Maybe I can play the same game with the other known force, which was, at that time, known as the electromagnetic force — we know of others today, but at that time that was the only other one people were thinking about.
Tal vez, yo podría aplicar el mismo principio con otra fuerza, que en esa época era conocida como fuerza electromagnética — sabemos de otras ahora, pero en esa época esa era la única en la que pensaba la gente.