translation.en: We know a lot about four forces. There must be a lot more, but those are at very, very small distances, and we haven't really interacted with them very much yet.
translation.zh: 对基本粒子的四种作用力我们已经相当了解，但未知的部分肯定更多。 但对极其微小尺度的物质 我们还所知甚少。