Cosmic rays are responsible for...aurorae (c), otherwise known as the northern and southern lights. But why are they not seen in equatorial regions? Remember that cosmic rays are charged particles, and thus, low energy cosmic rays have a tendency to follow magnetic field lines. The magnetic field lines of the earth pass through the north and south poles and hence most charged particles traveling towards the earth end up traversing the atmosphere close to the poles. As was discussed earlier in the quiz, these charged particles (mainly electrons produced in cosmic ray showers) can excite electrons in nitrogen and oxygen, two elements that are abundant in the earth's atmosphere. When the electrons drop back down to a lower energy state, photons are emitted and hence, on a grander scale, aurorae are produced. A picture of one such aurora is shown below.
Cosmic rays have similar effects to radiation on the human body. For the average human living at sea level, cosmic rays do not pose a serious health risk.However, people on airplanes are most likely to be adversely affected by cosmic rays, since they are higher up in the earth's atmosphere. Energetic cosmic rays can knock out the electrons of living tissue, and in doing so, break chemical bonds, perhaps providing a site for cancer to develop. However, it has not been proven that cosmic rays are responsible for causing cancer among airline passengers (b). Nevertheless, Lufthansa, a German airline, forbids pregnant stewardesses from working on their planes, to protect against any adverse effects of cosmic rays that might affect the babies. This issue does beg the question, however, that if cosmic rays were shown to be responsible for someone's cancer, who would get sued? I suppose we'll have to figure out where cosmic rays come from first and then this question can be answered. Further discussion of the radiation effects of cosmic rays can be found on pp. 146-148 of Michael Friedlander's Cosmic Rays.
Cosmic rays may also indirectly be responsible for the depletion of the ozone layer (a). If cosmic rays directly depleted the ozone layer, there would be no ozone layer left, since cosmic rays have been around for a long, long time. Chlorine is the element that breaks down the ozone layer. Chlorine is released when ultraviolet radiation interacts with manmade chlorofluorocarbons (CFCs). However, an experiment in 2001 involving simulated cosmic rays and CFCs produced similar results. For a NASA astronomer's perspective on the issue, click here.
Cosmic rays are NOT responsible for the expansion of the universe (d). The expansion of the universe occurs, as far as we know, due to a really big explosion that took place a long time ago, also known as the Big Bang.
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