Courtesy Wikimedia CommonsDid you know it takes two-and-a-half times more energy for us humans to walk on sand than on a hard surface? We can reduce that expenditure (to one-and-a-half times the effort) by running but the fact remains getting across sand is not easy for us. It's a different story for some of our animal friends. Some creatures, such as the ghost crab (Ocypode cordimana), can move effortlessly across a heap of sand like they're skating on ice. Others, such as the sand skink (Neoseps reynoldsi), can swim through sand like they're swimming through water. Read here about how scientists at Georgia Institute of Technology in Atlanta (along with colleagues at the University of Pennsylvania and Northwestern) have been studying such creatures to help design robots that will be able to move effortlessly through sand and other complex terrains.