辐射来自于外层空间（宇宙射线），以及在土壤，水和空气中的天然放射性物质。
The radiation comes from space (cosmic rays) as well as natural radioactive materials found in the soil, water and air.
科学家们仍致力于发明到达外层空间的新方法。
The scientists are still working on inventing new methods of reaching outer space.
让我们共同努力，为子孙后代保留这片净土，确保广袤无垠的外层空间永远造福于全人类。
Let's make concerted efforts in preserving the vastness of outer space a tranquil place for the benefit of our future generations.
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