Time dilation. Length contraction. The fact that time moves faster at your face than it does at your feet. These are all experimentally verified consequences of the Special Theory of Relativity, proposed in 1905 by Albert Einstein. But the theory also helped explain one of the most nagging questions of modern physics, namely: how anything other than light can move. Minutephysics' Henry Reich explains, with the help of some sliding switcheroos. [Via Henry Reich]