With the previously inconcievable yet unquestioningly fatal threat presented by the use of matter cannons as weapons against fellow humans, a solution had to be found. While laser weaponry proved to be quicker to fire, and more precise, that didn’t help a ship that was taken by surprise. No, simply creating a weapon to cut off another weapon is not enough. The task of finding a way to defend against a weapon that hits you with your own mass at speeds approaching 1C was presumed to be difficult, and with obvious reason. What could withstand an attack like that?
When the answer came, it seemed so simple that it frustrated nearly everyone who had tried to come up with a solution. While it’s impossible to stop the matter cannon from being as powerful as it is, it is possible to disperse the energy at the point of contact. By creating a thinner, lighter layer of metal set upon a currogated layer of similarly thin metal, it effectively reduces the mass at point of contact and provides light cushioning against the blow to the actual hull beneath.
This isn’t enough to completely protect a ship against a matter cannon, no, but it adds a great amount of protection, reducing the impact enough that the danger from a matter cannon went from “instantly fatal” to “survivable.” As of yet, no better defense has been made, or if it has been, it’s not publicly available.