Bone mass density; Elderly people; Osteoporosis.

骨密度；老年人；骨质疏松。

youdao

The gravity field out of the earth depends on the interior mass density distribution of the earth.

地球外部重力场是由地球内部物质分布决定的。

youdao

Hence, the rest-mass of the neutrino being non-vanishing would influence greatly the mass density and further the evolution of the universe.

因此，中微子是否具有静止质量，将极大地影响着宇宙中的质量密度，从而影响着宇宙演化的进程。

youdao

Ah, but density is mass over volume.

但密度是质量除以体积

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