<P> Because of atmospheric refraction, and also because the sun is a disc rather than a point, the midnight sun may be experienced at latitudes slightly below the polar circle, though not exceeding one degree (depending on local conditions). For example, Iceland is known for its midnight sun, even though most of it (Grímsey is the exception) is slightly south of the Arctic Circle . For the same reasons, the period of sunlight at the poles is slightly longer than six months . Even the northern extremities of Scotland (and places at similar latitudes, such as St. Petersburg) experience twilight throughout the night in the northern sky at around the summer solstice . </P> <P> Observers at heights appreciably above sea level can experience extended periods of midnight sun as a result of the "dip" of the horizon viewed from altitude . </P> <P> The term "midnight sun" refers to the consecutive 24 - hour periods of sunlight experienced north of the Arctic Circle and south of the Antarctic Circle . Other phenomena are sometimes referred to as "midnight sun", but they are caused by time zones and the observance of daylight saving time . For instance, in Fairbanks, Alaska, which is south of the Arctic Circle, the sun sets at 12: 47 am at the summer solstice . This is because Fairbanks is 51 minutes ahead of its idealized time zone (as most of the state is in one time zone) and Alaska observes daylight saving time . (Fairbanks is at about 147.72 degrees west, corresponding to UTC − 9 hours 51 minutes, and is on UTC − 9 in winter .) This means that solar culmination occurs at about 12: 51 pm instead of at 12 noon . </P> <P> If a precise moment for the genuine "midnight sun" is required, the observer's longitude, the local civil time and the equation of time must be taken into account . The moment of the sun's closest approach to the horizon coincides with its passing due north at the observer's position, which occurs only approximately at midnight in general . Each degree of longitude east of the Greenwich meridian makes the vital moment exactly 4 minutes earlier than midnight as shown on the clock, while each hour that the local civil time is ahead of coordinated universal time (UTC, also known as GMT) makes the moment an hour later . These two effects must be added . Furthermore, the equation of time (which depends on the date) must be added: a positive value on a given date means that the sun is running slightly ahead of its average position, so the value must be subtracted . </P>

When does the sun come out in antarctica