As others have said -- if the goal is to communicate with your descendants 500 years from now, I wouldn't use the web! And I wouldn't use CD-ROMs or Bitcoin I

As others have said -- if the goal is to communicate with your descendants 500 years from now, I wouldn't use the web! And I wouldn't use CD-ROMs or Bitcoin I would use something that's proven to last 500 years, which is basically "paper". This is just "the Lindy effect"