Lee DeWyze "Castles"

in a park with a small lake there is a tree house. Here the memories come back to life, the shadows of children persist over time, but one day that place will be razed to the ground, building a nuclear power station that will exploit the water of that lake.
Ionizing radiation into the water will produce a blue light (Cherenkov radiation) that will be projected into the universe in memory of that place