When a massive star explodes, it leaves behind a dense spinning core made entirely of neutrons.

当一个大质量的恒星爆炸时，它会留下一个完全由中子组成的高密度旋转核心。

Finally, at its center is most likely a dense core of material, probably composed of rock and metal.

最后，木星的中心是一个致密的核状物质，应该是由岩石和金属构成的。

Our home planet has a dense metal core, a thick viscous rock mantle, and a thin crust.

我们的这颗星球有稠密的金属核，粘稠的岩石地幔和薄薄的地壳。

Only the extremely dense, extremely massive core is left.

只剩下密度极大、质量极大的地核。

The hotter the temperature, the denser the core, the more you can ram things together and actually form bigger and bigger atoms over time.

温度越高，核密度越大，就有越多的物质发生撞击，随着时间的推移，就会形成越来越大的原子。

Before the impact, Jupiter had a dense central core of heavy elements, and the rest of the planet was made up of hydrogen and helium.

撞击前，木星的核心是由重元素组成的密集核心，其余部分则由氢和氦组成。

Collisions broke almost all of them apart, though, and that's why we see asteroids with different compositions: some are from the denser core, others from the lighter crust.

然而，撞击使它们几乎全部解体，这就是为什么我们看到的小行星有着不同组成成分的原因了：它们一些来自密度更大的核心，另一些来自更轻的地壳。

They travel further to work and school, have more cars and drive them further, heat and cool bigger homes, and maintain bigger yards, negating the compact efficiency of the dense urban cores they surround.

他们上班和上学的路程更远，拥有更多的汽车，并把它们开得更远，为更大的房屋供暖和制冷，并维持更大的院子，否定了他们周围密集的城市核心区的紧凑效率。