Video Transcript
Which of the following would be
exposed to more natural nuclear radiation in a day? (A) An astronaut in orbit around
Earth, outside Earth’s atmosphere. (B) A person on the surface of
Earth.
This question asks about nuclear
radiation from natural sources that are found outside and inside Earth’s
atmosphere. Earth is a natural source of
nuclear radiation because radioactive minerals are found in some of the rocks. The closer to the center of the
Earth, the more naturally occurring nuclear radiation from these rocks is
present.
Remember that natural sources of
nuclear radiation are also present throughout the universe. Stars are one such source, and the
Sun is one such star. This radiation is called cosmic
radiation. Earth’s atmosphere absorbs much of
the cosmic radiation that enters the atmosphere. But some cosmic radiation reaches
the surface of the Earth. So, a person on Earth’s surface
receives less cosmic radiation than a person outside the atmosphere. However, the person on Earth’s
surface receives more natural radiation that originates from rocks. The question is then, which is more
intense, cosmic radiation or radiation from Earth?
To understand which is more
intense, it is helpful to consider that radiation can pass through the air more
easily than it can pass through the ground. Cosmic radiation must pass through
the air to reach a person on the surface of Earth, whereas radiation from rocks must
pass through the ground. Because of this, the cosmic
radiation is more intense than the radiation from Earth. We see then that the correct answer
is option (A): an astronaut in orbit around Earth, outside Earth’s atmosphere.
