How far is it to the sky?

Mrs B found this lovely book for me. It contains this page

Which begs the question: how far away is the sky? This led me to find out about the Karman line https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line Karman calculated the altitude at which an aircraft would not be able to travel fast enough to generate enough lift to support itself without travelling faster than the orbital speed for that altitude. So this is where the sky is said to end and space begins. It's arbitrary but I like that it is based on a calculation.
There was a new moon tonight just visible through the trees.

So