[StarrKingGrad]

Originally Posted by Stranger

just wondering if you could explain the holographic principle in more detail, i couldn't get much out of the wiki site, as I have not yet take an elementary physics class, so much of the terminology went over my head.

I can't explain it, since my degree is in theology, not physics. I asked a physicist in my congregation to give me a two to three sentence summary, and here's what he said (like most physicists, he took more than three sentences, but that's true of theologians as well, so I won't complain):

In physics, we understand the world around us in terms of mathematical models. For example, we can write an equation that tells us how much energy is required to stop a car of a certain weight going at a certain speed, and we can use this to design brakes for automobiles.

Mathematically, objects in three dimensions can be described by equations in just two dimensions through a process called projection. It's difficult to show exactly what this means without graphs and equations, but think of it as something like your shadow--it is a two dimensional representation on the surface of the Earth of a three dimensional object (you).

A hologram is a two dimensional image that looks like a three dimensional object. If you haven't seen one, look at the funny colored sticker on most credit cards. It's obviously flat, but the object looks like it has depth, too. A hologram of an object tells you a lot more about the object than that object's shadow does. This is, in essence, the holographic principle--it says that all of the information needed to describe a three-dimensional world can be condensed into just two dimensions.

To be clear, I'm not saying that we can take one of our dimensions and throw it out the window (i.e., the holographic principle does not say that east and west and north and south are real, but up and down are illusions). If the principle is true, then the "real" two dimensions are constructed in a very different manner than east/west, north/south, and up/down.

One trend in modern physics is to think of our universe as containing not space, time, matter, and energy, but rather information (remember, physics is about building mathematical models of the real world, and information is something that can be described easily with math). If that concept is correct, then there really could be no difference between a three-dimensional object and its two-dimensional holographic projection, so we could say that the third dimension really is just an illusion.

Is the holographic principle true? It's hard to say. We certainly don't have a full-blown model of the universe that can be described holographically. On the other hand, theoretical results from the study of black holes (objects that are so massive that even light cannot escape their gravity) indicate that the information content of a black hole is proportional to the surface area of that black hole, rather to than the black hole's volume. That's a tough concept to grasp--if I told you that a balloon filled with water weighs exactly the same balloon filled to the same size with air, you'd (quite rightly) think I was crazy--but there are very good reasons to believe that's exactly the way black holes behave with respect to information.

Why does this matter? On a superficial level, it doesn't--we experience the universe in three dimensions, and if it's really just a two dimensional universe of information that appears to us to be a three dimensional universe of matter and energy, what difference does that make to us? It is important to physicists, however, since it turns out that many calculations are much easier to do when we think of information in two dimensions rather than matter and energy in three dimensions. Moreover, the holographic principle is our best explanation of the way black holes work--but if it's true for black holes, it has to be true for the rest of the universe, too, including you and me.

Let me add that there is currently no experimental evidence directly saying that ours is "really" a two dimensional world. There is a chance that, once the Large Hadron Collider in Europe begins operations this year, experiments will help us to see whether holographic models stand up. At the same time, there is no evidence today that would disprove the holographic principle.

In summary, it may truly be that we live in a holographic universe, and we cannot abandon the hypothesis out of hand, but it would not be accurate to say that our universe has been proved to be holographic. One dominant lesson from physics in the last 100 years or so is that the way universe really works is usually far stranger than we imagine, and, any way you look at it, the holographic principle is strange.