THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet 70 Falmouth Street Portland, Maine 04103 43.6667° N 70.2667° W Founded January 1970 Julian date: 2457660.16 "Go forth undaunted. Yes, pretending to do so works, too." THE DAILY ASTRONOMER Wednesday, September 28, 2016 Cold Misconceptions Bob and Phil retired a few years ago. They were the highly agreeable, if not particularly brain-burdened, pair who helped us address a variety of astronomical misconceptions. They are now in some remote paradise far removed from the cares and trials of the everyday world. We are still seeking out their replacements, a task that has proven much more difficult than we initially believed it would be. While we scour the glacial plains of the DA realm for two characters of equal amicability, we will look into some common astronomical misconceptions ourselves. Forgive us if we, unlike Bob and Phil, don't set our heads on fire, stuff ourselves in wells, or plunge headlong into cloud forms in a desperate search for elusive silver linings. Instead, we'll proceed safely and prudently as we tackle some common misconceptions. Those that we'll address today are all cold-weather related, as we are now moving through autumn en route to winter and couldn't be happier. *The last touch of twilight illuminates an Arctic mountain range. Image: Annette Mossbacher* *1. The North Pole is dark for six months of the year.* If Earth had no atmosphere, the North Pole would go dark six months of the year. However, we do have an atmosphere, as evidenced by our ability remain alive by breathing in it. The atmosphere also scatters light and make astronomy even more complicated. The Sun rises at the North Pole just before the vernal equinox and remains in the sky until just after the autumnal equinox. The Sun is just now setting at the North Pole. For a few weeks, the North Pole experiences perpetual civil twilight as the Sun descends further below the horizon. Civil twilight -which we call "dusk,"- occurs when the Sun is below the horizon, but still within six degrees of it. Civil twilight at the North Pole won't end until mid October. Nautical twilight, when the Sun is more than six, but less than twelve degrees of the horizon, is the period of time when the brightest stars appear, but the horizon remains visible. Nautical twilight won't end until late October. Astronomical twilight, when the Sun is more than twelve but less than eighteen degrees of the horizon, follows nautical twilight won't end until mid November. However, one would be hard pressed to distinguish between night and astronomical twilight. Nautical twilight begins at the North Pole around early to mid February and then civil twilight starts in late Feb/early March. So, the North Pole is truly dark between Halloween and Valentine's Day. A long night, indeed, but certainly not six months in duration.