我们星球的磁场为太阳提供了保护屏障 Our planet's magnetic field creates a protective barrier against the sun's
有害辐射。没有它，生活就不可能存在。 harmful radiation. Without it life could not exist.
但是我们的磁场是如何开始的呢？直到最近，科学家们才相信 But how did our magnetic field begin? Until recently scientists believed the
磁场是由外核的旋转铁水产生的 field originated from the swirling liquid iron of the outer core as it does
今天。 today.
但是新证据表明，古代磁场实际上可能具有 But new evidence suggests that the ancient magnetic field may actually have
起源于地幔内部深处的巨大岩浆海洋， originated from a giant magma ocean deep inside the mantle that existed between
4.5和25亿年前。 4.5 and 2.5 billion years ago.
然后，在地球形成二十亿年之后，地幔开始 Then, two billion years after the Earth was formed, the liquid mantle started to
芯开始释放其滞留的热量时凝固。 solidify while the core began to release its trapped heat.
来自堆芯的热量运动触发了对流流体运动，其强度足以 The movement of heat from the core triggered a convective fluid motion strong enough
产生磁场。 to generate a magnetic field.
大约十亿年前，内核冷却到足以开始凝固。 About half a billion years ago, the inner core cooled enough to start solidifying.
直到今天，坚实的核心不断发展， To this day the solid core continues to grow,
推动产生我们所知的地球磁场的力 driving the forces that produced the Earth's magnetic field as we know it
今天。 today.