The turtles have particles of magnetite, a magnetic mineral, in their brains.

海龟中有铁颗粒，这是一种性物。

This magnetite basically helps them to orient in the right direction.

这种铁基本上可以帮助它们以正确方向定向。

Magnetite is the most magnetic natural metal on earth.

铁是地上最具性天然金属。

Like peanuts, magnetite is more dense and should sit at the bottom.

像花生一样，铁密度更，所以应该位于底部。

The magnetite likely plays a role in orienting sea turtles to Earth's magnetic poles, similar to a compass.

铁可能在将海龟定向到地极方面起作用，类似于指南针。

The first theory is that animals have tiny magnetite particles in their bodies that act as magnetic receptors.

第一个理论是，动物体内有微小铁颗粒，作为感受器发挥作用。

And that proof came in the form of a miraculous little mineral called magnetite.

而这种证据以一种被称为铁神奇物形式出现。

Which, again, are magnetite. Over here are iron oxide.

又是铁。这里是氧化铁。

The very first magnets that anyone knew about were natural magnets called lodestone or magnetite.

最早铁是天然石，称为石或铁。

If the house was built on magnetic ore...

要是这房子下面有铁。

Third, it just doesn't make sense that bacteria on Mars would produce magnetite.

第三，火星上细菌会产生铁是没有意义。

A lot of homing pigeons also have what is called magnetite in their beaks and magnetoreceptors in their nervous system or brains.

很多信鸽喙中也有所谓铁，神经系统或中有感受器。

Basalt is a volcanic rock composed of agite and sometimes plagioclase and magnetite, which says nothing.

玄武岩是一种火山岩， 主要由辉石构成， 有时还含有斜长石和铁，这些成分本身并无特别含义。

Lodestone, scientists and humans have known this for hundreds of years, are naturally magnetized pieces of magnetite.

天然石， 科学家和人类几百年前就知道，它是自然化铁块。

What they didn't know at the time was they had passed by a succession of magnet mines.

他们哪里知道他们经过是一座座铁山。

Earth bacteria have the magnetite grains because they allow them to follow the Earth's strong magnetic field.

地细菌具有铁颗粒， 因为它们使它们能够跟随地强场。

The magnetite points north, then south, the north again, and so on, providing proof that the seafloor was spreading.

铁先是指向北方， 接着转向南方，再指回北方， 如此反复，提供了海底扩张证据。

It's much too weak to follow, which means that magnetite grains would be completely useless to Martian bacteria.

它太弱了，无法追踪，这意味着铁颗粒对火星细菌来说完全没有用处。

The same process could also explain why volcano scientists find that the mineral magnetite rises to higher layers in Earth's crust than would be expected.

同样过程也可以解释为什么火山科学家发现物铁在地壳中能上升到比预期更高层。

But there's actually a more precise way to tell that Africa was once near the South Pole, and once again, it's magnetite.

实际上， 有一种更精确方法可以证明非洲曾靠近南极，那就是铁。