Satellites have long been used to track ice extent (area), but calculating the thickness of the marine floes requires the overflying spacecraft to gauge the difference between the top of the ice surface and the top of the water - a relatively simple calculation then gives the overall volume.

BBC: Launch success for Esa's Cryosat-2 ice mission

When buying a pen, he takes time to gauge how the pen feels in his hand the thickness, weight and length have to feel right or he may write more clumsily than usual.

WSJ: Jan-Patrick Schmitz of Montblanc on Choosing the Right Pen