Supernova explosions pose a threat to human life, however small. When a star explodes, most of its energy will be absorbed in the vast emptiness of space. Cosmic rays would be diffused by magnetic fields, and most of the damaging light would not affect life on Earth. But it is believed long-term exposure to blue-enhanced light could interfere with life. Those who study chronobiology, or the effects of biological timing, have found that low levels of blue light can strongly affect the endocrine systems of mammals by causing physiological and alerting responses. Blue-enhanced light is associated with reduced levels of melatonin production and affects circadian rhythms. For these reasons, it is sometimes prescribed to counteract seasonal affective disorder (SAD) or winter depression. Blue light can increase insomnia, reduce resistance to infection and is being studied as a possible risk of cancer.

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