The blue whale’s body adjusts to the polar tide
and the tropics, each latitude calibrating
her breath. A nursing mother produces
fifty gallons of milk per day; her calf
grows ten pounds an hour.
It’s purely mathematical, what we’ve known
about her dive: rate per second, depth.
It’s a miracle, the narrator says, as we watch her
recede from the boat
with their camera suctioned to her back—
now we’ll get to see—
and she begins to descend. The narrator
goes quiet. First gray,
overtake the screen.
I listen to her disappear
as the camera slips off, again, ending
what we can know of her, that great pulse
and signal to follow—