8/17/2010

Far Out Conspiracy Theories

Go to: The Moon Hoax by by Darryl Cunningham
I was just watching the Mythbusters episode (not for the first time) referenced by this comic, and naturally picked up on the aspects that dealt with photography: such as the luminosity of the moon's surface makes it a useful source of fill light; that topography affects the direction of the shadows; that the lack of an atmosphere affects lighting conditions on the moon so that starlight is relatively faint and the sky is pitch black (not directly tackled in the episode). Phil Plait's description on his website is fairly self-evident, at least to me:
Pretend for a moment you are an astronaut on the surface of the Moon. You want to take a picture of your fellow space traveler. The Sun is low off the horizon, since all the lunar landings were done at local morning. How do you set your camera? The lunar landscape is brightly lit by the Sun, of course, and your friend is wearing a white spacesuit also brilliantly lit by the Sun. To take a picture of a bright object with a bright background, you need to set the exposure time to be fast, and close down the aperture setting too; that's like the pupil in your eye constricting to let less light in when you walk outside on a sunny day. 

So the picture you take is set for bright objects. Stars are faint objects! In the fast exposure, they simply do not have time to register on the film. It has nothing to do with the sky being black or the lack of air, it's just a matter of exposure time. If you were to go outside here on Earth on the darkest night imaginable and take a picture with the exact same camera settings the astronauts used, you won't see any stars! 
But the most entertaining part of the episode was watching Adam Savage replicate the low gravity conditions of the moon's surface via flying a plane through a series of parabolic arcs. Now that's a trip I'm curious enough to risk upchucking for.