Sunrise is the time at which the first part of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the (variously defined) point at which the sky begins to lighten, some time before the sun itself appears, ending twilight. Because atmospheric refraction causes the sun to be seen while it is still below the horizon, both sunrise and sunset are, from one point of view, optical illusions. The sun also appears larger on the horizon, but this is another optical illusion, similar to the moon illusion.

The apparent westward revolution of Sun around the earth after rising out of the horizon is due to the Earth's eastward rotation. This illusion is so convincing that most cultures had mythologies and religions built around the geocentric model. This same effect can be seen with near-polar satellites as well. (