On 09/07/2014 12:43, Micaela Addison Kemp wrote:
Noctilucent clouds form at 80/85 km (50 miles) high, which is close to the edge of space (there is very little air at that height).
I was wondering about this statement (80 km is not very high) but found that it was correct: it is the same height that the Lockheed SR-71 “Blackbird” flies at:
There is so little air at that height that most aircraft cannot function. Also, the curvature of the earth can be seen, as can the stars. It is a magical place where the Earth begins to become space (there is a marvellous sequence in a movie called “The Right Stuff”--1983, also a book--that allowed me to spot that).
--------- Alex Kemp