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Holographic Principle Projection

  1. Aug 30, 2014 #1
    Hi. I have a question about the Holographic Principle. I've been looking up things about it for a while now, and I think I understand it. The total content of a space is propositional to the area surrounding it and not the volume. The thing I'm having trouble with is how everything seems 3d. I'm going to assume we are not a projection of light (right?), so how does the "projection" work?

    I'm not that good with math or physics so please keep it simple. Thanks.
  2. jcsd
  3. Aug 30, 2014 #2

    Simon Bridge

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    Welcome to PF;
    Unfortunately this is not something to be explained in terms of something anyone not good at maths or physics will likely be familiar with so it is unlikely anyone can help you much except in a shallow way. I could say it is like how each part of a hologram contains the entire picture in 3D? That help?
  4. Aug 30, 2014 #3


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    The simplest hologram is what you get from the two slits experiment. The two slits produce a set of interference fringes. If you 'develop' that pattern on film and shine light through the fringe pattern, an image of two slits will be formed.
    To make a hologram, an object is illuminated with a laser (you need good, coherent light for this to work) and you also use a 'reference beam', with a half silvered mirror. The hologram is the (much more complex) interference pattern formed on a film, placed near the object. The light falling on any one part of the film is due to the interference of light from all parts of the object (not' behind it', of course). Each part of the film sees a different view of the object so the interference pattern is different on different places on the film. Shining light on the developed image of the interference pattern will produce an interference pattern that is different in each direction. This interference pattern is a reconstructed view of the original object - seen from that direction. So, as you move your head / use binocular vision, you will see a different view of the original object. That looks like a 3D image.

    However, you don't get 'something for nothing'. The image you see will be coarser than the detail of the original object; it is a approximate view - not as good as if you used film (many different images) to record the object from many directions.
  5. Aug 31, 2014 #4
    This is just an anecdote of a simple and practical application of this principle that some may find interesting, especially with how our brains deal with interference patterns.

    I met an artist in Western Colorado who for many years painted mountain scenes by sitting for many hours "out in it". As she grew older this became more difficult plus mountain weather can change very rapidly, sometimes to interesting lighting effects, but often, debilitating.

    She began taking photos and painting from those. This didn't work well. She describes those painting attempts as "flat". She tried higher resolutions and still had unsatisfactory results. Then she bought a Stereo Camera, one with two lenses that approximates the distance between our eyes, taking two simultaneous photos that are later viewed through a Stereoscope. This, according to her, and actually I could see the difference too, gave satisfactory, lifelike results with depth.
  6. Aug 31, 2014 #5
    If you are talking about cosmology, the holographic principle refers to the ability to find out what is happening in a room by looking at what happens on the walls. So it's a dimensional thing, by looking at something in say a 4D space you can infer what's happening in the 5D space.
  7. Sep 1, 2014 #6


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    Is that not an entirely different use of the term? The EM radiation with which we observe space is not coherent.
  8. Sep 1, 2014 #7
    Yes, this is what I'm talking about. What I want to know is how they "connect" to each other.

    For example, if I bite an apple, you can tell by just looking at what's going on on the wall. My question is how does the wall know I bit the apple on the inside space? Is there some kind of connection between the inside and wall, or does the same information exist both on the wall and on the inside?
  9. Sep 1, 2014 #8
    Yeah, not sure. I assumed the OP was talking about the cosmological holographic principle but mixing up a couple of ideas.
  10. Sep 1, 2014 #9
    I think, and I am out of my depth here, that the internal space is projected on to the surface and therefore it is a one way transformation, an observation, a shadow if you like. Like looking through a keyhole, does the room know you are looking?
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