First, the Greeks were not technologically advanced enough to make a large sheet of copper. The lecturer refutes this point by saying that the burning mirror were not a single shape of mirror. The burning mirror could have been made with mirror pieces with the specifications of a precise parabolic shape. Thus, this point contradicts what the reading stated, that Greeks were not capable of build that weapon with several meters wide that focus sunlight with sufficient intensity to set ships on fire.
Second, the burning mirror