How many punch cards does it take to...

[Bofinn]

CDs and DVDs are certainly not a perfect medium, but they are the current best-available choice for long-term data storage.
"Best-available?" I'd go for punch cards. As long as you keep them away from fire and water, exclude rodents, ... ok, maybe punch cards aren't the most durable. How many thousands of cards would you need to store a typical MP3, anyway?

Hmmm... 3 minutes of music at 1 MB per minute is 3 MB. A standard ("IBM") punch card holds 80 columns of 12 bits each or 120 bytes. So 25,000 cards should be sufficient for a single song. With compression, you could reduce that by about zero percent. To put it another way, it would take about five four-drawer filing cabinets of punch cards to hold one CD's worth of music, encoded in MP3.

Storing the CD's contents losslessly, that is, without MP3 compression, is a bit less practical: an audio CD holds about 890 MB of data. (That's more data than a CD-ROM due to less overhead for error correction: the uncorrected error rate for CD audio is 1 in 10^12, vs. 1 in 10^15 for CD-ROM, if memory serves.) A single CD would take 7.4 million punch cards, assuming no error correction or other overhead. That's about 70 four-drawer filing cabinets: a single-car garage. My CD collection is rather modest, at a few hundred CDs. I could store it in punch card format if I bought a couple of houses. In the moderately-low-end part of San Francisco where I live (sort of), houses typically sell for about $800,000. The rest of the arithmetic is left as an exercise for the reader.