To explain this, they hypothesize that galaxies must contain a great deal of missing matter which cannot be detected.
为了解释这一点,他们假定银河系一定包含了大量无法探测到的不明物质。
They hypothesize that language diversity must be about history, cultural differences, mountains or oceans dividing populations.
他们假设,语言多样性一定与历史、文化差异、山脉或海洋分隔人口有关。