Saturday, January 31, 2009


The Earth and Moon at True Separation

A while back, NASA released a beautiful image from the HIRISE satellite, which was orbiting Mars at the time, that showed the Earth and the Moon in a single shot.

It occurred to me that the apparent separation of the bodies was probably significantly less than actual, so I did the math to calculate the number of pixels that ought to separate them based on their sizes in the image. In case you're interested, the ratio of the Moon's average distance from Earth to its diameter is about 110. Then I created a new image that showed how far apart they ought to be to reflect reality.

The corrected image makes me think a few things.
  1. There is an awful lot of nothing out there.
  2. Those Apollo missions were astonishing.
  3. When somebody tells you that x of y lined up end to end would reach to the moon and back, it's probably further than you think.
  4. Gravity is a wacky, wacky force. It seems unintuitive that any attractive force could hold two bodies together at that distance. (There must be a really cheesy declaration of devotion to be derived from that.)

Following this post up with the Unix script was an interesting decision. In my first pass I was struck by the contrast of the two, probably based mostly on scale. But on a second look they don't seem so different. They are both creations, simply one by a master and one by a comparitive, but none the less wonderfully made child of the master. There's your cheese devo.
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