How far is it to the sky?

Print source: Planet Earth by Peter Murray
The Child's World, Inc. 1993
Distributed by Encyclopaedia Britannica Educational Corp.

This book has gorgeous photographs and discusses the atmosphere, which it describes as a blanket of gasses. The troposphere extends from the Earth's surface outward approximately five miles. The various layers continue upward for over 600 miles, so the "sky" actually starts at Earth's surface. (The ozone layer, which protects us from the sun's radiation, is about twenty miles above the Earth.)


Blogging, using Wikipedia:

"Sky" is defined as "the part of the atmosphere or of outer space visible from the surface of any astronomical object." It also says that "during the day the Sun can be seen in the sky, unless covered by the clouds." To be more accurate, it should probably say that the Sun can be seen "through the sky," and the clouds just block/obscure our view of the Sun. I prefer their definition of "the denser gaseous zone of a planet's atmosphere" which would confirm that the sky starts at Earth's surface.


Using Credo Reference from National Louis' online library:

The New Penguin Dictionary of Science defines horizon as "the line dividing the Earth and the sky." This definition also confirms that the sky starts at the surface of the Earth.