How High Can You Fly?

Here are a couple more vacation photos...













Notice that the bottom photo may seem to have been taken from a greater
altitude, although that is not the case.  The top one is not
really a
vacation photo; it's from the href="http://antwrp.gsfc.nasa.gov/apod/ap060724.html">Astronomy
Picture of the Day site.  (Credit: href="http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts121/121_crew.html">STS-121
Crew, href="http://www.nasa.gov/mission_pages/station/expeditions/expedition13/index.html">Expedition
13 Crew, NASA)



The top one was taken from a Space Shuttle; the bottom one was taken
from a Boeing 737-500.  The use of a wide-angle lens, and the
placement of the horizon close to the top of the picture, causes the
horizon to look as though it is has greater curvature; this causes the
appearance of a higher altitude.  



The top photo shows a greater color gradient in the sky, which is a
clue that it is the one that actually was taken from a greater
altitude.