From Today I Found Out:

The beam itself measured 2000 gray as it entered Bugorski’s skull and about 3000 gray when it exited on the other side.  A “gray” is an SI unit of energy absorbed from ionizing radiation.  One gray is equal to the absorption of one joule of radiation energy by one kilogram of matter.  An example where this is commonly used is in X-rays.  For reference, absorption of over 5 grays at any time usually leads to death within 14 days.  However, no one before had ever experienced radiation in the form of a proton beam moving at about the speed of light.

I’m posting this out because it immediately made me think of the interview we did with Dr. DiRuggiero for last week’s 365 Days of Astronomy podcast:

The organism we’re working on at the moment is Halobacterium.  They’re fairly resistant to radiation.  We measure the resistance to radiation as the D10, which corresponds to the radiation doses for which 10% of a population survive.  So the D10 of the organism, that is called the wild type.  The regular organism is five kilo Gray—that’s measured radioactivity—which is pretty high.  This is 5000 Gray, and humans are killed by five Gray.  Those survive 5000 Gray; humans died with five Grays.