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Human eyes are amazingly powerful. While orbiting Earth, astronauts have spotted the wakes of oceangoing ships. And even people with poor vision can sort through complex visual details.
However, human eyes are weak compared to the eyes of some other animals. Snakes, for example, see infrared light that is invisible to the human eye. Humans have learned to make up for their visual drawbacks by inventing machines that can see for them. Some magnify the things we cannot see. Others peer into faraway places we can only dream of seeing on our own.
