end of his career Bohr took a more interpretative role and
struggled more and more with the philosophical issues of quantum
mechanics First, he came up with the idea of complementarity.
He noted that the wave and particle views of an object exclude
each other totally but conceded that both are needed in order
to fully understand the properties of the object. He suggested
that the interpretation to use depends on what apparatus are
used to view the object. Electrons look like particles if
probed with photons, but like waves if diffracted through
a crystal lattice. Bohr dragged the ideas of matrix mechanics,
the Heisenberg uncertainty principle, Born's probability interpretation
and the idea of complementarity together into a single interpretation
of quantum mechanics – dubbed The Copenhagen Interpretation.