I recently played my way through the Mass Effect game series, and one of the ideas I found most intriguing was the emphasis placed on "time capsules" sent from one cycle to the next: not only did several Prothean messages last until the in-game present, but presumably each cycle had done the same in an unbroken line, at least going back as far as the development of the Crucible.
Assuming modern-day technology (not Mass Effect-era), would it be possible for humans to leave a message that would confidently be received 50,000 years in the future? Do we have any storage mediums that would last that long, or preservation techniques that could work on that scale? Obviously there are ways that a message could last that long (such as a rock carving inside a dry, untouched cave), but things happen. Caves fill with water, earthquakes crack them open, etc.
But if we had a message that must survive 50,000 years into the future and still be understandable, what would be our best bet for delivering it?
