A cave is a natural opening in the ground with a hollow space beneath the surface large enough for people to enter.

洞穴是地面上的一个自然开口，地面下面有一个中空的空间，足够人进去。

In the center of these osteons, there are hollow spaces called Haversian canals, which contain the blood supply and innervation for the bone cells.

在这些骨单位的中心，这个中空的部分被称作哈弗斯管，提供了为骨细胞供应血液以及神经支配的空间。

In the months before a dinosaur lays its eggs, it will store up calcium in the hollow spaces inside its bones.

在恐龙产卵前的几个月里，它会将钙储存在骨骼内的空腔中。

And, when paleontologists scan fossils of some dinosaur bones, like vertebrae, they often find hollow spaces inside the bones where the air sacs used to sit.

而且， 当古生物学家扫描某些恐龙骨骼（如椎骨）的化石时，他们经常会在骨骼内部发现气囊所在的空腔。

We are, for example, exploring alternative solutions for compressing or jamming particles that include external fields, like magnetic attraction between adjacent particles or tension created by fibres and pulleys that could be interwoven in the hollow space within the particles.

CHIARA：例如，我们正在探索压缩或干扰颗粒的替代解决方案， 其中包括外部场， 例如相邻颗粒之间的磁引力或由纤维和滑轮产生的张力， 这些纤维和滑轮可以交织在颗粒内的中空空间中。