保护地球，探索宇宙，发现文明
2023年9月23日 Afternoon Analemma Image Credit & Copyright: Ian Griffin (Otago Museum) Explanation: An analemma is that figure-8 curve you get when you mark the position of the Sun at the same time each day for one year. To make this one, a 4×5 pinhole camera was set up looking north in southern New Zealand skies. The shutter was briefly opened each cl...
2021年10月5日 Sunrise at the South Pole Image Credit & Copyright: Martin Wolf (U. Wisconsin), IceCube Neutrino Obs., NSF; ht: Alice Allen Explanation: Sunrise at the South Pole is different. Usually a welcome sight, it follows months of darkness — and begins months of sunshine. At Earth’s poles, it can take weeks for the Sun to rise, in contras...
2021年9月22日 Equinox on a Spinning Earth Image Credit: Meteosat 9, NASA, earthobservatory, Robert Simmon Explanation: When does the line between night and day become vertical? Today. Today is an equinox on planet Earth, a time of year when day and night are most nearly equal. At an equinox, the Earth’s terminator — the dividing line between day and...
2020年10月02日 Biking to the Moon Image Credit & Copyright: Susan Snow Explanation: As you watched October’s first Full Moon rise last night, the Full Moon closest to the northern autumnal equinox, you were probably asking yourself, “How long would it take to bike to the Moon?” Sure, Apollo 11 astronauts made the trip in 1969, from launch...
2020年9月22日 Equinox in the Sky Image Credit & Copyright: Luca Vanzella Explanation: Does the Sun set in the same direction every day? No, the direction of sunset depends on the time of the year. Although the Sun always sets approximately toward the west, on an equinox like today the Sun sets directly toward the west. After today’s September equinox...
2019 September 28 An Analemma of the Sun Image Credit & Copyright: Gyorgy Soponyai Explanation: This week the equinox found the Sun near the middle, but not at the crossing point, of an analemma in its annual trek through planet Earth’s skies. In this scenic view, that graceful, figure-8-shaped curve was intentionally posed above the iconic Danube...