16:37 Everyone seems to assume that the DM particle or particles couple with the nuclear Weak force. It might, as the neutrino does. But then again, there is no guaranty of that. It could interact only via the gravitational force, in which case we would only ever be able to observe it gravitationally... which is fine. Gravity is a perfectly valid way of observing things. One should be careful to avoid the irrationality of EM Chauvinism.