然而，大约在同一时间，科学家们意识到彗星可能含有衰变的放射性同位素，这些同位素可能使彗星内部的温度升高到导致内部进化的温度。
About the same time, though, scientists realized comets might contain decaying radioactive isotopes that could have warmed cometary interiors to temperatures that caused the interiors to evolve.
这么大的原子核不可能是稳定的，但在足够长的时间内，在真空附近组装一个原子核以观察真空的衰变是可能的。
A nucleus that large cannot be stable, but it might be possible to assemble one next to a vacuum for long enough to observe the decay of the vacuum.
食品中的放射性碘直接引起人们的关注，但是它的半衰期相对较短并将在短时间内自然衰变。
Radioactive iodine in food is of immediate concern, but it has a relatively short half-life and will naturally decay over a short time frame.
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