|Star Trek's "Holodeck"|
The concept of a hologram is probably different to what you would expect. It is actually nothing to do with "3D photography". In fact holography is more like storing sound data on a CD. The sound isn't actually on the CD, but the information that is needed for your stereo to convert that data back to sound is. This is what holograms do - they store the information about a 3D object on a film in a way that it can be "recreated" as long as you have that film. They use lasers and the concept of interference to "record" how an object looks and with this information they can recreate the 3D image of what the object looks like without it being there.
One of the coolest things about a hologram is that each part of the hologram contains all of the information about the object. For example, if you made a hologram of your self, and then cut it in half, and looked at it again, if wouldn't only show half of you. It would still show all of you, but with less quality. If you cut it in half again, then it still shows all of you, but even less quality. Every part of the holographic film contains all of the information!
In physics, there is a very important speed limit - the speed of light. Not even information can ever travel faster than light. Or so we thought. But recent discoveries in quantum mechanics have proved otherwise. There are certain particles that stay connected to each other somehow: it doesn't matter whether they are 10 cm apart or 10 billion light years, they each "know" what is happening to the other one. This flies in the face of our current understanding of physics.
So where does the hologram come into it? Well, some pretty brainy guys have suggested that our universe is actually more complex than we have realised. Our closely held theories are actually just scraping the surface of reality. Here is a good analogy: Imagine an aquarium containing a fish. Imagine also that you are unable to see the aquarium directly and your knowledge about it and what it contains comes from two television cameras, one directed at the aquarium's front and the other directed at its side. As you stare at the two television monitors, you might assume that the fish on each of the screens are separate entities. After all, because the cameras are set at different angles, each of the images will be slightly different. But as you continue to watch the two fish, you will eventually become aware that there is a certain relationship between them. When one turns, the other also makes a slightly different but corresponding turn; when one faces the front, the other always faces toward the side. If you remain unaware of the full scope of the situation, you might even conclude that the fish must be instantaneously communicating with one another, but this is clearly not the case.
So, like the fish in the example, our universe may actually be more deeply connected than we thought, and these strange particles that don't behave as we expect might actually be the same thing. Like in a hologram, these things look like they are separate, but in fact the information for them is stored in the same place. Perhaps it is our perception that is wrong.
Another reason that the hologram idea is getting some attention is that the universe seems to have a maximum resolution. If you thing of a computer screen, then the resolution is dependent on how many pixels you have. We all have the notion that the scenery that we look at with our own eyes has an infinite resolution, but that isn't the case. there is actually a maximum resolution that we can get, just like an image on a screen. However, this maximum resolution is in three dimensions, if you can visualize that.
So our universe has a number of properties that have caused scientists to wonder if it is a giant, complex hologram.
Makes you think.
PS: Don't ever believe a scientist if they try to tell you they have got it all figured out.