中微子占有中子质量的43％左右，如果把宇宙看成一个大中子，中微子则占宇宙总质量的43％，它就是所谓“暗物质”。

Neutrinos occupy about 43% of the neutron mass, If the universe as a medium and large child, Neutrino accounted for 43% of total mass of the universe, It is the so-called "dark matter".

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给定元素的所有同位素都含有相同的质子数，但它们的中子数不同，因此它们的原子质量也不同。

All the isotopes of a given element have the same number of protons, but differ in their number of neutrons, and hence in their atomic mass.

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每一个中子或者质子的质量都是一个电子的两千倍。

Each proton (or neutron) has about two thousand times the mass of an electron.

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