<sub>Question inspired by [Neil deGrasse Tyson's tweet](https://twitter.com/neiltyson/status/678999135203143680):</sub>
>In @StarWars #TheForceAwakens, BB-8, a smooth rolling metal spherical ball, would have skidded uncontrollably on sand.

Is this ever explained in-universe? 
How was BB-8 able to travel through the sand without skidding? 
-