What does a CD mean to a cow?

Passing thought: Imagine two people conversing using their Nokias. The information is ferried between them through space in form of light waves. Would it be possible to monitor the physical properties of the space and infer the information being exchanged? One may point out that the cell phone data is garbled for obvious reasons. But would it be possible to determine atleast this garbled data by performing a suitable measurement on the space, somehow?

Eavesdropping on people's conversations is not really the topic. It is rather about the nature of information.

Is there a theoretical limit to how much information a given volume of space may possibly
contain irrespective of the method used for storing/encoding this information? There can be two possibilies:

1. Yes, there is a limit.
2. No, there isn't a limit.

If it turns out that the first case is true, then it would imply that there must be something in the fabric of this universe - some key ingredient which serves as a universal currency of information. This would mean that a general purpose instrument which can quantitate information contained in the given object space should be achievable.
But if it happens that the second case is true then information would turn out to be indeed something very personal - so that each individual can have the freedom of interpreting this information the way way he pleases. That there wont be such thing as a universally true information or a universally false information for a given obeject space under scrutiny. In such a case it would not be possible to develop a generic tool or quantitating the information content Which is :-( So, clearly in this case infomation exchange is possible only if the two parties agree on the information content.

Passing thought: Your Win-Zip program which you use to compress data does its thing like this[2]. A CD contains data stored along the tracks. In each track there are two possible features - a small pit and no pit corressponding 0 and 1 or otherwise. A 700Mb of such a CD would contain an entire DivX of The Da vinci Code. One would be able to watch it if one has a CD-ROM to decode the engraved data. But what if one does not have such a specific device? Does the information contained in this CD affect the properties of the physical space it occupies so that a suitable measurement on this space would reveal the movie data indirectly?

Casual Mention: "Biology is the domain of the complex. It takes 3 * 10.pow(9) bases = 6 * 10.pow(9) bits of information to specify the DNA that determines a human being".[1]

But what is in it for the biologist? Well, putting it rather (very) bluntly,
If the information is found to be universal as opposed to personal then a given space, say a space which contains only a single DNA fragment, can be analysed by using some tool to come up with the absolute information content of the space; DNA sequence in this case. Outrageous. I know.

Theres more actually, but by now I have either forgotten to mention those things/ too lazy to type anymore/ its lunch time :P
Maybe some other day. . .

Interesting reads:

1. http://www.cs.auckland.ac.nz/CDMTCS/chaitin/***
2. http://en.wikipedia.org/wiki/Data_compression
3. http://www.faqs.org/faqs/compression-faq/part2/section-4.html
   

*** = Must read.