1. The Sun makes up 99% of the solar system mass See here
2. The Sun is large enough that approximately 1.3 million Earths could fit inside (squashed in)
3. In most species of bird, it is the male who sings not the female See here
4. The bones of a pigeon weigh less than its feathers See here
5. Sound travels much faster through steel than it does air (sound travels at 5100 m/s through steel, 1480 m/s through water and 330 m/s through air) See here
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.