Bats have an engineering problem: how to find their way and find their prey in the absence of light.
蝙蝠们遇到了一个技术上的难题：如何在没有光线的条件下认路和捕食。
2
Darkness is in reality the absence of light. Light we can study, but not darkness.
黑暗其实是因为缺少光的缘故，我们可以研究光线，但无法研究黑暗。
3
The study found that monarch butterflies have an internal sense of direction that allowed them to get from one point to another even in the absence of light by sensing the Earth's magnetic field.