Overview

Little has changed in Compact Disc (CD) physics since the origin of CD audio discs in 1980. This is due in part to the desire to maintain physical compatibility with an established base of installed units, and because the structure of CD media was both groundbreaking and nearly ideal for this function.

Digital Versatile Discs (DVDs) are an evolutionary growth of CD s with slight changes. Considering the development of DVD follows the CD by 14 years, you can see that the CD was truly a revolutionary creation in its time. It is important to understand that both CDs and DVDs are electro optical devices, as opposed to nearly all other compter peripherals which are electromagnetic. There are no magnetic fields in the reading or recording of these discs, therefore, they are immune to magnetic fields of any strength, unlike hard drives

Due to its immunity to magnetic fields, CD and DVD media is unaffected by Electromagnetic Pulse (EMP) effects, X-rays, and other sources of electromagnetic radiation. The primary consideration with recordable CD media (and to a lesser extent, manufactured media) is energy transfer. It takes a significant amount of energy to affect the media that the writing laser transfers to the disc. Rewritable discs (Compact Disc - ReWriteable [CD-RW], Digital Versatile Disc - Rewriteable [DVD-RW], and Digital Versatile Disc - Rewriteable [DVD+RW]) require even more energy to erase or rewrite data.

This is in direct contrast to floppy disks and hard drives, which can be affected by electromagnetic devices...