# Wrapping my head around holography

by lookbehindu
 P: 10 Having trouble wrapping my head around holography after watching/reading a ton of stuff on the topic. What I think I have found to be true is that real holograms are 3D images captured onto film that are able to be viewed at any angle through the naked eye. So the concept of a 3d image or video floating in midair is not really a hologram. Also what makes me confused is "The world as a hologram". I believe I get the basic concept of having all "data" about this world being stored somewhere outside the universe and us being a "projection" of that data but does that mean we are analogous to the film and the data which is stored "outside" is the original object which the laser shines on to create the hologram? If anyone can provide me with helpful info that would be great. Thanks!
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P: 12,365
 Quote by lookbehindu Having trouble wrapping my head around holography after watching/reading a ton of stuff on the topic. What I think I have found to be true is that real holograms are 3D images captured onto film that are able to be viewed at any angle through the naked eye.
Well... not any angle ... have you seen any holograms in real life?

 So the concept of a 3d image or video floating in midair is not really a hologram.
Have you seen:
http://www.opticsinfobase.org/oe/abs...oe-20-22-25130

 Also what makes me confused is "The world as a hologram". I believe I get the basic concept of having all "data" about this world being stored somewhere outside the universe and us being a "projection" of that data but does that mean we are analogous to the film and the data which is stored "outside" is the original object which the laser shines on to create the hologram?
No.
You mean stuff like this:
http://beforeitsnews.com/space/2012/...h-1658888.html
... it's an analogy. The pop science folks are trying to describe the granularity of space time as like a newspaper photograph only 3D ... and a hologram is a 3D photograph so...
P: 10
 Quote by Simon Bridge Well... not any angle ... have you seen any holograms in real life?
well since its film definitely not ANY angle but that's like saying you can look at the Mona Lisa from behind... What I meant was you can view the static film from an angle that allows until you can't and the image will look dynamic so:

    _________________

HOLOGRAM
_________________
/   |    \
/    |     \
/     |      \
/      |       \
/       |        \
/        |         \
/         |          \
/          |           \
 Quote by Simon Bridge Have you seen: http://www.opticsinfobase.org/oe/abs...oe-20-22-25130
I have to check that out when I have time to focus and take in all that information thanks.

 Quote by Simon Bridge No. You mean stuff like this: http://beforeitsnews.com/space/2012/...h-1658888.html ... it's an analogy. The pop science folks are trying to describe the granularity of space time as like a newspaper photograph only 3D ... and a hologram is a 3D photograph so...
Do you have a link to a video of what ACTUALLY constitutes a hologram (I know Tupac's is a Pepper ghost and that is what the majority of video results are). I think I just realized what I thought was a hologram is a lenticular print actually so now I'm thoroughly confused and genuinely have no clue.

P: 10

http://www.world3d.com/lenticular-gl.../hologram.html

 Hologram – A 3D image that is created using lasers. Although they are often confused with lenticular (because both can display depth), they are really two very different products.
Guess I don't feel so stupid that I confused the two.
 P: 10 This is the first video I've found that seems to show a real hologram. It's pretty cool, but according to this the object is placed in the path of the laser (labeled object) to capture it on the film. How was it done in the architecture case? Was a scaled model placed where the label object is (It looked extremely detailed)? How are live holograms displayed? Is such a thing even possible? Thanks
P: 72
 Quote by Simon Bridge ... it's an analogy. The pop science folks are trying to describe the granularity of space time as like a newspaper photograph only 3D ... and a hologram is a 3D photograph so...
Thats not what they mean. A hologram has information about the entire image at every point. Its a 2D surface with information that can be projected to reconstruct the wavefront reflected off of a 3D object. When scientists say the universe could be a hologram, they mean that our perceived 3D space could be a projection of a 2D surface.

Think about it. A hologram reproduces the same wavefront of light that bounced off the original object. The light from a hologram behaves in every way as if it were in fact reflected by the original object. Since the Electromagnetic force is pretty much the only one that we perceive through our natural senses, it seems to me that I should be incapable of telling the difference between a "real" world and a holographic one if the EM wavefront that is perceived by my senses is the same. Not that the holographic universe would lack any forces that exist in the "real" world.

A hologram with larger area has finer image quality because of the reciprocal nature of diffraction, if you tear one in half you can still see the whole image but it gets fuzzier. If the universe is a hologram then its gotta be really huge (duh.. its the universe), giving a resolution much much finer than an atom. From the "Before its News" article it sounds to me like they are detecting the "fuzz" due to the finite area of the universe, but it could be something else for all I know.
P: 72
 Quote by lookbehindu does that mean we are analogous to the film and the data which is stored "outside" is the original object which the laser shines on to create the hologram?
We are the data that is stored on the film. Space is the hologram. Space doesn't exist but the data on the film does represent a bunch of interactions (the universe) that act as though they exist in space, except for the fuzzyness mentioned in that article i suppose.
 Sci Advisor P: 887 Brian Greene does a nice job explaining holography in his newest book, "The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos" :)
P: 2,470
 Quote by Greg-ulate Thats not what they mean. A hologram has information about the entire image at every point. Its a 2D surface with information that can be projected to reconstruct the wavefront reflected off of a 3D object. When scientists say the universe could be a hologram, they mean that our perceived 3D space could be a projection of a 2D surface.
You've got that backwards. Holographic interpretations require extra dimensions. It is a description of our 4D space in 5+ dimensions, where the special metric of the extra dimensions helps simplify some of the physics. Otherwise, the extra dimensions are redundant and carry no information about position of particles.

The most straightforward example I'm familiar with is the 5D Anti-De Sitter space (AdS5). When the extra dimension of AdS5 is truncated, you end up with some of the nice features of QCD right away, and you even get a basic mass ladder for fermion fields.

This is hardcore field theory, so I'm a little hazy on the details, but that's the gist of it. Holographic QM has almost nothing to do with classic holography, and you shouldn't be trying to understand it as an analogy.
P: 10
 Quote by K^2 You've got that backwards. Holographic interpretations require extra dimensions. It is a description of our 4D space in 5+ dimensions, where the special metric of the extra dimensions helps simplify some of the physics. Otherwise, the extra dimensions are redundant and carry no information about position of particles. The most straightforward example I'm familiar with is the 5D Anti-De Sitter space (AdS5). When the extra dimension of AdS5 is truncated, you end up with some of the nice features of QCD right away, and you even get a basic mass ladder for fermion fields. This is hardcore field theory, so I'm a little hazy on the details, but that's the gist of it. Holographic QM has almost nothing to do with classic holography, and you shouldn't be trying to understand it as an analogy.
SO the concept of the world as a hologram does not derive from the concept of regular holograms??? Also does anyone have another video depicting a hologram. The architecture video I found really fascinated me but I can't seem to find anything else.