That most stable form is defined as zero.

最稳定的形式被定义为零。

If the diamonds came up much slower than that, the gradually-decreasing pressure would let the carbon atoms shift back into other stable forms like graphite.

如果钻石上升速度比上述速度慢得多的话，逐渐减小的压力会将碳原子转化为其他稳定的形式，如石墨。

So scientists created a baseline by setting the standard free energy change of formation for an element in its most stable form at standard state to zero.

因此，科学家通过将标准状态下最稳定形式的元素的标准自由能形成变化设置为零来创建基线。

Since absolute enthalpy is unknowable though, we have to be measuring from a baseline, and that baseline is that individual elements' most stable form at standard state.

由于绝对焓是不可知的， 我们必须从基线开始测量，而该基线是单个元素在标准状态下最稳定的形式。