To fling a light into the future

I believe that if and when are to go extinct, the whole sum of human
knowledge and culture should be preserved somehow for future
civilizations to see. If future sapients arise on Earth, then the
knowledge preserved could be a huge boost to their civilization,
depending on their level of advancement, if alien species were to come
to Earth, then the knowledge preserved could shed light on the
mysterious structures still apparent far into the future, such as Mt.
Rushmore, and on the species who built them, us. On a more short-term
scale, if humans are long-lived as a species, then we should do more to
warn our future descendants about the dangers of nuclear silos,
essentially signs saying “Keep Out: Dangerous Radiation Within”.

If our future descendants somewhere along the line had lost
civilization, only to rebuild it, then we should both make sure they
know to stay away from nuclear sites as well as making it even more
prudent to preserve our knowledge in case disaster strikes. After all, it is imperative that we find some way to preserve our knowledge to serve as our ultimate legacy, for millions of years from now it won’t matter what the color of your skin was, or what creed you adhered to, the only thing that will matter will be the collective memory of mankind, in this way, we are all remembered, even if not individually, certainly as a species.