Not all sounds made by animals serve as language.

动物发出的声音不都是用作语言交际。

There has long been a superstition among mariners that porpoises will save drowning men by pushing them to the surface, or protect them from sharks by surrounding them in defensive formation.

长期以来，海员中流传着一种迷信的说法，认为海豚会把快要淹死的人托到水面，救人性命；或在人们周围列队保护，使他们免遭鲨鱼伤害。

concludes that it must be the gateway to world that lies beyond.

日落处想必是通往遥远世界的大门。

But even in the most favourable circumstances only a small fraction of the creatures that die are preserved in this way before decay sets in or, even more likely, before scavengers eat them.

即使是在最有利的环境中，死去的生物中也只有一小部分能在开始腐烂前，或更可能在被食腐动物吃掉之前，被这样保存下来。

It is the one world in the Solar System that is most like the Earth.

火星是太阳系里与地球最接近的一颗行星。

like the cooling of a hot kettle or the wearing-out of a pair of shoes.

就像一壶热水迟早会凉下来，一双鞋渐渐会磨破一样。