A Perturbation of Light

I was disturbed in the night
by my granddaughter tip-toeing the corridor –
no sound, no sign
but a subtle change in the light
through my door
so slight her little body,
so soft her foot
as she felt her way along the carpet
and yet enough to wake me as I lay.
The course of the universe
may be altered–
so they say–
by a butterfly
though our own identity
may be doubted as solid integrity
for one electron will shift another
without a touch –
and an atom move a star –
so why then should we be concerned
if a perturbation of light
is all we are.