Defraction and Refraction
Holograms take advantage of some pretty amazing physics. For example, on a piece of holographic film, the entire image is recorded on every piece of the film. You can cut up the film into as many pieces as you like and it will still reproduce the full image that was recorded on it. Imagine if your DVD worked this way!
If you make a hologram of a magnifying glass, the image of the magnifying glass produced by the hologram will magnify other parts of the hologram!
So how the heck does it do that? Is holographic film some magic technology? Not at all. It turns out, however, that Light is. Holographic film “records” the interference patterns that light waves make when they cross each other.
This is actually an old technology. We have been manipulating light in this way with radio for many decades now.
see: Carrier waves and Information waves.
To understand how this works, we first need to discuss the mechanics of what happens when light reflects off of an object.
The Miracle Known as the Reflection of Light
The problem with miracles, sometimes, is that we give them such unimpressive names, like “reflection”.
When a “beam of light” shines on a reflective object, the object first “absorbs” the light, chews on it for a bit, and then it either “sends it back” out into the world, or swallows it.
It all depends on the atomic structure of the object and the motion (energy) of the electrons. Either way, in the case of a reflective material, light is being trasformed into matter and then transformed back into light.
So, the photons are absorbed by the electrons, causing them to wiggle, and thus increasing the atom’s energy. Two things can happen from here: If the electron is “loosely” connected (outer shell electrons), it will speed up enough to emit a photon back out. This is the reflection of light.
If the electron is tightly connected (inner shell electrons), it cannot wiggle freely enough to emit the photon back out (due to friction) but it does wiggle as much as it can. This wiggling, combined with the friction o being more tightly “packed” causes the atom to vibrate, producing heat. This is the absorption of light.
Notice, however, that what we call absorption is just a special case of reflection, because as we know, heat is a form of invisible radiation. The light is still “reflected”, we just can’t see all of it!
In other words, the light is absorbed, filtered through the object and reflected back out, but we only see certain portions (colors) of what is filtered back out because some of what comes back out is in the form of infrared (heat) radiation, which is invisible to the human eye.
Color is an atomic fingerprint
Color is a fundamental property – of atoms. Let me say this again: color is not a property of light, but of matter. This is one of those very deep statements that sinks in further and further as understanding deepens. We don’t talk in this way, because we are lazy and have more important things to do, but if we slow down and get precise, we can see the cold, hard facts at work – and they are miraculous!
Few ideas get me as excited as this idea of the unity of matter and light. After all, light does not just originate from empty space. It originates – from matter!
All matter radiates light all the time.
Yes, this includes you and your radiating nose and ears, but before we go down that path, lets finish this description of reflection.
Here comes a big aha moment…
There is a very deep-seated sort of identity between electrons and photons.
So I like to think of color, not as an object simply reflecting light, but as an object emitting light. It is the same mechanism, but the concept of reflection does not fully denote the facts.
Light becomes matter and then matter converts itself back to light. This is quite amazing. We call this miracle, “the reflection of light.” But understanding the mechanics of what has happened will help us to understand holograms.
Making a Hologram
if we take a beam of light and split it into 2, with the first beam directed to a piece of film and the second beam directed to an object and then to the same piece of film so that we end up with both beams meeting on the piece of film then we have recorded the information of a light beam and embedded the information of an object together in such a way as to produce a hologram.
We were in the process of describing how an object filters light like a crystal. We said that color reveals the atomic structure of the object that produces, or “reflects” it. This is why we can tell what stars are made of. By analyzing the wavelength of the light any object filters back to the observer, we can deduce the atomic structure of the object.
I already introduced the concept of matter chewing on a photon and spitting it back out and I suggested that this “new” photon encodes some sort of information about the object that can be retrieved from the photon.
This is a powerful idea. It leads us down the road to ideas about quantum bits of data and how the events of the universe can be understood in terms of quantum mechanical computation of quantum bits of information.
But that is a story for another post.
Right now, we are focused on understanding how a hologram works and why on earth would someone claim that the universe has some sort of holographic “properties”. What could all of this possibly mean?
One of the difficulties I had in understanding a hologram is the fact that the image is not recorded on the film: it is RECREATED from the film.
When two “beams of light” cross paths (Ghostbusters reference goes here) they create interference patterns (think of two waves in a lake moving toward each other). If these interference patterns are recorded on film, the image of
The Black Hole War
Computing the Universe