any observation and that the job of physics is to describe, as best as
possible, this reality. Bohr, taking the lessons of quantum mechanics
to heart, maintained that acts of observation place fundamental
limits on what we are able to know about the universe, and this will
necessarily limit the capacity of any physical theory to describe what
kind of reality might exist independent of our observations. Bohr
and Einstein engaged in many dialogues related to these deep, foun-
dational issues in physics and challenged one another with thought
experiments.
In August 1932 there was a conference in Bohr’s home city of Copen-
hagen, Denmark, of clinicians interested in the application of light to
treat skin conditions—the International Congress on Light Therapy.
Because Niels Bohr was the most famous scientist in town, the con-
gress extended an invitation to him to give a keynote lecture at the
meeting. Bohr accepted the invitation to speak and proceeded to use
the occasion to think deeply about the physical description of living
organisms in new and unprecedented ways.