by justgrimes at http://www.flickr.com/photos/notbrucelee/8016173775/ CC BY-SA 2.0

By Bidgee (Own work) [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

By Bidgee (Own work) [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

By NJGW at en.wikipedia [Public domain], from Wikimedia Commons

By U.S. Navy/PH3 Alta I. Cutler [Public domain], via Wikimedia Commons

By NASA/Ben Cooper [Public domain], via Wikimedia Commons

Image Credit: NASA/JPL-Caltech/Cornell.

'Suspended Stairs' by Dave Gingrich at http://www.flickr.com/photos/ndanger/20827120/ CC BY-SA 2.0

'Suspended Stairs' by Dave Gingrich at http://www.flickr.com/photos/ndanger/20827120/ CC BY-SA 2.0