Comets can be seen with the naked eye, and sometimes they are spectacularly bright and beautiful, so humans have undoubtedly been observing comets since time immemorial. On the other hand, comets are usually visible only for short periods of time—a few days or weeks—so almost all comet sightings have gone unrecorded and were misunderstood for most of that human history. For these and other reasons, a great deal of mythology and superstition has been associated with comets through-out the ages.