What is one way Earth's atmosphere protects us from space threats?

• A. It blocks most harmful ultraviolet radiation.
• B. It blocks all solar radiation.
• C. It reflects all visible light.
• D. It warms the surface immediately.

Answer: (A)

The atmosphere blocks most harmful ultraviolet radiation. The ozone layer in the upper atmosphere absorbs the Sun’s UV-B and UV-C rays, which are the versions of ultraviolet light most damaging to DNA and living tissues. By preventing those rays from reaching the surface, the atmosphere helps protect us from skin cancer, cataracts, and genetic damage.

Visible light passes through the atmosphere, which is why we can see and why we still get daylight. It doesn’t reflect all visible light, and the idea that the atmosphere warms the surface immediately isn’t accurate—the warming comes from heat trapped and re-radiated over time, not an instant effect. While the atmosphere and magnetic field do help shield against some space radiation, the clearest and most direct protection described here is the absorption of ultraviolet radiation by the ozone layer.