Ecclesiastes 3:11

For the longest time I have had trouble understanding the phrase in Ecclesiastes 3:11 "the world in their heart", or as other versions put it "eternity in their heart." As I thought about it last night this came to me: "the world (universe) is seemingly endless, and eternity has no end. Therefore "no man can find out the work that God maketh from the beginning to the end" because the world and eternity are endless and we don't know what things God is still going to do in that eternal future." "He hath made every thing beautiful in his time: also he hath set the world in their heart, so that no man can find out the work that God maketh from the beginning to the end." Ecc 3:11 Now I get it!