Another major source of inspiration is the theme of time and eternity, mortality and frailty, the small span of our lives when we compare it to the timelessness of the land we live on. Compare the "three score and ten" years of the figure lost in this picture with the two thousand year old towering redwood trees that were saplings when the Roman Empire ruled.
And time is 'funny stuff, can we really travel through time? Yes of course, but only in one direction and the tantalizing prospect is the imagination of traveling backwards and forwards at will.
Then there is eternity: is that just a lot of time, perhaps even an infinite amount, more than the 4 billion years of the solar system, more than the twenty billion of the universe.