Well you learn something new every day. Apparently the gray is the SI unit of "absorbed radiation dose due to ionizing radiation". To be precise, 1 gray = the absorption of 1 joule of energy, in the form of ionizing radiation, by 1 kg of matter.
Now, since Iain Gray has been made redundant by Jim Murphy, surely his time would be better employed swimming up and down the Gare Loch absorbing all the radiation our marvellous nuclear subs spit out. Indeed, as well as helping clean up the environment he could also provide a timely boost to tourism. People would come from far and wide to see this increasingly endangered Gray wail.