system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how are DVDs mass produced.

Title says it all.
gpt
It's hard to think about at first because everyone has a CD burner now. You think "how can they make millions of these" without spending a ton of a bunch of CD burners.

But CDs made in factories are actually different than CDs you burn. CDs in factories are actually full of tiny little bumps. It's actually basically the same as an old record when you think about it. They take master copies, the originals, of the CDs, make molds of it, and use them to quickly press into CDs, similar to how you can press the PlayDoh Lid into PlayDoh and get a copy of it. So why are your CDs so smooth? They put a thin layer of coating over the whole thing to make them more scratch resistant. If you think they're easy to ruin now, imagine having direct access to all the little bumps that represent the 1's and 0's of the data stored on them!


As a side note to this, how does your CD Burner work? If it's just a laser, it can't physically press into the CD can it? This is why you need special CDs to burn with. Instead of having bumps all over them, they're simply a chemical compound inside of them. When you burn a CD, the laser actually melts the chemicals inside the CD(hence the term burn) to form the same types of bumps you get from a factory. Obviously this takes longer because it goes over the whole CD and isn't just a mold being pressed into it.

And another fun fact! Instead of burning bumps into a CD, re-writable CDs actually have a chemical that changes colors when being burned. The laser melts the chemical to a certain color instead of a bump. Being able to read this color is why CD-RWs don't work in all radios.