on your thumb. You'll notice a blurry edge around your thumb, try not to let that distract you. If you do it just right, you'll notice the books 'squeeze' together and become sharper to your view. If you focus around the edge of your thumb you'll notice straight lines bend around your thumb in a distance. You can do this with any object in a distance, but a book shelf seems to do well because of the vertical lines. The 'focus' effect can be observed even more clearly by putting your finger and thumb into a squeezing position without touching each other and looking through that small seam between - the closer your finger and thumb come the more sharper objects at a distance become. If you wear glasses or contacts - take them off/out and this effect can be observed even more drastically.

    Is this 'warping' effect caused by gravitation lensing or is this some other effect?
  2. jcsd
  3. Sep 6, 2010 #2


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    No. Gravitational lensing would not be strong enough to be perceptible by eye unless you had a huge amount of mass between your eye and the books.
  4. Sep 6, 2010 #3
    That’s what I assumed as well, it doesn't change the fact the optical effect is occurring. I made a video to demonstrate the effect.

    Last edited by a moderator: Apr 25, 2017
  5. Sep 6, 2010 #4


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    There are two effects here:
    1] Diffraction - waves tend to bend around objects. Light does so, just like waves in a lake manage to get into a harbour.

    2] Aperature. An object seen through a large (or absent) aperature is the sum total of all rays from source to focal plane. With a small aperature (or a partial aperature causes by something nearby) some light rays are blocked, which has an effect on the sharpness and location of the resultant image.

    I play with this while watching TV in bed without my glasses. I use my fingers to "pinch" the image in various ways and watch how it sharpens and distorts the image.
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