The ratio of heavy and light isotopes of carbon found in the tree rings told them many secrets about the trees and their environment.

红杉树年轮中重碳同位素和轻碳同位素的比率，能透露关于树和环境的许多秘密。

That carbon atom can be either the " light" isotope, with six neutrons in its nucleus, or the heavy isotope, which has seven.

该碳原子可以是“轻”同位素（其原子核中有六个中子），也可以是重同位素（其原子核中有七个中子）。

Most uranium atoms have a total of 238 protons and neutrons, but roughly one in every 140 lacks three neutrons, and this lighter isotope is less tightly bound.

大多数铀原子总共有 238个质子和中子，但是每140个原子中大约 有一个缺少三个中子，而且这种较轻的同位素结构并不紧密。

Helion's suggestion is to start with 3He (two protons and a neutron), a light isotope of helium which is an intermediate stage in the solar reaction.

Helion 的建议是从 3He（两个质子和一个中子）开始，它是氦的轻同位素， 是太阳反应的中间阶段。