When I'm 100 years old, I will leave the world with a message.
A message of what the world is like at that moment, so others will know this when they find this information in the even more distant future. It will contain the following information:
Clouds in the sky are created by evaporated water from the oceans. They are moved by the wind and they rain down the water in the mountains. This rain gets in the river where it flows towards the ocean. When the river meets the ocean, the circle continues.
(You never know which obvious seeming information of the present might seem amazing in the future)