Don Cox wrote: > > On 26/06/03, [log in to unmask] wrote: > > > Finally, digital optical media such as CD's, DVD's and the like. These > > will be, if anything, even more inaccessible! It will take > > submicroscopic observation to see that there is anything which even > > MIGHT contain data (our neo-Indiana may set out to analyze the light > > patterns they reflect?)! Even if the existence of pits and non-pits is > > discovered, and the use of digital information deduced, the ones and > > zeros still have to be decoded by a sophisticated algorithm before any > > data can be accessed! > > Actually light microscopy is sufficient to show the data on a CD. If you > don't demand real time playback, the data could be reconstructed with a > rigged up microscope and motor. > > The archaeologist might have problems guessing what error-correction was > used, unless documents such as the Sony book survived. > > Regards > -- > Don Cox > [log in to unmask] Conjecture about preserving data for archaeologists or alien visitors is amusing but not very applicable. Any archival media should be evaluated every "few" years to detect any degradation and to allow a copy to be made if any risk is detected. Transfer to media using updated technology should be anticipated every 20 years or so. Material that is centuries, or even decades, old can be expected to be severely degraded, as is now being discovered with film. Material that is thousands of years old usually contains very limited information, digitally equivalent to a few bytes, not GB, and its limited visual content must be painstakingly reconstructed. In context, information can be carved into granite, cast into titanium, or whatever you like. Such efforts can only preserve very limited amounts of information (cave drawings anyone), and lingual or pictoral content would probably be just as difficult to interpret eons hence as coded digital data would be. Jerry Media Sciences, Inc.